From a48fbe2ee7c9acb0b5c3422d46039e08af683207 Mon Sep 17 00:00:00 2001
From: Anton Afanasyeu <a.afanasieff@gmail.com>
Date: Sat, 16 May 2026 13:35:48 +0200
Subject: [PATCH] proto changes, 1:m initial

---
 app/src/main/AndroidManifest.xml              |   6 +-
 .../com/foxx/androidcast/CastActiveState.java |  18 +
 .../java/com/foxx/androidcast/CastConfig.java |   7 +
 .../com/foxx/androidcast/CastSettings.java    |  19 +-
 .../java/com/foxx/androidcast/DeviceInfo.java | 128 +++++++
 .../com/foxx/androidcast/IntentExtras.java    |  15 +
 .../com/foxx/androidcast/MainActivity.java    |   6 +
 .../foxx/androidcast/PermissionHelper.java    |  93 ++++-
 .../foxx/androidcast/PlatformCastSupport.java |  11 +
 .../java/com/foxx/androidcast/SettingsUi.java |  56 ++-
 .../com/foxx/androidcast/VersionInfo.java     |  18 +
 .../com/foxx/androidcast/VersionUtils.java    |  64 ++++
 .../diagnostics/CastDiagnosticsFormatter.java | 322 ++++++++++++++++++
 .../diagnostics/CastDiagnosticsLabels.java    | 125 +++++++
 .../diagnostics/CastDiagnosticsScorer.java    |  62 ++++
 .../discovery/DiscoveryManager.java           | 138 +++++++-
 .../foxx/androidcast/media/AacAdtsHelper.java |  60 ++++
 .../androidcast/media/PcmLevelAnalyzer.java   |  67 ++++
 .../androidcast/network/CastCodecFlags.java   |  53 +++
 .../network/CastFramingContext.java           |  26 ++
 .../androidcast/network/CastPacketFramer.java | 104 ++++++
 .../androidcast/network/CastProtoHeader.java  | 131 +++++++
 .../androidcast/network/CastProtocol.java     |  43 +++
 .../androidcast/network/CastTransport.java    |   2 +
 .../androidcast/network/TcpCastTransport.java |  29 +-
 .../androidcast/network/UdpCastTransport.java |  82 ++++-
 .../network/control/NetworkStatsSnapshot.java |  28 ++
 .../PassThroughNetworkControlPlane.java       |  13 +
 .../androidcast/receiver/AudioDecoder.java    | 307 ++++++++++++++---
 .../receiver/PlaybackViewState.java           |  21 ++
 .../receiver/ReceiverActivity.java            |   3 +-
 .../receiver/ReceiverCastService.java         | 107 ++++--
 .../receiver/ReceiverPlaybackActivity.java    |   8 +-
 .../androidcast/receiver/ReceiverSession.java |  28 +-
 .../androidcast/receiver/StreamMetrics.java   | 199 +++++++----
 .../foxx/androidcast/sender/AudioCapture.java | 203 +++++++++--
 .../foxx/androidcast/sender/AudioEncoder.java |  20 ++
 .../androidcast/sender/CastFanoutPump.java    | 130 +++++++
 .../sender/CastReceiverTarget.java            |  29 ++
 .../foxx/androidcast/sender/CastSendPump.java |  10 +-
 .../androidcast/sender/DeviceListAdapter.java | 147 ++++----
 .../sender/MultiCastCoordinator.java          | 201 +++++++++++
 .../androidcast/sender/ScreenCastService.java | 167 +++++++--
 .../androidcast/sender/SenderActivity.java    | 161 +++++++--
 .../sender/SenderAudioMetrics.java            |  61 ++++
 .../sender/SenderStreamMetrics.java           |  14 +-
 .../foxx/androidcast/sender/VideoEncoder.java |  27 +-
 .../foxx/androidcast/ui/ZoomPanContainer.java | 134 ++++++++
 app/src/main/res/layout/activity_playback.xml |  21 +-
 app/src/main/res/layout/activity_sender.xml   |   7 +-
 .../res/layout/activity_settings_panel.xml    |  19 ++
 app/src/main/res/values/strings.xml           |  13 +
 52 files changed, 3411 insertions(+), 352 deletions(-)
 create mode 100644 app/src/main/java/com/foxx/androidcast/CastActiveState.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/DeviceInfo.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/VersionInfo.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/VersionUtils.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/diagnostics/CastDiagnosticsFormatter.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/diagnostics/CastDiagnosticsLabels.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/diagnostics/CastDiagnosticsScorer.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/media/AacAdtsHelper.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/media/PcmLevelAnalyzer.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/network/CastCodecFlags.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/network/CastFramingContext.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/network/CastPacketFramer.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/network/CastProtoHeader.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/receiver/PlaybackViewState.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/sender/CastFanoutPump.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/sender/CastReceiverTarget.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/sender/MultiCastCoordinator.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/sender/SenderAudioMetrics.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/ui/ZoomPanContainer.java

diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index ce550b6..0d18ca3 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -10,6 +10,8 @@
     <uses-permission android:name="android.permission.FOREGROUND_SERVICE_MEDIA_PLAYBACK" />
     <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
     <uses-permission android:name="android.permission.WAKE_LOCK" />
+    <uses-permission android:name="android.permission.RECORD_AUDIO" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_MICROPHONE" />
 
     <application
         android:allowBackup="true"
@@ -48,8 +50,8 @@
         <service
             android:name=".sender.ScreenCastService"
             android:exported="false"
-            android:stopWithTask="true"
-            android:foregroundServiceType="mediaProjection" />
+            android:stopWithTask="false"
+            android:foregroundServiceType="mediaProjection|microphone" />
 
         <service
             android:name=".receiver.ReceiverCastService"
diff --git a/app/src/main/java/com/foxx/androidcast/CastActiveState.java b/app/src/main/java/com/foxx/androidcast/CastActiveState.java
new file mode 100644
index 0000000..fd8e798
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/CastActiveState.java
@@ -0,0 +1,18 @@
+package com.foxx.androidcast;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/** Process-wide cast session flags for UI back-key handling. */
+public final class CastActiveState {
+    private static final AtomicBoolean senderCasting = new AtomicBoolean(false);
+
+    private CastActiveState() {}
+
+    public static void setSenderCasting(boolean active) {
+        senderCasting.set(active);
+    }
+
+    public static boolean isSenderCasting() {
+        return senderCasting.get();
+    }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/CastConfig.java b/app/src/main/java/com/foxx/androidcast/CastConfig.java
index 1e95e82..f874b1e 100644
--- a/app/src/main/java/com/foxx/androidcast/CastConfig.java
+++ b/app/src/main/java/com/foxx/androidcast/CastConfig.java
@@ -3,8 +3,15 @@ package com.foxx.androidcast;
 /** Shared constants for the LAN cast POC. */
 public final class CastConfig {
     public static final int DISCOVERY_PORT = 41234;
+    /** One UDP browse pass duration (progress bar on sender). */
+    public static final long DISCOVERY_SCAN_PASS_MS = 4_000;
     public static final int CAST_PORT = 41235;
     public static final String DISCOVERY_MAGIC = "ACAST1";
+
+    /** When true, sender list allows selecting multiple receivers (1:N cast). */
+    public static final boolean MULTI_RECEIVER_ENABLED = true;
+
+    public static final int MAX_RECEIVERS = 5;
     public static final String DEFAULT_PIN = "1234";
 
     public static final String TRANSPORT_TCP = "tcp";
diff --git a/app/src/main/java/com/foxx/androidcast/CastSettings.java b/app/src/main/java/com/foxx/androidcast/CastSettings.java
index 6e39d7e..7222549 100644
--- a/app/src/main/java/com/foxx/androidcast/CastSettings.java
+++ b/app/src/main/java/com/foxx/androidcast/CastSettings.java
@@ -5,7 +5,7 @@ import java.io.Serializable;
 /** User-selected cast parameters (passed sender → service → receiver via protocol). */
 public class CastSettings implements Serializable {
     public static final String EXTRA = "cast_settings";
-    public static final int SETTINGS_VERSION = 2;
+    public static final int SETTINGS_VERSION = 3;
 
     public enum Quality {
         LOW(1_500_000, 24),
@@ -41,6 +41,14 @@ public class CastSettings implements Serializable {
      * Capture size. {@link #HD_720P} caps height only (width follows aspect — e.g. 1532×720).
      * {@link #FIXED_720P} fits inside 1280×720 box.
      */
+    /** How the system screen-capture consent dialog behaves (sender only). */
+    public enum CaptureMode {
+        /** Whole display (default). */
+        FULL_SCREEN,
+        /** Android 14+: system picker can target a single app (better app audio capture). */
+        USER_CHOICE
+    }
+
     public enum Resolution {
         FULL(1.0f, 0, 0),
         THREE_QUARTERS(0.75f, 0, 0),
@@ -69,6 +77,7 @@ public class CastSettings implements Serializable {
     private AdjustmentPreset adjustmentPreset = AdjustmentPreset.AUTO;
     private BitrateMode bitrateMode = BitrateMode.AUTO;
     private NetworkAdoption networkAdoption = NetworkAdoption.AUTO;
+    private CaptureMode captureMode = PlatformCastSupport.defaultCaptureMode();
     /** Filled after codec handshake (e.g. video/avc). */
     private transient String negotiatedVideoMime;
 
@@ -176,4 +185,12 @@ public class CastSettings implements Serializable {
     public void setNegotiatedVideoMime(String negotiatedVideoMime) {
         this.negotiatedVideoMime = negotiatedVideoMime;
     }
+
+    public CaptureMode getCaptureMode() {
+        return captureMode;
+    }
+
+    public void setCaptureMode(CaptureMode captureMode) {
+        this.captureMode = captureMode != null ? captureMode : CaptureMode.FULL_SCREEN;
+    }
 }
diff --git a/app/src/main/java/com/foxx/androidcast/DeviceInfo.java b/app/src/main/java/com/foxx/androidcast/DeviceInfo.java
new file mode 100644
index 0000000..af92703
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/DeviceInfo.java
@@ -0,0 +1,128 @@
+package com.foxx.androidcast;
+
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.media.MediaDrm;
+import android.os.Build;
+import android.provider.Settings;
+
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.Locale;
+import java.util.UUID;
+
+/**
+ * Stable device identity for cast handshakes. Survives app reinstall when possible
+ * (Widevine ID + per-app ANDROID_ID hash). Cached in {@link SharedPreferences}.
+ */
+public final class DeviceInfo {
+  private static final String PREFS = "androidcast_device";
+  private static final String KEY_UUID = "device_uuid";
+  private static final UUID WIDEVINE_UUID =
+      UUID.fromString("edef8ba9-79d6-4ace-a3c8-27dcd51d21ed");
+
+  private static volatile String cachedUuid;
+
+  private DeviceInfo() {}
+
+  /** Returns a stable UUID string for this device (app-singleton). */
+  public static String getDeviceUuid(Context context) {
+    if (cachedUuid != null) {
+      return cachedUuid;
+    }
+    synchronized (DeviceInfo.class) {
+      if (cachedUuid != null) {
+        return cachedUuid;
+      }
+      Context app = context.getApplicationContext();
+      SharedPreferences prefs = app.getSharedPreferences(PREFS, Context.MODE_PRIVATE);
+      String stored = prefs.getString(KEY_UUID, null);
+      if (stored != null && !stored.isEmpty()) {
+        cachedUuid = stored;
+        return cachedUuid;
+      }
+      String generated = generateStableUuid(app);
+      prefs.edit().putString(KEY_UUID, generated).apply();
+      cachedUuid = generated;
+      return cachedUuid;
+    }
+  }
+
+  /** Lower 32 bits of hashed UUID for {@code placeholder_id} in proto headers. */
+  public static int getPlaceholderId(Context context) {
+    return (int) (hashUuid(getDeviceUuid(context)) & 0xFFFFFFFFL);
+  }
+
+  private static String generateStableUuid(Context context) {
+    StringBuilder material = new StringBuilder();
+    material.append("androidcast:");
+    String androidId = Settings.Secure.getString(
+        context.getContentResolver(), Settings.Secure.ANDROID_ID);
+    if (androidId != null && !androidId.isEmpty()) {
+      material.append(androidId);
+    }
+    byte[] widevine = readWidevineId();
+    if (widevine != null && widevine.length > 0) {
+      material.append(':');
+      for (byte b : widevine) {
+        material.append(String.format(Locale.US, "%02x", b));
+      }
+    }
+    material.append(':').append(Build.BOARD).append(':').append(Build.DEVICE);
+    return uuidFromSha256(material.toString());
+  }
+
+  private static byte[] readWidevineId() {
+    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN_MR2) {
+      return null;
+    }
+    MediaDrm drm = null;
+    try {
+      drm = new MediaDrm(WIDEVINE_UUID);
+      return drm.getPropertyByteArray(MediaDrm.PROPERTY_DEVICE_UNIQUE_ID);
+    } catch (Exception ignored) {
+      return null;
+    } finally {
+      if (drm != null) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
+          drm.close();
+        } else {
+          drm.release();
+        }
+      }
+    }
+  }
+
+  private static String uuidFromSha256(String material) {
+    try {
+      MessageDigest md = MessageDigest.getInstance("SHA-256");
+      byte[] digest = md.digest(material.getBytes(StandardCharsets.UTF_8));
+      long msb = 0;
+      long lsb = 0;
+      for (int i = 0; i < 8; i++) {
+        msb = (msb << 8) | (digest[i] & 0xff);
+      }
+      for (int i = 8; i < 16; i++) {
+        lsb = (lsb << 8) | (digest[i] & 0xff);
+      }
+      return new UUID(msb, lsb).toString();
+    } catch (NoSuchAlgorithmException e) {
+      return UUID.randomUUID().toString();
+    }
+  }
+
+  private static long hashUuid(String uuid) {
+    try {
+      MessageDigest md = MessageDigest.getInstance("SHA-256");
+      byte[] digest = md.digest(uuid.getBytes(StandardCharsets.UTF_8));
+      long h = 0;
+      for (int i = 0; i < 8; i++) {
+        h = (h << 8) | (digest[i] & 0xff);
+      }
+      return h;
+    } catch (NoSuchAlgorithmException e) {
+      return uuid.hashCode();
+    }
+  }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/IntentExtras.java b/app/src/main/java/com/foxx/androidcast/IntentExtras.java
index 36aad5d..768e340 100644
--- a/app/src/main/java/com/foxx/androidcast/IntentExtras.java
+++ b/app/src/main/java/com/foxx/androidcast/IntentExtras.java
@@ -3,6 +3,10 @@ package com.foxx.androidcast;
 import android.content.Intent;
 import android.os.Build;
 
+import com.foxx.androidcast.sender.CastReceiverTarget;
+
+import java.util.ArrayList;
+
 /** API 33+ safe extras helpers. */
 public final class IntentExtras {
     private IntentExtras() {}
@@ -26,4 +30,15 @@ public final class IntentExtras {
         }
         return (CastSettings) intent.getSerializableExtra(CastSettings.EXTRA);
     }
+
+    @SuppressWarnings("unchecked")
+    public static ArrayList<CastReceiverTarget> getReceiverTargets(Intent intent, String key) {
+        if (intent == null) {
+            return null;
+        }
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
+            return intent.getSerializableExtra(key, ArrayList.class);
+        }
+        return (ArrayList<CastReceiverTarget>) intent.getSerializableExtra(key);
+    }
 }
diff --git a/app/src/main/java/com/foxx/androidcast/MainActivity.java b/app/src/main/java/com/foxx/androidcast/MainActivity.java
index c6cd2b0..feb50a3 100644
--- a/app/src/main/java/com/foxx/androidcast/MainActivity.java
+++ b/app/src/main/java/com/foxx/androidcast/MainActivity.java
@@ -24,6 +24,12 @@ public class MainActivity extends AppCompatActivity {
                 startActivity(new Intent(this, ReceiverActivity.class)));
     }
 
+    @Override
+    protected void onResume() {
+        super.onResume();
+        PermissionHelper.remindIfMissing(this, false);
+    }
+
     @Override
     public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
         super.onRequestPermissionsResult(requestCode, permissions, grantResults);
diff --git a/app/src/main/java/com/foxx/androidcast/PermissionHelper.java b/app/src/main/java/com/foxx/androidcast/PermissionHelper.java
index ae47acb..0403b0e 100644
--- a/app/src/main/java/com/foxx/androidcast/PermissionHelper.java
+++ b/app/src/main/java/com/foxx/androidcast/PermissionHelper.java
@@ -2,41 +2,122 @@ package com.foxx.androidcast;
 
 import android.Manifest;
 import android.app.Activity;
+import android.content.Intent;
 import android.content.pm.PackageManager;
+import android.net.Uri;
 import android.os.Build;
+import android.provider.Settings;
 
+import androidx.appcompat.app.AlertDialog;
 import androidx.core.app.ActivityCompat;
 import androidx.core.content.ContextCompat;
 
 import java.util.ArrayList;
 import java.util.List;
 
-/** Requests runtime permissions needed for LAN cast POC. */
+/** Requests and explains runtime permissions for LAN cast. */
 public final class PermissionHelper {
     public static final int REQUEST_CODE = 1001;
 
+    public static final class PermissionItem {
+        public final String permission;
+        public final String label;
+        public final boolean required;
+
+        PermissionItem(String permission, String label, boolean required) {
+            this.permission = permission;
+            this.label = label;
+            this.required = required;
+        }
+    }
+
     private PermissionHelper() {}
 
     public static boolean hasAll(Activity activity) {
-        return missing(activity).isEmpty();
+        return missing(activity, false).isEmpty();
+    }
+
+    public static boolean hasAllForAudio(Activity activity) {
+        return missing(activity, true).isEmpty();
     }
 
     public static void request(Activity activity) {
-        List<String> missing = missing(activity);
+        request(activity, false);
+    }
+
+    public static void requestForCast(Activity activity, boolean audioEnabled) {
+        request(activity, audioEnabled);
+    }
+
+    /** Shows a dialog listing missing permissions; offers request or app settings. */
+    public static void remindIfMissing(Activity activity, boolean includeAudio) {
+        List<PermissionItem> missing = describeMissing(activity, includeAudio);
+        if (missing.isEmpty()) {
+            return;
+        }
+        StringBuilder body = new StringBuilder();
+        for (PermissionItem item : missing) {
+            body.append("• ").append(item.label);
+            body.append(item.required ? " (required)\n" : " (recommended)\n");
+        }
+        new AlertDialog.Builder(activity)
+                .setTitle(R.string.permissions_missing_title)
+                .setMessage(body.toString().trim())
+                .setPositiveButton(R.string.permissions_grant, (d, w) ->
+                        ActivityCompat.requestPermissions(activity,
+                                permissionsOnly(missing), REQUEST_CODE))
+                .setNeutralButton(R.string.permissions_app_settings, (d, w) -> openAppSettings(activity))
+                .setNegativeButton(android.R.string.cancel, null)
+                .show();
+    }
+
+    private static void request(Activity activity, boolean includeAudio) {
+        List<String> missing = missing(activity, includeAudio);
         if (!missing.isEmpty()) {
             ActivityCompat.requestPermissions(
                     activity, missing.toArray(new String[0]), REQUEST_CODE);
         }
     }
 
-    private static List<String> missing(Activity activity) {
-        List<String> needed = new ArrayList<>();
+    private static List<String> missing(Activity activity, boolean includeAudio) {
+        List<PermissionItem> items = describeMissing(activity, includeAudio);
+        List<String> perms = new ArrayList<>();
+        for (PermissionItem item : items) {
+            perms.add(item.permission);
+        }
+        return perms;
+    }
+
+    private static List<PermissionItem> describeMissing(Activity activity, boolean includeAudio) {
+        List<PermissionItem> needed = new ArrayList<>();
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
             if (ContextCompat.checkSelfPermission(activity, Manifest.permission.POST_NOTIFICATIONS)
                     != PackageManager.PERMISSION_GRANTED) {
-                needed.add(Manifest.permission.POST_NOTIFICATIONS);
+                needed.add(new PermissionItem(Manifest.permission.POST_NOTIFICATIONS,
+                        "Notifications (cast status)", true));
+            }
+        }
+        if (includeAudio && PlatformCastSupport.isAudioCaptureSupported()) {
+            if (ContextCompat.checkSelfPermission(activity, Manifest.permission.RECORD_AUDIO)
+                    != PackageManager.PERMISSION_GRANTED) {
+                needed.add(new PermissionItem(Manifest.permission.RECORD_AUDIO,
+                        "Microphone (fallback when no app audio)", false));
             }
         }
         return needed;
     }
+
+    private static String[] permissionsOnly(List<PermissionItem> items) {
+        String[] arr = new String[items.size()];
+        for (int i = 0; i < items.size(); i++) {
+            arr[i] = items.get(i).permission;
+        }
+        return arr;
+    }
+
+    private static void openAppSettings(Activity activity) {
+        Intent intent = new Intent(Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
+        intent.setData(Uri.fromParts("package", activity.getPackageName(), null));
+        activity.startActivity(intent);
+    }
 }
diff --git a/app/src/main/java/com/foxx/androidcast/PlatformCastSupport.java b/app/src/main/java/com/foxx/androidcast/PlatformCastSupport.java
index 5d50b47..a430f05 100644
--- a/app/src/main/java/com/foxx/androidcast/PlatformCastSupport.java
+++ b/app/src/main/java/com/foxx/androidcast/PlatformCastSupport.java
@@ -14,6 +14,17 @@ public final class PlatformCastSupport {
         return Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q;
     }
 
+    /** Per-app / window picker for MediaProjection (Android 14+). */
+    public static boolean isCaptureUserChoiceSupported() {
+        return Build.VERSION.SDK_INT >= Build.VERSION_CODES.UPSIDE_DOWN_CAKE;
+    }
+
+    public static CastSettings.CaptureMode defaultCaptureMode() {
+        return isCaptureUserChoiceSupported()
+                ? CastSettings.CaptureMode.USER_CHOICE
+                : CastSettings.CaptureMode.FULL_SCREEN;
+    }
+
     /** Applies default audio flag: on for Android 10+, off otherwise. */
     public static void applyDefaultAudioSetting(CastSettings settings) {
         settings.setAudioEnabled(isAudioCaptureSupported());
diff --git a/app/src/main/java/com/foxx/androidcast/SettingsUi.java b/app/src/main/java/com/foxx/androidcast/SettingsUi.java
index c38b590..04e050c 100644
--- a/app/src/main/java/com/foxx/androidcast/SettingsUi.java
+++ b/app/src/main/java/com/foxx/androidcast/SettingsUi.java
@@ -1,10 +1,12 @@
 package com.foxx.androidcast;
 
+import android.os.Build;
 import android.view.View;
 import android.widget.AdapterView;
 import android.widget.ArrayAdapter;
 import android.widget.CheckBox;
 import android.widget.Spinner;
+import android.widget.TextView;
 
 import androidx.appcompat.app.AppCompatActivity;
 
@@ -12,12 +14,31 @@ import com.foxx.androidcast.sender.CodecCatalog;
 
 import java.util.ArrayList;
 import java.util.List;
-
 /** Binds cast option spinners/checkbox to {@link CastSettings}. */
 public final class SettingsUi {
     private SettingsUi() {}
 
+    public static void bindSender(AppCompatActivity activity, CastSettings settings) {
+        bindCommon(activity, settings);
+        bindCaptureModeSender(activity, settings);
+        PlatformCastSupport.bindAudioCheckbox(activity, activity.findViewById(R.id.checkbox_audio), settings);
+    }
+
+    public static void bindReceiver(AppCompatActivity activity, CastSettings settings) {
+        bindCommon(activity, settings);
+        View captureRow = activity.findViewById(R.id.layout_capture_mode);
+        if (captureRow != null) {
+            captureRow.setVisibility(View.GONE);
+        }
+        PlatformCastSupport.bindAudioCheckbox(activity, activity.findViewById(R.id.checkbox_audio), settings);
+    }
+
+    /** @deprecated use {@link #bindSender} or {@link #bindReceiver} */
     public static void bind(AppCompatActivity activity, CastSettings settings) {
+        bindSender(activity, settings);
+    }
+
+    private static void bindCommon(AppCompatActivity activity, CastSettings settings) {
         PlatformCastSupport.applyDefaultAudioSetting(settings);
 
         Spinner transport = activity.findViewById(R.id.spinner_transport);
@@ -27,7 +48,6 @@ public final class SettingsUi {
         Spinner quality = activity.findViewById(R.id.spinner_quality);
         Spinner networkAdoption = activity.findViewById(R.id.spinner_network_adoption);
         Spinner resolution = activity.findViewById(R.id.spinner_resolution);
-        CheckBox audio = activity.findViewById(R.id.checkbox_audio);
 
         bindSpinner(activity, transport, new String[]{
                 activity.getString(R.string.transport_tcp),
@@ -78,8 +98,38 @@ public final class SettingsUi {
         bindSpinner(activity, resolution, resolutions,
                 position -> settings.setResolution(CastSettings.Resolution.values()[position]));
         resolution.setSelection(CastSettings.Resolution.HD_720P.ordinal());
+    }
 
-        PlatformCastSupport.bindAudioCheckbox(activity, audio, settings);
+    private static void bindCaptureModeSender(AppCompatActivity activity, CastSettings settings) {
+        Spinner captureMode = activity.findViewById(R.id.spinner_capture_mode);
+        TextView label = activity.findViewById(R.id.text_capture_mode_label);
+        if (captureMode == null) {
+            return;
+        }
+        if (PlatformCastSupport.isCaptureUserChoiceSupported()) {
+            bindSpinner(activity, captureMode, new String[]{
+                    activity.getString(R.string.capture_full_screen),
+                    activity.getString(R.string.capture_user_choice)
+            }, position -> settings.setCaptureMode(
+                    position == 1 ? CastSettings.CaptureMode.USER_CHOICE : CastSettings.CaptureMode.FULL_SCREEN));
+            captureMode.setSelection(settings.getCaptureMode() == CastSettings.CaptureMode.USER_CHOICE ? 1 : 0);
+            captureMode.setEnabled(true);
+            if (label != null) {
+                label.setText(R.string.label_capture_mode);
+            }
+        } else {
+            String unavailable = activity.getString(R.string.capture_user_choice_unavailable,
+                    Build.VERSION.SDK_INT);
+            bindSpinner(activity, captureMode, new String[]{
+                    activity.getString(R.string.capture_full_screen),
+                    unavailable
+            }, position -> settings.setCaptureMode(CastSettings.CaptureMode.FULL_SCREEN));
+            captureMode.setSelection(0);
+            captureMode.setEnabled(false);
+            if (label != null) {
+                label.setText(activity.getString(R.string.label_capture_mode_sender_only));
+            }
+        }
     }
 
     private interface IntConsumer {
diff --git a/app/src/main/java/com/foxx/androidcast/VersionInfo.java b/app/src/main/java/com/foxx/androidcast/VersionInfo.java
new file mode 100644
index 0000000..d08c86c
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/VersionInfo.java
@@ -0,0 +1,18 @@
+package com.foxx.androidcast;
+
+/**
+ * Application and protocol version strings (CI may replace via script).
+ * App and proto versions are independent.
+ */
+public final class VersionInfo {
+  /** Human-readable app release (default until CI injects). */
+  public static final String APP_VERSION_STRING = "00.00.00.0000";
+
+  /** Human-readable wire protocol / header version. */
+  public static final String PROTO_VERSION_STRING = "00.01.00.0001";
+
+  public static final long APP_VERSION = VersionUtils.parseToInt(APP_VERSION_STRING);
+  public static final long PROTO_VERSION = VersionUtils.parseToInt(PROTO_VERSION_STRING);
+
+  private VersionInfo() {}
+}
diff --git a/app/src/main/java/com/foxx/androidcast/VersionUtils.java b/app/src/main/java/com/foxx/androidcast/VersionUtils.java
new file mode 100644
index 0000000..7568d11
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/VersionUtils.java
@@ -0,0 +1,64 @@
+package com.foxx.androidcast;
+
+import java.util.Locale;
+
+/**
+ * Version string format {@code PP.MM.mmmm.BBBB} (e.g. {@code 00.01.0003.5621}) packed into uint64.
+ * Layout: placeholder(2) · major(2) · minor(4) · build(4) decimal digits.
+ */
+public final class VersionUtils {
+  private VersionUtils() {}
+
+  public static String format(int placeholder, int major, int minor, int build) {
+    return String.format(Locale.US, "%02d.%02d.%04d.%04d",
+        clamp(placeholder, 0, 99),
+        clamp(major, 0, 99),
+        clamp(minor, 0, 9999),
+        clamp(build, 0, 9999));
+  }
+
+  public static long toInt(int placeholder, int major, int minor, int build) {
+    long ph = clamp(placeholder, 0, 99);
+    long maj = clamp(major, 0, 99);
+    long min = clamp(minor, 0, 9999);
+    long bld = clamp(build, 0, 9999);
+    return ph * 10_000_000_000L + maj * 100_000_000L + min * 10_000L + bld;
+  }
+
+  public static long parseToInt(String version) {
+    if (version == null || version.isEmpty()) {
+      return 0L;
+    }
+    String[] parts = version.split("\\.");
+    int ph = parts.length > 0 ? parsePart(parts[0], 0) : 0;
+    int maj = parts.length > 1 ? parsePart(parts[1], 0) : 0;
+    int min = parts.length > 2 ? parsePart(parts[2], 0) : 0;
+    int bld = parts.length > 3 ? parsePart(parts[3], 0) : 0;
+    return toInt(ph, maj, min, bld);
+  }
+
+  public static String formatFromInt(long packed) {
+    if (packed < 0) {
+      packed = 0;
+    }
+    int build = (int) (packed % 10_000L);
+    packed /= 10_000L;
+    int minor = (int) (packed % 10_000L);
+    packed /= 10_000L;
+    int major = (int) (packed % 100L);
+    int placeholder = (int) (packed / 100L);
+    return format(placeholder, major, minor, build);
+  }
+
+  private static int parsePart(String s, int fallback) {
+    try {
+      return Integer.parseInt(s.trim());
+    } catch (NumberFormatException e) {
+      return fallback;
+    }
+  }
+
+  private static int clamp(int v, int min, int max) {
+    return Math.max(min, Math.min(max, v));
+  }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/diagnostics/CastDiagnosticsFormatter.java b/app/src/main/java/com/foxx/androidcast/diagnostics/CastDiagnosticsFormatter.java
new file mode 100644
index 0000000..9929806
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/diagnostics/CastDiagnosticsFormatter.java
@@ -0,0 +1,322 @@
+package com.foxx.androidcast.diagnostics;
+
+import com.foxx.androidcast.CastSettings;
+import com.foxx.androidcast.CastTuningEngine;
+import com.foxx.androidcast.media.CodecNegotiator;
+import com.foxx.androidcast.network.control.NetworkStatsSnapshot;
+import com.foxx.androidcast.receiver.StreamMetrics;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/** Builds HTML diagnostics overlay with red highlights for out-of-range metrics. */
+public final class CastDiagnosticsFormatter {
+    private static final String COLOR_OK = "#E0FFE0";
+    private static final String COLOR_WARN = "#FF6666";
+    private static final String COLOR_DIM = "#AAAAAA";
+
+    private CastDiagnosticsFormatter() {}
+
+    public static String formatHtml(StreamMetrics metrics, String transport, String videoCodec,
+            int streamW, int streamH, int renderW, int renderH, boolean idle,
+            CastSettings localSettings, CastSettings remoteSettings,
+            NetworkStatsSnapshot peer, NetworkStatsSnapshot lastLocal, int viewZoomPercent) {
+        float inFps = metrics.getInFps();
+        float renderFps = metrics.getRenderFps();
+        int bwInKbps = metrics.getBwInKbps();
+        long videoPackets = metrics.getVideoPackets();
+        long audioPackets = metrics.getAudioPackets();
+        long audioRendered = metrics.getAudioRenderedWrites();
+        long audioPcmSilent = metrics.getAudioPcmSilentBlocks();
+        long audioPcmAudible = metrics.getAudioPcmAudibleBlocks();
+        int audioVu = metrics.getAudioVuPercent();
+        float audioPeakDb = metrics.getAudioLastPeakDb();
+        float audioRmsDb = metrics.getAudioLastRmsDb();
+        long keyFrames = metrics.getKeyFrames();
+        long deltaFrames = metrics.getDeltaFrames();
+        int avgKb = metrics.getAvgKbPerFrame();
+        long idleMs = metrics.getLastFrameIdleMs();
+        int rttMs = metrics.getPeerRttMs();
+
+        CastSettings tuneSettings = remoteSettings != null ? remoteSettings : localSettings;
+        CastTuningEngine.EffectiveParams eff = CastTuningEngine.resolve(tuneSettings, peer);
+        int suggestedBwKbps = eff.videoBitrate / 1000;
+        int targetEncKbps = eff.videoBitrate / 1000;
+        int congestionLevel = 0;
+        float peerEncodeFps = 0f;
+        int peerSendKbps = metrics.getPeerSendKbps();
+        int peerRecvKbps = metrics.getPeerRecvKbps();
+        int peerQueue = 0;
+        int peerDroppedP = 0;
+        long peerAudioFrames = 0;
+        boolean peerAudioActive = false;
+        int peerCaptureVu = 0;
+        long peerCaptureSilent = 0;
+        long peerCaptureAudible = 0;
+        float peerCapturePeakDb = -96f;
+        float peerCaptureRmsDb = -96f;
+
+        if (peer != null) {
+            if (peer.rttMs > 0) {
+                rttMs = peer.rttMs;
+            }
+            peerSendKbps = peer.sendBitrateKbps;
+            peerRecvKbps = peer.recvBitrateKbps;
+            peerEncodeFps = peer.encodeFps;
+            peerQueue = peer.encodeQueueDepth;
+            peerDroppedP = peer.droppedPFrames;
+            peerAudioFrames = peer.audioFramesSent;
+            peerAudioActive = peer.audioActive;
+            congestionLevel = peer.congestionLevel;
+            if (peer.suggestedBitrateKbps > 0) {
+                suggestedBwKbps = peer.suggestedBitrateKbps;
+            }
+            if (peer.targetBitrateKbps > 0) {
+                targetEncKbps = peer.targetBitrateKbps;
+            }
+            peerCaptureVu = peer.audioCaptureVuPercent;
+            peerCaptureSilent = peer.audioCaptureSilentBlocks;
+            peerCaptureAudible = peer.audioCaptureAudibleBlocks;
+            peerCapturePeakDb = peer.audioCapturePeakDb;
+            peerCaptureRmsDb = peer.audioCaptureRmsDb;
+        }
+        if (lastLocal != null) {
+            congestionLevel = Math.max(congestionLevel, lastLocal.congestionLevel);
+        }
+
+        boolean audioRequested = remoteSettings != null && remoteSettings.isAudioRequested();
+        List<String> hints = buildHints(inFps, renderFps, bwInKbps, rttMs, videoPackets);
+
+        int quality = CastDiagnosticsScorer.compute(inFps, renderFps, bwInKbps, suggestedBwKbps,
+                rttMs, congestionLevel, audioPackets, audioRequested);
+        String qualityColor = quality >= 70 ? COLOR_OK : (quality >= 45 ? "#FFCC66" : COLOR_WARN);
+
+        String bitrateMode = CastDiagnosticsLabels.bitrateMode(
+                localSettings != null ? localSettings.getBitrateMode() : CastSettings.BitrateMode.AUTO);
+        String netAdopt = CastDiagnosticsLabels.networkAdoption(
+                localSettings != null ? localSettings.getNetworkAdoption() : CastSettings.NetworkAdoption.AUTO);
+        String ctrl = CastDiagnosticsLabels.congestionController();
+
+        StringBuilder html = new StringBuilder();
+        html.append("<font color='").append(COLOR_DIM).append("'>Transport: ")
+                .append(escape(transport != null ? transport.toUpperCase() : "?"))
+                .append("</font><br/>");
+
+        if (videoCodec != null && !videoCodec.isEmpty()) {
+            html.append("Codec: <font color='").append(COLOR_OK).append("'>")
+                    .append(escape(CodecNegotiator.displayName(videoCodec))).append("</font><br/>");
+        }
+
+        html.append("Stream: ").append(streamW).append('x').append(streamH);
+        if (viewZoomPercent != 0) {
+            html.append(" (").append(viewZoomPercent > 0 ? "+" : "").append(viewZoomPercent).append("%)");
+        }
+        if (renderW > 0 && renderH > 0 && (renderW != streamW || renderH != streamH)) {
+            html.append("  render: ").append(renderW).append('x').append(renderH);
+        }
+        html.append("<br/>");
+
+        html.append("In FPS: ").append(colored(formatFloat(inFps), inFps > 0 && inFps < 15f));
+        html.append("  Render FPS: ").append(colored(formatFloat(renderFps),
+                inFps > 8f && renderFps > 0 && renderFps < inFps * 0.75f));
+        html.append("<br/>");
+
+        html.append("BW in: ").append(colored(bwInKbps > 0 ? bwInKbps + " kbps" : "n/a",
+                suggestedBwKbps > 0 && bwInKbps > 0 && bwInKbps < suggestedBwKbps * 0.7f));
+        html.append("  RTT: ").append(colored(rttMs > 0 ? rttMs + " ms" : "n/a", rttMs > 350));
+        html.append("<br/>");
+
+        html.append("Suggested BW: ").append(colored(
+                suggestedBwKbps > 0 ? suggestedBwKbps + " kbps" : "n/a",
+                bwInKbps > 0 && suggestedBwKbps > 0 && bwInKbps < suggestedBwKbps * 0.85f));
+        html.append("  Target enc: ").append(colored(
+                targetEncKbps > 0 ? targetEncKbps + " kbps" : "n/a", false));
+        html.append("<br/>");
+
+        html.append("Congestion: ").append(colored(String.valueOf(congestionLevel), congestionLevel > 0));
+        html.append("<br/>");
+        html.append("Ctrl: ").append(escape(ctrl));
+        html.append("<br/>");
+        html.append("Mode: ").append(escape(bitrateMode));
+        html.append("<br/>");
+        html.append("Net: ").append(escape(netAdopt));
+        html.append("<br/>");
+
+        if (peerSendKbps > 0 || peerRecvKbps > 0 || peerEncodeFps > 0) {
+            html.append("<font color='").append(COLOR_DIM).append("'>Sender:</font> ");
+            if (peerEncodeFps > 0) {
+                html.append("enc ").append(colored(formatFloat(peerEncodeFps), peerEncodeFps < 12f));
+                html.append(' ');
+            }
+            html.append("tx ").append(peerSendKbps).append(" / rx ").append(peerRecvKbps).append(" kbps");
+            if (peerQueue > 8 || peerDroppedP > 0) {
+                html.append("  q").append(peerQueue);
+                if (peerDroppedP > 0) {
+                    html.append(" dropP=").append(peerDroppedP);
+                }
+            }
+            html.append("<br/>");
+            if (audioRequested && (peerCaptureSilent > 0 || peerCaptureAudible > 0 || peerCaptureVu > 0)) {
+                html.append("Sender cap VU: ").append(vuBarHtml(peerCaptureVu)).append(' ')
+                        .append(colored(peerCaptureVu + "%",
+                                peerCaptureVu < 3 && peerCaptureSilent > peerCaptureAudible));
+                html.append("  peak ").append(formatDb(peerCapturePeakDb))
+                        .append("  rms ").append(formatDb(peerCaptureRmsDb));
+                html.append("<br/>Sender PCM: silent ")
+                        .append(colored(String.valueOf(peerCaptureSilent),
+                                peerCaptureSilent > 20 && peerCaptureAudible == 0))
+                        .append("  audible ").append(String.valueOf(peerCaptureAudible));
+                if (peerCaptureSilent > 20 && peerCaptureAudible == 0) {
+                    html.append(" <font color='").append(COLOR_WARN).append("'>")
+                            .append("(sender capture silent)")
+                            .append("</font>");
+                }
+                html.append("<br/>");
+            }
+        }
+
+        if (remoteSettings != null) {
+            html.append("<font color='").append(COLOR_DIM).append("'>Sender prefs:</font><br/>")
+                    .append(escape(CastDiagnosticsLabels.adjustmentPreset(remoteSettings.getAdjustmentPreset())))
+                    .append("<br/>")
+                    .append(escape(CastDiagnosticsLabels.bitrateMode(remoteSettings.getBitrateMode())))
+                    .append("<br/>")
+                    .append(escape(CastDiagnosticsLabels.resolution(remoteSettings.getResolution())))
+                    .append("<br/>")
+                    .append(escape(CastDiagnosticsLabels.videoCodec(remoteSettings.getVideoCodec())))
+                    .append("<br/>")
+                    .append(escape(CastDiagnosticsLabels.captureMode(remoteSettings.getCaptureMode())));
+            if (audioRequested) {
+                html.append(" · audio");
+                if (peerAudioActive) {
+                    html.append(" (").append(peerAudioFrames).append(" frm)");
+                }
+            }
+            html.append("<br/>");
+        }
+
+        html.append("Video pkts: ").append(videoPackets);
+        html.append(" (IDR ").append(keyFrames).append(" / P ").append(deltaFrames).append(')');
+        if (videoPackets > 0) {
+            html.append("  ~").append(Math.max(1, avgKb)).append(" KB/frame");
+        }
+        html.append("<br/>");
+
+        html.append("Audio pkts: ").append(colored(String.valueOf(audioPackets),
+                audioRequested && audioPackets == 0 && videoPackets > 20));
+        html.append("  rendered: ").append(colored(String.valueOf(audioRendered),
+                audioRequested && audioPackets > 5 && audioRendered == 0));
+        if (audioRequested && audioPackets > 0 && audioRendered == 0) {
+            html.append(" (check receiver volume)");
+        }
+        if (audioRequested && audioPackets == 0 && videoPackets > 20) {
+            html.append(" <font color='").append(COLOR_DIM).append("'>")
+                    .append("(play media on sender)")
+                    .append("</font>");
+        } else if (audioRequested && audioPackets > 10 && audioRendered == 0) {
+            html.append(" <font color='").append(COLOR_WARN).append("'>")
+                    .append("(decode/render stalled)")
+                    .append("</font>");
+        } else if (audioRequested && audioRendered > 15 && audioPcmAudible == 0
+                && audioPcmSilent > 15) {
+            html.append(" <font color='").append(COLOR_WARN).append("'>")
+                    .append("(decoded PCM is silence)")
+                    .append("</font>");
+            if (peerCaptureSilent > 20 && peerCaptureAudible == 0) {
+                html.append(" <font color='").append(COLOR_WARN).append("'>")
+                        .append("(fix on sender: Choose app, Android 14+)")
+                        .append("</font>");
+            }
+        }
+        html.append("<br/>");
+
+        if (audioRequested && audioRendered > 0) {
+            html.append("Audio VU: ").append(vuBarHtml(audioVu)).append(' ')
+                    .append(colored(audioVu + "%", audioVu < 3 && audioPcmSilent > audioPcmAudible));
+            html.append("  peak ").append(formatDb(audioPeakDb))
+                    .append("  rms ").append(formatDb(audioRmsDb));
+            html.append("<br/>PCM blocks: silent ")
+                    .append(colored(String.valueOf(audioPcmSilent),
+                            audioPcmSilent > 20 && audioPcmAudible == 0))
+                    .append("  audible ").append(String.valueOf(audioPcmAudible));
+            html.append("<br/>");
+        }
+
+        for (String hint : hints) {
+            html.append("<font color='").append(COLOR_WARN).append("'>")
+                    .append(escape(hint)).append("</font><br/>");
+        }
+
+        html.append("Quality: <font color='").append(qualityColor).append("'>")
+                .append(quality).append(" — ").append(CastDiagnosticsScorer.label(quality))
+                .append("</font><br/>");
+
+        html.append("<font color='").append(COLOR_DIM).append("'>State: ")
+                .append(idle ? "idle (awaiting)" : "streaming");
+        if (idleMs >= 0) {
+            html.append("  last frame: ").append(idleMs).append(" ms ago");
+        }
+        html.append("</font>");
+
+        return html.toString();
+    }
+
+    private static List<String> buildHints(float inFps, float renderFps, int bwInKbps,
+            int rttMs, long videoPackets) {
+        List<String> hints = new ArrayList<>();
+        if (inFps > 0 && inFps < 8f) {
+            hints.add("Hint: low In FPS → sender encode stall / TCP backlog");
+        }
+        if (bwInKbps > 0 && bwInKbps < 350 && inFps < 8f && videoPackets > 30) {
+            hints.add("Hint: very low BW — static screen or throttled encoder");
+        }
+        if (rttMs > 450 && inFps < 15f) {
+            hints.add("Hint: high RTT — Wi‑Fi congestion");
+        }
+        if (inFps > 12f && renderFps > 0 && renderFps < inFps * 0.7f) {
+            hints.add("Hint: decode slower than network (try H.264 or lower res)");
+        }
+        return hints;
+    }
+
+    private static String colored(String text, boolean bad) {
+        return "<font color='" + (bad ? COLOR_WARN : COLOR_OK) + "'>" + escape(text) + "</font>";
+    }
+
+    private static String escape(String s) {
+        if (s == null) {
+            return "";
+        }
+        return s.replace("&", "&amp;").replace("<", "&lt;");
+    }
+
+    private static String formatFloat(float v) {
+        if (v <= 0f) {
+            return "n/a";
+        }
+        return String.format(java.util.Locale.US, "%.1f", v);
+    }
+
+    private static String formatDb(float db) {
+        if (db <= -90f) {
+            return "-∞";
+        }
+        return String.format(java.util.Locale.US, "%.0f dB", db);
+    }
+
+    private static String vuBarHtml(int percent) {
+        int width = 16;
+        int filled = Math.min(width, (percent * width + 50) / 100);
+        StringBuilder b = new StringBuilder("<font color='#555'>[</font>");
+        for (int i = 0; i < width; i++) {
+            if (i < filled) {
+                String c = i < width * 2 / 3 ? "#66FF66" : (i < width * 5 / 6 ? "#FFCC00" : "#FF4444");
+                b.append("<font color='").append(c).append("'>█</font>");
+            } else {
+                b.append("<font color='#333'>░</font>");
+            }
+        }
+        b.append("<font color='#555'>]</font>");
+        return b.toString();
+    }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/diagnostics/CastDiagnosticsLabels.java b/app/src/main/java/com/foxx/androidcast/diagnostics/CastDiagnosticsLabels.java
new file mode 100644
index 0000000..b01c36f
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/diagnostics/CastDiagnosticsLabels.java
@@ -0,0 +1,125 @@
+package com.foxx.androidcast.diagnostics;
+
+import com.foxx.androidcast.CastSettings;
+
+/** Human-readable names for diagnostics (no bare AUTO enum tokens). */
+public final class CastDiagnosticsLabels {
+    private CastDiagnosticsLabels() {}
+
+    public static String congestionController() {
+        return "PassThroughNetworkControlPlane (heartbeat stats)";
+    }
+
+    public static String bitrateMode(CastSettings.BitrateMode mode) {
+        if (mode == null) {
+            return "CastTuningEngine (default)";
+        }
+        switch (mode) {
+            case NONE:
+                return "Uncapped encoder bitrate";
+            case QUALITY:
+                return "Quality bias (+25% bitrate)";
+            case SPEED:
+                return "Speed bias (−35% bitrate, ≤24 fps)";
+            case BALANCED:
+                return "Balanced preset";
+            case ROBUST_LESS:
+                return "RobustLess (UDP, −45% bitrate)";
+            case ESTIMATED:
+                return "CastTuningEngine bandwidth estimate";
+            case AUTO:
+            default:
+                return "CastTuningEngine (preset + peer stats)";
+        }
+    }
+
+    public static String networkAdoption(CastSettings.NetworkAdoption mode) {
+        if (mode == null) {
+            return "No extra network scaling";
+        }
+        switch (mode) {
+            case QUALITY:
+                return "Quality bias (+10% bitrate)";
+            case SPEED:
+                return "Speed bias (−30% bitrate)";
+            case ESTIMATED:
+                return "CastTuningEngine recv-bitrate cap";
+            case AUTO:
+            default:
+                return "No extra network scaling";
+        }
+    }
+
+    public static String adjustmentPreset(CastSettings.AdjustmentPreset preset) {
+        if (preset == null) {
+            return "CastTuningEngine default";
+        }
+        switch (preset) {
+            case NONE:
+                return "No preset adjustments";
+            case QUALITY:
+                return "Quality (+15% bitrate, +2 fps)";
+            case SPEED:
+                return "Speed (−15% bitrate)";
+            case PERFORMANCE:
+                return "Performance (−15% bitrate, stable fps)";
+            case AUTO:
+            default:
+                return "CastTuningEngine adaptive preset";
+        }
+    }
+
+    public static String resolution(CastSettings.Resolution res) {
+        if (res == null) {
+            return "Device default";
+        }
+        switch (res) {
+            case FULL:
+                return "Full display";
+            case THREE_QUARTERS:
+                return "75% display scale";
+            case HALF:
+                return "50% display scale";
+            case HD_720P:
+                return "720p long-edge cap";
+            case FIXED_1080P:
+                return "Fixed 1080p box";
+            case FIXED_720P:
+                return "Fixed 720p box";
+            case ADAPTIVE:
+                return "Adaptive (CastTuningEngine + peer)";
+            default:
+                return res.name();
+        }
+    }
+
+    public static String videoCodec(CastSettings.VideoCodec codec) {
+        if (codec == null) {
+            return "CodecNegotiator preference list";
+        }
+        switch (codec) {
+            case H264:
+                return "H.264 (forced)";
+            case H265:
+                return "H.265 (forced)";
+            case PASSTHROUGH:
+                return "Passthrough (debug, unimplemented)";
+            case AUTO:
+            default:
+                return "CodecNegotiator (HEVC→AVC→VP9→VP8)";
+        }
+    }
+
+    public static String captureMode(CastSettings.CaptureMode mode) {
+        if (mode == null) {
+            return "Entire screen";
+        }
+        switch (mode) {
+            case USER_CHOICE:
+                return "Choose app or screen (Android 14+)";
+            case FULL_SCREEN:
+            default:
+                return "Entire screen";
+        }
+    }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/diagnostics/CastDiagnosticsScorer.java b/app/src/main/java/com/foxx/androidcast/diagnostics/CastDiagnosticsScorer.java
new file mode 100644
index 0000000..951a912
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/diagnostics/CastDiagnosticsScorer.java
@@ -0,0 +1,62 @@
+package com.foxx.androidcast.diagnostics;
+
+/** Heuristic stream quality score (0–100) from live metrics. */
+public final class CastDiagnosticsScorer {
+    private CastDiagnosticsScorer() {}
+
+    public static int compute(float inFps, float renderFps, int bwInKbps, int suggestedBwKbps,
+            int rttMs, int congestionLevel, long audioPackets, boolean audioRequested) {
+        int score = 100;
+        if (inFps > 0 && inFps < 12f) {
+            score -= 25;
+        } else if (inFps > 0 && inFps < 20f) {
+            score -= 12;
+        }
+        if (inFps > 5f && renderFps > 0 && renderFps < inFps * 0.7f) {
+            score -= 22;
+        } else if (inFps > 5f && renderFps > 0 && renderFps < inFps * 0.85f) {
+            score -= 10;
+        }
+        if (suggestedBwKbps > 0 && bwInKbps > 0 && bwInKbps < suggestedBwKbps * 0.55f) {
+            score -= 20;
+        } else if (suggestedBwKbps > 0 && bwInKbps > 0 && bwInKbps < suggestedBwKbps * 0.75f) {
+            score -= 10;
+        }
+        if (rttMs > 600) {
+            score -= 18;
+        } else if (rttMs > 350) {
+            score -= 8;
+        }
+        if (congestionLevel >= 2) {
+            score -= 15;
+        } else if (congestionLevel >= 1) {
+            score -= 6;
+        }
+        if (audioRequested && audioPackets == 0) {
+            score -= 8;
+        }
+        if (score < 0) {
+            return 0;
+        }
+        if (score > 100) {
+            return 100;
+        }
+        return score;
+    }
+
+    public static String label(int score) {
+        if (score >= 85) {
+            return "Excellent";
+        }
+        if (score >= 70) {
+            return "Good";
+        }
+        if (score >= 50) {
+            return "Fair";
+        }
+        if (score >= 30) {
+            return "Poor";
+        }
+        return "Bad";
+    }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/discovery/DiscoveryManager.java b/app/src/main/java/com/foxx/androidcast/discovery/DiscoveryManager.java
index b16b843..044494c 100644
--- a/app/src/main/java/com/foxx/androidcast/discovery/DiscoveryManager.java
+++ b/app/src/main/java/com/foxx/androidcast/discovery/DiscoveryManager.java
@@ -7,6 +7,11 @@ import android.os.Looper;
 import android.util.Log;
 
 import com.foxx.androidcast.CastConfig;
+import com.foxx.androidcast.DeviceInfo;
+import com.foxx.androidcast.network.CastCodecFlags;
+import com.foxx.androidcast.network.CastPacketFramer;
+import com.foxx.androidcast.network.CastProtoHeader;
+import com.foxx.androidcast.network.CastProtocol;
 
 import org.json.JSONObject;
 
@@ -28,6 +33,14 @@ public class DiscoveryManager {
 
     public interface Listener {
         void onDevicesUpdated(List<DiscoveredDevice> devices);
+
+        /** UDP browse socket is active. */
+        default void onScanStarted() {
+        }
+
+        /** Browse pass finished (timeout or {@link #stop()}). */
+        default void onScanEnded() {
+        }
     }
 
     public static final class DiscoveredDevice {
@@ -36,13 +49,26 @@ public class DiscoveryManager {
         public final int port;
         public final String transport;
         public final long lastSeenMs;
+        public final int videoCodecs;
+        public final int audioCodecs;
+        public final int placeholderId;
+        public final long protoVersion;
 
         public DiscoveredDevice(String name, String host, int port, String transport, long lastSeenMs) {
+            this(name, host, port, transport, lastSeenMs, 0, 0, 0, 0L);
+        }
+
+        public DiscoveredDevice(String name, String host, int port, String transport, long lastSeenMs,
+                int videoCodecs, int audioCodecs, int placeholderId, long protoVersion) {
             this.name = name;
             this.host = host;
             this.port = port;
             this.transport = transport;
             this.lastSeenMs = lastSeenMs;
+            this.videoCodecs = videoCodecs;
+            this.audioCodecs = audioCodecs;
+            this.placeholderId = placeholderId;
+            this.protoVersion = protoVersion;
         }
     }
 
@@ -70,6 +96,7 @@ public class DiscoveryManager {
         if (!running.compareAndSet(false, true)) {
             return;
         }
+        notifyScanStarted();
         executor.execute(this::browseLoop);
     }
 
@@ -99,11 +126,16 @@ public class DiscoveryManager {
         startAnnouncing(deviceName, port, transport, true);
     }
 
-    public void startAnnouncing(String deviceName, int port, String transport, boolean listening) {
+    public void startAnnouncing(Context context, String deviceName, int port, String transport,
+            boolean listening) {
         if (!running.compareAndSet(false, true)) {
             return;
         }
-        executor.execute(() -> announceLoop(deviceName, port, transport, listening));
+        executor.execute(() -> announceLoop(context, deviceName, port, transport, listening));
+    }
+
+    public void startAnnouncing(String deviceName, int port, String transport, boolean listening) {
+        startAnnouncing(appContext, deviceName, port, transport, listening);
     }
 
     private void browseLoop() {
@@ -113,11 +145,17 @@ public class DiscoveryManager {
             sock.setReuseAddress(true);
             sock.bind(new InetSocketAddress(CastConfig.DISCOVERY_PORT));
             sock.setBroadcast(true);
+            sock.setSoTimeout(300);
             byte[] buf = new byte[1024];
-            while (running.get()) {
+            long deadline = System.currentTimeMillis() + CastConfig.DISCOVERY_SCAN_PASS_MS;
+            while (running.get() && System.currentTimeMillis() < deadline) {
                 DatagramPacket packet = new DatagramPacket(buf, buf.length);
-                sock.receive(packet);
-                handlePacket(packet);
+                try {
+                    sock.receive(packet);
+                    handlePacket(packet);
+                } catch (java.net.SocketTimeoutException ignored) {
+                    // keep listening until pass ends
+                }
             }
         } catch (Exception e) {
             if (running.get()) {
@@ -127,11 +165,38 @@ public class DiscoveryManager {
             socket = null;
             releaseMulticastLock();
             running.set(false);
+            notifyScanEnded();
         }
     }
 
-    private void announceLoop(String deviceName, int port, String transport, boolean listening) {
+    private void notifyScanStarted() {
+        if (listener == null) {
+            return;
+        }
+        mainHandler.post(() -> {
+            if (listener != null) {
+                listener.onScanStarted();
+            }
+        });
+    }
+
+    private void notifyScanEnded() {
+        if (listener == null) {
+            return;
+        }
+        mainHandler.post(() -> {
+            if (listener != null) {
+                listener.onScanEnded();
+            }
+        });
+    }
+
+    private void announceLoop(Context context, String deviceName, int port, String transport,
+            boolean listening) {
         acquireMulticastLock();
+        int placeholderId = DeviceInfo.getPlaceholderId(context);
+        int videoMask = CastCodecFlags.localDecoderVideoMask();
+        int audioMask = CastCodecFlags.localAudioMask();
         try (DatagramSocket sock = new DatagramSocket()) {
             socket = sock;
             sock.setBroadcast(true);
@@ -142,9 +207,17 @@ public class DiscoveryManager {
                 json.put("port", port);
                 json.put("transport", transport);
                 json.put("listening", listening);
-                byte[] data = json.toString().getBytes(StandardCharsets.UTF_8);
+                json.put("device_uuid", DeviceInfo.getDeviceUuid(context));
+                byte[] jsonBytes = json.toString().getBytes(StandardCharsets.UTF_8);
+                CastProtoHeader hdr = CastProtoHeader.forDiscovery(placeholderId, videoMask, audioMask);
+                byte[] wire;
+                try {
+                    wire = CastPacketFramer.frame(hdr, CastProtocol.MSG_HELLO, jsonBytes);
+                } catch (Exception e) {
+                    wire = jsonBytes;
+                }
                 InetAddress broadcast = InetAddress.getByName("255.255.255.255");
-                DatagramPacket packet = new DatagramPacket(data, data.length, broadcast, CastConfig.DISCOVERY_PORT);
+                DatagramPacket packet = new DatagramPacket(wire, wire.length, broadcast, CastConfig.DISCOVERY_PORT);
                 sock.send(packet);
                 Thread.sleep(2000);
             }
@@ -161,8 +234,40 @@ public class DiscoveryManager {
 
     private void handlePacket(DatagramPacket packet) {
         try {
-            String text = new String(packet.getData(), packet.getOffset(), packet.getLength(),
-                    StandardCharsets.UTF_8);
+            byte[] raw = packet.getData();
+            int off = packet.getOffset();
+            int len = packet.getLength();
+            String text;
+            int videoCodecs = 0;
+            int audioCodecs = 0;
+            int placeholderId = 0;
+            long protoVersion = 0L;
+            int bodyOff = off;
+            int bodyLen = len;
+            if (len >= CastProtoHeader.HEADER_SIZE_V1 && readMagicLe(raw, off) == CastProtoHeader.MAGIC) {
+                CastProtoHeader hdr = CastProtoHeader.decode(raw, off, len);
+                if (hdr.verifyChecksum() && hdr.hsType == CastProtoHeader.HS_SDP) {
+                    videoCodecs = hdr.videoCodecs;
+                    audioCodecs = hdr.audioCodecs;
+                    placeholderId = hdr.placeholderId;
+                    protoVersion = hdr.protoVersion;
+                }
+                bodyOff = off + hdr.headerSize;
+                bodyLen = len - hdr.headerSize;
+                if (bodyLen > 5) {
+                    byte type = raw[bodyOff];
+                    int plen = readIntBe(raw, bodyOff + 1);
+                    if (plen >= 0 && bodyOff + 5 + plen <= off + len) {
+                        text = new String(raw, bodyOff + 5, plen, StandardCharsets.UTF_8);
+                    } else {
+                        text = new String(raw, bodyOff, bodyLen, StandardCharsets.UTF_8);
+                    }
+                } else {
+                    text = new String(raw, bodyOff, bodyLen, StandardCharsets.UTF_8);
+                }
+            } else {
+                text = new String(raw, off, len, StandardCharsets.UTF_8);
+            }
             JSONObject json = new JSONObject(text);
             if (!CastConfig.DISCOVERY_MAGIC.equals(json.optString("magic"))) {
                 return;
@@ -175,13 +280,24 @@ public class DiscoveryManager {
             }
             String host = packet.getAddress().getHostAddress();
             String key = host + ":" + port;
-            DiscoveredDevice device = new DiscoveredDevice(name, host, port, transport, System.currentTimeMillis());
+            DiscoveredDevice device = new DiscoveredDevice(name, host, port, transport,
+                    System.currentTimeMillis(), videoCodecs, audioCodecs, placeholderId, protoVersion);
             devices.put(key, device);
             notifyListener();
         } catch (Exception ignored) {
         }
     }
 
+    private static int readMagicLe(byte[] b, int off) {
+        return (b[off] & 0xff) | ((b[off + 1] & 0xff) << 8)
+                | ((b[off + 2] & 0xff) << 16) | ((b[off + 3] & 0xff) << 24);
+    }
+
+    private static int readIntBe(byte[] b, int off) {
+        return ((b[off] & 0xff) << 24) | ((b[off + 1] & 0xff) << 16)
+                | ((b[off + 2] & 0xff) << 8) | (b[off + 3] & 0xff);
+    }
+
     private void notifyListener() {
         if (listener == null) {
             return;
diff --git a/app/src/main/java/com/foxx/androidcast/media/AacAdtsHelper.java b/app/src/main/java/com/foxx/androidcast/media/AacAdtsHelper.java
new file mode 100644
index 0000000..4c4e5f0
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/media/AacAdtsHelper.java
@@ -0,0 +1,60 @@
+package com.foxx.androidcast.media;
+
+/** Prepends ADTS sync word so AAC decoders accept encoder access units. */
+public final class AacAdtsHelper {
+    private AacAdtsHelper() {}
+
+    public static byte[] wrapIfNeeded(byte[] aacFrame, int sampleRate, int channelCount) {
+        if (aacFrame == null || aacFrame.length == 0) {
+            return aacFrame;
+        }
+        if (aacFrame.length >= 2 && (aacFrame[0] & 0xFF) == 0xFF && (aacFrame[1] & 0xF0) == 0xF0) {
+            return aacFrame;
+        }
+        int profile = 2;
+        int freqIdx = sampleRateIndex(sampleRate);
+        int chanCfg = Math.max(1, Math.min(7, channelCount));
+        int frameLen = aacFrame.length + 7;
+        byte[] adts = new byte[frameLen];
+        adts[0] = (byte) 0xFF;
+        adts[1] = (byte) 0xF1;
+        adts[2] = (byte) (((profile - 1) << 6) + (freqIdx << 2) + (chanCfg >> 2));
+        adts[3] = (byte) (((chanCfg & 3) << 6) + (frameLen >> 11));
+        adts[4] = (byte) ((frameLen & 0x7FF) >> 3);
+        adts[5] = (byte) (((frameLen & 7) << 5) + 0x1F);
+        adts[6] = (byte) 0xFC;
+        System.arraycopy(aacFrame, 0, adts, 7, aacFrame.length);
+        return adts;
+    }
+
+    private static int sampleRateIndex(int sampleRate) {
+        switch (sampleRate) {
+            case 96000:
+                return 0;
+            case 88200:
+                return 1;
+            case 64000:
+                return 2;
+            case 48000:
+                return 3;
+            case 44100:
+                return 4;
+            case 32000:
+                return 5;
+            case 24000:
+                return 6;
+            case 22050:
+                return 7;
+            case 16000:
+                return 8;
+            case 12000:
+                return 9;
+            case 11025:
+                return 10;
+            case 8000:
+                return 11;
+            default:
+                return 4;
+        }
+    }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/media/PcmLevelAnalyzer.java b/app/src/main/java/com/foxx/androidcast/media/PcmLevelAnalyzer.java
new file mode 100644
index 0000000..dd8aaac
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/media/PcmLevelAnalyzer.java
@@ -0,0 +1,67 @@
+package com.foxx.androidcast.media;
+
+/** Peak/RMS analysis for 16-bit little-endian PCM. */
+public final class PcmLevelAnalyzer {
+    /** ~-46 dBFS; below this counts as silence. */
+    public static final float SILENT_PEAK_THRESHOLD = 0.005f;
+
+    public static final class Levels {
+        public final float peak;
+        public final float rms;
+        public final boolean silent;
+
+        Levels(float peak, float rms, boolean silent) {
+            this.peak = peak;
+            this.rms = rms;
+            this.silent = silent;
+        }
+
+        public float peakDb() {
+            if (peak <= 1e-9f) {
+                return -96f;
+            }
+            return (float) (20.0 * Math.log10(peak));
+        }
+    }
+
+    private PcmLevelAnalyzer() {}
+
+    public static Levels analyze(byte[] pcm, int length) {
+        if (pcm == null || length < 2) {
+            return new Levels(0f, 0f, true);
+        }
+        int samples = length / 2;
+        long sumSq = 0;
+        int peakAbs = 0;
+        for (int i = 0; i + 1 < length; i += 2) {
+            short s = (short) ((pcm[i] & 0xff) | (pcm[i + 1] << 8));
+            int a = Math.abs(s);
+            if (a > peakAbs) {
+                peakAbs = a;
+            }
+            sumSq += (long) s * s;
+        }
+        float peak = peakAbs / 32768f;
+        float rms = samples > 0
+                ? (float) Math.sqrt(sumSq / (double) samples) / 32768f
+                : 0f;
+        boolean silent = peak < SILENT_PEAK_THRESHOLD && rms < SILENT_PEAK_THRESHOLD * 0.7f;
+        return new Levels(peak, rms, silent);
+    }
+
+    /** 0–100 visual level from RMS (scaled for speech/music). */
+    public static int vuPercent(float rms) {
+        if (rms <= 0f) {
+            return 0;
+        }
+        float db = (float) (20.0 * Math.log10(rms + 1e-9));
+        float norm = (db + 60f) / 60f;
+        if (norm < 0f) {
+            norm = 0f;
+        }
+        if (norm > 1f) {
+            norm = 1f;
+        }
+        return Math.round(norm * 100f);
+    }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/network/CastCodecFlags.java b/app/src/main/java/com/foxx/androidcast/network/CastCodecFlags.java
new file mode 100644
index 0000000..e0feba0
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/network/CastCodecFlags.java
@@ -0,0 +1,53 @@
+package com.foxx.androidcast.network;
+
+import android.media.MediaFormat;
+
+import com.foxx.androidcast.sender.CodecCatalog;
+
+import java.util.List;
+
+/** Video/audio codec bitmasks in {@link CastProtoHeader}. */
+public final class CastCodecFlags {
+  public static final int VIDEO_UNKNOWN = 0;
+  public static final int VIDEO_H264 = 1;
+  public static final int VIDEO_H265 = 2;
+  public static final int VIDEO_VP8 = 4;
+  public static final int VIDEO_VP9 = 8;
+
+  public static final int AUDIO_UNKNOWN = 0;
+  public static final int AUDIO_PCM = 1;
+  public static final int AUDIO_AAC = 2;
+
+  private CastCodecFlags() {}
+
+  public static int videoMaskFromMimes(List<String> mimes) {
+    int mask = 0;
+    if (mimes == null) {
+      return mask;
+    }
+    for (String mime : mimes) {
+      if (MediaFormat.MIMETYPE_VIDEO_AVC.equalsIgnoreCase(mime)) {
+        mask |= VIDEO_H264;
+      } else if (MediaFormat.MIMETYPE_VIDEO_HEVC.equalsIgnoreCase(mime)) {
+        mask |= VIDEO_H265;
+      } else if (MediaFormat.MIMETYPE_VIDEO_VP8.equalsIgnoreCase(mime)) {
+        mask |= VIDEO_VP8;
+      } else if (MediaFormat.MIMETYPE_VIDEO_VP9.equalsIgnoreCase(mime)) {
+        mask |= VIDEO_VP9;
+      }
+    }
+    return mask;
+  }
+
+  public static int localVideoMask() {
+    return videoMaskFromMimes(CodecCatalog.localEncoderMimes());
+  }
+
+  public static int localDecoderVideoMask() {
+    return videoMaskFromMimes(CodecCatalog.localDecoderMimes());
+  }
+
+  public static int localAudioMask() {
+    return AUDIO_AAC | AUDIO_PCM;
+  }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/network/CastFramingContext.java b/app/src/main/java/com/foxx/androidcast/network/CastFramingContext.java
new file mode 100644
index 0000000..491a514
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/network/CastFramingContext.java
@@ -0,0 +1,26 @@
+package com.foxx.androidcast.network;
+
+/** Per-session values written into {@link CastProtoHeader}. */
+public final class CastFramingContext {
+  public final int sessionId;
+  public final int placeholderId;
+  public final int videoCodecs;
+  public final int audioCodecs;
+
+  public CastFramingContext(int sessionId, int placeholderId, int videoCodecs, int audioCodecs) {
+    this.sessionId = sessionId;
+    this.placeholderId = placeholderId;
+    this.videoCodecs = videoCodecs;
+    this.audioCodecs = audioCodecs;
+  }
+
+  public CastProtoHeader newHeader(byte hsType) {
+    CastProtoHeader h = new CastProtoHeader();
+    h.hsType = hsType;
+    h.sessionId = sessionId;
+    h.placeholderId = placeholderId;
+    h.videoCodecs = videoCodecs;
+    h.audioCodecs = audioCodecs;
+    return h;
+  }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/network/CastPacketFramer.java b/app/src/main/java/com/foxx/androidcast/network/CastPacketFramer.java
new file mode 100644
index 0000000..9fd50bc
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/network/CastPacketFramer.java
@@ -0,0 +1,104 @@
+package com.foxx.androidcast.network;
+
+import java.io.ByteArrayOutputStream;
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.EOFException;
+import java.io.IOException;
+import java.io.InputStream;
+
+/** Wraps {@link CastProtoHeader} + {@link CastProtocol} message body. */
+public final class CastPacketFramer {
+  private CastPacketFramer() {}
+
+  public static byte[] frame(CastProtoHeader header, byte type, byte[] payload) throws IOException {
+    ByteArrayOutputStream bos = new ByteArrayOutputStream();
+    DataOutputStream dos = new DataOutputStream(bos);
+    CastProtocol.writeMessage(dos, type, payload);
+    byte[] inner = bos.toByteArray();
+    header.recomputeChecksum();
+    byte[] hdr = header.encode();
+    byte[] out = new byte[hdr.length + inner.length];
+    System.arraycopy(hdr, 0, out, 0, hdr.length);
+    System.arraycopy(inner, 0, out, hdr.length, inner.length);
+    return out;
+  }
+
+  public static CastProtocol.Message unframe(byte[] wire) throws IOException {
+    if (wire == null || wire.length < CastProtoHeader.HEADER_SIZE_V1 + 5) {
+      throw new IOException("Frame too short");
+    }
+    CastProtoHeader hdr = CastProtoHeader.decode(wire, 0, wire.length);
+    if (!hdr.verifyChecksum()) {
+      throw new IOException("Header checksum mismatch");
+    }
+    int innerOff = hdr.headerSize;
+    if (wire.length < innerOff + 5) {
+      throw new IOException("Missing message body");
+    }
+    DataInputStream dis = new DataInputStream(
+        new java.io.ByteArrayInputStream(wire, innerOff, wire.length - innerOff));
+    return CastProtocol.readMessage(dis);
+  }
+
+  /**
+   * Reads one framed message from a TCP stream (blocking).
+   * Returns null if stream ends before a full frame.
+   */
+  public static CastProtocol.Message readFramedMessage(InputStream in) throws IOException {
+    byte[] magicBuf = readFully(in, 4);
+    if (magicBuf == null) {
+      return null;
+    }
+    int magic = (magicBuf[0] & 0xff) | ((magicBuf[1] & 0xff) << 8)
+        | ((magicBuf[2] & 0xff) << 16) | ((magicBuf[3] & 0xff) << 24);
+    if (magic != CastProtoHeader.MAGIC) {
+      throw new IOException("Bad magic on wire: 0x" + Integer.toHexString(magic));
+    }
+    byte[] restHdr = readFully(in, CastProtoHeader.HEADER_SIZE_V1 - 4);
+    if (restHdr == null) {
+      return null;
+    }
+    byte[] headerBytes = new byte[CastProtoHeader.HEADER_SIZE_V1];
+    System.arraycopy(magicBuf, 0, headerBytes, 0, 4);
+    System.arraycopy(restHdr, 0, headerBytes, 4, restHdr.length);
+    CastProtoHeader hdr = CastProtoHeader.decode(headerBytes, 0, headerBytes.length);
+    if (!hdr.verifyChecksum()) {
+      throw new IOException("Header checksum mismatch");
+    }
+    byte type = (byte) in.read();
+    if (type < 0) {
+      return null;
+    }
+    byte[] lenBuf = readFully(in, 4);
+    if (lenBuf == null) {
+      return null;
+    }
+    int len = ((lenBuf[0] & 0xff) << 24) | ((lenBuf[1] & 0xff) << 16)
+        | ((lenBuf[2] & 0xff) << 8) | (lenBuf[3] & 0xff);
+    if (len < 0 || len > 4 * 1024 * 1024) {
+      throw new IOException("Invalid payload length: " + len);
+    }
+    byte[] payload = len == 0 ? new byte[0] : readFully(in, len);
+    if (payload == null && len > 0) {
+      return null;
+    }
+    return new CastProtocol.Message(type, payload);
+  }
+
+  private static byte[] readFully(InputStream in, int n) throws IOException {
+    byte[] buf = new byte[n];
+    int off = 0;
+    while (off < n) {
+      int r = in.read(buf, off, n - off);
+      if (r < 0) {
+        if (off == 0) {
+          return null;
+        }
+        throw new EOFException("Short read");
+      }
+      off += r;
+    }
+    return buf;
+  }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/network/CastProtoHeader.java b/app/src/main/java/com/foxx/androidcast/network/CastProtoHeader.java
new file mode 100644
index 0000000..0bffc8d
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/network/CastProtoHeader.java
@@ -0,0 +1,131 @@
+package com.foxx.androidcast.network;
+
+import com.foxx.androidcast.VersionInfo;
+
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.util.zip.CRC32;
+
+/**
+ * Fixed binary header prefixed to every cast/discovery packet (little-endian).
+ * v1 size = 48 bytes.
+ */
+public final class CastProtoHeader {
+  public static final int MAGIC = 0xDEADBABE;
+  public static final int HEADER_SIZE_V1 = 48;
+
+  public static final byte HS_DEFAULT = 0;
+  public static final byte HS_SDP = 1;
+
+  public int magic = MAGIC;
+  public long protoVersion = VersionInfo.PROTO_VERSION;
+  public int headerSize = HEADER_SIZE_V1;
+  public int flags;
+  public int reserved;
+  public byte hsType = HS_DEFAULT;
+  public int videoCodecs;
+  public int audioCodecs;
+  public int placeholderId;
+  public int sessionId;
+  public int checksum;
+
+  public static CastProtoHeader forCast(int sessionId, int placeholderId, int videoCodecs, int audioCodecs) {
+    CastProtoHeader h = new CastProtoHeader();
+    h.hsType = HS_DEFAULT;
+    h.sessionId = sessionId;
+    h.placeholderId = placeholderId;
+    h.videoCodecs = videoCodecs;
+    h.audioCodecs = audioCodecs;
+    h.recomputeChecksum();
+    return h;
+  }
+
+  public static CastProtoHeader forDiscovery(int placeholderId, int videoCodecs, int audioCodecs) {
+    CastProtoHeader h = new CastProtoHeader();
+    h.hsType = HS_SDP;
+    h.sessionId = 0;
+    h.placeholderId = placeholderId;
+    h.videoCodecs = videoCodecs;
+    h.audioCodecs = audioCodecs;
+    h.recomputeChecksum();
+    return h;
+  }
+
+  public void recomputeChecksum() {
+    checksum = 0;
+    checksum = (int) crc32(encode());
+  }
+
+  public boolean verifyChecksum() {
+    int saved = checksum;
+    checksum = 0;
+    int expected = (int) crc32(encode());
+    checksum = saved;
+    return saved == expected;
+  }
+
+  public byte[] encode() {
+    ByteBuffer buf = ByteBuffer.allocate(HEADER_SIZE_V1).order(ByteOrder.LITTLE_ENDIAN);
+    buf.putInt(magic);
+    buf.putLong(protoVersion);
+    buf.putInt(headerSize);
+    buf.putInt(flags);
+    buf.putInt(reserved);
+    buf.put(hsType);
+    buf.put((byte) 0);
+    buf.put((byte) 0);
+    buf.put((byte) 0);
+    buf.putInt(videoCodecs);
+    buf.putInt(audioCodecs);
+    buf.putInt(placeholderId);
+    buf.putInt(sessionId);
+    buf.putInt(0);
+    byte[] out = buf.array();
+    checksum = (int) crc32(out);
+    ByteBuffer.wrap(out).order(ByteOrder.LITTLE_ENDIAN).putInt(44, checksum);
+    return out;
+  }
+
+  public static CastProtoHeader decode(byte[] bytes, int offset, int length) throws java.io.IOException {
+    if (length < HEADER_SIZE_V1) {
+      throw new java.io.IOException("Header too short: " + length);
+    }
+    ByteBuffer buf = ByteBuffer.wrap(bytes, offset, length).order(ByteOrder.LITTLE_ENDIAN);
+    CastProtoHeader h = new CastProtoHeader();
+    h.magic = buf.getInt();
+    if (h.magic != MAGIC) {
+      throw new java.io.IOException("Bad magic: 0x" + Integer.toHexString(h.magic));
+    }
+    h.protoVersion = buf.getLong();
+    h.headerSize = buf.getInt();
+    h.flags = buf.getInt();
+    h.reserved = buf.getInt();
+    h.hsType = buf.get();
+    buf.get();
+    buf.get();
+    buf.get();
+    h.videoCodecs = buf.getInt();
+    h.audioCodecs = buf.getInt();
+    h.placeholderId = buf.getInt();
+    h.sessionId = buf.getInt();
+    h.checksum = buf.getInt();
+    if (h.headerSize < HEADER_SIZE_V1) {
+      h.headerSize = HEADER_SIZE_V1;
+    }
+    return h;
+  }
+
+  private static long crc32(byte[] data) {
+    CRC32 crc = new CRC32();
+    int checksumOffset = 44;
+    crc.update(data, 0, checksumOffset);
+    crc.update((byte) 0);
+    crc.update((byte) 0);
+    crc.update((byte) 0);
+    crc.update((byte) 0);
+    if (data.length > checksumOffset + 4) {
+      crc.update(data, checksumOffset + 4, data.length - checksumOffset - 4);
+    }
+    return crc.getValue();
+  }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/network/CastProtocol.java b/app/src/main/java/com/foxx/androidcast/network/CastProtocol.java
index afa27a3..a685620 100644
--- a/app/src/main/java/com/foxx/androidcast/network/CastProtocol.java
+++ b/app/src/main/java/com/foxx/androidcast/network/CastProtocol.java
@@ -31,6 +31,8 @@ public final class CastProtocol {
     public static final byte MSG_AUDIO_CONSENT = 13;
     public static final byte MSG_CODEC_CAPS = 14;
     public static final byte MSG_CODEC_SELECTED = 15;
+    /** UDP outer wrapper: payload is {@link CastPacketFramer} wire bytes. */
+    public static final byte MSG_WIRE_PACKET = 127;
 
     private CastProtocol() {}
 
@@ -77,6 +79,7 @@ public final class CastProtocol {
         dos.writeInt(settings.getAdjustmentPreset().ordinal());
         dos.writeInt(settings.getBitrateMode().ordinal());
         dos.writeInt(settings.getNetworkAdoption().ordinal());
+        dos.writeInt(settings.getCaptureMode().ordinal());
         dos.flush();
         return bos.toByteArray();
     }
@@ -108,6 +111,10 @@ public final class CastProtocol {
                 settings.setNetworkAdoption(readEnum(CastSettings.NetworkAdoption.values(), dis.readInt(),
                         CastSettings.NetworkAdoption.AUTO));
             }
+            if (dis.available() > 0) {
+                settings.setCaptureMode(readEnum(CastSettings.CaptureMode.values(), dis.readInt(),
+                        CastSettings.CaptureMode.FULL_SCREEN));
+            }
         } else {
             dis.reset();
             settings.setTransport(dis.readUTF());
@@ -248,6 +255,8 @@ public final class CastProtocol {
         return local.getTransport().equals(remote.getTransport());
     }
 
+    private static final byte NETWORK_STATS_VERSION = 3;
+
     public static byte[] networkStatsPayload(NetworkStatsSnapshot s) throws IOException {
         java.io.ByteArrayOutputStream bos = new java.io.ByteArrayOutputStream();
         DataOutputStream dos = new DataOutputStream(bos);
@@ -259,6 +268,21 @@ public final class CastProtocol {
         dos.writeInt(s.recvBitrateKbps);
         dos.writeInt(s.congestionLevel);
         dos.writeInt(s.jitterMs);
+        dos.writeByte(NETWORK_STATS_VERSION);
+        dos.writeFloat(s.encodeFps);
+        dos.writeInt(s.encodeQueueDepth);
+        dos.writeInt(s.droppedPFrames);
+        dos.writeByte(s.audioActive ? 1 : 0);
+        dos.writeLong(s.audioFramesSent);
+        dos.writeInt(s.suggestedBitrateKbps);
+        dos.writeInt(s.targetBitrateKbps);
+        if (NETWORK_STATS_VERSION >= 3) {
+            dos.writeByte(Math.max(0, Math.min(100, s.audioCaptureVuPercent)));
+            dos.writeLong(s.audioCaptureSilentBlocks);
+            dos.writeLong(s.audioCaptureAudibleBlocks);
+            dos.writeFloat(s.audioCapturePeakDb);
+            dos.writeFloat(s.audioCaptureRmsDb);
+        }
         dos.flush();
         return bos.toByteArray();
     }
@@ -274,6 +298,25 @@ public final class CastProtocol {
         s.recvBitrateKbps = dis.readInt();
         s.congestionLevel = dis.readInt();
         s.jitterMs = dis.readInt();
+        if (dis.available() > 0) {
+            byte ver = dis.readByte();
+            if (ver >= 2) {
+                s.encodeFps = dis.readFloat();
+                s.encodeQueueDepth = dis.readInt();
+                s.droppedPFrames = dis.readInt();
+                s.audioActive = dis.readByte() != 0;
+                s.audioFramesSent = dis.readLong();
+                s.suggestedBitrateKbps = dis.readInt();
+                s.targetBitrateKbps = dis.readInt();
+                if (ver >= 3 && dis.available() > 0) {
+                    s.audioCaptureVuPercent = dis.readByte() & 0xff;
+                    s.audioCaptureSilentBlocks = dis.readLong();
+                    s.audioCaptureAudibleBlocks = dis.readLong();
+                    s.audioCapturePeakDb = dis.readFloat();
+                    s.audioCaptureRmsDb = dis.readFloat();
+                }
+            }
+        }
         return s;
     }
 
diff --git a/app/src/main/java/com/foxx/androidcast/network/CastTransport.java b/app/src/main/java/com/foxx/androidcast/network/CastTransport.java
index fc39519..c59354b 100644
--- a/app/src/main/java/com/foxx/androidcast/network/CastTransport.java
+++ b/app/src/main/java/com/foxx/androidcast/network/CastTransport.java
@@ -5,6 +5,8 @@ import java.io.IOException;
 
 /** Pluggable stream transport (TCP or UDP). */
 public interface CastTransport extends Closeable {
+    /** Optional proto header context; ignored when null. */
+    default void setFramingContext(CastFramingContext context) {}
     /** Server: bind and wait for first peer datagram / connection. */
     void listen(int port) throws IOException;
 
diff --git a/app/src/main/java/com/foxx/androidcast/network/TcpCastTransport.java b/app/src/main/java/com/foxx/androidcast/network/TcpCastTransport.java
index 4a42757..0d6383a 100644
--- a/app/src/main/java/com/foxx/androidcast/network/TcpCastTransport.java
+++ b/app/src/main/java/com/foxx/androidcast/network/TcpCastTransport.java
@@ -14,9 +14,10 @@ import java.net.SocketTimeoutException;
 /** Reliable message transport over TCP (serialized send/receive). */
 public class TcpCastTransport implements CastTransport {
     private static final int CONNECT_TIMEOUT_MS = 10_000;
-    private static final int HEADER_BYTES = 5; // type + int length
+    private static final int LEGACY_HEADER_BYTES = 5;
 
     private final Object sendLock = new Object();
+    private CastFramingContext framingContext;
     private final Object receiveLock = new Object();
 
     private ServerSocket serverSocket;
@@ -77,13 +78,25 @@ public class TcpCastTransport implements CastTransport {
         out = new DataOutputStream(new BufferedOutputStream(socket.getOutputStream()));
     }
 
+    @Override
+    public void setFramingContext(CastFramingContext context) {
+        this.framingContext = context;
+    }
+
     @Override
     public void send(byte type, byte[] payload) throws IOException {
         synchronized (sendLock) {
             if (socket == null || socket.isClosed() || out == null) {
                 throw new IOException("Socket closed");
             }
-            CastProtocol.writeMessage(out, type, payload);
+            if (framingContext != null) {
+                CastProtoHeader hdr = framingContext.newHeader(CastProtoHeader.HS_DEFAULT);
+                byte[] wire = CastPacketFramer.frame(hdr, type, payload);
+                out.write(wire);
+                out.flush();
+            } else {
+                CastProtocol.writeMessage(out, type, payload);
+            }
         }
     }
 
@@ -102,6 +115,9 @@ public class TcpCastTransport implements CastTransport {
             }
             try {
                 socket.setSoTimeout(0);
+                if (framingContext != null) {
+                    return readFramedMessage();
+                }
                 return CastProtocol.readMessage(in);
             } catch (SocketTimeoutException e) {
                 return null;
@@ -116,10 +132,15 @@ public class TcpCastTransport implements CastTransport {
         }
     }
 
+    private CastProtocol.Message readFramedMessage() throws IOException {
+        return CastPacketFramer.readFramedMessage(bufferedIn);
+    }
+
     private boolean waitForHeader(int timeoutMs) throws IOException {
+        int need = framingContext != null ? CastProtoHeader.HEADER_SIZE_V1 : LEGACY_HEADER_BYTES;
         long deadline = System.currentTimeMillis() + timeoutMs;
         while (System.currentTimeMillis() < deadline) {
-            if (bufferedIn.available() >= HEADER_BYTES) {
+            if (bufferedIn.available() >= need) {
                 return true;
             }
             try {
@@ -129,7 +150,7 @@ public class TcpCastTransport implements CastTransport {
                 return false;
             }
         }
-        return bufferedIn.available() >= HEADER_BYTES;
+        return bufferedIn.available() >= need;
     }
 
     @Override
diff --git a/app/src/main/java/com/foxx/androidcast/network/UdpCastTransport.java b/app/src/main/java/com/foxx/androidcast/network/UdpCastTransport.java
index 3d04722..4e36078 100644
--- a/app/src/main/java/com/foxx/androidcast/network/UdpCastTransport.java
+++ b/app/src/main/java/com/foxx/androidcast/network/UdpCastTransport.java
@@ -8,6 +8,7 @@ import java.net.DatagramPacket;
 import java.net.DatagramSocket;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
+import java.net.SocketException;
 import java.net.SocketTimeoutException;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
@@ -15,23 +16,31 @@ import java.util.concurrent.ConcurrentHashMap;
 /** Best-effort message transport over UDP with fragmentation. */
 public class UdpCastTransport implements CastTransport {
     private static final byte[] MAGIC = {'A', 'C', 'U', 'D'};
-    private static final int HEADER = 16;
+    /** magic(4) + type(1) + msgId(4) + fragIdx(2) + fragCnt(2) + totalLen(4) */
+    private static final int HEADER = 17;
+    private static final int MAX_RELIABLE_BYTES = 8 * 1024;
 
     private DatagramSocket socket;
     private InetSocketAddress peer;
     private int nextMessageId = 1;
+    private volatile boolean listening;
 
     private final Map<Integer, Reassembly> pending = new ConcurrentHashMap<>();
+    private CastFramingContext framingContext;
+
+    public boolean isListening() {
+        return listening && socket != null && !socket.isClosed();
+    }
 
     @Override
     public void prepareListen(int port) throws IOException {
-        if (socket != null && !socket.isClosed()) {
+        if (isListening()) {
             return;
         }
-        socket = new DatagramSocket(null);
-        socket.setReuseAddress(true);
-        socket.bind(new InetSocketAddress(port));
+        openSocket();
+        socket.bind(new InetSocketAddress(InetAddress.getByName("0.0.0.0"), port));
         socket.setSoTimeout(500);
+        listening = true;
     }
 
     @Override
@@ -41,9 +50,25 @@ public class UdpCastTransport implements CastTransport {
 
     @Override
     public void connect(String host, int port) throws IOException {
-        socket = new DatagramSocket();
+        openSocket();
         peer = new InetSocketAddress(host, port);
         socket.setSoTimeout(500);
+        listening = false;
+    }
+
+    private void openSocket() throws SocketException {
+        if (socket != null && !socket.isClosed()) {
+            return;
+        }
+        socket = new DatagramSocket(null);
+        socket.setReuseAddress(true);
+        socket.setReceiveBufferSize(512 * 1024);
+        socket.setSendBufferSize(512 * 1024);
+    }
+
+    @Override
+    public void setFramingContext(CastFramingContext context) {
+        this.framingContext = context;
     }
 
     @Override
@@ -51,7 +76,24 @@ public class UdpCastTransport implements CastTransport {
         if (peer == null) {
             throw new IOException("UDP peer not set");
         }
-        byte[] body = payload == null ? new byte[0] : payload;
+        byte[] body;
+        byte wireType = type;
+        if (framingContext != null) {
+            CastProtoHeader hdr = framingContext.newHeader(CastProtoHeader.HS_DEFAULT);
+            body = CastPacketFramer.frame(hdr, type, payload);
+            wireType = CastProtocol.MSG_WIRE_PACKET;
+        } else {
+            body = payload == null ? new byte[0] : payload;
+        }
+        if (body.length <= MAX_RELIABLE_BYTES) {
+            sendOnce(wireType, body);
+            sendOnce(wireType, body);
+        } else {
+            sendOnce(wireType, body);
+        }
+    }
+
+    private void sendOnce(byte type, byte[] body) throws IOException {
         int messageId = nextMessageId++;
         int chunkSize = CastConfig.UDP_CHUNK_SIZE - HEADER;
         int fragments = Math.max(1, (body.length + chunkSize - 1) / chunkSize);
@@ -66,6 +108,9 @@ public class UdpCastTransport implements CastTransport {
 
     @Override
     public CastProtocol.Message receive(int timeoutMs) throws IOException {
+        if (socket == null || socket.isClosed()) {
+            return null;
+        }
         long deadline = System.currentTimeMillis() + timeoutMs;
         while (System.currentTimeMillis() < deadline) {
             int remaining = (int) Math.max(1, deadline - System.currentTimeMillis());
@@ -105,13 +150,16 @@ public class UdpCastTransport implements CastTransport {
         byte[] chunk = new byte[payloadLen];
         System.arraycopy(data, HEADER, chunk, 0, payloadLen);
 
+        CastProtocol.Message raw;
         if (fragCount <= 1) {
-            if (totalLen != payloadLen) {
+            if (totalLen != payloadLen && totalLen > 0 && totalLen <= payloadLen) {
                 byte[] trimmed = new byte[totalLen];
-                System.arraycopy(chunk, 0, trimmed, 0, Math.min(totalLen, payloadLen));
-                return new CastProtocol.Message(type, trimmed);
+                System.arraycopy(chunk, 0, trimmed, 0, totalLen);
+                raw = new CastProtocol.Message(type, trimmed);
+            } else {
+                raw = new CastProtocol.Message(type, chunk);
             }
-            return new CastProtocol.Message(type, chunk);
+            return unwrapWire(raw);
         }
 
         Reassembly r = pending.get(messageId);
@@ -124,7 +172,14 @@ public class UdpCastTransport implements CastTransport {
             return null;
         }
         pending.remove(messageId);
-        return new CastProtocol.Message(type, r.assemble());
+        return unwrapWire(new CastProtocol.Message(type, r.assemble()));
+    }
+
+    private static CastProtocol.Message unwrapWire(CastProtocol.Message raw) throws IOException {
+        if (raw.type == CastProtocol.MSG_WIRE_PACKET) {
+            return CastPacketFramer.unframe(raw.payload);
+        }
+        return raw;
     }
 
     private static byte[] buildPacket(
@@ -170,15 +225,18 @@ public class UdpCastTransport implements CastTransport {
     @Override
     public void releaseConnection() {
         peer = null;
+        pending.clear();
     }
 
     @Override
     public void close() {
+        listening = false;
         if (socket != null) {
             socket.close();
             socket = null;
         }
         pending.clear();
+        peer = null;
     }
 
     private static final class Reassembly {
diff --git a/app/src/main/java/com/foxx/androidcast/network/control/NetworkStatsSnapshot.java b/app/src/main/java/com/foxx/androidcast/network/control/NetworkStatsSnapshot.java
index 91052d7..74cdb70 100644
--- a/app/src/main/java/com/foxx/androidcast/network/control/NetworkStatsSnapshot.java
+++ b/app/src/main/java/com/foxx/androidcast/network/control/NetworkStatsSnapshot.java
@@ -11,6 +11,22 @@ public class NetworkStatsSnapshot {
     public int congestionLevel;
     public int jitterMs;
 
+    /** v2 extension: sender encode FPS (receiver: decode/render FPS). */
+    public float encodeFps;
+    public int encodeQueueDepth;
+    public int droppedPFrames;
+    public boolean audioActive;
+    public long audioFramesSent;
+    public int suggestedBitrateKbps;
+    public int targetBitrateKbps;
+
+    /** v3: sender pre-encode PCM levels (receiver: post-decode levels in overlay only). */
+    public int audioCaptureVuPercent;
+    public long audioCaptureSilentBlocks;
+    public long audioCaptureAudibleBlocks;
+    public float audioCapturePeakDb;
+    public float audioCaptureRmsDb;
+
     public NetworkStatsSnapshot copy() {
         NetworkStatsSnapshot c = new NetworkStatsSnapshot();
         c.sequence = sequence;
@@ -21,6 +37,18 @@ public class NetworkStatsSnapshot {
         c.recvBitrateKbps = recvBitrateKbps;
         c.congestionLevel = congestionLevel;
         c.jitterMs = jitterMs;
+        c.encodeFps = encodeFps;
+        c.encodeQueueDepth = encodeQueueDepth;
+        c.droppedPFrames = droppedPFrames;
+        c.audioActive = audioActive;
+        c.audioFramesSent = audioFramesSent;
+        c.suggestedBitrateKbps = suggestedBitrateKbps;
+        c.targetBitrateKbps = targetBitrateKbps;
+        c.audioCaptureVuPercent = audioCaptureVuPercent;
+        c.audioCaptureSilentBlocks = audioCaptureSilentBlocks;
+        c.audioCaptureAudibleBlocks = audioCaptureAudibleBlocks;
+        c.audioCapturePeakDb = audioCapturePeakDb;
+        c.audioCaptureRmsDb = audioCaptureRmsDb;
         return c;
     }
 }
diff --git a/app/src/main/java/com/foxx/androidcast/network/control/PassThroughNetworkControlPlane.java b/app/src/main/java/com/foxx/androidcast/network/control/PassThroughNetworkControlPlane.java
index 845c7ec..8a24de6 100644
--- a/app/src/main/java/com/foxx/androidcast/network/control/PassThroughNetworkControlPlane.java
+++ b/app/src/main/java/com/foxx/androidcast/network/control/PassThroughNetworkControlPlane.java
@@ -17,6 +17,16 @@ public class PassThroughNetworkControlPlane implements NetworkControlPlane {
     private long statsWindowStartMs;
     private long sendWindowBytes;
     private long sendWindowStartMs;
+    private StatsEnricher statsEnricher;
+
+    /** Optional hook to attach encode/decode metrics before stats are sent. */
+    public interface StatsEnricher {
+        void enrich(NetworkStatsSnapshot snapshot, long nowMs);
+    }
+
+    public void setStatsEnricher(StatsEnricher enricher) {
+        this.statsEnricher = enricher;
+    }
 
     @Override
     public NetworkControlAdvice tick(long nowMs) {
@@ -75,6 +85,9 @@ public class PassThroughNetworkControlPlane implements NetworkControlPlane {
         s.recvBitrateKbps = estimateRecvKbps(nowMs);
         s.congestionLevel = 0;
         s.jitterMs = 0;
+        if (statsEnricher != null) {
+            statsEnricher.enrich(s, nowMs);
+        }
         return s;
     }
 
diff --git a/app/src/main/java/com/foxx/androidcast/receiver/AudioDecoder.java b/app/src/main/java/com/foxx/androidcast/receiver/AudioDecoder.java
index 66aaa04..9abe17d 100644
--- a/app/src/main/java/com/foxx/androidcast/receiver/AudioDecoder.java
+++ b/app/src/main/java/com/foxx/androidcast/receiver/AudioDecoder.java
@@ -1,90 +1,310 @@
 package com.foxx.androidcast.receiver;
 
+import android.content.Context;
 import android.media.AudioAttributes;
 import android.media.AudioFormat;
+import android.media.AudioManager;
 import android.media.AudioTrack;
 import android.media.MediaCodec;
 import android.media.MediaFormat;
+import android.os.Handler;
+import android.os.HandlerThread;
 import android.util.Log;
 
+import com.foxx.androidcast.media.AacAdtsHelper;
+import com.foxx.androidcast.media.PcmLevelAnalyzer;
+
 import java.io.IOException;
 import java.nio.ByteBuffer;
-
-/** AAC decoder → AudioTrack playback. */
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+/** AAC decoder → AudioTrack; input and output run on separate threads. */
 public class AudioDecoder {
     private static final String TAG = "AudioDecoder";
     private static final String MIME = MediaFormat.MIMETYPE_AUDIO_AAC;
 
+    public interface RenderCallback {
+        void onPcmRendered(int bytes, PcmLevelAnalyzer.Levels levels);
+    }
+
+    public static final class Stats {
+        public long framesQueued;
+        public long framesFed;
+        public long pcmBytesWritten;
+        public long pcmSilentBlocks;
+        public long pcmAudibleBlocks;
+        public long decodeErrors;
+        public float lastPeak;
+        public float lastRms;
+    }
+
+    private final Context appContext;
+    private final HandlerThread workerThread = new HandlerThread("AudioDecoderCtrl");
+    private Handler worker;
+    private final LinkedBlockingQueue<PendingFrame> inputQueue = new LinkedBlockingQueue<>(128);
+    private final Stats stats = new Stats();
+
     private MediaCodec codec;
     private AudioTrack track;
-    private boolean configured;
+    private volatile boolean configured;
+    private volatile boolean draining;
+    private Thread drainThread;
+    private int sampleRate = 44100;
+    private int channels = 2;
+    private boolean useAdtsMode;
+    private RenderCallback renderCallback;
+
+    private static final class PendingFrame {
+        final long ptsUs;
+        final byte[] data;
+
+        PendingFrame(long ptsUs, byte[] data) {
+            this.ptsUs = ptsUs;
+            this.data = data;
+        }
+    }
+
+    public AudioDecoder(Context context) {
+        this.appContext = context.getApplicationContext();
+        workerThread.start();
+        worker = new Handler(workerThread.getLooper());
+    }
+
+    public void setRenderCallback(RenderCallback callback) {
+        this.renderCallback = callback;
+    }
+
+    public Stats getStats() {
+        return stats;
+    }
 
     public void configure(int sampleRate, int channels, byte[] csd0) throws IOException {
-        MediaFormat format = MediaFormat.createAudioFormat(MIME, sampleRate, channels);
-        if (csd0 != null && csd0.length > 0) {
-            format.setByteBuffer("csd-0", ByteBuffer.wrap(csd0));
-        }
-        codec = MediaCodec.createDecoderByType(MIME);
-        codec.configure(format, null, null, 0);
-        codec.start();
+        final IOException[] error = new IOException[1];
+        final Object lock = new Object();
+        worker.post(() -> {
+            try {
+                releaseOnWorker();
+                AudioDecoder.this.sampleRate = sampleRate;
+                AudioDecoder.this.channels = channels;
+                useAdtsMode = csd0 == null || csd0.length < 2;
 
-        int channelMask = channels >= 2 ? AudioFormat.CHANNEL_OUT_STEREO : AudioFormat.CHANNEL_OUT_MONO;
+                MediaFormat format = MediaFormat.createAudioFormat(MIME, sampleRate, channels);
+                if (useAdtsMode) {
+                    format.setInteger(MediaFormat.KEY_IS_ADTS, 1);
+                } else {
+                    format.setByteBuffer("csd-0", ByteBuffer.wrap(csd0));
+                }
+                codec = MediaCodec.createDecoderByType(MIME);
+                codec.configure(format, null, null, 0);
+                codec.start();
+                createAudioTrack(sampleRate, channels);
+                configured = true;
+                draining = true;
+                startDrainThread();
+                Log.i(TAG, "Audio ready " + sampleRate + "Hz ch=" + channels
+                        + " mode=" + (useAdtsMode ? "ADTS" : "raw+csd")
+                        + " csdLen=" + (csd0 != null ? csd0.length : 0));
+            } catch (IOException e) {
+                error[0] = e;
+            } catch (Exception e) {
+                error[0] = new IOException(e);
+            } finally {
+                synchronized (lock) {
+                    lock.notifyAll();
+                }
+            }
+        });
+        synchronized (lock) {
+            try {
+                lock.wait(5000);
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+            }
+        }
+        if (error[0] != null) {
+            throw error[0];
+        }
+    }
+
+    private void startDrainThread() {
+        drainThread = new Thread(this::drainLoop, "AudioDecoderDrain");
+        drainThread.start();
+    }
+
+    private void createAudioTrack(int sampleRate, int channels) {
+        int channelMask = channels >= 2
+                ? AudioFormat.CHANNEL_OUT_STEREO
+                : AudioFormat.CHANNEL_OUT_MONO;
         int minBuf = AudioTrack.getMinBufferSize(sampleRate, channelMask, AudioFormat.ENCODING_PCM_16BIT);
+        int bufSize = Math.max(minBuf * 8, 65536);
         track = new AudioTrack.Builder()
                 .setAudioAttributes(new AudioAttributes.Builder()
                         .setUsage(AudioAttributes.USAGE_MEDIA)
-                        .setContentType(AudioAttributes.CONTENT_TYPE_MOVIE)
+                        .setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
                         .build())
                 .setAudioFormat(new AudioFormat.Builder()
                         .setEncoding(AudioFormat.ENCODING_PCM_16BIT)
                         .setSampleRate(sampleRate)
                         .setChannelMask(channelMask)
                         .build())
-                .setBufferSizeInBytes(minBuf * 4)
+                .setBufferSizeInBytes(bufSize)
                 .setTransferMode(AudioTrack.MODE_STREAM)
                 .build();
+        track.setVolume(1.0f);
+        requestAudioFocus();
         track.play();
-        configured = true;
+        Log.i(TAG, "AudioTrack play state=" + track.getPlayState());
     }
 
     public void queueFrame(long ptsUs, byte[] data) {
-        if (!configured || codec == null) {
+        if (data == null || data.length == 0) {
             return;
         }
-        try {
-            int inIndex = codec.dequeueInputBuffer(5_000);
-            if (inIndex < 0) {
-                return;
-            }
-            ByteBuffer buffer = codec.getInputBuffer(inIndex);
-            if (buffer == null) {
-                return;
-            }
-            buffer.clear();
-            buffer.put(data);
-            codec.queueInputBuffer(inIndex, 0, data.length, ptsUs, 0);
+        stats.framesQueued++;
+        if (!inputQueue.offer(new PendingFrame(ptsUs, data.clone()))) {
+            inputQueue.poll();
+            inputQueue.offer(new PendingFrame(ptsUs, data.clone()));
+        }
+    }
 
-            MediaCodec.BufferInfo info = new MediaCodec.BufferInfo();
-            int outIndex = codec.dequeueOutputBuffer(info, 5_000);
-            while (outIndex >= 0) {
-                ByteBuffer outBuf = codec.getOutputBuffer(outIndex);
-                if (outBuf != null && info.size > 0 && track != null) {
-                    byte[] pcm = new byte[info.size];
-                    outBuf.position(info.offset);
-                    outBuf.limit(info.offset + info.size);
-                    outBuf.get(pcm);
-                    track.write(pcm, 0, pcm.length);
+    private void drainLoop() {
+        MediaCodec.BufferInfo info = new MediaCodec.BufferInfo();
+        while (draining) {
+            try {
+                PendingFrame frame = inputQueue.poll(5, TimeUnit.MILLISECONDS);
+                if (frame != null && codec != null) {
+                    feedFrameSync(frame, info);
+                }
+                drainOutputSync(info);
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+                break;
+            } catch (Exception e) {
+                stats.decodeErrors++;
+                if (draining) {
+                    Log.w(TAG, "drainLoop: " + e.getMessage());
                 }
-                codec.releaseOutputBuffer(outIndex, false);
-                outIndex = codec.dequeueOutputBuffer(info, 0);
             }
-        } catch (Exception e) {
-            Log.e(TAG, "Audio decode error", e);
+        }
+    }
+
+    private void feedFrameSync(PendingFrame frame, MediaCodec.BufferInfo info) {
+        byte[] data = frame.data;
+        if (useAdtsMode) {
+            data = AacAdtsHelper.wrapIfNeeded(data, sampleRate, channels);
+        }
+        int inIndex = codec.dequeueInputBuffer(10_000);
+        if (inIndex < 0) {
+            return;
+        }
+        ByteBuffer buffer = codec.getInputBuffer(inIndex);
+        if (buffer == null) {
+            return;
+        }
+        buffer.clear();
+        buffer.put(data);
+        codec.queueInputBuffer(inIndex, 0, data.length, frame.ptsUs, 0);
+        stats.framesFed++;
+        drainOutputSync(info);
+    }
+
+    private void drainOutputSync(MediaCodec.BufferInfo info) {
+        if (codec == null) {
+            return;
+        }
+        for (;;) {
+            int outIndex = codec.dequeueOutputBuffer(info, 0);
+            if (outIndex == MediaCodec.INFO_TRY_AGAIN_LATER) {
+                break;
+            }
+            if (outIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
+                Log.i(TAG, "Decoder output: " + codec.getOutputFormat());
+                continue;
+            }
+            if (outIndex < 0) {
+                continue;
+            }
+            ByteBuffer outBuf = codec.getOutputBuffer(outIndex);
+            if (outBuf != null && info.size > 0 && track != null
+                    && (info.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) == 0) {
+                byte[] pcm = new byte[info.size];
+                outBuf.position(info.offset);
+                outBuf.limit(info.offset + info.size);
+                outBuf.get(pcm);
+                PcmLevelAnalyzer.Levels levels = PcmLevelAnalyzer.analyze(pcm, pcm.length);
+                stats.lastPeak = levels.peak;
+                stats.lastRms = levels.rms;
+                if (levels.silent) {
+                    stats.pcmSilentBlocks++;
+                } else {
+                    stats.pcmAudibleBlocks++;
+                }
+                int written = writePcm(pcm);
+                if (written > 0) {
+                    stats.pcmBytesWritten += written;
+                    if (renderCallback != null) {
+                        renderCallback.onPcmRendered(written, levels);
+                    }
+                }
+            }
+            codec.releaseOutputBuffer(outIndex, false);
+        }
+    }
+
+    private int writePcm(byte[] pcm) {
+        int total = 0;
+        int offset = 0;
+        while (offset < pcm.length) {
+            int w = track.write(pcm, offset, pcm.length - offset);
+            if (w <= 0) {
+                break;
+            }
+            total += w;
+            offset += w;
+        }
+        return total;
+    }
+
+    private void requestAudioFocus() {
+        AudioManager am = (AudioManager) appContext.getSystemService(Context.AUDIO_SERVICE);
+        if (am != null) {
+            am.requestAudioFocus(focusChange -> {
+            }, AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN);
         }
     }
 
     public void release() {
+        final Object lock = new Object();
+        worker.post(() -> {
+            releaseOnWorker();
+            synchronized (lock) {
+                lock.notifyAll();
+            }
+        });
+        synchronized (lock) {
+            try {
+                lock.wait(2000);
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+            }
+        }
+    }
+
+    private void releaseOnWorker() {
+        draining = false;
         configured = false;
+        inputQueue.clear();
+        if (drainThread != null) {
+            drainThread.interrupt();
+            try {
+                drainThread.join(1500);
+            } catch (InterruptedException ignored) {
+                Thread.currentThread().interrupt();
+            }
+            drainThread = null;
+        }
         if (codec != null) {
             try {
                 codec.stop();
@@ -102,4 +322,9 @@ public class AudioDecoder {
             track = null;
         }
     }
+
+    public void releaseAndQuit() {
+        release();
+        workerThread.quitSafely();
+    }
 }
diff --git a/app/src/main/java/com/foxx/androidcast/receiver/PlaybackViewState.java b/app/src/main/java/com/foxx/androidcast/receiver/PlaybackViewState.java
new file mode 100644
index 0000000..d8268a0
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/receiver/PlaybackViewState.java
@@ -0,0 +1,21 @@
+package com.foxx.androidcast.receiver;
+
+/** Zoom/pan state for receiver diagnostics (updated from playback UI). */
+public final class PlaybackViewState {
+    private static volatile int zoomPercent;
+
+    private PlaybackViewState() {}
+
+    public static void setZoomPercent(int percent) {
+        zoomPercent = percent;
+    }
+
+    /** Deviation from 100% scale, e.g. +15 or −10. */
+    public static int getZoomPercent() {
+        return zoomPercent;
+    }
+
+    public static void reset() {
+        zoomPercent = 0;
+    }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/receiver/ReceiverActivity.java b/app/src/main/java/com/foxx/androidcast/receiver/ReceiverActivity.java
index 4df6d87..965567b 100644
--- a/app/src/main/java/com/foxx/androidcast/receiver/ReceiverActivity.java
+++ b/app/src/main/java/com/foxx/androidcast/receiver/ReceiverActivity.java
@@ -93,7 +93,7 @@ public class ReceiverActivity extends AppCompatActivity {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_receiver);
         PermissionHelper.request(this);
-        SettingsUi.bind(this, castSettings);
+        SettingsUi.bindReceiver(this, castSettings);
 
         statusText = findViewById(R.id.text_status);
         pinInput = findViewById(R.id.edit_pin);
@@ -129,6 +129,7 @@ public class ReceiverActivity extends AppCompatActivity {
     @Override
     protected void onResume() {
         super.onResume();
+        PermissionHelper.remindIfMissing(this, allowAudioCheck.isChecked());
         updateKeepScreenOn();
     }
 
diff --git a/app/src/main/java/com/foxx/androidcast/receiver/ReceiverCastService.java b/app/src/main/java/com/foxx/androidcast/receiver/ReceiverCastService.java
index 7f55172..6b93eea 100644
--- a/app/src/main/java/com/foxx/androidcast/receiver/ReceiverCastService.java
+++ b/app/src/main/java/com/foxx/androidcast/receiver/ReceiverCastService.java
@@ -20,8 +20,10 @@ import com.foxx.androidcast.ICastStatusCallback;
 import com.foxx.androidcast.IntentExtras;
 import com.foxx.androidcast.R;
 import com.foxx.androidcast.CastConfig;
+import com.foxx.androidcast.diagnostics.CastDiagnosticsFormatter;
 import com.foxx.androidcast.discovery.DiscoveryManager;
 import com.foxx.androidcast.network.control.NetworkStatsSnapshot;
+import com.foxx.androidcast.network.control.PassThroughNetworkControlPlane;
 
 import java.util.Arrays;
 
@@ -75,6 +77,8 @@ public class ReceiverCastService extends Service {
     private String activePin = com.foxx.androidcast.CastConfig.DEFAULT_PIN;
     private final StreamMetrics streamMetrics = new StreamMetrics();
     private String negotiatedVideoMime;
+    private CastSettings remoteCastSettings;
+    private NetworkStatsSnapshot lastLocalStats;
     private boolean streamIdle;
     private long lastVideoFrameMs;
 
@@ -161,7 +165,15 @@ public class ReceiverCastService extends Service {
         return START_STICKY;
     }
 
+    private final Object sessionLock = new Object();
+
     private void restartListening(String pin) {
+        synchronized (sessionLock) {
+            restartListeningLocked(pin);
+        }
+    }
+
+    private void restartListeningLocked(String pin) {
         stopSessionOnly();
         resetStreamState();
         phase = Phase.LISTENING;
@@ -176,9 +188,11 @@ public class ReceiverCastService extends Service {
             audioDecoder.release();
         }
         videoDecoder = new VideoDecoder();
-        audioDecoder = new AudioDecoder();
+        audioDecoder = new AudioDecoder(this);
+        audioDecoder.setRenderCallback((pcmBytes, levels) -> streamMetrics.onAudioRendered(
+                pcmBytes, levels.peak, levels.rms, levels.silent));
 
-        session = new ReceiverSession(pin, settings, new ReceiverSession.Listener() {
+        session = new ReceiverSession(this, pin, settings, new ReceiverSession.Listener() {
             @Override
             public void onListening() {
                 mainHandler.post(ReceiverCastService.this::startDiscoveryAnnouncing);
@@ -191,6 +205,11 @@ public class ReceiverCastService extends Service {
 
             @Override
             public void onAuthenticated(String senderName, CastSettings remoteSettings, String videoMime) {
+                synchronized (ReceiverCastService.this) {
+                    if (remoteSettings != null && remoteSettings.isAudioRequested() && allowIncomingAudio) {
+                        audioAccepted = true;
+                    }
+                }
                 mainHandler.post(() -> onSenderConnected(senderName, remoteSettings, videoMime));
             }
 
@@ -240,16 +259,27 @@ public class ReceiverCastService extends Service {
                     }
                 }
                 final boolean accepted = accept;
+                if (accepted && audioDecoder != null) {
+                    try {
+                        audioDecoder.configure(sampleRate, channels, csd0);
+                    } catch (Exception e) {
+                        Log.e(TAG, "Audio configure on config msg failed", e);
+                    }
+                }
                 mainHandler.post(() -> onAudioConfigReceived(sampleRate, channels, csd0, accepted));
             }
 
             @Override
             public void onAudioFrame(long ptsUs, byte[] data) {
                 final int frameBytes = data != null ? data.length : 0;
-                mainHandler.post(() -> streamMetrics.onAudioPacket(frameBytes));
-                if (Boolean.TRUE.equals(audioAccepted) && audioDecoder != null) {
+                final boolean accept;
+                synchronized (ReceiverCastService.this) {
+                    accept = Boolean.TRUE.equals(audioAccepted);
+                }
+                if (accept && audioDecoder != null) {
                     audioDecoder.queueFrame(ptsUs, data);
                 }
+                mainHandler.post(() -> streamMetrics.onAudioPacket(frameBytes));
             }
 
             @Override
@@ -265,7 +295,7 @@ public class ReceiverCastService extends Service {
             public void onPeerNetworkStats(NetworkStatsSnapshot stats) {
                 mainHandler.post(() -> streamMetrics.onPeerStats(stats));
             }
-        });
+        }, this::enrichReceiverStats);
         session.start();
         updateStatus(getString(R.string.receiver_ready, pin, settings.getTransport().toUpperCase()));
         openPlaybackAwaiting(R.string.playback_listening);
@@ -275,7 +305,7 @@ public class ReceiverCastService extends Service {
     private void onSenderConnected(String senderName, CastSettings remoteSettings, String videoMime) {
         phase = Phase.CONNECTED;
         negotiatedVideoMime = videoMime;
-        audioAccepted = null;
+        remoteCastSettings = remoteSettings;
         streamIdle = false;
         streamMetrics.reset();
         lastVideoFrameMs = 0;
@@ -305,13 +335,24 @@ public class ReceiverCastService extends Service {
     private void onSenderDisconnected() {
         phase = Phase.LISTENING;
         audioAccepted = null;
+        remoteCastSettings = null;
         streamIdle = false;
         lastVideoFrameMs = 0;
-        enterAwaitingMode(R.string.playback_stream_lost, true);
+        negotiatedVideoMime = null;
+        enterAwaitingMode(R.string.playback_stream_ended, true);
         updateStatus(getString(R.string.waiting_sender));
+        closePlaybackUi();
+        openReceiverSetupUi();
         Log.i(TAG, "Sender disconnected");
     }
 
+    private void openReceiverSetupUi() {
+        Intent intent = new Intent(this, ReceiverActivity.class);
+        intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TOP
+                | Intent.FLAG_ACTIVITY_SINGLE_TOP);
+        startActivity(intent);
+    }
+
     private void checkStreamIdle() {
         if (phase != Phase.STREAMING || streamIdle || lastVideoFrameMs <= 0) {
             return;
@@ -372,30 +413,19 @@ public class ReceiverCastService extends Service {
         pendingAudioChannels = channels;
         pendingAudioCsd = csd0;
         if (accepted) {
-            configureAudioIfAccepted();
             updateStatus(getString(R.string.audio_playing));
         } else {
             if (audioDecoder != null) {
                 audioDecoder.release();
-                audioDecoder = new AudioDecoder();
+                audioDecoder = new AudioDecoder(this);
+                audioDecoder.setRenderCallback((pcmBytes, levels) -> streamMetrics.onAudioRendered(
+                pcmBytes, levels.peak, levels.rms, levels.silent));
             }
             updateStatus(getString(R.string.audio_skipped));
         }
         Log.i(TAG, "Audio consent: " + accepted);
     }
 
-    private void configureAudioIfAccepted() {
-        if (!Boolean.TRUE.equals(audioAccepted) || audioDecoder == null) {
-            return;
-        }
-        try {
-            audioDecoder.configure(pendingAudioRate, pendingAudioChannels, pendingAudioCsd);
-        } catch (Exception e) {
-            Log.e(TAG, "Audio configure failed", e);
-            updateStatus("Audio: " + e.getMessage());
-        }
-    }
-
     private void onStreamConfigReceived(int width, int height, byte[] csd0, byte[] csd1) {
         com.foxx.androidcast.media.StreamDimensionResolver.Size size =
                 com.foxx.androidcast.media.StreamDimensionResolver.resolve(width, height, csd0);
@@ -488,6 +518,11 @@ public class ReceiverCastService extends Service {
             session.stop();
             session = null;
         }
+        try {
+            Thread.sleep(80);
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+        }
     }
 
     private void acquireWakeLock() {
@@ -562,15 +597,41 @@ public class ReceiverCastService extends Service {
         mainHandler.post(() -> streamMetrics.onRenderedFrame());
     }
 
+    private void enrichReceiverStats(NetworkStatsSnapshot s, long nowMs) {
+        s.encodeFps = streamMetrics.getDecodeFps();
+        NetworkStatsSnapshot peer = streamMetrics.getLastPeer();
+        CastSettings tune = remoteCastSettings != null ? remoteCastSettings : settings;
+        com.foxx.androidcast.CastTuningEngine.EffectiveParams eff =
+                com.foxx.androidcast.CastTuningEngine.resolve(tune, peer);
+        s.suggestedBitrateKbps = eff.videoBitrate / 1000;
+        s.targetBitrateKbps = eff.videoBitrate / 1000;
+        if (s.recvBitrateKbps > 0 && eff.videoBitrate / 1000 > s.recvBitrateKbps * 1.15f) {
+            s.congestionLevel = Math.max(s.congestionLevel, 1);
+        }
+        float inFps = streamMetrics.getInFps();
+        float renderFps = streamMetrics.getRenderFps();
+        if (inFps > 12f && renderFps > 0 && renderFps < inFps * 0.7f) {
+            s.congestionLevel = Math.max(s.congestionLevel, 2);
+        }
+        lastLocalStats = s.copy();
+    }
+
     private String buildDiagnosticsText() {
-        return streamMetrics.format(
+        NetworkStatsSnapshot peer = streamMetrics.getLastPeer();
+        return CastDiagnosticsFormatter.formatHtml(
+                streamMetrics,
                 settings.getTransport(),
                 negotiatedVideoMime,
                 pendingWidth,
                 pendingHeight,
                 decoderWidth,
                 decoderHeight,
-                streamIdle);
+                streamIdle,
+                settings,
+                remoteCastSettings,
+                peer,
+                lastLocalStats,
+                PlaybackViewState.getZoomPercent());
     }
 
     private void attachSurface(Surface surface) {
diff --git a/app/src/main/java/com/foxx/androidcast/receiver/ReceiverPlaybackActivity.java b/app/src/main/java/com/foxx/androidcast/receiver/ReceiverPlaybackActivity.java
index 68c913d..ffbc216 100644
--- a/app/src/main/java/com/foxx/androidcast/receiver/ReceiverPlaybackActivity.java
+++ b/app/src/main/java/com/foxx/androidcast/receiver/ReceiverPlaybackActivity.java
@@ -27,6 +27,9 @@ import com.foxx.androidcast.ICastReceiverService;
 import com.foxx.androidcast.ICastStatusCallback;
 import com.foxx.androidcast.R;
 import com.foxx.androidcast.ui.AspectRatioFrameLayout;
+import com.foxx.androidcast.ui.ZoomPanContainer;
+
+import androidx.core.text.HtmlCompat;
 
 /**
  * Fullscreen display: dancing-robot overlay while listening / waiting;
@@ -133,8 +136,10 @@ public class ReceiverPlaybackActivity extends AppCompatActivity implements Surfa
 
         readSizeFromIntent(getIntent());
 
+        ZoomPanContainer zoomContainer = findViewById(R.id.zoom_container);
         aspectContainer = findViewById(R.id.aspect_container);
         surfaceView = findViewById(R.id.surface_playback);
+        zoomContainer.setOnZoomChangedListener(PlaybackViewState::setZoomPercent);
         awaitingOverlay = findViewById(R.id.overlay_awaiting);
         diagnosticsText = findViewById(R.id.text_diagnostics);
         robotView = findViewById(R.id.image_robot);
@@ -228,6 +233,7 @@ public class ReceiverPlaybackActivity extends AppCompatActivity implements Surfa
 
     private void showAwaitingOverlay(int messageResId) {
         streamRendering = false;
+        PlaybackViewState.reset();
         if (awaitingOverlay == null) {
             return;
         }
@@ -268,7 +274,7 @@ public class ReceiverPlaybackActivity extends AppCompatActivity implements Surfa
         try {
             String text = receiverService.getDiagnosticsText();
             if (text != null) {
-                diagnosticsText.setText(text);
+                diagnosticsText.setText(HtmlCompat.fromHtml(text, HtmlCompat.FROM_HTML_MODE_LEGACY));
             }
         } catch (RemoteException ignored) {
         }
diff --git a/app/src/main/java/com/foxx/androidcast/receiver/ReceiverSession.java b/app/src/main/java/com/foxx/androidcast/receiver/ReceiverSession.java
index 3b2cfb9..837a313 100644
--- a/app/src/main/java/com/foxx/androidcast/receiver/ReceiverSession.java
+++ b/app/src/main/java/com/foxx/androidcast/receiver/ReceiverSession.java
@@ -2,8 +2,13 @@ package com.foxx.androidcast.receiver;
 
 import android.util.Log;
 
+import android.content.Context;
+
 import com.foxx.androidcast.CastConfig;
 import com.foxx.androidcast.CastSettings;
+import com.foxx.androidcast.DeviceInfo;
+import com.foxx.androidcast.network.CastCodecFlags;
+import com.foxx.androidcast.network.CastFramingContext;
 import com.foxx.androidcast.network.CastProtocol;
 import com.foxx.androidcast.network.CastSession;
 import com.foxx.androidcast.network.CastTransport;
@@ -44,6 +49,7 @@ public class ReceiverSession {
         void onPeerNetworkStats(NetworkStatsSnapshot stats);
     }
 
+    private final Context appContext;
     private final String pin;
     private final CastSettings localSettings;
     private final Listener listener;
@@ -53,14 +59,25 @@ public class ReceiverSession {
     private CastSession session;
     private CastTransport listenTransport;
     private NetworkFeedbackManager networkFeedback;
+    private PassThroughNetworkControlPlane.StatsEnricher statsEnricher;
 
-    public ReceiverSession(String pin, CastSettings localSettings, Listener listener) {
+    public ReceiverSession(Context context, String pin, CastSettings localSettings, Listener listener) {
+        this(context, pin, localSettings, listener, null);
+    }
+
+    public ReceiverSession(Context context, String pin, CastSettings localSettings, Listener listener,
+            PassThroughNetworkControlPlane.StatsEnricher statsEnricher) {
+        this.appContext = context.getApplicationContext();
         this.pin = pin;
         this.localSettings = localSettings;
         this.listener = listener;
+        this.statsEnricher = statsEnricher;
     }
 
     public void start() {
+        if (running.get()) {
+            stop();
+        }
         if (!running.compareAndSet(false, true)) {
             return;
         }
@@ -95,6 +112,11 @@ public class ReceiverSession {
             try {
                 if (listenTransport == null) {
                     listenTransport = CastTransportFactory.create(localSettings);
+                    listenTransport.setFramingContext(new CastFramingContext(
+                            0,
+                            DeviceInfo.getPlaceholderId(appContext),
+                            CastCodecFlags.localDecoderVideoMask(),
+                            CastCodecFlags.localAudioMask()));
                     session = new CastSession(listenTransport);
                     session.prepareListen(CastConfig.CAST_PORT);
                     listener.onListening();
@@ -104,6 +126,10 @@ public class ReceiverSession {
                     session = new CastSession(listenTransport);
                 }
                 networkFeedback = new NetworkFeedbackManager(session, false);
+                if (networkFeedback.getPlane() instanceof PassThroughNetworkControlPlane) {
+                    ((PassThroughNetworkControlPlane) networkFeedback.getPlane())
+                            .setStatsEnricher(statsEnricher);
+                }
                 session.acceptClient();
                 CastSession.HandshakeResult hs = session.serverHandshake(pin, localSettings);
                 listener.onAuthenticated(hs.senderName, hs.settings, hs.negotiatedVideoMime);
diff --git a/app/src/main/java/com/foxx/androidcast/receiver/StreamMetrics.java b/app/src/main/java/com/foxx/androidcast/receiver/StreamMetrics.java
index ee49085..c62727a 100644
--- a/app/src/main/java/com/foxx/androidcast/receiver/StreamMetrics.java
+++ b/app/src/main/java/com/foxx/androidcast/receiver/StreamMetrics.java
@@ -6,6 +6,12 @@ import com.foxx.androidcast.network.control.NetworkStatsSnapshot;
 public final class StreamMetrics {
     private long videoPackets;
     private long audioPackets;
+    private long audioRenderedWrites;
+    private long audioPcmSilentBlocks;
+    private long audioPcmAudibleBlocks;
+    private float audioVuSmoothed;
+    private float audioLastPeakDb;
+    private float audioLastRmsDb;
     private long keyFrames;
     private long deltaFrames;
     private long videoBytes;
@@ -21,10 +27,17 @@ public final class StreamMetrics {
     private int peerRttMs;
     private int peerRecvKbps;
     private int peerSendKbps;
+    private NetworkStatsSnapshot lastPeer;
 
     public synchronized void reset() {
         videoPackets = 0;
         audioPackets = 0;
+        audioRenderedWrites = 0;
+        audioPcmSilentBlocks = 0;
+        audioPcmAudibleBlocks = 0;
+        audioVuSmoothed = 0f;
+        audioLastPeakDb = -96f;
+        audioLastRmsDb = -96f;
         keyFrames = 0;
         deltaFrames = 0;
         videoBytes = 0;
@@ -40,6 +53,7 @@ public final class StreamMetrics {
         peerRttMs = 0;
         peerRecvKbps = 0;
         peerSendKbps = 0;
+        lastPeer = null;
     }
 
     public synchronized void onVideoPacket(boolean keyFrame, int bytes) {
@@ -74,6 +88,51 @@ public final class StreamMetrics {
         audioBytes += bytes;
     }
 
+    public synchronized void onAudioRendered(int pcmBytes, float peak, float rms, boolean silent) {
+        if (pcmBytes > 0) {
+            audioRenderedWrites++;
+        }
+        if (silent) {
+            audioPcmSilentBlocks++;
+        } else {
+            audioPcmAudibleBlocks++;
+        }
+        float instant = Math.max(peak, rms);
+        audioVuSmoothed = instant > audioVuSmoothed
+                ? instant * 0.35f + audioVuSmoothed * 0.65f
+                : instant * 0.12f + audioVuSmoothed * 0.88f;
+        if (peak > 1e-9f) {
+            audioLastPeakDb = (float) (20.0 * Math.log10(peak));
+        }
+        if (rms > 1e-9f) {
+            audioLastRmsDb = (float) (20.0 * Math.log10(rms));
+        }
+    }
+
+    public synchronized long getAudioRenderedWrites() {
+        return audioRenderedWrites;
+    }
+
+    public synchronized long getAudioPcmSilentBlocks() {
+        return audioPcmSilentBlocks;
+    }
+
+    public synchronized long getAudioPcmAudibleBlocks() {
+        return audioPcmAudibleBlocks;
+    }
+
+    public synchronized int getAudioVuPercent() {
+        return com.foxx.androidcast.media.PcmLevelAnalyzer.vuPercent(audioVuSmoothed);
+    }
+
+    public synchronized float getAudioLastPeakDb() {
+        return audioLastPeakDb;
+    }
+
+    public synchronized float getAudioLastRmsDb() {
+        return audioLastRmsDb;
+    }
+
     public synchronized void onRenderedFrame() {
         renderedFrames++;
         lastRenderedFrameMs = System.currentTimeMillis();
@@ -83,72 +142,89 @@ public final class StreamMetrics {
         if (peer == null) {
             return;
         }
+        lastPeer = peer;
         peerRttMs = peer.rttMs;
         peerRecvKbps = peer.recvBitrateKbps;
         peerSendKbps = peer.sendBitrateKbps;
     }
 
+    public synchronized NetworkStatsSnapshot getLastPeer() {
+        return lastPeer;
+    }
+
     public synchronized long getLastVideoPacketMs() {
         return lastVideoPacketMs;
     }
 
-    public synchronized String format(String transport, String videoCodec, int streamW, int streamH, int renderW,
-            int renderH, boolean idle) {
+    public synchronized float getInFps() {
         long now = System.currentTimeMillis();
         float inFps = lastSecondInFps > 0 ? lastSecondInFps : computeFps(videoPackets, firstVideoPacketMs, now);
-        float renderFps = computeFps(renderedFrames, firstVideoPacketMs, lastRenderedFrameMs);
-        int localKbps = computeLocalKbps(now);
-        long idleMs = lastVideoPacketMs > 0 ? now - lastVideoPacketMs : -1;
+        return inFps;
+    }
 
+    public synchronized float getRenderFps() {
+        long now = System.currentTimeMillis();
+        return computeFps(renderedFrames, firstVideoPacketMs, lastRenderedFrameMs > 0 ? lastRenderedFrameMs : now);
+    }
+
+    public synchronized int getBwInKbps() {
+        return computeLocalKbps(System.currentTimeMillis());
+    }
+
+    public synchronized long getVideoPackets() {
+        return videoPackets;
+    }
+
+    public synchronized long getAudioPackets() {
+        return audioPackets;
+    }
+
+    public synchronized long getKeyFrames() {
+        return keyFrames;
+    }
+
+    public synchronized long getDeltaFrames() {
+        return deltaFrames;
+    }
+
+    public synchronized int getAvgKbPerFrame() {
+        if (videoPackets <= 0) {
+            return 0;
+        }
+        return (int) (videoBytes / videoPackets / 1024);
+    }
+
+    public synchronized long getLastFrameIdleMs() {
+        if (lastVideoPacketMs <= 0) {
+            return -1;
+        }
+        return System.currentTimeMillis() - lastVideoPacketMs;
+    }
+
+    public synchronized int getPeerRttMs() {
+        return peerRttMs;
+    }
+
+    public synchronized int getPeerSendKbps() {
+        return peerSendKbps;
+    }
+
+    public synchronized int getPeerRecvKbps() {
+        return peerRecvKbps;
+    }
+
+    public synchronized float getDecodeFps() {
+        return getRenderFps();
+    }
+
+    /** Plain-text fallback (tests / logging). */
+    public synchronized String format(String transport, String videoCodec, int streamW, int streamH, int renderW,
+            int renderH, boolean idle) {
         StringBuilder sb = new StringBuilder();
-        sb.append("Transport: ").append(transport != null ? transport.toUpperCase() : "?").append('\n');
-        if (videoCodec != null && !videoCodec.isEmpty()) {
-            sb.append("Codec: ").append(
-                    com.foxx.androidcast.media.CodecNegotiator.displayName(videoCodec)).append('\n');
-        }
-        sb.append("Stream: ").append(streamW).append('x').append(streamH);
-        if (renderW > 0 && renderH > 0 && (renderW != streamW || renderH != streamH)) {
-            sb.append("  render: ").append(renderW).append('x').append(renderH);
-        }
-        sb.append('\n');
-        sb.append("In FPS: ").append(formatFloat(inFps));
-        sb.append("  Render FPS: ").append(formatFloat(renderFps)).append('\n');
-        sb.append("BW in (est): ").append(localKbps > 0 ? localKbps + " kbps" : "n/a");
-        sb.append("  RTT: ").append(peerRttMs > 0 ? peerRttMs + " ms" : "n/a").append('\n');
-        if (peerRecvKbps > 0 || peerSendKbps > 0) {
-            sb.append("Sender (peer): tx ").append(peerSendKbps).append(" / rx ")
-                    .append(peerRecvKbps).append(" kbps\n");
-        }
-        sb.append("Video pkts: ").append(videoPackets);
-        sb.append(" (IDR ").append(keyFrames).append(" / P ").append(deltaFrames).append(')');
-        if (videoPackets > 0) {
-            int avgKb = (int) (videoBytes / videoPackets / 1024);
-            sb.append("  ~").append(Math.max(1, avgKb)).append(" KB/frame");
-        }
-        sb.append('\n');
-        if (inFps > 0 && inFps < 8f) {
-            sb.append("Hint: low In FPS → sender encode stall / tiny frames / TCP backlog\n");
-        }
-        if (localKbps > 0 && localKbps < 350 && inFps < 8f && videoPackets > 30) {
-            sb.append("Hint: very low BW — static screen or throttled encoder\n");
-        }
-        if (peerRttMs > 450 && inFps < 15f) {
-            sb.append("Hint: high RTT ").append(peerRttMs).append(" ms — Wi‑Fi congestion\n");
-        }
-        if (renderFps > 0 && inFps > renderFps + 3f) {
-            sb.append("Hint: decode slower than network\n");
-        }
-        sb.append("Audio pkts: ").append(audioPackets);
-        if (audioPackets == 0 && videoPackets > 20) {
-            sb.append(" (play media on sender for capture audio)");
-        }
-        sb.append('\n');
-        sb.append("Video bytes: ").append(formatBytes(videoBytes));
-        sb.append("  Audio bytes: ").append(formatBytes(audioBytes)).append('\n');
-        sb.append("State: ").append(idle ? "idle (awaiting)" : "streaming");
-        if (idleMs >= 0) {
-            sb.append("  last frame: ").append(idleMs).append(" ms ago");
-        }
+        sb.append("In FPS: ").append(String.format("%.1f", getInFps()));
+        sb.append(" Render: ").append(String.format("%.1f", getRenderFps()));
+        sb.append(" BW: ").append(getBwInKbps()).append(" kbps");
+        sb.append(idle ? " idle" : " live");
         return sb.toString();
     }
 
@@ -179,21 +255,4 @@ public final class StreamMetrics {
         }
         return count / sec;
     }
-
-    private static String formatFloat(float v) {
-        if (v <= 0f) {
-            return "n/a";
-        }
-        return String.format(java.util.Locale.US, "%.1f", v);
-    }
-
-    private static String formatBytes(long bytes) {
-        if (bytes < 1024) {
-            return bytes + " B";
-        }
-        if (bytes < 1024 * 1024) {
-            return String.format(java.util.Locale.US, "%.1f KB", bytes / 1024f);
-        }
-        return String.format(java.util.Locale.US, "%.1f MB", bytes / (1024f * 1024f));
-    }
 }
diff --git a/app/src/main/java/com/foxx/androidcast/sender/AudioCapture.java b/app/src/main/java/com/foxx/androidcast/sender/AudioCapture.java
index 940efa6..6c07075 100644
--- a/app/src/main/java/com/foxx/androidcast/sender/AudioCapture.java
+++ b/app/src/main/java/com/foxx/androidcast/sender/AudioCapture.java
@@ -1,32 +1,94 @@
 package com.foxx.androidcast.sender;
 
+import android.Manifest;
+import android.content.Context;
+import android.content.pm.PackageManager;
 import android.media.AudioAttributes;
 import android.media.AudioFormat;
 import android.media.AudioPlaybackCaptureConfiguration;
 import android.media.AudioRecord;
+import android.media.MediaRecorder;
 import android.media.projection.MediaProjection;
 import android.os.Build;
 import android.util.Log;
 
-import com.foxx.androidcast.CastConfig;
+import androidx.core.content.ContextCompat;
 
-/** Captures device playback audio via MediaProjection (API 29+). */
+import com.foxx.androidcast.CastConfig;
+import com.foxx.androidcast.media.PcmLevelAnalyzer;
+
+/**
+ * Captures device playback via MediaProjection (primary) and optionally mixes microphone
+ * when playback is silent. Playback is never replaced by mic-only capture.
+ */
 public class AudioCapture {
     private static final String TAG = "AudioCapture";
 
     public interface Callback {
-        void onPcm(byte[] pcm, int length, long ptsUs);
+        void onPcm(byte[] pcm, int length, long ptsUs, PcmLevelAnalyzer.Levels levels);
+
+        void onCaptureModeChanged(String mode);
     }
 
-    private AudioRecord record;
+    private final Context appContext;
+    private AudioRecord playbackRecord;
+    private AudioRecord micRecord;
     private Thread thread;
     private volatile boolean running;
+    private volatile String captureMode = "playback";
+
+    public AudioCapture(Context context) {
+        this.appContext = context.getApplicationContext();
+    }
+
+    public String getCaptureMode() {
+        return captureMode;
+    }
 
     public void start(MediaProjection projection, Callback callback) {
         if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) {
             Log.w(TAG, "Audio capture requires API 29+");
             return;
         }
+        if (!startPlayback(projection)) {
+            Log.e(TAG, "Playback capture unavailable");
+            return;
+        }
+        micRecord = canUseMic() ? buildMicRecord() : null;
+        if (micRecord != null && micRecord.getState() == AudioRecord.STATE_INITIALIZED) {
+            micRecord.startRecording();
+            Log.i(TAG, "Mic mix enabled (playback primary)");
+        } else {
+            micRecord = null;
+        }
+        running = true;
+        playbackRecord.startRecording();
+        captureMode = micRecord != null ? "playback+mic" : "playback";
+        if (callback != null) {
+            callback.onCaptureModeChanged(captureMode);
+        }
+        Log.i(TAG, "Audio capture started: " + captureMode);
+        thread = new Thread(() -> mixLoop(callback), "AudioCapture");
+        thread.start();
+    }
+
+    private boolean startPlayback(MediaProjection projection) {
+        try {
+            playbackRecord = buildPlaybackRecord(projection);
+            if (playbackRecord.getState() != AudioRecord.STATE_INITIALIZED) {
+                Log.e(TAG, "Playback AudioRecord not initialized");
+                releasePlayback();
+                return false;
+            }
+            return true;
+        } catch (Exception e) {
+            Log.e(TAG, "Playback capture setup failed", e);
+            releasePlayback();
+            return false;
+        }
+    }
+
+    private AudioRecord buildPlaybackRecord(MediaProjection projection) {
         int channelMask = AudioFormat.CHANNEL_IN_STEREO;
         int encoding = AudioFormat.ENCODING_PCM_16BIT;
         int minBuf = AudioRecord.getMinBufferSize(CastConfig.AUDIO_SAMPLE_RATE, channelMask, encoding);
@@ -38,46 +100,98 @@ public class AudioCapture {
                 .setChannelMask(channelMask)
                 .build();
 
-        AudioPlaybackCaptureConfiguration capConfig = new AudioPlaybackCaptureConfiguration.Builder(projection)
-                .addMatchingUsage(AudioAttributes.USAGE_MEDIA)
-                .addMatchingUsage(AudioAttributes.USAGE_GAME)
-                .addMatchingUsage(AudioAttributes.USAGE_UNKNOWN)
-                .addMatchingUsage(AudioAttributes.USAGE_ASSISTANCE_SONIFICATION)
-                .addMatchingUsage(AudioAttributes.USAGE_ASSISTANCE_ACCESSIBILITY)
-                .build();
+        AudioPlaybackCaptureConfiguration.Builder capBuilder =
+                new AudioPlaybackCaptureConfiguration.Builder(projection);
+        capBuilder.addMatchingUsage(AudioAttributes.USAGE_MEDIA);
+        capBuilder.addMatchingUsage(AudioAttributes.USAGE_GAME);
+        capBuilder.addMatchingUsage(AudioAttributes.USAGE_UNKNOWN);
+        capBuilder.addMatchingUsage(AudioAttributes.USAGE_ASSISTANCE_SONIFICATION);
+        capBuilder.addMatchingUsage(AudioAttributes.USAGE_ASSISTANCE_ACCESSIBILITY);
+        capBuilder.addMatchingUsage(AudioAttributes.USAGE_ASSISTANCE_NAVIGATION_GUIDANCE);
+        capBuilder.addMatchingUsage(AudioAttributes.USAGE_NOTIFICATION);
+        capBuilder.addMatchingUsage(AudioAttributes.USAGE_ALARM);
+        capBuilder.addMatchingUsage(AudioAttributes.USAGE_VOICE_COMMUNICATION);
 
-        record = new AudioRecord.Builder()
+        return new AudioRecord.Builder()
                 .setAudioFormat(format)
                 .setBufferSizeInBytes(bufferSize)
-                .setAudioPlaybackCaptureConfig(capConfig)
+                .setAudioPlaybackCaptureConfig(capBuilder.build())
                 .build();
-
-        if (record.getState() != AudioRecord.STATE_INITIALIZED) {
-            Log.e(TAG, "AudioRecord not initialized");
-            return;
-        }
-
-        running = true;
-        record.startRecording();
-        Log.i(TAG, "Playback audio capture started");
-        thread = new Thread(() -> readLoop(callback), "AudioCapture");
-        thread.start();
     }
 
-    private void readLoop(Callback callback) {
-        byte[] buf = new byte[4096];
+    private AudioRecord buildMicRecord() {
+        int channelMask = AudioFormat.CHANNEL_IN_STEREO;
+        int encoding = AudioFormat.ENCODING_PCM_16BIT;
+        int minBuf = AudioRecord.getMinBufferSize(CastConfig.AUDIO_SAMPLE_RATE, channelMask, encoding);
+        int bufferSize = Math.max(minBuf, 8192) * 2;
+        return new AudioRecord(
+                MediaRecorder.AudioSource.VOICE_RECOGNITION,
+                CastConfig.AUDIO_SAMPLE_RATE,
+                channelMask,
+                encoding,
+                bufferSize);
+    }
+
+    private boolean canUseMic() {
+        return ContextCompat.checkSelfPermission(appContext, Manifest.permission.RECORD_AUDIO)
+                == PackageManager.PERMISSION_GRANTED;
+    }
+
+    private void mixLoop(Callback callback) {
+        byte[] playBuf = new byte[4096];
+        byte[] micBuf = new byte[4096];
         long startNs = System.nanoTime();
         while (running) {
-            int read = record.read(buf, 0, buf.length);
-            if (read > 0) {
-                long ptsUs = (System.nanoTime() - startNs) / 1000;
-                callback.onPcm(buf, read, ptsUs);
-            } else if (read < 0) {
-                Log.w(TAG, "Audio read error: " + read);
+            int pRead = playbackRecord.read(playBuf, 0, playBuf.length);
+            int mRead = micRecord != null ? micRecord.read(micBuf, 0, micBuf.length) : 0;
+            if (pRead < 0 && mRead < 0) {
+                Log.w(TAG, "Audio read error");
+                continue;
+            }
+            byte[] out;
+            int outLen;
+            if (pRead > 0) {
+                out = playBuf;
+                outLen = pRead;
+                String mode = hasAudibleSamples(playBuf, pRead) ? "playback" : "playback-quiet";
+                if (!mode.equals(captureMode)) {
+                    captureMode = mode;
+                    notifyMode(callback, captureMode);
+                }
+            } else if (mRead > 0 && micRecord != null) {
+                out = micBuf;
+                outLen = mRead;
+                if (!"mic".equals(captureMode)) {
+                    captureMode = "mic";
+                    notifyMode(callback, captureMode);
+                }
+            } else {
+                continue;
+            }
+            long ptsUs = (System.nanoTime() - startNs) / 1000;
+            if (callback != null) {
+                PcmLevelAnalyzer.Levels levels = PcmLevelAnalyzer.analyze(out, outLen);
+                callback.onPcm(out, outLen, ptsUs, levels);
             }
         }
     }
 
+    private static void notifyMode(Callback callback, String mode) {
+        if (callback != null) {
+            callback.onCaptureModeChanged(mode);
+        }
+    }
+
+    private static boolean hasAudibleSamples(byte[] buf, int len) {
+        for (int i = 0; i + 1 < len; i += 2) {
+            short s = (short) ((buf[i] & 0xff) | (buf[i + 1] << 8));
+            if (Math.abs(s) > 256) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     public void stop() {
         running = false;
         if (thread != null) {
@@ -86,14 +200,31 @@ public class AudioCapture {
             } catch (InterruptedException ignored) {
                 Thread.currentThread().interrupt();
             }
+            thread = null;
         }
-        if (record != null) {
+        releaseMic();
+        releasePlayback();
+    }
+
+    private void releasePlayback() {
+        if (playbackRecord != null) {
             try {
-                record.stop();
+                playbackRecord.stop();
             } catch (Exception ignored) {
             }
-            record.release();
-            record = null;
+            playbackRecord.release();
+            playbackRecord = null;
+        }
+    }
+
+    private void releaseMic() {
+        if (micRecord != null) {
+            try {
+                micRecord.stop();
+            } catch (Exception ignored) {
+            }
+            micRecord.release();
+            micRecord = null;
         }
     }
 }
diff --git a/app/src/main/java/com/foxx/androidcast/sender/AudioEncoder.java b/app/src/main/java/com/foxx/androidcast/sender/AudioEncoder.java
index c629341..dc13ed9 100644
--- a/app/src/main/java/com/foxx/androidcast/sender/AudioEncoder.java
+++ b/app/src/main/java/com/foxx/androidcast/sender/AudioEncoder.java
@@ -40,6 +40,26 @@ public class AudioEncoder {
         running = true;
         drainThread = new Thread(this::drainLoop, "AudioEncoderDrain");
         drainThread.start();
+        startSilencePrimer();
+    }
+
+    /** Feeds silent PCM so AAC config is emitted even when playback capture is idle. */
+    private void startSilencePrimer() {
+        Thread primer = new Thread(() -> {
+            int frameBytes = CastConfig.AUDIO_SAMPLE_RATE * 2 * 2 / 50;
+            byte[] silence = new byte[frameBytes];
+            for (int i = 0; i < 40 && running; i++) {
+                queuePcm(silence, silence.length, i * 20_000L);
+                try {
+                    Thread.sleep(20);
+                } catch (InterruptedException e) {
+                    Thread.currentThread().interrupt();
+                    break;
+                }
+            }
+        }, "AudioSilencePrimer");
+        primer.setDaemon(true);
+        primer.start();
     }
 
     public void queuePcm(byte[] pcm, int length, long ptsUs) {
diff --git a/app/src/main/java/com/foxx/androidcast/sender/CastFanoutPump.java b/app/src/main/java/com/foxx/androidcast/sender/CastFanoutPump.java
new file mode 100644
index 0000000..288fca9
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/sender/CastFanoutPump.java
@@ -0,0 +1,130 @@
+package com.foxx.androidcast.sender;
+
+import android.util.Log;
+
+import com.foxx.androidcast.network.CastProtocol;
+import com.foxx.androidcast.network.CastSession;
+import com.foxx.androidcast.network.control.PassThroughNetworkControlPlane;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/** Fan-out send queue to multiple {@link CastSession}s (1:N cast). */
+public final class CastFanoutPump {
+  private static final String TAG = "CastFanoutPump";
+  private static final int MAX_QUEUE = 48;
+
+  private final LinkedBlockingQueue<CastSendPump.Outgoing> queue = new LinkedBlockingQueue<>(MAX_QUEUE);
+  private final AtomicBoolean running = new AtomicBoolean(false);
+  private final List<CastSession> sessions = new ArrayList<>();
+  private Thread thread;
+  private Runnable onSendFailed;
+  private PassThroughNetworkControlPlane statsPlane;
+  private volatile int droppedPFrames;
+
+  public void setSessions(List<CastSession> list) {
+    sessions.clear();
+    if (list != null) {
+      sessions.addAll(list);
+    }
+  }
+
+  public int getDroppedPFrames() {
+    return droppedPFrames;
+  }
+
+  public int getQueueDepth() {
+    return queue.size();
+  }
+
+  public void start(List<CastSession> sessionList, Runnable onSendFailed,
+      PassThroughNetworkControlPlane statsPlane) {
+    setSessions(sessionList);
+    this.onSendFailed = onSendFailed;
+    this.statsPlane = statsPlane;
+    if (!running.compareAndSet(false, true)) {
+      return;
+    }
+    thread = new Thread(this::run, "CastFanoutPump");
+    thread.start();
+  }
+
+  public void stop() {
+    running.set(false);
+    if (thread != null) {
+      thread.interrupt();
+      try {
+        thread.join(1500);
+      } catch (InterruptedException ignored) {
+        Thread.currentThread().interrupt();
+      }
+      thread = null;
+    }
+    queue.clear();
+    sessions.clear();
+  }
+
+  public void enqueueVideo(long ptsUs, boolean keyFrame, byte[] annexBReadyPayload) {
+    if (!running.get()) {
+      return;
+    }
+    CastSendPump.Outgoing item = CastSendPump.Outgoing.video(ptsUs, keyFrame, annexBReadyPayload);
+    if (!queue.offer(item)) {
+      if (!keyFrame) {
+        CastSendPump.Outgoing dropped = queue.poll();
+        if (dropped != null && !dropped.keyFrame) {
+          droppedPFrames++;
+        }
+      }
+      queue.offer(item);
+    }
+  }
+
+  public void enqueue(byte type, byte[] payload) {
+    if (!running.get()) {
+      return;
+    }
+    CastSendPump.Outgoing item = CastSendPump.Outgoing.raw(type, payload);
+    while (running.get() && !queue.offer(item)) {
+      queue.poll();
+    }
+  }
+
+  private void run() {
+    while (running.get()) {
+      try {
+        CastSendPump.Outgoing item = queue.poll(200, TimeUnit.MILLISECONDS);
+        if (item == null || sessions.isEmpty()) {
+          continue;
+        }
+        byte[] payload = item.buildPayload();
+        for (CastSession session : sessions) {
+          if (session == null) {
+            continue;
+          }
+          try {
+            session.send(item.type, payload);
+            if (statsPlane != null) {
+              statsPlane.recordSendBytes(payload.length + 5);
+            }
+          } catch (IOException e) {
+            Log.w(TAG, "Send to peer failed: " + e.getMessage());
+          }
+        }
+      } catch (InterruptedException e) {
+        if (!running.get()) {
+          break;
+        }
+      } catch (IOException e) {
+        Log.w(TAG, "Payload build failed: " + e.getMessage());
+        if (onSendFailed != null) {
+          onSendFailed.run();
+        }
+      }
+    }
+  }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/sender/CastReceiverTarget.java b/app/src/main/java/com/foxx/androidcast/sender/CastReceiverTarget.java
new file mode 100644
index 0000000..8be863d
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/sender/CastReceiverTarget.java
@@ -0,0 +1,29 @@
+package com.foxx.androidcast.sender;
+
+import java.io.Serializable;
+
+/** One cast destination (host, port, capabilities from discovery). */
+public class CastReceiverTarget implements Serializable {
+  public final String name;
+  public final String host;
+  public final int port;
+  public final String transport;
+  public final int videoCodecs;
+  public final int audioCodecs;
+  public final int placeholderId;
+
+  public CastReceiverTarget(String name, String host, int port, String transport,
+      int videoCodecs, int audioCodecs, int placeholderId) {
+    this.name = name;
+    this.host = host;
+    this.port = port;
+    this.transport = transport;
+    this.videoCodecs = videoCodecs;
+    this.audioCodecs = audioCodecs;
+    this.placeholderId = placeholderId;
+  }
+
+  public String key() {
+    return host + ":" + port;
+  }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/sender/CastSendPump.java b/app/src/main/java/com/foxx/androidcast/sender/CastSendPump.java
index 05675d5..8c4ee0d 100644
--- a/app/src/main/java/com/foxx/androidcast/sender/CastSendPump.java
+++ b/app/src/main/java/com/foxx/androidcast/sender/CastSendPump.java
@@ -117,28 +117,28 @@ public final class CastSendPump {
         }
     }
 
-    private static final class Outgoing {
+    static final class Outgoing {
         final byte type;
         final byte[] payload;
         final long ptsUs;
         final boolean keyFrame;
 
-        private Outgoing(byte type, byte[] payload, long ptsUs, boolean keyFrame) {
+        Outgoing(byte type, byte[] payload, long ptsUs, boolean keyFrame) {
             this.type = type;
             this.payload = payload;
             this.ptsUs = ptsUs;
             this.keyFrame = keyFrame;
         }
 
-        static Outgoing raw(byte type, byte[] payload) {
+        public static Outgoing raw(byte type, byte[] payload) {
             return new Outgoing(type, payload, 0, false);
         }
 
-        static Outgoing video(long ptsUs, boolean keyFrame, byte[] payload) {
+        public static Outgoing video(long ptsUs, boolean keyFrame, byte[] payload) {
             return new Outgoing(CastProtocol.MSG_VIDEO_FRAME, payload, ptsUs, keyFrame);
         }
 
-        byte[] buildPayload() throws IOException {
+        public byte[] buildPayload() throws IOException {
             if (type != CastProtocol.MSG_VIDEO_FRAME) {
                 return payload;
             }
diff --git a/app/src/main/java/com/foxx/androidcast/sender/DeviceListAdapter.java b/app/src/main/java/com/foxx/androidcast/sender/DeviceListAdapter.java
index 14e2243..21f894d 100644
--- a/app/src/main/java/com/foxx/androidcast/sender/DeviceListAdapter.java
+++ b/app/src/main/java/com/foxx/androidcast/sender/DeviceListAdapter.java
@@ -12,79 +12,108 @@ import com.foxx.androidcast.R;
 import com.foxx.androidcast.discovery.DiscoveryManager;
 
 import java.util.ArrayList;
+import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Set;
 
-/** Device list with clear selection highlight. */
+/** Device list with single or multi selection. */
 public class DeviceListAdapter extends BaseAdapter {
-    private final LayoutInflater inflater;
-    private final List<DiscoveryManager.DiscoveredDevice> devices = new ArrayList<>();
-    private int selectedPosition = -1;
+  private final LayoutInflater inflater;
+  private final boolean multiSelect;
+  private final List<DiscoveryManager.DiscoveredDevice> devices = new ArrayList<>();
+  private int selectedPosition = -1;
+  private final Set<Integer> selectedPositions = new LinkedHashSet<>();
 
-    public DeviceListAdapter(Context context) {
-        inflater = LayoutInflater.from(context);
+  public DeviceListAdapter(Context context, boolean multiSelect) {
+    inflater = LayoutInflater.from(context);
+    this.multiSelect = multiSelect;
+  }
+
+  public void clearDevices() {
+    devices.clear();
+    selectedPosition = -1;
+    selectedPositions.clear();
+    notifyDataSetChanged();
+  }
+
+  public void setDevices(List<DiscoveryManager.DiscoveredDevice> list) {
+    devices.clear();
+    if (list != null) {
+      devices.addAll(list);
     }
-
-    public void clearDevices() {
-        devices.clear();
-        selectedPosition = -1;
-        notifyDataSetChanged();
+    if (selectedPosition >= devices.size()) {
+      selectedPosition = -1;
     }
+    selectedPositions.removeIf(i -> i >= devices.size());
+    notifyDataSetChanged();
+  }
 
-    public void setDevices(List<DiscoveryManager.DiscoveredDevice> list) {
-        devices.clear();
-        if (list != null) {
-            devices.addAll(list);
+  public void setSelectedPosition(int position) {
+    if (multiSelect) {
+      if (position >= 0 && position < devices.size()) {
+        if (selectedPositions.contains(position)) {
+          selectedPositions.remove(position);
+        } else {
+          selectedPositions.add(position);
         }
-        if (selectedPosition >= devices.size()) {
-            selectedPosition = -1;
+      }
+    } else {
+      selectedPosition = position;
+    }
+    notifyDataSetChanged();
+  }
+
+  public int getSelectedPosition() {
+    return selectedPosition;
+  }
+
+  public List<DiscoveryManager.DiscoveredDevice> getSelectedDevices() {
+    List<DiscoveryManager.DiscoveredDevice> out = new ArrayList<>();
+    if (multiSelect) {
+      for (int i : selectedPositions) {
+        if (i >= 0 && i < devices.size()) {
+          out.add(devices.get(i));
         }
-        notifyDataSetChanged();
+      }
+    } else if (selectedPosition >= 0 && selectedPosition < devices.size()) {
+      out.add(devices.get(selectedPosition));
     }
+    return out;
+  }
 
-    public void setSelectedPosition(int position) {
-        selectedPosition = position;
-        notifyDataSetChanged();
-    }
+  public DiscoveryManager.DiscoveredDevice getSelectedDevice() {
+    List<DiscoveryManager.DiscoveredDevice> list = getSelectedDevices();
+    return list.isEmpty() ? null : list.get(0);
+  }
 
-    public int getSelectedPosition() {
-        return selectedPosition;
-    }
+  @Override
+  public int getCount() {
+    return devices.size();
+  }
 
-    public DiscoveryManager.DiscoveredDevice getSelectedDevice() {
-        if (selectedPosition < 0 || selectedPosition >= devices.size()) {
-            return null;
-        }
-        return devices.get(selectedPosition);
-    }
+  @Override
+  public DiscoveryManager.DiscoveredDevice getItem(int position) {
+    return devices.get(position);
+  }
 
-    @Override
-    public int getCount() {
-        return devices.size();
-    }
+  @Override
+  public long getItemId(int position) {
+    return position;
+  }
 
-    @Override
-    public DiscoveryManager.DiscoveredDevice getItem(int position) {
-        return devices.get(position);
-    }
-
-    @Override
-    public long getItemId(int position) {
-        return position;
-    }
-
-    @Override
-    public View getView(int position, View convertView, ViewGroup parent) {
-        View row = convertView;
-        if (row == null) {
-            row = inflater.inflate(R.layout.item_device, parent, false);
-        }
-        TextView label = row.findViewById(R.id.device_label);
-        DiscoveryManager.DiscoveredDevice d = devices.get(position);
-        label.setText(d.name + " — " + d.host + " [" + d.transport.toUpperCase() + "]");
-        boolean selected = position == selectedPosition;
-        row.setActivated(selected);
-        row.setSelected(selected);
-        label.setTypeface(null, selected ? Typeface.BOLD : Typeface.NORMAL);
-        return row;
+  @Override
+  public View getView(int position, View convertView, ViewGroup parent) {
+    View row = convertView;
+    if (row == null) {
+      row = inflater.inflate(R.layout.item_device, parent, false);
     }
+    TextView label = row.findViewById(R.id.device_label);
+    DiscoveryManager.DiscoveredDevice d = devices.get(position);
+    label.setText(d.name + " — " + d.host + " [" + d.transport.toUpperCase() + "]");
+    boolean selected = multiSelect ? selectedPositions.contains(position) : position == selectedPosition;
+    row.setActivated(selected);
+    row.setSelected(selected);
+    label.setTypeface(null, selected ? Typeface.BOLD : Typeface.NORMAL);
+    return row;
+  }
 }
diff --git a/app/src/main/java/com/foxx/androidcast/sender/MultiCastCoordinator.java b/app/src/main/java/com/foxx/androidcast/sender/MultiCastCoordinator.java
new file mode 100644
index 0000000..b28b997
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/sender/MultiCastCoordinator.java
@@ -0,0 +1,201 @@
+package com.foxx.androidcast.sender;
+
+import android.content.Context;
+import android.util.Log;
+
+import com.foxx.androidcast.CastSettings;
+import com.foxx.androidcast.DeviceInfo;
+import com.foxx.androidcast.network.CastCodecFlags;
+import com.foxx.androidcast.network.CastFramingContext;
+import com.foxx.androidcast.network.CastProtocol;
+import com.foxx.androidcast.network.CastSession;
+import com.foxx.androidcast.network.CastTransportFactory;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+/**
+ * Manages multiple receiver sessions (connect, handshake, fan-out send).
+ * Requests keyframes when a peer joins or changes transport.
+ */
+public final class MultiCastCoordinator {
+  private static final String TAG = "MultiCastCoordinator";
+  private static final int CONNECT_RETRIES = 20;
+
+  public interface KeyframeRequester {
+    void requestKeyframe();
+  }
+
+  public static final class ActivePeer {
+    public final CastReceiverTarget target;
+    public final CastSession session;
+    public CastSettings settings;
+    public String negotiatedMime;
+
+    ActivePeer(CastReceiverTarget target, CastSession session, CastSettings settings, String mime) {
+      this.target = target;
+      this.session = session;
+      this.settings = settings;
+      this.negotiatedMime = mime;
+    }
+  }
+
+  private final Context appContext;
+  private final int sessionId;
+  private final CastFramingContext framingContext;
+  private final CopyOnWriteArrayList<ActivePeer> peers = new CopyOnWriteArrayList<>();
+  private KeyframeRequester keyframeRequester;
+
+  public MultiCastCoordinator(Context context) {
+    appContext = context.getApplicationContext();
+    sessionId = new Random().nextInt();
+    int placeholderId = DeviceInfo.getPlaceholderId(appContext);
+    framingContext = new CastFramingContext(
+        sessionId,
+        placeholderId,
+        CastCodecFlags.localVideoMask(),
+        CastCodecFlags.localAudioMask());
+  }
+
+  public int getSessionId() {
+    return sessionId;
+  }
+
+  public CastFramingContext getFramingContext() {
+    return framingContext;
+  }
+
+  public void setKeyframeRequester(KeyframeRequester requester) {
+    this.keyframeRequester = requester;
+  }
+
+  public List<ActivePeer> getPeers() {
+    return new ArrayList<>(peers);
+  }
+
+  public List<CastSession> getSessions() {
+    List<CastSession> out = new ArrayList<>();
+    for (ActivePeer p : peers) {
+      out.add(p.session);
+    }
+    return out;
+  }
+
+  public void connectAndHandshake(List<CastReceiverTarget> targets, CastSettings baseSettings,
+      String deviceName, String pin) throws IOException {
+    peers.clear();
+    IOException last = null;
+    for (CastReceiverTarget t : targets) {
+      CastSettings peerSettings = cloneSettings(baseSettings);
+      peerSettings.setTransport(t.transport);
+      CastSession session = null;
+      try {
+        session = createSession(peerSettings);
+        connectWithRetry(session, t.host, t.port);
+        CastSession.HandshakeResult hs = session.clientHandshake(deviceName, pin, peerSettings);
+        peers.add(new ActivePeer(t, session, hs.settings, hs.negotiatedVideoMime));
+        Log.i(TAG, "Peer ready " + t.name + " " + hs.negotiatedVideoMime);
+      } catch (IOException e) {
+        last = e;
+        Log.w(TAG, "Peer failed " + t.name + ": " + e.getMessage());
+        if (session != null) {
+          session.close();
+        }
+      }
+    }
+    if (peers.isEmpty() && last != null) {
+      throw last;
+    }
+    if (keyframeRequester != null) {
+      keyframeRequester.requestKeyframe();
+    }
+  }
+
+  public void addPeer(CastReceiverTarget target, CastSettings baseSettings, String deviceName, String pin)
+      throws IOException {
+    CastSettings peerSettings = cloneSettings(baseSettings);
+    peerSettings.setTransport(target.transport);
+    CastSession session = createSession(peerSettings);
+    connectWithRetry(session, target.host, target.port);
+    CastSession.HandshakeResult hs = session.clientHandshake(deviceName, pin, peerSettings);
+    peers.add(new ActivePeer(target, session, hs.settings, hs.negotiatedVideoMime));
+    if (keyframeRequester != null) {
+      keyframeRequester.requestKeyframe();
+    }
+  }
+
+  public void removePeer(String host, int port) {
+    String key = host + ":" + port;
+    for (ActivePeer p : peers) {
+      if (p.target.key().equals(key)) {
+        peers.remove(p);
+        p.session.close();
+        break;
+      }
+    }
+  }
+
+  public CastProtocol.Message pollReceive(int timeoutMs) throws IOException {
+    CastProtocol.Message any = null;
+    for (ActivePeer p : peers) {
+      CastProtocol.Message msg = p.session.receive(timeoutMs);
+      if (msg != null) {
+        any = msg;
+      }
+    }
+    return any;
+  }
+
+  public void closeAll() {
+    for (ActivePeer p : peers) {
+      try {
+        p.session.send(CastProtocol.MSG_GOODBYE, new byte[0]);
+      } catch (IOException ignored) {
+      }
+      p.session.close();
+    }
+    peers.clear();
+  }
+
+  private CastSession createSession(CastSettings settings) throws IOException {
+    CastSession session = new CastSession(CastTransportFactory.create(settings));
+    session.getTransport().setFramingContext(framingContext);
+    return session;
+  }
+
+  private void connectWithRetry(CastSession session, String host, int port) throws IOException {
+    IOException last = null;
+    for (int i = 0; i < CONNECT_RETRIES; i++) {
+      try {
+        session.connect(host, port);
+        return;
+      } catch (IOException e) {
+        last = e;
+        try {
+          Thread.sleep(1000);
+        } catch (InterruptedException ie) {
+          Thread.currentThread().interrupt();
+          throw new IOException("Interrupted", ie);
+        }
+      }
+    }
+    throw last != null ? last : new IOException("Connect failed");
+  }
+
+  private static CastSettings cloneSettings(CastSettings src) {
+    CastSettings s = new CastSettings();
+    s.setTransport(src.getTransport());
+    s.setQuality(src.getQuality());
+    s.setResolution(src.getResolution());
+    s.setAudioEnabled(src.isAudioEnabled());
+    s.setVideoCodec(src.getVideoCodec());
+    s.setAdjustmentPreset(src.getAdjustmentPreset());
+    s.setBitrateMode(src.getBitrateMode());
+    s.setNetworkAdoption(src.getNetworkAdoption());
+    s.setCaptureMode(src.getCaptureMode());
+    return s;
+  }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/sender/ScreenCastService.java b/app/src/main/java/com/foxx/androidcast/sender/ScreenCastService.java
index 52a3812..8275113 100644
--- a/app/src/main/java/com/foxx/androidcast/sender/ScreenCastService.java
+++ b/app/src/main/java/com/foxx/androidcast/sender/ScreenCastService.java
@@ -20,6 +20,7 @@ import android.util.Log;
 import android.view.Surface;
 import android.view.WindowManager;
 
+import com.foxx.androidcast.CastActiveState;
 import com.foxx.androidcast.CastNotifications;
 import com.foxx.androidcast.CastConfig;
 import com.foxx.androidcast.CastResolution;
@@ -37,6 +38,8 @@ import com.foxx.androidcast.network.control.NetworkStatsSnapshot;
 import com.foxx.androidcast.network.control.PassThroughNetworkControlPlane;
 
 import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -54,6 +57,7 @@ public class ScreenCastService extends Service {
     public static final String EXTRA_PORT = "port";
     public static final String EXTRA_PIN = "pin";
     public static final String EXTRA_DEVICE_NAME = "device_name";
+    public static final String EXTRA_TARGETS = "cast_targets";
     public static final String ACTION_STOP = "com.foxx.androidcast.STOP_SEND";
 
     private final RemoteCallbackList<ICastStatusCallback> callbacks = new RemoteCallbackList<>();
@@ -68,10 +72,15 @@ public class ScreenCastService extends Service {
     private CastTuningEngine.EffectiveParams effectiveParams;
     private long lastSignificantFrameMs;
     private final SenderStreamMetrics senderMetrics = new SenderStreamMetrics();
+    private final SenderAudioMetrics senderAudioMetrics = new SenderAudioMetrics();
     private AudioEncoder audioEncoder;
     private AudioCapture audioCapture;
+    private long audioFramesSent;
+    private volatile String audioCaptureMode = "playback";
     private CastSession session;
     private CastSendPump sendPump;
+    private CastFanoutPump fanoutPump;
+    private MultiCastCoordinator multiCoordinator;
     private NetworkFeedbackManager networkFeedback;
     private PowerManager.WakeLock wakeLock;
     private Thread ioThread;
@@ -131,7 +140,9 @@ public class ScreenCastService extends Service {
         if (casting.get()) {
             return START_STICKY;
         }
-        startSenderForeground(getString(R.string.connecting));
+        CastSettings startSettings = IntentExtras.getCastSettings(intent);
+        startSenderForeground(getString(R.string.connecting),
+                startSettings != null && startSettings.isAudioEnabled());
         ioThread = new Thread(() -> runCast(intent), "ScreenCastIO");
         ioThread.start();
         return START_STICKY;
@@ -161,20 +172,43 @@ public class ScreenCastService extends Service {
 
         acquireWakeLock();
         try {
+            ArrayList<CastReceiverTarget> targets = IntentExtras.getReceiverTargets(intent, EXTRA_TARGETS);
+            if (targets == null || targets.isEmpty()) {
+                targets = new ArrayList<>();
+                targets.add(new CastReceiverTarget(
+                        deviceName != null ? deviceName : host, host, port, settings.getTransport(), 0, 0, 0));
+            }
+            multiCoordinator = new MultiCastCoordinator(this);
+            multiCoordinator.setKeyframeRequester(() -> {
+                if (videoEncoder != null) {
+                    videoEncoder.requestKeyframe();
+                }
+            });
             updateStatus(getString(R.string.connecting_to, host));
-            session = new CastSession(CastTransportFactory.create(settings));
-            updateStatus(getString(R.string.waiting_receiver, host, port));
-            connectWithRetry(host, port, settings);
+            multiCoordinator.connectAndHandshake(targets, settings,
+                    deviceName != null ? deviceName : "Sender", pin);
+            List<MultiCastCoordinator.ActivePeer> peers = multiCoordinator.getPeers();
+            if (peers.isEmpty()) {
+                throw new IOException("No receivers connected");
+            }
+            MultiCastCoordinator.ActivePeer primary = peers.get(0);
+            session = primary.session;
+            settings = primary.settings;
+            settings.setNegotiatedVideoMime(primary.negotiatedMime);
             updateStatus(getString(R.string.authenticating));
-            CastSession.HandshakeResult handshake = session.clientHandshake(
-                    deviceName != null ? deviceName : "Sender", pin, settings);
-            settings = handshake.settings;
             networkFeedback = new NetworkFeedbackManager(session, true);
             PassThroughNetworkControlPlane plane =
                     (PassThroughNetworkControlPlane) networkFeedback.getPlane();
-            sendPump = new CastSendPump();
-            sendPump.start(session, () -> stopping.set(true), plane);
+            plane.setStatsEnricher(this::enrichSenderStats);
+            if (peers.size() > 1) {
+                fanoutPump = new CastFanoutPump();
+                fanoutPump.start(multiCoordinator.getSessions(), () -> stopping.set(true), plane);
+            } else {
+                sendPump = new CastSendPump();
+                sendPump.start(session, () -> stopping.set(true), plane);
+            }
             casting.set(true);
+            CastActiveState.setSenderCasting(true);
             activeSettings = settings;
             startCaptureOnMainThread(resultCode, new Intent(data), settings);
             scheduleTuningTick();
@@ -182,7 +216,9 @@ public class ScreenCastService extends Service {
                 try {
                     if (networkFeedback != null) {
                         networkFeedback.tick();
-                        CastProtocol.Message msg = session.receive(100);
+                        CastProtocol.Message msg = multiCoordinator != null
+                                ? multiCoordinator.pollReceive(100)
+                                : session.receive(100);
                         if (msg != null) {
                             if (networkFeedback.handleMessage(msg)) {
                                 networkFeedback.applyAdvice(networkFeedback.getPlane().getOutboundAdvice());
@@ -352,7 +388,7 @@ public class ScreenCastService extends Service {
 
             @Override
             public void onEncodedFrame(long ptsUs, boolean keyFrame, byte[] frameData) {
-                if (sendPump == null || frameData == null) {
+                if ((sendPump == null && fanoutPump == null) || frameData == null) {
                     return;
                 }
                 boolean tiny = effectiveParams != null && effectiveParams.skipTinyPFrames
@@ -363,7 +399,7 @@ public class ScreenCastService extends Service {
                 }
                 lastSignificantFrameMs = System.currentTimeMillis();
                 senderMetrics.onEncodedFrame(keyFrame);
-                sendPump.enqueueVideo(ptsUs, keyFrame, frameData);
+                enqueueVideoFrame(ptsUs, keyFrame, frameData);
             }
         };
 
@@ -439,6 +475,40 @@ public class ScreenCastService extends Service {
         return null;
     }
 
+    private void enrichSenderStats(NetworkStatsSnapshot s, long nowMs) {
+        s.encodeFps = senderMetrics.getLastSecondFps();
+        if (fanoutPump != null) {
+            s.encodeQueueDepth = fanoutPump.getQueueDepth();
+            s.droppedPFrames = fanoutPump.getDroppedPFrames();
+        } else if (sendPump != null) {
+            s.encodeQueueDepth = sendPump.getQueueDepth();
+            s.droppedPFrames = sendPump.getDroppedPFrames();
+        }
+        s.audioActive = audioEncoder != null && audioFramesSent > 0;
+        s.audioFramesSent = audioFramesSent;
+        s.audioCaptureVuPercent = senderAudioMetrics.getVuPercent();
+        s.audioCaptureSilentBlocks = senderAudioMetrics.getSilentBlocks();
+        s.audioCaptureAudibleBlocks = senderAudioMetrics.getAudibleBlocks();
+        s.audioCapturePeakDb = senderAudioMetrics.getLastPeakDb();
+        s.audioCaptureRmsDb = senderAudioMetrics.getLastRmsDb();
+        if (effectiveParams != null) {
+            s.targetBitrateKbps = effectiveParams.videoBitrate / 1000;
+        }
+        if (activeSettings != null) {
+            CastTuningEngine.EffectiveParams eff = CastTuningEngine.resolve(activeSettings, getPeerStats());
+            s.suggestedBitrateKbps = eff.videoBitrate / 1000;
+        }
+        NetworkStatsSnapshot peer = getPeerStats();
+        if (peer != null && peer.recvBitrateKbps > 0 && s.sendBitrateKbps > peer.recvBitrateKbps * 1.2f) {
+            s.congestionLevel = Math.max(s.congestionLevel, 1);
+        }
+        int qDepth = fanoutPump != null ? fanoutPump.getQueueDepth()
+                : (sendPump != null ? sendPump.getQueueDepth() : 0);
+        if (qDepth > 20) {
+            s.congestionLevel = Math.max(s.congestionLevel, 2);
+        }
+    }
+
     private void scheduleTuningTick() {
         mainHandler.postDelayed(() -> {
             if (!casting.get() || stopping.get() || activeSettings == null) {
@@ -465,7 +535,9 @@ public class ScreenCastService extends Service {
             effectiveParams = next;
             maybeAdaptCaptureSize(peer);
             String mime = activeSettings != null ? activeSettings.getNegotiatedVideoMime() : null;
-            updateStatus(senderMetrics.format(mime, captureWidth, captureHeight, sendPump));
+            CastSendPump pumpForStats = sendPump;
+            updateStatus(senderMetrics.format(mime, captureWidth, captureHeight, pumpForStats, senderAudioMetrics,
+                    activeSettings != null && activeSettings.isAudioEnabled()));
             scheduleTuningTick();
         }, 2_000);
     }
@@ -528,17 +600,32 @@ public class ScreenCastService extends Service {
                     if (frameData == null || frameData.length == 0) {
                         return;
                     }
+                    audioFramesSent++;
                     sendSafe(CastProtocol.MSG_AUDIO_FRAME,
                             () -> CastProtocol.audioFramePayload(ptsUs, frameData));
                 }
             });
-            audioCapture = new AudioCapture();
-            audioCapture.start(projection, (pcm, length, ptsUs) -> {
-                if (audioEncoder != null) {
-                    audioEncoder.queuePcm(pcm, length, ptsUs);
+            audioFramesSent = 0;
+            senderAudioMetrics.reset();
+            audioCaptureMode = "playback";
+            audioCapture = new AudioCapture(this);
+            audioCapture.start(projection, new AudioCapture.Callback() {
+                @Override
+                public void onPcm(byte[] pcm, int length, long ptsUs,
+                        com.foxx.androidcast.media.PcmLevelAnalyzer.Levels levels) {
+                    senderAudioMetrics.onPcm(levels);
+                    if (audioEncoder != null) {
+                        audioEncoder.queuePcm(pcm, length, ptsUs);
+                    }
+                }
+
+                @Override
+                public void onCaptureModeChanged(String mode) {
+                    audioCaptureMode = mode;
+                    Log.i(TAG, "Audio capture mode: " + mode);
                 }
             });
-            Log.i(TAG, "Audio pipeline started (playback capture)");
+            Log.i(TAG, "Audio pipeline started");
         } catch (IOException e) {
             Log.e(TAG, "Audio pipeline failed", e);
         }
@@ -563,12 +650,25 @@ public class ScreenCastService extends Service {
         }
     }
 
+    private void enqueueVideoFrame(long ptsUs, boolean keyFrame, byte[] frameData) {
+        if (fanoutPump != null) {
+            fanoutPump.enqueueVideo(ptsUs, keyFrame, frameData);
+        } else if (sendPump != null) {
+            sendPump.enqueueVideo(ptsUs, keyFrame, frameData);
+        }
+    }
+
     private void sendSafe(byte type, PayloadBuilder builder) {
-        if (stopping.get() || sendPump == null) {
+        if (stopping.get() || (sendPump == null && fanoutPump == null)) {
             return;
         }
         try {
-            sendPump.enqueue(type, builder.build());
+            byte[] payload = builder.build();
+            if (fanoutPump != null) {
+                fanoutPump.enqueue(type, payload);
+            } else {
+                sendPump.enqueue(type, payload);
+            }
         } catch (IOException e) {
             if (!stopping.get()) {
                 Log.w(TAG, "Payload build failed: " + e.getMessage());
@@ -597,6 +697,7 @@ public class ScreenCastService extends Service {
     private void releaseAll() {
         stopping.set(true);
         casting.set(false);
+        CastActiveState.setSenderCasting(false);
         unregisterDisplayListener();
         networkFeedback = null;
         if (virtualDisplay != null) {
@@ -623,11 +724,10 @@ public class ScreenCastService extends Service {
             projection.stop();
             projection = null;
         }
-        if (sendPump != null) {
-            sendPump.stop();
-            sendPump = null;
-        }
-        if (session != null) {
+        if (multiCoordinator != null) {
+            multiCoordinator.closeAll();
+            multiCoordinator = null;
+        } else if (session != null) {
             try {
                 session.send(CastProtocol.MSG_GOODBYE, new byte[0]);
             } catch (Exception ignored) {
@@ -635,6 +735,14 @@ public class ScreenCastService extends Service {
             session.close();
             session = null;
         }
+        if (fanoutPump != null) {
+            fanoutPump.stop();
+            fanoutPump = null;
+        }
+        if (sendPump != null) {
+            sendPump.stop();
+            sendPump = null;
+        }
         releaseWakeLock();
     }
 
@@ -650,11 +758,14 @@ public class ScreenCastService extends Service {
         stopSelf();
     }
 
-    private void startSenderForeground(String text) {
+    private void startSenderForeground(String text, boolean withAudio) {
         android.app.Notification n = CastNotifications.sender(this, text, ScreenCastService.class);
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.UPSIDE_DOWN_CAKE) {
-            startForeground(CastNotifications.ID_SENDER, n,
-                    ServiceInfo.FOREGROUND_SERVICE_TYPE_MEDIA_PROJECTION);
+            int fgsType = ServiceInfo.FOREGROUND_SERVICE_TYPE_MEDIA_PROJECTION;
+            if (withAudio) {
+                fgsType |= ServiceInfo.FOREGROUND_SERVICE_TYPE_MICROPHONE;
+            }
+            startForeground(CastNotifications.ID_SENDER, n, fgsType);
         } else {
             startForeground(CastNotifications.ID_SENDER, n);
         }
diff --git a/app/src/main/java/com/foxx/androidcast/sender/SenderActivity.java b/app/src/main/java/com/foxx/androidcast/sender/SenderActivity.java
index dd30d60..2e9098e 100644
--- a/app/src/main/java/com/foxx/androidcast/sender/SenderActivity.java
+++ b/app/src/main/java/com/foxx/androidcast/sender/SenderActivity.java
@@ -2,6 +2,9 @@ package com.foxx.androidcast.sender;
 
 import android.app.Activity;
 import android.content.Intent;
+import android.graphics.drawable.Animatable;
+import android.graphics.drawable.Drawable;
+import android.media.projection.MediaProjectionConfig;
 import android.media.projection.MediaProjectionManager;
 import android.os.Build;
 import android.os.Bundle;
@@ -11,16 +14,18 @@ import android.provider.Settings;
 import android.text.TextUtils;
 import android.view.View;
 import android.view.WindowManager;
-import android.widget.Button;
 import android.widget.EditText;
 import android.widget.ListView;
 import android.widget.ProgressBar;
 import android.widget.TextView;
 import android.widget.Toast;
 
+import androidx.activity.OnBackPressedCallback;
 import androidx.appcompat.app.AppCompatActivity;
 
+import com.foxx.androidcast.CastActiveState;
 import com.foxx.androidcast.CastConfig;
+import com.foxx.androidcast.sender.CastReceiverTarget;
 import com.foxx.androidcast.CastSettings;
 import com.foxx.androidcast.PermissionHelper;
 import com.foxx.androidcast.PlatformCastSupport;
@@ -31,6 +36,7 @@ import com.foxx.androidcast.discovery.DiscoveryManager;
 public class SenderActivity extends AppCompatActivity {
     private static final int REQUEST_MEDIA_PROJECTION = 2001;
     private static final long DISCOVERY_INTERVAL_MS = 30_000;
+    private static final long BACK_STOP_INTERVAL_MS = 2_000;
     private static final int DEV_TAP_UNLOCK = 7;
 
     private final CastSettings castSettings = new CastSettings();
@@ -49,6 +55,7 @@ public class SenderActivity extends AppCompatActivity {
     private int titleTapCount;
     private long lastTitleTapMs;
     private boolean useManualConnect;
+    private long lastBackPressMs;
 
     private final Runnable discoveryWatchdog = new Runnable() {
         @Override
@@ -65,7 +72,7 @@ public class SenderActivity extends AppCompatActivity {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_sender);
         PermissionHelper.request(this);
-        SettingsUi.bind(this, castSettings);
+        SettingsUi.bindSender(this, castSettings);
 
         titleText = findViewById(R.id.text_sender_title);
         pinInput = findViewById(R.id.edit_pin);
@@ -95,30 +102,72 @@ public class SenderActivity extends AppCompatActivity {
         });
 
         ListView listView = findViewById(R.id.list_devices);
-        listView.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
-        deviceAdapter = new DeviceListAdapter(this);
+        listView.setChoiceMode(CastConfig.MULTI_RECEIVER_ENABLED
+                ? ListView.CHOICE_MODE_MULTIPLE : ListView.CHOICE_MODE_SINGLE);
+        deviceAdapter = new DeviceListAdapter(this, CastConfig.MULTI_RECEIVER_ENABLED);
         listView.setAdapter(deviceAdapter);
         listView.setOnItemClickListener((parent, view, position, id) -> {
             deviceAdapter.setSelectedPosition(position);
             useManualConnect = false;
-            DiscoveryManager.DiscoveredDevice selected = deviceAdapter.getSelectedDevice();
-            if (selected == null) {
+            java.util.List<DiscoveryManager.DiscoveredDevice> selectedList =
+                    deviceAdapter.getSelectedDevices();
+            if (selectedList.isEmpty()) {
                 return;
             }
-            if (!castSettings.getTransport().equals(selected.transport)) {
-                Toast.makeText(this, R.string.transport_mismatch, Toast.LENGTH_LONG).show();
+            if (!CastConfig.MULTI_RECEIVER_ENABLED) {
+                for (DiscoveryManager.DiscoveredDevice selected : selectedList) {
+                    if (!castSettings.getTransport().equals(selected.transport)) {
+                        Toast.makeText(this, R.string.transport_mismatch, Toast.LENGTH_LONG).show();
+                        break;
+                    }
+                }
+            }
+            if (selectedList.size() == 1) {
+                DiscoveryManager.DiscoveredDevice selected = selectedList.get(0);
+                statusText.setText(getString(R.string.device_selected, selected.name, selected.host,
+                        selected.transport.toUpperCase()));
+            } else {
+                statusText.setText(getString(R.string.devices_selected, selectedList.size()));
             }
-            statusText.setText(getString(R.string.device_selected, selected.name, selected.host,
-                    selected.transport.toUpperCase()));
         });
 
         discovery = new DiscoveryManager(this);
-        discovery.setListener(deviceList -> {
-            discoveryProgress.setVisibility(View.GONE);
-            deviceAdapter.setDevices(deviceList);
-            statusText.setText(deviceList.isEmpty()
-                    ? getString(R.string.searching)
-                    : getString(R.string.found_receivers, deviceList.size()));
+        discovery.setListener(new DiscoveryManager.Listener() {
+            @Override
+            public void onDevicesUpdated(java.util.List<DiscoveryManager.DiscoveredDevice> deviceList) {
+                deviceAdapter.setDevices(deviceList);
+                statusText.setText(deviceList.isEmpty()
+                        ? getString(R.string.searching)
+                        : getString(R.string.found_receivers, deviceList.size()));
+            }
+
+            @Override
+            public void onScanStarted() {
+                showDiscoveryProgress();
+            }
+
+            @Override
+            public void onScanEnded() {
+                hideDiscoveryProgress();
+            }
+        });
+
+        getOnBackPressedDispatcher().addCallback(this, new OnBackPressedCallback(true) {
+            @Override
+            public void handleOnBackPressed() {
+                if (CastActiveState.isSenderCasting()) {
+                    long now = System.currentTimeMillis();
+                    if (now - lastBackPressMs < BACK_STOP_INTERVAL_MS) {
+                        stopCastingAndExit();
+                    } else {
+                        lastBackPressMs = now;
+                        Toast.makeText(SenderActivity.this,
+                                R.string.press_back_again_to_stop_cast, Toast.LENGTH_SHORT).show();
+                    }
+                } else {
+                    finish();
+                }
+            }
         });
 
         findViewById(R.id.btn_refresh).setOnClickListener(v -> restartDiscovery());
@@ -130,6 +179,12 @@ public class SenderActivity extends AppCompatActivity {
         });
     }
 
+    @Override
+    protected void onResume() {
+        super.onResume();
+        PermissionHelper.remindIfMissing(this, castSettings.isAudioEnabled());
+    }
+
     @Override
     protected void onStart() {
         super.onStart();
@@ -143,6 +198,7 @@ public class SenderActivity extends AppCompatActivity {
         if (discovery != null) {
             discovery.stop();
         }
+        hideDiscoveryProgress();
         super.onStop();
     }
 
@@ -155,7 +211,6 @@ public class SenderActivity extends AppCompatActivity {
     private void restartDiscoveryInternal(boolean userRefresh) {
         deviceAdapter.clearDevices();
         statusText.setText(userRefresh ? R.string.rescanning : R.string.searching);
-        discoveryProgress.setVisibility(View.VISIBLE);
         if (discovery != null) {
             discovery.stop();
             discovery.clearDevices();
@@ -163,7 +218,36 @@ public class SenderActivity extends AppCompatActivity {
         discovery.startBrowsing();
     }
 
+    private void showDiscoveryProgress() {
+        discoveryProgress.setVisibility(View.VISIBLE);
+        discoveryProgress.bringToFront();
+        Drawable indeterminate = discoveryProgress.getIndeterminateDrawable();
+        if (indeterminate instanceof Animatable) {
+            ((Animatable) indeterminate).start();
+        }
+    }
+
+    private void hideDiscoveryProgress() {
+        discoveryProgress.setVisibility(View.GONE);
+        Drawable indeterminate = discoveryProgress.getIndeterminateDrawable();
+        if (indeterminate instanceof Animatable) {
+            ((Animatable) indeterminate).stop();
+        }
+    }
+
+    private void stopCastingAndExit() {
+        Intent stop = new Intent(this, ScreenCastService.class);
+        stop.setAction(ScreenCastService.ACTION_STOP);
+        startService(stop);
+        CastActiveState.setSenderCasting(false);
+        finish();
+    }
+
     private void startCastFlow() {
+        PermissionHelper.remindIfMissing(this, castSettings.isAudioEnabled());
+        if (!PermissionHelper.hasAll(this)) {
+            return;
+        }
         if (castSettings.isPassthrough()) {
             Toast.makeText(this, R.string.codec_passthrough_unavailable, Toast.LENGTH_LONG).show();
             return;
@@ -190,29 +274,53 @@ public class SenderActivity extends AppCompatActivity {
             }
             pendingDeviceName = host;
         } else {
-            DiscoveryManager.DiscoveredDevice selected = deviceAdapter.getSelectedDevice();
-            if (selected == null) {
+            java.util.List<DiscoveryManager.DiscoveredDevice> selectedList =
+                    deviceAdapter.getSelectedDevices();
+            if (selectedList.isEmpty()) {
                 Toast.makeText(this, R.string.select_receiver, Toast.LENGTH_SHORT).show();
                 return;
             }
-            if (!castSettings.getTransport().equals(selected.transport)) {
-                Toast.makeText(this, R.string.transport_mismatch, Toast.LENGTH_LONG).show();
+            if (CastConfig.MULTI_RECEIVER_ENABLED && selectedList.size() > CastConfig.MAX_RECEIVERS) {
+                Toast.makeText(this, getString(R.string.too_many_receivers, CastConfig.MAX_RECEIVERS),
+                        Toast.LENGTH_LONG).show();
                 return;
             }
-            pendingHost = selected.host;
-            pendingPort = selected.port;
-            pendingDeviceName = selected.name;
+            pendingTargets = new java.util.ArrayList<>();
+            for (DiscoveryManager.DiscoveredDevice d : selectedList) {
+                if (!CastConfig.MULTI_RECEIVER_ENABLED
+                        && !castSettings.getTransport().equals(d.transport)) {
+                    Toast.makeText(this, R.string.transport_mismatch, Toast.LENGTH_LONG).show();
+                    return;
+                }
+                pendingTargets.add(new CastReceiverTarget(d.name, d.host, d.port, d.transport,
+                        d.videoCodecs, d.audioCodecs, d.placeholderId));
+            }
+            DiscoveryManager.DiscoveredDevice first = selectedList.get(0);
+            pendingHost = first.host;
+            pendingPort = first.port;
+            pendingDeviceName = selectedList.size() > 1
+                    ? first.name + " +" + (selectedList.size() - 1) : first.name;
         }
 
         pendingPin = pin;
         MediaProjectionManager mgr = (MediaProjectionManager) getSystemService(MEDIA_PROJECTION_SERVICE);
-        startActivityForResult(mgr.createScreenCaptureIntent(), REQUEST_MEDIA_PROJECTION);
+        startActivityForResult(createScreenCaptureIntent(mgr), REQUEST_MEDIA_PROJECTION);
+    }
+
+    private android.content.Intent createScreenCaptureIntent(MediaProjectionManager mgr) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.UPSIDE_DOWN_CAKE
+                && castSettings.getCaptureMode() == CastSettings.CaptureMode.USER_CHOICE) {
+            MediaProjectionConfig config = MediaProjectionConfig.createConfigForUserChoice();
+            return mgr.createScreenCaptureIntent(config);
+        }
+        return mgr.createScreenCaptureIntent();
     }
 
     private String pendingPin;
     private String pendingHost;
     private int pendingPort;
     private String pendingDeviceName;
+    private java.util.ArrayList<CastReceiverTarget> pendingTargets;
 
     @Override
     protected void onActivityResult(int requestCode, int resultCode, Intent data) {
@@ -237,6 +345,9 @@ public class SenderActivity extends AppCompatActivity {
         serviceIntent.putExtra(ScreenCastService.EXTRA_PIN, pendingPin);
         serviceIntent.putExtra(ScreenCastService.EXTRA_DEVICE_NAME, pendingDeviceName != null ? pendingDeviceName : deviceName);
         serviceIntent.putExtra(CastSettings.EXTRA, castSettings);
+        if (pendingTargets != null && !pendingTargets.isEmpty()) {
+            serviceIntent.putExtra(ScreenCastService.EXTRA_TARGETS, pendingTargets);
+        }
 
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
             startForegroundService(serviceIntent);
diff --git a/app/src/main/java/com/foxx/androidcast/sender/SenderAudioMetrics.java b/app/src/main/java/com/foxx/androidcast/sender/SenderAudioMetrics.java
new file mode 100644
index 0000000..16e1b43
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/sender/SenderAudioMetrics.java
@@ -0,0 +1,61 @@
+package com.foxx.androidcast.sender;
+
+import com.foxx.androidcast.media.PcmLevelAnalyzer;
+
+/** Pre-encode PCM level stats on the sender. */
+public final class SenderAudioMetrics {
+    private long silentBlocks;
+    private long audibleBlocks;
+    private float vuSmoothed;
+    private float lastPeakDb = -96f;
+    private float lastRmsDb = -96f;
+
+    public synchronized void onPcm(PcmLevelAnalyzer.Levels levels) {
+        if (levels == null) {
+            return;
+        }
+        if (levels.silent) {
+            silentBlocks++;
+        } else {
+            audibleBlocks++;
+        }
+        float instant = Math.max(levels.peak, levels.rms);
+        vuSmoothed = instant > vuSmoothed
+                ? instant * 0.35f + vuSmoothed * 0.65f
+                : instant * 0.12f + vuSmoothed * 0.88f;
+        if (levels.peak > 1e-9f) {
+            lastPeakDb = levels.peakDb();
+        }
+        if (levels.rms > 1e-9f) {
+            lastRmsDb = (float) (20.0 * Math.log10(levels.rms));
+        }
+    }
+
+    public synchronized void reset() {
+        silentBlocks = 0;
+        audibleBlocks = 0;
+        vuSmoothed = 0f;
+        lastPeakDb = -96f;
+        lastRmsDb = -96f;
+    }
+
+    public synchronized long getSilentBlocks() {
+        return silentBlocks;
+    }
+
+    public synchronized long getAudibleBlocks() {
+        return audibleBlocks;
+    }
+
+    public synchronized int getVuPercent() {
+        return PcmLevelAnalyzer.vuPercent(vuSmoothed);
+    }
+
+    public synchronized float getLastPeakDb() {
+        return lastPeakDb;
+    }
+
+    public synchronized float getLastRmsDb() {
+        return lastRmsDb;
+    }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/sender/SenderStreamMetrics.java b/app/src/main/java/com/foxx/androidcast/sender/SenderStreamMetrics.java
index 9693656..aecd2d4 100644
--- a/app/src/main/java/com/foxx/androidcast/sender/SenderStreamMetrics.java
+++ b/app/src/main/java/com/foxx/androidcast/sender/SenderStreamMetrics.java
@@ -27,6 +27,10 @@ public final class SenderStreamMetrics {
         windowFrames++;
     }
 
+    public synchronized float getLastSecondFps() {
+        return lastSecondFps;
+    }
+
     public synchronized void onNetworkSample(int sendKbps, int rttMs) {
         if (sendKbps > 0) {
             lastSendKbps = sendKbps;
@@ -36,7 +40,8 @@ public final class SenderStreamMetrics {
         }
     }
 
-    public synchronized String format(String videoCodec, int captureW, int captureH, CastSendPump pump) {
+    public synchronized String format(String videoCodec, int captureW, int captureH, CastSendPump pump,
+            SenderAudioMetrics audio, boolean audioEnabled) {
         float fps = lastSecondFps > 0 ? lastSecondFps : 0f;
         StringBuilder sb = new StringBuilder();
         if (videoCodec != null && !videoCodec.isEmpty()) {
@@ -60,6 +65,13 @@ public final class SenderStreamMetrics {
                 }
             }
         }
+        if (audioEnabled && audio != null) {
+            int vu = audio.getVuPercent();
+            sb.append(" · aud ").append(vu).append('%');
+            if (audio.getAudibleBlocks() == 0 && audio.getSilentBlocks() > 30) {
+                sb.append(" (silent cap)");
+            }
+        }
         return sb.toString();
     }
 }
diff --git a/app/src/main/java/com/foxx/androidcast/sender/VideoEncoder.java b/app/src/main/java/com/foxx/androidcast/sender/VideoEncoder.java
index 5fa6c34..7066c04 100644
--- a/app/src/main/java/com/foxx/androidcast/sender/VideoEncoder.java
+++ b/app/src/main/java/com/foxx/androidcast/sender/VideoEncoder.java
@@ -32,6 +32,20 @@ public class VideoEncoder {
     private Thread drainThread;
     private String mime;
 
+    /** Request an IDR (keyframe) on the next opportunity. */
+    public void requestKeyframe() {
+        if (codec == null || !running) {
+            return;
+        }
+        try {
+            Bundle params = new Bundle();
+            params.putInt(MediaCodec.PARAMETER_KEY_REQUEST_SYNC_FRAME, 0);
+            codec.setParameters(params);
+        } catch (Exception e) {
+            Log.w(TAG, "Keyframe request failed: " + e.getMessage());
+        }
+    }
+
     public Surface prepare(int width, int height, String mime, CastTuningEngine.EffectiveParams params,
             Callback callback) throws IOException {
         this.width = width;
@@ -101,19 +115,6 @@ public class VideoEncoder {
         }
     }
 
-    public void requestKeyframe() {
-        if (codec == null) {
-            return;
-        }
-        try {
-            Bundle params = new Bundle();
-            params.putInt(MediaCodec.PARAMETER_KEY_REQUEST_SYNC_FRAME, 0);
-            codec.setParameters(params);
-        } catch (Exception e) {
-            Log.w(TAG, "Keyframe request failed", e);
-        }
-    }
-
     public void stop() {
         running = false;
         if (drainThread != null) {
diff --git a/app/src/main/java/com/foxx/androidcast/ui/ZoomPanContainer.java b/app/src/main/java/com/foxx/androidcast/ui/ZoomPanContainer.java
new file mode 100644
index 0000000..6ed77c4
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/ui/ZoomPanContainer.java
@@ -0,0 +1,134 @@
+package com.foxx.androidcast.ui;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.view.GestureDetector;
+import android.view.MotionEvent;
+import android.view.ScaleGestureDetector;
+import android.widget.FrameLayout;
+
+/**
+ * Pinch-zoom (5% steps) and two-finger pan over video content.
+ * Reports zoom deviation from 100% via {@link OnZoomChangedListener}.
+ */
+public class ZoomPanContainer extends FrameLayout {
+    public interface OnZoomChangedListener {
+        void onZoomPercentChanged(int zoomPercent);
+    }
+
+    private static final float STEP = 0.05f;
+    private static final float MIN_SCALE = 0.50f;
+    private static final float MAX_SCALE = 3.00f;
+
+    private float scale = 1f;
+    private float panX;
+    private float panY;
+    private OnZoomChangedListener zoomListener;
+
+    private final ScaleGestureDetector scaleDetector;
+    private final GestureDetector panDetector;
+    private float lastSpan = -1f;
+
+    public ZoomPanContainer(Context context) {
+        this(context, null);
+    }
+
+    public ZoomPanContainer(Context context, AttributeSet attrs) {
+        super(context, attrs);
+        scaleDetector = new ScaleGestureDetector(context, new ScaleListener());
+        panDetector = new GestureDetector(context, new PanListener());
+    }
+
+    public void setOnZoomChangedListener(OnZoomChangedListener listener) {
+        this.zoomListener = listener;
+    }
+
+    public void resetTransform() {
+        scale = 1f;
+        panX = 0f;
+        panY = 0f;
+        applyTransform();
+        notifyZoom();
+    }
+
+    public int getZoomPercent() {
+        return Math.round((scale - 1f) * 100f);
+    }
+
+    @Override
+    public boolean onTouchEvent(MotionEvent event) {
+        boolean scaled = scaleDetector.onTouchEvent(event);
+        boolean panned = panDetector.onTouchEvent(event);
+        if (event.getActionMasked() == MotionEvent.ACTION_UP
+                || event.getActionMasked() == MotionEvent.ACTION_CANCEL) {
+            lastSpan = -1f;
+        }
+        return scaled || panned || super.onTouchEvent(event);
+    }
+
+    private final class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
+        @Override
+        public boolean onScale(ScaleGestureDetector detector) {
+            float span = detector.getCurrentSpan();
+            if (lastSpan < 0) {
+                lastSpan = span;
+                return true;
+            }
+            float ratio = span / lastSpan;
+            lastSpan = span;
+            if (ratio > 1.02f) {
+                applyStep(1f + STEP);
+            } else if (ratio < 0.98f) {
+                applyStep(1f - STEP);
+            }
+            return true;
+        }
+    }
+
+    private void applyStep(float factor) {
+        float target = scale * factor;
+        target = Math.max(MIN_SCALE, Math.min(MAX_SCALE, target));
+        int quantized = Math.round(target * 20f);
+        scale = quantized / 20f;
+        applyTransform();
+        notifyZoom();
+    }
+
+    private final class PanListener extends GestureDetector.SimpleOnGestureListener {
+        @Override
+        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
+            if (e1 == null || e2 == null || e2.getPointerCount() < 2) {
+                return false;
+            }
+            panX -= distanceX;
+            panY -= distanceY;
+            applyTransform();
+            return true;
+        }
+    }
+
+    private void applyTransform() {
+        if (getChildCount() == 0) {
+            return;
+        }
+        android.view.View child = getChildAt(0);
+        child.setPivotX(child.getWidth() / 2f);
+        child.setPivotY(child.getHeight() / 2f);
+        child.setScaleX(scale);
+        child.setScaleY(scale);
+        child.setTranslationX(panX);
+        child.setTranslationY(panY);
+    }
+
+    private void notifyZoom() {
+        if (zoomListener != null) {
+            zoomListener.onZoomPercentChanged(getZoomPercent());
+        }
+    }
+
+    @Override
+    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
+        super.onLayout(changed, left, top, right, bottom);
+        applyTransform();
+    }
+}
diff --git a/app/src/main/res/layout/activity_playback.xml b/app/src/main/res/layout/activity_playback.xml
index eb7beac..6186e97 100644
--- a/app/src/main/res/layout/activity_playback.xml
+++ b/app/src/main/res/layout/activity_playback.xml
@@ -4,19 +4,26 @@
     android:layout_height="match_parent"
     android:background="#000000">
 
-    <com.foxx.androidcast.ui.AspectRatioFrameLayout
-        android:id="@+id/aspect_container"
+    <com.foxx.androidcast.ui.ZoomPanContainer
+        android:id="@+id/zoom_container"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:layout_gravity="center">
 
-        <SurfaceView
-            android:id="@+id/surface_playback"
+        <com.foxx.androidcast.ui.AspectRatioFrameLayout
+            android:id="@+id/aspect_container"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
-            android:layout_gravity="center"
-            android:keepScreenOn="true" />
-    </com.foxx.androidcast.ui.AspectRatioFrameLayout>
+            android:layout_gravity="center">
+
+            <SurfaceView
+                android:id="@+id/surface_playback"
+                android:layout_width="match_parent"
+                android:layout_height="match_parent"
+                android:layout_gravity="center"
+                android:keepScreenOn="true" />
+        </com.foxx.androidcast.ui.AspectRatioFrameLayout>
+    </com.foxx.androidcast.ui.ZoomPanContainer>
 
     <include
         layout="@layout/overlay_stream_awaiting"
diff --git a/app/src/main/res/layout/activity_sender.xml b/app/src/main/res/layout/activity_sender.xml
index 9ad839b..a1e4b77 100644
--- a/app/src/main/res/layout/activity_sender.xml
+++ b/app/src/main/res/layout/activity_sender.xml
@@ -106,8 +106,11 @@
                     android:id="@+id/progress_discovery"
                     style="?android:attr/progressBarStyleHorizontal"
                     android:layout_width="match_parent"
-                    android:layout_height="4dp"
-                    android:layout_gravity="bottom"
+                    android:layout_height="match_parent"
+                    android:layout_gravity="center"
+                    android:alpha="0.85"
+                    android:clickable="false"
+                    android:focusable="false"
                     android:indeterminate="true"
                     android:visibility="gone" />
             </FrameLayout>
diff --git a/app/src/main/res/layout/activity_settings_panel.xml b/app/src/main/res/layout/activity_settings_panel.xml
index b357305..5e5117b 100644
--- a/app/src/main/res/layout/activity_settings_panel.xml
+++ b/app/src/main/res/layout/activity_settings_panel.xml
@@ -88,6 +88,25 @@
         android:layout_width="match_parent"
         android:layout_height="wrap_content" />
 
+    <LinearLayout
+        android:id="@+id/layout_capture_mode"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="8dp"
+        android:orientation="vertical">
+
+        <TextView
+            android:id="@+id/text_capture_mode_label"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/label_capture_mode" />
+
+        <Spinner
+            android:id="@+id/spinner_capture_mode"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content" />
+    </LinearLayout>
+
     <CheckBox
         android:id="@+id/checkbox_audio"
         android:layout_width="match_parent"
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index f0942a7..c56acf5 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -15,6 +15,11 @@
     <string name="label_transport">Transport</string>
     <string name="label_quality">Quality (bitrate / FPS)</string>
     <string name="label_resolution">Capture resolution</string>
+    <string name="label_capture_mode">Screen capture (sender phone)</string>
+    <string name="label_capture_mode_sender_only">Screen capture (sender phone only)</string>
+    <string name="capture_full_screen">Entire screen</string>
+    <string name="capture_user_choice">Choose app or screen (Android 14+)</string>
+    <string name="capture_user_choice_unavailable">App picker needs Android 14 (this device: API %1$d)</string>
     <string name="label_audio">Include audio (playback capture, Android 10+)</string>
     <string name="label_audio_unavailable">Audio unavailable (requires Android 10+)</string>
     <string name="audio_unavailable_title">Video only</string>
@@ -52,6 +57,7 @@
     <string name="select_receiver">Select a receiver first</string>
     <string name="enter_pin">Enter PIN</string>
     <string name="capture_denied">Screen capture permission denied</string>
+    <string name="audio_mic_permission_hint">Allow microphone for audio cast fallback when nothing is playing on the sender.</string>
     <string name="casting_started">Casting started</string>
     <string name="found_receivers">Found %1$d receiver(s)</string>
     <string name="receiver_ready">Ready — PIN %1$s · %2$s</string>
@@ -74,6 +80,11 @@
     <string name="playback_listening">Listening for cast — awaiting sender…</string>
     <string name="playback_awaiting_stream">Awaiting for stream to come…</string>
     <string name="playback_stream_lost">Stream lost — awaiting for stream to come…</string>
+    <string name="playback_stream_ended">Cast ended — waiting for sender…</string>
+    <string name="press_back_again_to_stop_cast">Press Back again to stop casting</string>
+    <string name="permissions_missing_title">Permissions needed</string>
+    <string name="permissions_grant">Grant</string>
+    <string name="permissions_app_settings">App settings</string>
     <string name="receiver_starting">Starting receiver service…</string>
     <string name="receiver_listening">Listening for cast</string>
     <string name="waiting_surface">Connected — open video surface…</string>
@@ -91,6 +102,8 @@
     <string name="playback_opened">Fullscreen playback %1$dx%2$d</string>
     <string name="playback_rendering">Video playing</string>
     <string name="device_selected">Selected: %1$s (%2$s, %3$s)</string>
+    <string name="devices_selected">Selected %1$d receivers</string>
+    <string name="too_many_receivers">Select at most %1$d receivers</string>
     <string name="audio_consent_title">Play cast audio?</string>
     <string name="audio_consent_message">The sender is streaming audio. Play it on this device?</string>
     <string name="audio_consent_yes">Play audio</string>