From 367a21e37a099ea76fff7374e55841c15b438a31 Mon Sep 17 00:00:00 2001
From: Anton Afanasyeu <a.afanasieff@gmail.com>
Date: Fri, 15 May 2026 20:37:44 +0200
Subject: [PATCH] snap

---
 .../java/com/foxx/androidcast/CastConfig.java |   6 +
 .../com/foxx/androidcast/CastResolution.java  |  55 +++--
 .../com/foxx/androidcast/CastSettings.java    |  79 ++++++-
 .../foxx/androidcast/CastTuningEngine.java    | 173 +++++++++++++++
 .../java/com/foxx/androidcast/SettingsUi.java | 173 ++++++++++++---
 .../discovery/DiscoveryManager.java           |  61 ++++--
 .../androidcast/media/CodecNegotiator.java    |  75 +++++++
 .../androidcast/network/CastProtocol.java     |  90 +++++++-
 .../foxx/androidcast/network/CastSession.java |  48 ++++-
 .../PassThroughNetworkControlPlane.java       |   4 +
 .../receiver/ReceiverCastService.java         |  34 ++-
 .../androidcast/receiver/ReceiverSession.java |   4 +-
 .../androidcast/receiver/StreamMetrics.java   |  24 ++-
 .../androidcast/receiver/VideoDecoder.java    |  25 ++-
 .../foxx/androidcast/sender/AudioCapture.java |   5 +
 .../foxx/androidcast/sender/CastSendPump.java |  20 +-
 .../foxx/androidcast/sender/CodecCatalog.java |  87 ++++++++
 .../androidcast/sender/EncoderKeepalive.java  |  46 ++++
 .../androidcast/sender/ScreenCastService.java | 202 +++++++++++++++---
 .../androidcast/sender/SenderActivity.java    | 121 +++++++++--
 .../sender/SenderStreamMetrics.java           |  65 ++++++
 .../foxx/androidcast/sender/VideoEncoder.java |  40 ++--
 app/src/main/res/layout/activity_sender.xml   |  67 +++++-
 .../res/layout/activity_settings_panel.xml    |  44 ++++
 app/src/main/res/values/strings.xml           |  31 ++-
 25 files changed, 1400 insertions(+), 179 deletions(-)
 create mode 100644 app/src/main/java/com/foxx/androidcast/CastTuningEngine.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/media/CodecNegotiator.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/sender/CodecCatalog.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/sender/EncoderKeepalive.java
 create mode 100644 app/src/main/java/com/foxx/androidcast/sender/SenderStreamMetrics.java

diff --git a/app/src/main/java/com/foxx/androidcast/CastConfig.java b/app/src/main/java/com/foxx/androidcast/CastConfig.java
index 3e41ef1..1e95e82 100644
--- a/app/src/main/java/com/foxx/androidcast/CastConfig.java
+++ b/app/src/main/java/com/foxx/androidcast/CastConfig.java
@@ -13,6 +13,12 @@ public final class CastConfig {
     /** Seconds between IDR frames (1 = faster recovery, slightly more bandwidth). */
     public static final int VIDEO_I_FRAME_INTERVAL = 1;
 
+    /** Request sync frames on this interval when the screen is static (Mediatek stall workaround). */
+    public static final long KEYFRAME_KEEPALIVE_MS = 2_000;
+
+    /** P-frames smaller than this are treated as empty and not sent (unless keepalive IDR). */
+    public static final int MIN_SIGNIFICANT_FRAME_BYTES = 400;
+
     public static final int AUDIO_SAMPLE_RATE = 44100;
     public static final int AUDIO_CHANNEL_COUNT = 2;
     public static final int AUDIO_BITRATE = 128_000;
diff --git a/app/src/main/java/com/foxx/androidcast/CastResolution.java b/app/src/main/java/com/foxx/androidcast/CastResolution.java
index 13ef2a8..9a2655e 100644
--- a/app/src/main/java/com/foxx/androidcast/CastResolution.java
+++ b/app/src/main/java/com/foxx/androidcast/CastResolution.java
@@ -2,6 +2,8 @@ package com.foxx.androidcast;
 
 import android.util.DisplayMetrics;
 
+import com.foxx.androidcast.network.control.NetworkStatsSnapshot;
+
 /** Computes encoder VirtualDisplay size from display metrics and user settings. */
 public final class CastResolution {
     private CastResolution() {}
@@ -19,26 +21,53 @@ public final class CastResolution {
     }
 
     public static Size compute(DisplayMetrics display, CastSettings settings) {
+        return compute(display, settings, null);
+    }
+
+    public static Size compute(DisplayMetrics display, CastSettings settings, NetworkStatsSnapshot peer) {
         int displayW = display.widthPixels & ~1;
         int displayH = display.heightPixels & ~1;
         float scale = settings.getResolutionScale();
-        int encW = Math.max(2, ((int) (displayW * scale)) & ~1);
-        int encH = Math.max(2, ((int) (displayH * scale)) & ~1);
+        int encW = even(Math.max(2, (int) (displayW * scale)));
+        int encH = even(Math.max(2, (int) (displayH * scale)));
 
-        int maxH = settings.getMaxHeight();
-        if (maxH > 0 && encH > maxH) {
-            float ratio = (float) maxH / encH;
-            encH = maxH & ~1;
-            encW = Math.max(2, ((int) (encW * ratio)) & ~1);
-        }
-        int maxW = settings.getMaxWidth();
-        if (maxW > 0 && encW > maxW) {
-            float ratio = (float) maxW / encW;
-            encW = maxW & ~1;
-            encH = Math.max(2, ((int) (encH * ratio)) & ~1);
+        CastTuningEngine.CaptureLimits limits = CastTuningEngine.resolveCaptureLimits(settings, peer);
+        int maxH = limits.maxHeight > 0 ? limits.maxHeight : settings.getMaxHeight();
+        int maxW = limits.maxWidth > 0 ? limits.maxWidth : settings.getMaxWidth();
+
+        if (maxH > 0 && maxW == 0) {
+            int[] capped = capLongEdge(encW, encH, maxH);
+            encW = capped[0];
+            encH = capped[1];
+        } else {
+            if (maxH > 0 && encH > maxH) {
+                float ratio = (float) maxH / encH;
+                encH = even(maxH);
+                encW = even(Math.max(2, (int) (encW * ratio)));
+            }
+            if (maxW > 0 && encW > maxW) {
+                float ratio = (float) maxW / encW;
+                encW = even(maxW);
+                encH = even(Math.max(2, (int) (encH * ratio)));
+            }
         }
 
         int density = Math.max(120, (int) (display.densityDpi * scale));
         return new Size(encW, encH, density);
     }
+
+    /** Caps the longer side (orientation-independent 720p height-cap mode). */
+    private static int[] capLongEdge(int width, int height, int maxLong) {
+        int longEdge = Math.max(width, height);
+        if (longEdge <= maxLong) {
+            return new int[] {width, height};
+        }
+        float ratio = (float) maxLong / longEdge;
+        return new int[] {even(Math.max(2, (int) (width * ratio))),
+                even(Math.max(2, (int) (height * ratio)))};
+    }
+
+    private static int even(int v) {
+        return Math.max(2, v & ~1);
+    }
 }
diff --git a/app/src/main/java/com/foxx/androidcast/CastSettings.java b/app/src/main/java/com/foxx/androidcast/CastSettings.java
index c8a3538..6e39d7e 100644
--- a/app/src/main/java/com/foxx/androidcast/CastSettings.java
+++ b/app/src/main/java/com/foxx/androidcast/CastSettings.java
@@ -5,6 +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 enum Quality {
         LOW(1_500_000, 24),
@@ -20,12 +21,34 @@ public class CastSettings implements Serializable {
         }
     }
 
-    /** Capture scale relative to physical display (1.0 = native). */
+    public enum VideoCodec {
+        AUTO, H264, H265, PASSTHROUGH
+    }
+
+    public enum AdjustmentPreset {
+        AUTO, NONE, QUALITY, SPEED, PERFORMANCE
+    }
+
+    public enum BitrateMode {
+        AUTO, NONE, QUALITY, SPEED, BALANCED, ROBUST_LESS, ESTIMATED
+    }
+
+    public enum NetworkAdoption {
+        AUTO, QUALITY, SPEED, ESTIMATED
+    }
+
+    /**
+     * Capture size. {@link #HD_720P} caps height only (width follows aspect — e.g. 1532×720).
+     * {@link #FIXED_720P} fits inside 1280×720 box.
+     */
     public enum Resolution {
         FULL(1.0f, 0, 0),
         THREE_QUARTERS(0.75f, 0, 0),
         HALF(0.5f, 0, 0),
-        HD_720P(1.0f, 720, 1280);
+        HD_720P(1.0f, 720, 0),
+        FIXED_1080P(0f, 1080, 1920),
+        FIXED_720P(0f, 720, 1280),
+        ADAPTIVE(1.0f, 0, 0);
 
         public final float scale;
         public final int maxHeight;
@@ -42,6 +65,12 @@ public class CastSettings implements Serializable {
     private Quality quality = Quality.MEDIUM;
     private Resolution resolution = Resolution.HD_720P;
     private boolean audioEnabled;
+    private VideoCodec videoCodec = VideoCodec.AUTO;
+    private AdjustmentPreset adjustmentPreset = AdjustmentPreset.AUTO;
+    private BitrateMode bitrateMode = BitrateMode.AUTO;
+    private NetworkAdoption networkAdoption = NetworkAdoption.AUTO;
+    /** Filled after codec handshake (e.g. video/avc). */
+    private transient String negotiatedVideoMime;
 
     public CastSettings() {
         PlatformCastSupport.applyDefaultAudioSetting(this);
@@ -79,11 +108,43 @@ public class CastSettings implements Serializable {
         this.audioEnabled = audioEnabled;
     }
 
-    /** Raw user toggle; may be true on old platforms but {@link #isAudioEnabled()} stays false. */
     public boolean isAudioRequested() {
         return audioEnabled;
     }
 
+    public VideoCodec getVideoCodec() {
+        return videoCodec;
+    }
+
+    public void setVideoCodec(VideoCodec videoCodec) {
+        this.videoCodec = videoCodec;
+    }
+
+    public AdjustmentPreset getAdjustmentPreset() {
+        return adjustmentPreset;
+    }
+
+    public void setAdjustmentPreset(AdjustmentPreset adjustmentPreset) {
+        this.adjustmentPreset = adjustmentPreset;
+    }
+
+    public BitrateMode getBitrateMode() {
+        return bitrateMode;
+    }
+
+    public void setBitrateMode(BitrateMode bitrateMode) {
+        this.bitrateMode = bitrateMode;
+    }
+
+    public NetworkAdoption getNetworkAdoption() {
+        return networkAdoption;
+    }
+
+    public void setNetworkAdoption(NetworkAdoption networkAdoption) {
+        this.networkAdoption = networkAdoption;
+    }
+
+    /** Legacy: raw quality bitrate. Prefer {@link CastTuningEngine#resolve}. */
     public int getVideoBitrate() {
         return quality.videoBitrate;
     }
@@ -103,4 +164,16 @@ public class CastSettings implements Serializable {
     public int getMaxWidth() {
         return resolution.maxWidth;
     }
+
+    public boolean isPassthrough() {
+        return videoCodec == VideoCodec.PASSTHROUGH;
+    }
+
+    public String getNegotiatedVideoMime() {
+        return negotiatedVideoMime;
+    }
+
+    public void setNegotiatedVideoMime(String negotiatedVideoMime) {
+        this.negotiatedVideoMime = negotiatedVideoMime;
+    }
 }
diff --git a/app/src/main/java/com/foxx/androidcast/CastTuningEngine.java b/app/src/main/java/com/foxx/androidcast/CastTuningEngine.java
new file mode 100644
index 0000000..bfa8136
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/CastTuningEngine.java
@@ -0,0 +1,173 @@
+package com.foxx.androidcast;
+
+import com.foxx.androidcast.network.control.NetworkStatsSnapshot;
+
+/** Resolves AUTO presets into concrete encoder/network/capture parameters. */
+public final class CastTuningEngine {
+    private CastTuningEngine() {}
+
+    public static final class EffectiveParams {
+        public final int videoBitrate;
+        public final int videoFps;
+        public final int keyframeIntervalSec;
+        public final boolean requestLowLatency;
+        public final boolean skipTinyPFrames;
+
+        EffectiveParams(int videoBitrate, int videoFps, int keyframeIntervalSec,
+                boolean requestLowLatency, boolean skipTinyPFrames) {
+            this.videoBitrate = videoBitrate;
+            this.videoFps = videoFps;
+            this.keyframeIntervalSec = keyframeIntervalSec;
+            this.requestLowLatency = requestLowLatency;
+            this.skipTinyPFrames = skipTinyPFrames;
+        }
+    }
+
+    public static final class CaptureLimits {
+        public final int maxWidth;
+        public final int maxHeight;
+
+        public CaptureLimits(int maxWidth, int maxHeight) {
+            this.maxWidth = maxWidth;
+            this.maxHeight = maxHeight;
+        }
+    }
+
+    public static CaptureLimits resolveCaptureLimits(CastSettings settings, NetworkStatsSnapshot peer) {
+        CastSettings.Resolution mode = settings.getResolution();
+        int capLong = 0;
+        int boxW = 0;
+        int boxH = 0;
+
+        switch (mode) {
+            case HD_720P:
+                capLong = 720;
+                break;
+            case FIXED_1080P:
+                boxW = 1920;
+                boxH = 1080;
+                break;
+            case FIXED_720P:
+                boxW = 1280;
+                boxH = 720;
+                break;
+            case ADAPTIVE:
+                capLong = 720;
+                if (peer != null) {
+                    if (peer.recvBitrateKbps > 0 && peer.recvBitrateKbps < 800) {
+                        capLong = 480;
+                    } else if (peer.recvBitrateKbps > 0 && peer.recvBitrateKbps < 1500) {
+                        capLong = 540;
+                    }
+                    if (peer.rttMs > 500) {
+                        capLong = Math.min(capLong, 540);
+                    }
+                    if (peer.rttMs > 800) {
+                        capLong = Math.min(capLong, 480);
+                    }
+                }
+                break;
+            default:
+                return new CaptureLimits(settings.getMaxWidth(), settings.getMaxHeight());
+        }
+
+        if (boxW > 0 && boxH > 0) {
+            return new CaptureLimits(boxW, boxH);
+        }
+        return new CaptureLimits(0, capLong);
+    }
+
+    public static EffectiveParams resolve(CastSettings settings, NetworkStatsSnapshot peerStats) {
+        CastSettings.Quality quality = settings.getQuality();
+        int bitrate = quality.videoBitrate;
+        int fps = quality.videoFps;
+        int gop = CastConfig.VIDEO_I_FRAME_INTERVAL;
+        boolean lowLatency = true;
+        boolean skipTiny = true;
+
+        switch (settings.getAdjustmentPreset()) {
+            case NONE:
+                lowLatency = false;
+                skipTiny = false;
+                break;
+            case QUALITY:
+                bitrate = (int) (bitrate * 1.15f);
+                fps = Math.min(30, fps + 2);
+                gop = 2;
+                break;
+            case PERFORMANCE:
+                bitrate = (int) (bitrate * 0.85f);
+                fps = Math.max(24, fps);
+                break;
+            case SPEED:
+            case AUTO:
+            default:
+                break;
+        }
+
+        switch (settings.getBitrateMode()) {
+            case NONE:
+                bitrate = Integer.MAX_VALUE / 4;
+                break;
+            case QUALITY:
+                bitrate = (int) (bitrate * 1.25f);
+                break;
+            case SPEED:
+                bitrate = (int) (bitrate * 0.65f);
+                fps = Math.min(fps, 24);
+                break;
+            case ROBUST_LESS:
+                if (CastConfig.TRANSPORT_UDP.equals(settings.getTransport())) {
+                    bitrate = (int) (bitrate * 0.55f);
+                    gop = 1;
+                }
+                break;
+            case ESTIMATED:
+            case BALANCED:
+            case AUTO:
+            default:
+                bitrate = applyBandwidthEstimate(peerStats, bitrate);
+                break;
+        }
+
+        switch (settings.getNetworkAdoption()) {
+            case QUALITY:
+                bitrate = (int) (bitrate * 1.1f);
+                break;
+            case SPEED:
+                bitrate = (int) (bitrate * 0.7f);
+                fps = Math.min(fps, 24);
+                break;
+            case ESTIMATED:
+                bitrate = applyBandwidthEstimate(peerStats, bitrate);
+                break;
+            case AUTO:
+            default:
+                break;
+        }
+
+        bitrate = Math.max(600_000, Math.min(16_000_000, bitrate));
+        fps = Math.max(15, Math.min(30, fps));
+        return new EffectiveParams(bitrate, fps, gop, lowLatency, skipTiny);
+    }
+
+    private static int applyBandwidthEstimate(NetworkStatsSnapshot peer, int bitrate) {
+        if (peer == null) {
+            return bitrate;
+        }
+        if (peer.rttMs > 400) {
+            float factor = Math.max(0.35f, 1f - (peer.rttMs - 400) / 2000f);
+            bitrate = (int) (bitrate * factor);
+        }
+        if (peer.recvBitrateKbps > 0) {
+            int target = peer.recvBitrateKbps * 900;
+            if (target < bitrate) {
+                bitrate = Math.max(600_000, target);
+            }
+        }
+        if (peer.sendBitrateKbps > 0 && peer.sendBitrateKbps * 1000 < bitrate) {
+            bitrate = Math.max(600_000, peer.sendBitrateKbps * 950);
+        }
+        return bitrate;
+    }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/SettingsUi.java b/app/src/main/java/com/foxx/androidcast/SettingsUi.java
index b00e0ad..c38b590 100644
--- a/app/src/main/java/com/foxx/androidcast/SettingsUi.java
+++ b/app/src/main/java/com/foxx/androidcast/SettingsUi.java
@@ -8,7 +8,10 @@ import android.widget.Spinner;
 
 import androidx.appcompat.app.AppCompatActivity;
 
-import com.foxx.androidcast.R;
+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 {
@@ -18,60 +21,172 @@ public final class SettingsUi {
         PlatformCastSupport.applyDefaultAudioSetting(settings);
 
         Spinner transport = activity.findViewById(R.id.spinner_transport);
+        Spinner videoCodec = activity.findViewById(R.id.spinner_video_codec);
+        Spinner adjustment = activity.findViewById(R.id.spinner_adjustment);
+        Spinner bitrateMode = activity.findViewById(R.id.spinner_bitrate_mode);
         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);
 
-        String[] transports = {
+        bindSpinner(activity, transport, new String[]{
                 activity.getString(R.string.transport_tcp),
                 activity.getString(R.string.transport_udp)
-        };
-        transport.setAdapter(new ArrayAdapter<>(activity, android.R.layout.simple_spinner_dropdown_item, transports));
-        transport.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
-            @Override
-            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
-                settings.setTransport(position == 1 ? CastConfig.TRANSPORT_UDP : CastConfig.TRANSPORT_TCP);
+        }, position -> settings.setTransport(
+                position == 1 ? CastConfig.TRANSPORT_UDP : CastConfig.TRANSPORT_TCP));
+
+        List<CastSettings.VideoCodec> codecs = CodecCatalog.supportedChoices();
+        List<String> codecLabels = new ArrayList<>();
+        for (CastSettings.VideoCodec c : codecs) {
+            codecLabels.add(labelVideoCodec(activity, c));
+        }
+        bindSpinner(activity, videoCodec, codecLabels.toArray(new String[0]), position -> {
+            if (position >= 0 && position < codecs.size()) {
+                settings.setVideoCodec(codecs.get(position));
             }
-
-            @Override
-            public void onNothingSelected(AdapterView<?> parent) {}
         });
+        selectCodecSpinner(videoCodec, codecs, settings.getVideoCodec());
 
-        String[] qualities = {
+        bindEnumSpinner(activity, adjustment, CastSettings.AdjustmentPreset.values(),
+                SettingsUi::labelAdjustment, settings.getAdjustmentPreset().ordinal(),
+                p -> settings.setAdjustmentPreset(CastSettings.AdjustmentPreset.values()[p]));
+
+        bindEnumSpinner(activity, bitrateMode, CastSettings.BitrateMode.values(),
+                SettingsUi::labelBitrateMode, settings.getBitrateMode().ordinal(),
+                p -> settings.setBitrateMode(CastSettings.BitrateMode.values()[p]));
+
+        bindSpinner(activity, quality, new String[]{
                 activity.getString(R.string.quality_low),
                 activity.getString(R.string.quality_medium),
                 activity.getString(R.string.quality_high)
-        };
-        quality.setAdapter(new ArrayAdapter<>(activity, android.R.layout.simple_spinner_dropdown_item, qualities));
-        quality.setSelection(1);
-        resolution.setSelection(CastSettings.Resolution.HD_720P.ordinal());
-        quality.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
-            @Override
-            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
-                settings.setQuality(CastSettings.Quality.values()[position]);
-            }
+        }, position -> settings.setQuality(CastSettings.Quality.values()[position]));
+        quality.setSelection(CastSettings.Quality.MEDIUM.ordinal());
 
-            @Override
-            public void onNothingSelected(AdapterView<?> parent) {}
-        });
+        bindEnumSpinner(activity, networkAdoption, CastSettings.NetworkAdoption.values(),
+                SettingsUi::labelNetworkAdoption, settings.getNetworkAdoption().ordinal(),
+                p -> settings.setNetworkAdoption(CastSettings.NetworkAdoption.values()[p]));
 
         String[] resolutions = {
                 activity.getString(R.string.resolution_full),
                 activity.getString(R.string.resolution_75),
                 activity.getString(R.string.resolution_half),
-                activity.getString(R.string.resolution_720p)
+                activity.getString(R.string.resolution_720p),
+                activity.getString(R.string.resolution_fixed_1080p),
+                activity.getString(R.string.resolution_fixed_720p),
+                activity.getString(R.string.resolution_adaptive)
         };
-        resolution.setAdapter(new ArrayAdapter<>(activity, android.R.layout.simple_spinner_dropdown_item, resolutions));
-        resolution.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
+        bindSpinner(activity, resolution, resolutions,
+                position -> settings.setResolution(CastSettings.Resolution.values()[position]));
+        resolution.setSelection(CastSettings.Resolution.HD_720P.ordinal());
+
+        PlatformCastSupport.bindAudioCheckbox(activity, audio, settings);
+    }
+
+    private interface IntConsumer {
+        void accept(int position);
+    }
+
+    private interface LabelProvider<T> {
+        String label(AppCompatActivity activity, T value);
+    }
+
+    private static <T extends Enum<T>> void bindEnumSpinner(AppCompatActivity activity, Spinner spinner,
+            T[] values, LabelProvider<T> labels, int selection, IntConsumer onSelect) {
+        String[] items = new String[values.length];
+        for (int i = 0; i < values.length; i++) {
+            items[i] = labels.label(activity, values[i]);
+        }
+        bindSpinner(activity, spinner, items, onSelect);
+        if (selection >= 0 && selection < values.length) {
+            spinner.setSelection(selection);
+        }
+    }
+
+    private static void bindSpinner(AppCompatActivity activity, Spinner spinner, String[] items,
+            IntConsumer onSelect) {
+        spinner.setAdapter(new ArrayAdapter<>(activity, android.R.layout.simple_spinner_dropdown_item, items));
+        spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
             @Override
             public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
-                settings.setResolution(CastSettings.Resolution.values()[position]);
+                onSelect.accept(position);
             }
 
             @Override
             public void onNothingSelected(AdapterView<?> parent) {}
         });
+    }
 
-        PlatformCastSupport.bindAudioCheckbox(activity, audio, settings);
+    private static void selectCodecSpinner(Spinner spinner, List<CastSettings.VideoCodec> codecs,
+            CastSettings.VideoCodec selected) {
+        for (int i = 0; i < codecs.size(); i++) {
+            if (codecs.get(i) == selected) {
+                spinner.setSelection(i);
+                return;
+            }
+        }
+    }
+
+    private static String labelVideoCodec(AppCompatActivity activity, CastSettings.VideoCodec codec) {
+        switch (codec) {
+            case H264:
+                return activity.getString(R.string.codec_h264);
+            case H265:
+                return activity.getString(R.string.codec_h265);
+            case PASSTHROUGH:
+                return activity.getString(R.string.codec_passthrough);
+            case AUTO:
+            default:
+                return activity.getString(R.string.option_auto);
+        }
+    }
+
+    private static String labelAdjustment(AppCompatActivity activity, CastSettings.AdjustmentPreset p) {
+        switch (p) {
+            case NONE:
+                return activity.getString(R.string.option_none);
+            case QUALITY:
+                return activity.getString(R.string.option_quality);
+            case SPEED:
+                return activity.getString(R.string.option_speed);
+            case PERFORMANCE:
+                return activity.getString(R.string.option_performance);
+            case AUTO:
+            default:
+                return activity.getString(R.string.option_auto);
+        }
+    }
+
+    private static String labelBitrateMode(AppCompatActivity activity, CastSettings.BitrateMode m) {
+        switch (m) {
+            case NONE:
+                return activity.getString(R.string.option_none);
+            case QUALITY:
+                return activity.getString(R.string.option_quality);
+            case SPEED:
+                return activity.getString(R.string.option_speed);
+            case BALANCED:
+                return activity.getString(R.string.option_balanced);
+            case ROBUST_LESS:
+                return activity.getString(R.string.option_robust_less);
+            case ESTIMATED:
+                return activity.getString(R.string.option_estimated);
+            case AUTO:
+            default:
+                return activity.getString(R.string.option_auto);
+        }
+    }
+
+    private static String labelNetworkAdoption(AppCompatActivity activity, CastSettings.NetworkAdoption n) {
+        switch (n) {
+            case QUALITY:
+                return activity.getString(R.string.option_quality);
+            case SPEED:
+                return activity.getString(R.string.option_speed);
+            case ESTIMATED:
+                return activity.getString(R.string.option_estimated);
+            case AUTO:
+            default:
+                return activity.getString(R.string.option_auto);
+        }
     }
 }
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 bb3383a..b16b843 100644
--- a/app/src/main/java/com/foxx/androidcast/discovery/DiscoveryManager.java
+++ b/app/src/main/java/com/foxx/androidcast/discovery/DiscoveryManager.java
@@ -53,8 +53,10 @@ public class DiscoveryManager {
     private final ConcurrentHashMap<String, DiscoveredDevice> devices = new ConcurrentHashMap<>();
 
     private Listener listener;
+    private volatile DatagramSocket socket;
+    private final Object lockGuard = new Object();
     private WifiManager.MulticastLock multicastLock;
-    private DatagramSocket socket;
+    private int multicastHolds;
 
     public DiscoveryManager(Context context) {
         this.appContext = context.getApplicationContext();
@@ -71,16 +73,23 @@ public class DiscoveryManager {
         executor.execute(this::browseLoop);
     }
 
+    /**
+     * Stops discovery I/O. The background loop releases the multicast lock in its {@code finally}
+     * block — do not release here (double-release crashed the sender when cast started).
+     */
     public void stop() {
         running.set(false);
-        if (socket != null) {
-            socket.close();
+        DatagramSocket toClose = socket;
+        socket = null;
+        if (toClose != null) {
+            try {
+                toClose.close();
+            } catch (Exception ignored) {
+            }
         }
-        releaseMulticastLock();
         devices.clear();
     }
 
-    /** Clears cached devices and notifies listener with an empty list. */
     public void clearDevices() {
         devices.clear();
         notifyListener();
@@ -115,7 +124,9 @@ public class DiscoveryManager {
                 Log.e(TAG, "Browse failed", e);
             }
         } finally {
+            socket = null;
             releaseMulticastLock();
+            running.set(false);
         }
     }
 
@@ -142,13 +153,16 @@ public class DiscoveryManager {
                 Log.e(TAG, "Announce failed", e);
             }
         } finally {
+            socket = null;
             releaseMulticastLock();
+            running.set(false);
         }
     }
 
     private void handlePacket(DatagramPacket packet) {
         try {
-            String text = new String(packet.getData(), packet.getOffset(), packet.getLength(), StandardCharsets.UTF_8);
+            String text = new String(packet.getData(), packet.getOffset(), packet.getLength(),
+                    StandardCharsets.UTF_8);
             JSONObject json = new JSONObject(text);
             if (!CastConfig.DISCOVERY_MAGIC.equals(json.optString("magic"))) {
                 return;
@@ -183,18 +197,37 @@ public class DiscoveryManager {
     }
 
     private void acquireMulticastLock() {
-        WifiManager wifi = (WifiManager) appContext.getSystemService(Context.WIFI_SERVICE);
-        if (wifi != null) {
-            multicastLock = wifi.createMulticastLock("androidcast-discovery");
-            multicastLock.setReferenceCounted(true);
-            multicastLock.acquire();
+        synchronized (lockGuard) {
+            if (multicastLock == null) {
+                WifiManager wifi = (WifiManager) appContext.getSystemService(Context.WIFI_SERVICE);
+                if (wifi == null) {
+                    return;
+                }
+                multicastLock = wifi.createMulticastLock("androidcast-discovery");
+                multicastLock.setReferenceCounted(false);
+            }
+            if (multicastHolds == 0) {
+                multicastLock.acquire();
+            }
+            multicastHolds++;
         }
     }
 
     private void releaseMulticastLock() {
-        if (multicastLock != null && multicastLock.isHeld()) {
-            multicastLock.release();
+        synchronized (lockGuard) {
+            if (multicastLock == null || multicastHolds <= 0) {
+                return;
+            }
+            multicastHolds--;
+            if (multicastHolds == 0) {
+                try {
+                    if (multicastLock.isHeld()) {
+                        multicastLock.release();
+                    }
+                } catch (RuntimeException e) {
+                    Log.w(TAG, "MulticastLock release: " + e.getMessage());
+                }
+            }
         }
-        multicastLock = null;
     }
 }
diff --git a/app/src/main/java/com/foxx/androidcast/media/CodecNegotiator.java b/app/src/main/java/com/foxx/androidcast/media/CodecNegotiator.java
new file mode 100644
index 0000000..5509b56
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/media/CodecNegotiator.java
@@ -0,0 +1,75 @@
+package com.foxx.androidcast.media;
+
+import android.media.MediaFormat;
+
+import com.foxx.androidcast.CastSettings;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Locale;
+import java.util.Set;
+
+/** Picks a video MIME type both sides support, honoring user preference when possible. */
+public final class CodecNegotiator {
+    private static final String[] PREFERENCE_ORDER = {
+            MediaFormat.MIMETYPE_VIDEO_HEVC,
+            MediaFormat.MIMETYPE_VIDEO_AVC,
+            MediaFormat.MIMETYPE_VIDEO_VP9,
+            MediaFormat.MIMETYPE_VIDEO_VP8,
+    };
+
+    private CodecNegotiator() {}
+
+    public static String negotiate(List<String> senderEncoders, List<String> receiverDecoders,
+            CastSettings.VideoCodec preference) {
+        Set<String> enc = new HashSet<>(senderEncoders);
+        Set<String> dec = new HashSet<>(receiverDecoders);
+        if (preference == CastSettings.VideoCodec.H264) {
+            return pick(MediaFormat.MIMETYPE_VIDEO_AVC, enc, dec);
+        }
+        if (preference == CastSettings.VideoCodec.H265) {
+            return pick(MediaFormat.MIMETYPE_VIDEO_HEVC, enc, dec);
+        }
+        for (String mime : PREFERENCE_ORDER) {
+            if (enc.contains(mime) && dec.contains(mime)) {
+                return mime;
+            }
+        }
+        if (dec.contains(MediaFormat.MIMETYPE_VIDEO_AVC) && enc.contains(MediaFormat.MIMETYPE_VIDEO_AVC)) {
+            return MediaFormat.MIMETYPE_VIDEO_AVC;
+        }
+        throw new IllegalStateException("No common video codec (sender=" + enc + " receiver=" + dec + ")");
+    }
+
+    private static String pick(String mime, Set<String> enc, Set<String> dec) {
+        if (enc.contains(mime) && dec.contains(mime)) {
+            return mime;
+        }
+        throw new IllegalStateException("Preferred codec not available on both sides: " + mime);
+    }
+
+    public static String displayName(String mime) {
+        if (mime == null) {
+            return "?";
+        }
+        if (MediaFormat.MIMETYPE_VIDEO_AVC.equals(mime)) {
+            return "H.264";
+        }
+        if (MediaFormat.MIMETYPE_VIDEO_HEVC.equals(mime)) {
+            return "H.265";
+        }
+        if (MediaFormat.MIMETYPE_VIDEO_VP9.equals(mime)) {
+            return "VP9";
+        }
+        if (MediaFormat.MIMETYPE_VIDEO_VP8.equals(mime)) {
+            return "VP8";
+        }
+        int slash = mime.lastIndexOf('/');
+        return slash >= 0 ? mime.substring(slash + 1).toUpperCase(Locale.US) : mime;
+    }
+
+    public static boolean isH264(String mime) {
+        return MediaFormat.MIMETYPE_VIDEO_AVC.equals(mime);
+    }
+}
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 0c02046..afa27a3 100644
--- a/app/src/main/java/com/foxx/androidcast/network/CastProtocol.java
+++ b/app/src/main/java/com/foxx/androidcast/network/CastProtocol.java
@@ -5,6 +5,8 @@ import com.foxx.androidcast.CastSettings;
 import com.foxx.androidcast.network.control.NetworkControlAdvice;
 import com.foxx.androidcast.network.control.NetworkStatsSnapshot;
 
+import android.media.MediaFormat;
+
 import java.io.DataInputStream;
 import java.io.DataOutputStream;
 import java.io.IOException;
@@ -27,6 +29,8 @@ public final class CastProtocol {
     public static final byte MSG_NETWORK_STATS = 11;
     public static final byte MSG_NETWORK_CONTROL = 12;
     public static final byte MSG_AUDIO_CONSENT = 13;
+    public static final byte MSG_CODEC_CAPS = 14;
+    public static final byte MSG_CODEC_SELECTED = 15;
 
     private CastProtocol() {}
 
@@ -64,10 +68,15 @@ public final class CastProtocol {
     public static byte[] castSettingsPayload(CastSettings settings) throws IOException {
         java.io.ByteArrayOutputStream bos = new java.io.ByteArrayOutputStream();
         DataOutputStream dos = new DataOutputStream(bos);
+        dos.writeInt(CastSettings.SETTINGS_VERSION);
         dos.writeUTF(settings.getTransport());
         dos.writeInt(settings.getQuality().ordinal());
         dos.writeInt(settings.getResolution().ordinal());
         dos.writeByte(settings.isAudioEnabled() ? 1 : 0);
+        dos.writeInt(settings.getVideoCodec().ordinal());
+        dos.writeInt(settings.getAdjustmentPreset().ordinal());
+        dos.writeInt(settings.getBitrateMode().ordinal());
+        dos.writeInt(settings.getNetworkAdoption().ordinal());
         dos.flush();
         return bos.toByteArray();
     }
@@ -75,15 +84,84 @@ public final class CastProtocol {
     public static CastSettings parseCastSettings(byte[] payload) throws IOException {
         DataInputStream dis = new DataInputStream(new java.io.ByteArrayInputStream(payload));
         CastSettings settings = new CastSettings();
-        settings.setTransport(dis.readUTF());
-        int q = dis.readInt();
-        int r = dis.readInt();
-        settings.setQuality(CastSettings.Quality.values()[q]);
-        settings.setResolution(CastSettings.Resolution.values()[r]);
-        settings.setAudioEnabled(dis.readByte() != 0);
+        dis.mark(64);
+        int first = dis.readInt();
+        if (first == CastSettings.SETTINGS_VERSION) {
+            settings.setTransport(dis.readUTF());
+            settings.setQuality(readEnum(CastSettings.Quality.values(), dis.readInt(), CastSettings.Quality.MEDIUM));
+            settings.setResolution(readEnum(CastSettings.Resolution.values(), dis.readInt(),
+                    CastSettings.Resolution.HD_720P));
+            settings.setAudioEnabled(dis.readByte() != 0);
+            if (dis.available() > 0) {
+                settings.setVideoCodec(readEnum(CastSettings.VideoCodec.values(), dis.readInt(),
+                        CastSettings.VideoCodec.AUTO));
+            }
+            if (dis.available() > 0) {
+                settings.setAdjustmentPreset(readEnum(CastSettings.AdjustmentPreset.values(), dis.readInt(),
+                        CastSettings.AdjustmentPreset.AUTO));
+            }
+            if (dis.available() > 0) {
+                settings.setBitrateMode(readEnum(CastSettings.BitrateMode.values(), dis.readInt(),
+                        CastSettings.BitrateMode.AUTO));
+            }
+            if (dis.available() > 0) {
+                settings.setNetworkAdoption(readEnum(CastSettings.NetworkAdoption.values(), dis.readInt(),
+                        CastSettings.NetworkAdoption.AUTO));
+            }
+        } else {
+            dis.reset();
+            settings.setTransport(dis.readUTF());
+            settings.setQuality(readEnum(CastSettings.Quality.values(), dis.readInt(), CastSettings.Quality.MEDIUM));
+            settings.setResolution(readEnum(CastSettings.Resolution.values(), dis.readInt(),
+                    CastSettings.Resolution.HD_720P));
+            settings.setAudioEnabled(dis.readByte() != 0);
+        }
         return settings;
     }
 
+    private static <T extends Enum<T>> T readEnum(T[] values, int ordinal, T fallback) {
+        if (ordinal >= 0 && ordinal < values.length) {
+            return values[ordinal];
+        }
+        return fallback;
+    }
+
+    public static byte[] codecCapsPayload(java.util.List<String> mimeTypes) throws IOException {
+        java.io.ByteArrayOutputStream bos = new java.io.ByteArrayOutputStream();
+        DataOutputStream dos = new DataOutputStream(bos);
+        dos.writeInt(mimeTypes != null ? mimeTypes.size() : 0);
+        if (mimeTypes != null) {
+            for (String mime : mimeTypes) {
+                dos.writeUTF(mime);
+            }
+        }
+        dos.flush();
+        return bos.toByteArray();
+    }
+
+    public static java.util.List<String> parseCodecCaps(byte[] payload) throws IOException {
+        DataInputStream dis = new DataInputStream(new java.io.ByteArrayInputStream(payload));
+        int n = dis.readInt();
+        java.util.List<String> list = new java.util.ArrayList<>(Math.max(0, n));
+        for (int i = 0; i < n; i++) {
+            list.add(dis.readUTF());
+        }
+        return list;
+    }
+
+    public static byte[] codecSelectedPayload(String mime) throws IOException {
+        java.io.ByteArrayOutputStream bos = new java.io.ByteArrayOutputStream();
+        DataOutputStream dos = new DataOutputStream(bos);
+        dos.writeUTF(mime != null ? mime : MediaFormat.MIMETYPE_VIDEO_AVC);
+        dos.flush();
+        return bos.toByteArray();
+    }
+
+    public static String parseCodecSelected(byte[] payload) throws IOException {
+        DataInputStream dis = new DataInputStream(new java.io.ByteArrayInputStream(payload));
+        return dis.readUTF();
+    }
+
     public static byte[] streamConfigPayload(int width, int height, byte[] csd0, byte[] csd1) throws IOException {
         java.io.ByteArrayOutputStream bos = new java.io.ByteArrayOutputStream();
         DataOutputStream dos = new DataOutputStream(bos);
diff --git a/app/src/main/java/com/foxx/androidcast/network/CastSession.java b/app/src/main/java/com/foxx/androidcast/network/CastSession.java
index 8440e90..3d97c52 100644
--- a/app/src/main/java/com/foxx/androidcast/network/CastSession.java
+++ b/app/src/main/java/com/foxx/androidcast/network/CastSession.java
@@ -1,18 +1,23 @@
 package com.foxx.androidcast.network;
 
 import com.foxx.androidcast.CastSettings;
+import com.foxx.androidcast.media.CodecNegotiator;
+import com.foxx.androidcast.sender.CodecCatalog;
 
 import java.io.IOException;
+import java.util.List;
 
 /** Auth handshake and message I/O over a {@link CastTransport}. */
 public class CastSession {
     public static final class HandshakeResult {
         public final String senderName;
         public final CastSettings settings;
+        public final String negotiatedVideoMime;
 
-        public HandshakeResult(String senderName, CastSettings settings) {
+        public HandshakeResult(String senderName, CastSettings settings, String negotiatedVideoMime) {
             this.senderName = senderName;
             this.settings = settings;
+            this.negotiatedVideoMime = negotiatedVideoMime;
         }
     }
 
@@ -42,7 +47,7 @@ public class CastSession {
         transport.connect(host, port);
     }
 
-    public void clientHandshake(String deviceName, String pin, CastSettings settings) throws IOException {
+    public HandshakeResult clientHandshake(String deviceName, String pin, CastSettings settings) throws IOException {
         transport.send(CastProtocol.MSG_HELLO, CastProtocol.helloPayload(deviceName));
         transport.send(CastProtocol.MSG_AUTH, CastProtocol.authPayload(pin));
         CastProtocol.Message reply = transport.receive(10_000);
@@ -50,11 +55,32 @@ public class CastSession {
             throw new IOException("Authentication failed");
         }
         transport.send(CastProtocol.MSG_CAST_SETTINGS, CastProtocol.castSettingsPayload(settings));
+        transport.send(CastProtocol.MSG_CODEC_CAPS, CastProtocol.codecCapsPayload(CodecCatalog.localEncoderMimes()));
+
+        String negotiated = null;
+        long deadline = System.currentTimeMillis() + 15_000;
+        while (System.currentTimeMillis() < deadline) {
+            CastProtocol.Message msg = transport.receive(2_000);
+            if (msg == null) {
+                continue;
+            }
+            if (msg.type == CastProtocol.MSG_CODEC_SELECTED) {
+                negotiated = CastProtocol.parseCodecSelected(msg.payload);
+                break;
+            }
+        }
+        if (negotiated == null) {
+            throw new IOException("Codec negotiation timeout");
+        }
+        settings.setNegotiatedVideoMime(negotiated);
+        return new HandshakeResult(deviceName, settings, negotiated);
     }
 
     public HandshakeResult serverHandshake(String expectedPin, CastSettings localSettings) throws IOException {
         String senderName = "Sender";
         boolean authed = false;
+        CastSettings remote = null;
+        List<String> senderCaps = null;
         long deadline = System.currentTimeMillis() + 30_000;
         while (System.currentTimeMillis() < deadline) {
             CastProtocol.Message msg = transport.receive(2_000);
@@ -75,18 +101,26 @@ public class CastSession {
                     }
                     break;
                 case CastProtocol.MSG_CAST_SETTINGS:
-                    if (!authed) {
-                        break;
-                    }
-                    CastSettings remote = CastProtocol.parseCastSettings(msg.payload);
+                    remote = CastProtocol.parseCastSettings(msg.payload);
                     if (!CastProtocol.transportMatches(localSettings, remote)) {
                         throw new IOException("Transport mismatch: receiver="
                                 + localSettings.getTransport() + " sender=" + remote.getTransport());
                     }
-                    return new HandshakeResult(senderName, remote);
+                    break;
+                case CastProtocol.MSG_CODEC_CAPS:
+                    senderCaps = CastProtocol.parseCodecCaps(msg.payload);
+                    break;
                 default:
                     break;
             }
+            if (authed && remote != null && senderCaps != null) {
+                List<String> receiverCaps = CodecCatalog.localDecoderMimes();
+                transport.send(CastProtocol.MSG_CODEC_CAPS, CastProtocol.codecCapsPayload(receiverCaps));
+                String mime = CodecNegotiator.negotiate(senderCaps, receiverCaps, remote.getVideoCodec());
+                transport.send(CastProtocol.MSG_CODEC_SELECTED, CastProtocol.codecSelectedPayload(mime));
+                remote.setNegotiatedVideoMime(mime);
+                return new HandshakeResult(senderName, remote, mime);
+            }
         }
         throw new IOException("Handshake timeout");
     }
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 87d0c7c..845c7ec 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
@@ -32,6 +32,10 @@ public class PassThroughNetworkControlPlane implements NetworkControlPlane {
         return outbound;
     }
 
+    public NetworkStatsSnapshot getLastPeerStats() {
+        return lastPeer != null ? lastPeer.copy() : null;
+    }
+
     @Override
     public void onPeerStats(NetworkStatsSnapshot stats) {
         lastPeer = stats != null ? stats.copy() : null;
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 2e94fcb..7f55172 100644
--- a/app/src/main/java/com/foxx/androidcast/receiver/ReceiverCastService.java
+++ b/app/src/main/java/com/foxx/androidcast/receiver/ReceiverCastService.java
@@ -74,6 +74,7 @@ public class ReceiverCastService extends Service {
     private PowerManager.WakeLock wakeLock;
     private String activePin = com.foxx.androidcast.CastConfig.DEFAULT_PIN;
     private final StreamMetrics streamMetrics = new StreamMetrics();
+    private String negotiatedVideoMime;
     private boolean streamIdle;
     private long lastVideoFrameMs;
 
@@ -189,8 +190,8 @@ public class ReceiverCastService extends Service {
             }
 
             @Override
-            public void onAuthenticated(String senderName, CastSettings remoteSettings) {
-                mainHandler.post(() -> onSenderConnected(senderName));
+            public void onAuthenticated(String senderName, CastSettings remoteSettings, String videoMime) {
+                mainHandler.post(() -> onSenderConnected(senderName, remoteSettings, videoMime));
             }
 
             @Override
@@ -271,16 +272,34 @@ public class ReceiverCastService extends Service {
         Log.i(TAG, "Listening PIN=" + pin + " audio=" + allowIncomingAudio);
     }
 
-    private void onSenderConnected(String senderName) {
+    private void onSenderConnected(String senderName, CastSettings remoteSettings, String videoMime) {
         phase = Phase.CONNECTED;
+        negotiatedVideoMime = videoMime;
         audioAccepted = null;
         streamIdle = false;
         streamMetrics.reset();
         lastVideoFrameMs = 0;
-        updateStatus(getString(R.string.casting_from, senderName));
+        String codecLabel = videoMime != null
+                ? com.foxx.androidcast.media.CodecNegotiator.displayName(videoMime) : "?";
+        updateStatus(getString(R.string.casting_from_codec, senderName, codecLabel));
         broadcastAuthenticated(senderName);
         openPlaybackAwaiting(R.string.playback_awaiting_stream);
-        Log.i(TAG, "Sender connected: " + senderName);
+        if (remoteSettings != null && remoteSettings.isAudioRequested() && allowIncomingAudio) {
+            audioAccepted = true;
+            sendAudioConsentAsync(true);
+            Log.i(TAG, "Audio accepted for sender (pre-config)");
+        } else if (remoteSettings != null && remoteSettings.isAudioRequested()) {
+            updateStatus(getString(R.string.audio_skipped));
+        }
+        Log.i(TAG, "Sender connected: " + senderName + " codec=" + videoMime);
+    }
+
+    private void sendAudioConsentAsync(final boolean accept) {
+        new Thread(() -> {
+            if (session != null) {
+                session.sendAudioConsent(accept);
+            }
+        }, "AudioConsent").start();
     }
 
     private void onSenderDisconnected() {
@@ -502,7 +521,9 @@ public class ReceiverCastService extends Service {
                 videoDecoder.release();
             }
             videoDecoder = new VideoDecoder();
-            videoDecoder.configure(pendingWidth, pendingHeight, pendingCsd0, pendingCsd1, attachedSurface,
+            String mime = negotiatedVideoMime != null ? negotiatedVideoMime
+                    : android.media.MediaFormat.MIMETYPE_VIDEO_AVC;
+            videoDecoder.configure(mime, pendingWidth, pendingHeight, pendingCsd0, pendingCsd1, attachedSurface,
                     new VideoDecoder.Listener() {
                         @Override
                         public void onFirstFrameRendered() {
@@ -544,6 +565,7 @@ public class ReceiverCastService extends Service {
     private String buildDiagnosticsText() {
         return streamMetrics.format(
                 settings.getTransport(),
+                negotiatedVideoMime,
                 pendingWidth,
                 pendingHeight,
                 decoderWidth,
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 4009734..3b2cfb9 100644
--- a/app/src/main/java/com/foxx/androidcast/receiver/ReceiverSession.java
+++ b/app/src/main/java/com/foxx/androidcast/receiver/ReceiverSession.java
@@ -24,7 +24,7 @@ public class ReceiverSession {
     public interface Listener {
         void onStatus(String status);
 
-        void onAuthenticated(String senderName, CastSettings remoteSettings);
+        void onAuthenticated(String senderName, CastSettings remoteSettings, String negotiatedVideoMime);
 
         void onStreamConfig(int width, int height, byte[] csd0, byte[] csd1);
 
@@ -106,7 +106,7 @@ public class ReceiverSession {
                 networkFeedback = new NetworkFeedbackManager(session, false);
                 session.acceptClient();
                 CastSession.HandshakeResult hs = session.serverHandshake(pin, localSettings);
-                listener.onAuthenticated(hs.senderName, hs.settings);
+                listener.onAuthenticated(hs.senderName, hs.settings, hs.negotiatedVideoMime);
                 postStatus("Streaming from " + hs.senderName);
                 readStream();
             } catch (java.io.EOFException e) {
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 0545239..ee49085 100644
--- a/app/src/main/java/com/foxx/androidcast/receiver/StreamMetrics.java
+++ b/app/src/main/java/com/foxx/androidcast/receiver/StreamMetrics.java
@@ -92,8 +92,8 @@ public final class StreamMetrics {
         return lastVideoPacketMs;
     }
 
-    public synchronized String format(String transport, int streamW, int streamH, int renderW, int renderH,
-            boolean idle) {
+    public synchronized String format(String transport, String videoCodec, int streamW, int streamH, int renderW,
+            int renderH, boolean idle) {
         long now = System.currentTimeMillis();
         float inFps = lastSecondInFps > 0 ? lastSecondInFps : computeFps(videoPackets, firstVideoPacketMs, now);
         float renderFps = computeFps(renderedFrames, firstVideoPacketMs, lastRenderedFrameMs);
@@ -102,6 +102,10 @@ public final class StreamMetrics {
 
         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);
@@ -122,13 +126,23 @@ public final class StreamMetrics {
             sb.append("  ~").append(Math.max(1, avgKb)).append(" KB/frame");
         }
         sb.append('\n');
-        if (inFps > 0 && inFps < 10f) {
-            sb.append("Hint: low In FPS → sender encode or TCP backlog\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).append('\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");
diff --git a/app/src/main/java/com/foxx/androidcast/receiver/VideoDecoder.java b/app/src/main/java/com/foxx/androidcast/receiver/VideoDecoder.java
index 02d8579..857f825 100644
--- a/app/src/main/java/com/foxx/androidcast/receiver/VideoDecoder.java
+++ b/app/src/main/java/com/foxx/androidcast/receiver/VideoDecoder.java
@@ -5,6 +5,7 @@ import android.media.MediaFormat;
 import android.util.Log;
 import android.view.Surface;
 
+import com.foxx.androidcast.media.CodecNegotiator;
 import com.foxx.androidcast.media.H264Bitstream;
 
 import java.io.IOException;
@@ -12,10 +13,9 @@ import java.nio.ByteBuffer;
 import java.util.ArrayDeque;
 import java.util.Queue;
 
-/** Thread-safe H.264 decoder feeding a Surface. */
+/** Thread-safe hardware video decoder feeding a Surface. */
 public class VideoDecoder {
     private static final String TAG = "VideoDecoder";
-    private static final String MIME = MediaFormat.MIMETYPE_VIDEO_AVC;
 
     public interface Listener {
         void onFirstFrameRendered();
@@ -32,26 +32,31 @@ public class VideoDecoder {
     private Listener listener;
     private boolean firstFrameNotified;
 
-    public void configure(int width, int height, byte[] csd0, byte[] csd1, Surface surface, Listener listener)
-            throws IOException {
+    private String mime = MediaFormat.MIMETYPE_VIDEO_AVC;
+
+    public void configure(String mime, int width, int height, byte[] csd0, byte[] csd1, Surface surface,
+            Listener listener) throws IOException {
         synchronized (lock) {
             releaseLocked();
             released = false;
             this.listener = listener;
+            this.mime = mime != null ? mime : MediaFormat.MIMETYPE_VIDEO_AVC;
             firstFrameNotified = false;
-            MediaFormat format = MediaFormat.createVideoFormat(MIME, width, height);
+            MediaFormat format = MediaFormat.createVideoFormat(this.mime, width, height);
             format.setInteger(MediaFormat.KEY_MAX_INPUT_SIZE, width * height * 2);
             if (csd0 != null && csd0.length > 0) {
-                format.setByteBuffer("csd-0", ByteBuffer.wrap(H264Bitstream.toAnnexB(csd0)));
+                byte[] c0 = CodecNegotiator.isH264(this.mime) ? H264Bitstream.toAnnexB(csd0) : csd0;
+                format.setByteBuffer("csd-0", ByteBuffer.wrap(c0));
             }
             if (csd1 != null && csd1.length > 0) {
-                format.setByteBuffer("csd-1", ByteBuffer.wrap(H264Bitstream.toAnnexB(csd1)));
+                byte[] c1 = CodecNegotiator.isH264(this.mime) ? H264Bitstream.toAnnexB(csd1) : csd1;
+                format.setByteBuffer("csd-1", ByteBuffer.wrap(c1));
             }
-            codec = MediaCodec.createDecoderByType(MIME);
+            codec = MediaCodec.createDecoderByType(this.mime);
             codec.configure(format, surface, null, 0);
             codec.start();
             configured = true;
-            Log.i(TAG, "Configured " + width + "x" + height);
+            Log.i(TAG, "Configured " + CodecNegotiator.displayName(this.mime) + " " + width + "x" + height);
             drainPendingLocked();
         }
     }
@@ -61,7 +66,7 @@ public class VideoDecoder {
             if (released || data == null || data.length == 0) {
                 return;
             }
-            byte[] annexB = H264Bitstream.toAnnexB(data);
+            byte[] annexB = CodecNegotiator.isH264(mime) ? H264Bitstream.toAnnexB(data) : data;
             if (!configured || codec == null) {
                 pending.add(new PendingFrame(ptsUs, keyFrame, annexB));
                 return;
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 0f95d59..940efa6 100644
--- a/app/src/main/java/com/foxx/androidcast/sender/AudioCapture.java
+++ b/app/src/main/java/com/foxx/androidcast/sender/AudioCapture.java
@@ -42,6 +42,8 @@ public class AudioCapture {
                 .addMatchingUsage(AudioAttributes.USAGE_MEDIA)
                 .addMatchingUsage(AudioAttributes.USAGE_GAME)
                 .addMatchingUsage(AudioAttributes.USAGE_UNKNOWN)
+                .addMatchingUsage(AudioAttributes.USAGE_ASSISTANCE_SONIFICATION)
+                .addMatchingUsage(AudioAttributes.USAGE_ASSISTANCE_ACCESSIBILITY)
                 .build();
 
         record = new AudioRecord.Builder()
@@ -57,6 +59,7 @@ public class AudioCapture {
 
         running = true;
         record.startRecording();
+        Log.i(TAG, "Playback audio capture started");
         thread = new Thread(() -> readLoop(callback), "AudioCapture");
         thread.start();
     }
@@ -69,6 +72,8 @@ public class AudioCapture {
             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);
             }
         }
     }
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 10d763b..05675d5 100644
--- a/app/src/main/java/com/foxx/androidcast/sender/CastSendPump.java
+++ b/app/src/main/java/com/foxx/androidcast/sender/CastSendPump.java
@@ -15,7 +15,6 @@ import java.util.concurrent.atomic.AtomicBoolean;
 public final class CastSendPump {
     private static final String TAG = "CastSendPump";
     private static final int MAX_QUEUE = 48;
-    private static final int MAX_P_FRAMES_BACKLOG = 36;
 
     private final LinkedBlockingQueue<Outgoing> queue = new LinkedBlockingQueue<>(MAX_QUEUE);
     private final AtomicBoolean running = new AtomicBoolean(false);
@@ -68,18 +67,17 @@ public final class CastSendPump {
             return;
         }
         Outgoing item = Outgoing.video(ptsUs, keyFrame, annexBReadyPayload);
-        if (keyFrame) {
-            queue.offer(item);
-            return;
-        }
-        if (queue.size() >= MAX_P_FRAMES_BACKLOG) {
-            droppedPFrames++;
-            return;
-        }
         if (!queue.offer(item)) {
-            queue.poll();
+            if (!keyFrame) {
+                Outgoing dropped = queue.poll();
+                if (dropped != null && !dropped.keyFrame) {
+                    droppedPFrames++;
+                }
+            }
             if (!queue.offer(item)) {
-                droppedPFrames++;
+                if (!keyFrame) {
+                    droppedPFrames++;
+                }
             }
         }
     }
diff --git a/app/src/main/java/com/foxx/androidcast/sender/CodecCatalog.java b/app/src/main/java/com/foxx/androidcast/sender/CodecCatalog.java
new file mode 100644
index 0000000..4a1875b
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/sender/CodecCatalog.java
@@ -0,0 +1,87 @@
+package com.foxx.androidcast.sender;
+
+import android.media.MediaCodecInfo;
+import android.media.MediaCodecList;
+import android.media.MediaFormat;
+import android.os.Build;
+
+import com.foxx.androidcast.CastSettings;
+
+import java.util.ArrayList;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+
+/** Discovers device video encoder/decoder MIME types. */
+public final class CodecCatalog {
+    private CodecCatalog() {}
+
+    public static List<CastSettings.VideoCodec> supportedChoices() {
+        List<CastSettings.VideoCodec> out = new ArrayList<>();
+        out.add(CastSettings.VideoCodec.AUTO);
+        Set<String> enc = new LinkedHashSet<>(localEncoderMimes());
+        if (enc.contains(MediaFormat.MIMETYPE_VIDEO_AVC)) {
+            out.add(CastSettings.VideoCodec.H264);
+        }
+        if (enc.contains(MediaFormat.MIMETYPE_VIDEO_HEVC)) {
+            out.add(CastSettings.VideoCodec.H265);
+        }
+        if (enc.contains(MediaFormat.MIMETYPE_VIDEO_VP8) || enc.contains(MediaFormat.MIMETYPE_VIDEO_VP9)) {
+            // UI lists AUTO; VP8/VP9 chosen via negotiation when both sides support
+        }
+        out.add(CastSettings.VideoCodec.PASSTHROUGH);
+        return out;
+    }
+
+    public static List<String> localEncoderMimes() {
+        return listCodecMimes(true);
+    }
+
+    public static List<String> localDecoderMimes() {
+        return listCodecMimes(false);
+    }
+
+    private static List<String> listCodecMimes(boolean encoder) {
+        Set<String> out = new LinkedHashSet<>();
+        String[] want = {
+                MediaFormat.MIMETYPE_VIDEO_AVC,
+                MediaFormat.MIMETYPE_VIDEO_HEVC,
+                MediaFormat.MIMETYPE_VIDEO_VP9,
+                MediaFormat.MIMETYPE_VIDEO_VP8,
+        };
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
+            MediaCodecList list = new MediaCodecList(MediaCodecList.REGULAR_CODECS);
+            for (MediaCodecInfo info : list.getCodecInfos()) {
+                if (info.isEncoder() != encoder) {
+                    continue;
+                }
+                for (String type : info.getSupportedTypes()) {
+                    for (String w : want) {
+                        if (w.equalsIgnoreCase(type)) {
+                            out.add(w);
+                        }
+                    }
+                }
+            }
+        } else {
+            int n = MediaCodecList.getCodecCount();
+            for (int i = 0; i < n; i++) {
+                MediaCodecInfo info = MediaCodecList.getCodecInfoAt(i);
+                if (info.isEncoder() != encoder) {
+                    continue;
+                }
+                for (String type : info.getSupportedTypes()) {
+                    for (String w : want) {
+                        if (w.equalsIgnoreCase(type)) {
+                            out.add(w);
+                        }
+                    }
+                }
+            }
+        }
+        if (out.isEmpty()) {
+            out.add(MediaFormat.MIMETYPE_VIDEO_AVC);
+        }
+        return new ArrayList<>(out);
+    }
+}
diff --git a/app/src/main/java/com/foxx/androidcast/sender/EncoderKeepalive.java b/app/src/main/java/com/foxx/androidcast/sender/EncoderKeepalive.java
new file mode 100644
index 0000000..74f4b3e
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/sender/EncoderKeepalive.java
@@ -0,0 +1,46 @@
+package com.foxx.androidcast.sender;
+
+import android.os.Handler;
+import android.os.Looper;
+import android.util.Log;
+
+import com.foxx.androidcast.CastConfig;
+
+/**
+ * Periodic keyframe requests so Mediatek/others don't stall on a static screen
+ * (encoder stops emitting; receiver hits idle overlay).
+ */
+public final class EncoderKeepalive {
+    private static final String TAG = "EncoderKeepalive";
+
+    private final Handler handler = new Handler(Looper.getMainLooper());
+    private VideoEncoder encoder;
+    private boolean running;
+
+    private final Runnable tick = new Runnable() {
+        @Override
+        public void run() {
+            if (!running || encoder == null) {
+                return;
+            }
+            encoder.requestKeyframe();
+            Log.d(TAG, "Keepalive keyframe requested");
+            handler.postDelayed(this, CastConfig.KEYFRAME_KEEPALIVE_MS);
+        }
+    };
+
+    public void start(VideoEncoder encoder) {
+        this.encoder = encoder;
+        if (running) {
+            return;
+        }
+        running = true;
+        handler.postDelayed(tick, CastConfig.KEYFRAME_KEEPALIVE_MS);
+    }
+
+    public void stop() {
+        running = false;
+        handler.removeCallbacks(tick);
+        encoder = null;
+    }
+}
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 b4ee14f..52a3812 100644
--- a/app/src/main/java/com/foxx/androidcast/sender/ScreenCastService.java
+++ b/app/src/main/java/com/foxx/androidcast/sender/ScreenCastService.java
@@ -21,8 +21,10 @@ import android.view.Surface;
 import android.view.WindowManager;
 
 import com.foxx.androidcast.CastNotifications;
+import com.foxx.androidcast.CastConfig;
 import com.foxx.androidcast.CastResolution;
 import com.foxx.androidcast.CastSettings;
+import com.foxx.androidcast.CastTuningEngine;
 import com.foxx.androidcast.ICastSenderService;
 import com.foxx.androidcast.ICastStatusCallback;
 import com.foxx.androidcast.IntentExtras;
@@ -31,6 +33,7 @@ import com.foxx.androidcast.network.CastProtocol;
 import com.foxx.androidcast.network.CastSession;
 import com.foxx.androidcast.network.CastTransportFactory;
 import com.foxx.androidcast.network.control.NetworkFeedbackManager;
+import com.foxx.androidcast.network.control.NetworkStatsSnapshot;
 import com.foxx.androidcast.network.control.PassThroughNetworkControlPlane;
 
 import java.io.IOException;
@@ -61,6 +64,10 @@ public class ScreenCastService extends Service {
     private MediaProjection projection;
     private VirtualDisplay virtualDisplay;
     private VideoEncoder videoEncoder;
+    private EncoderKeepalive encoderKeepalive;
+    private CastTuningEngine.EffectiveParams effectiveParams;
+    private long lastSignificantFrameMs;
+    private final SenderStreamMetrics senderMetrics = new SenderStreamMetrics();
     private AudioEncoder audioEncoder;
     private AudioCapture audioCapture;
     private CastSession session;
@@ -159,7 +166,9 @@ public class ScreenCastService extends Service {
             updateStatus(getString(R.string.waiting_receiver, host, port));
             connectWithRetry(host, port, settings);
             updateStatus(getString(R.string.authenticating));
-            session.clientHandshake(deviceName != null ? deviceName : "Sender", pin, settings);
+            CastSession.HandshakeResult handshake = session.clientHandshake(
+                    deviceName != null ? deviceName : "Sender", pin, settings);
+            settings = handshake.settings;
             networkFeedback = new NetworkFeedbackManager(session, true);
             PassThroughNetworkControlPlane plane =
                     (PassThroughNetworkControlPlane) networkFeedback.getPlane();
@@ -168,6 +177,7 @@ public class ScreenCastService extends Service {
             casting.set(true);
             activeSettings = settings;
             startCaptureOnMainThread(resultCode, new Intent(data), settings);
+            scheduleTuningTick();
             while (!stopping.get()) {
                 try {
                     if (networkFeedback != null) {
@@ -288,48 +298,28 @@ public class ScreenCastService extends Service {
         DisplayMetrics metrics = new DisplayMetrics();
         WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
         wm.getDefaultDisplay().getRealMetrics(metrics);
-        CastResolution.Size size = CastResolution.compute(metrics, settings);
+        CastResolution.Size size = CastResolution.compute(metrics, settings, getPeerStats());
         setupVideoPipeline(size, settings);
         registerDisplayListener();
 
-        if (settings.isAudioEnabled() && Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
-            audioEncoder = new AudioEncoder();
-            audioEncoder.prepare(new AudioEncoder.Callback() {
-                private boolean configSent;
-
-                @Override
-                public void onConfig(int sampleRate, int channels, byte[] csd0) {
-                    if (configSent || stopping.get()) {
-                        return;
-                    }
-                    configSent = true;
-                    sendSafe(CastProtocol.MSG_AUDIO_CONFIG,
-                            () -> CastProtocol.audioConfigPayload(sampleRate, channels, csd0));
-                }
-
-                @Override
-                public void onEncodedFrame(long ptsUs, byte[] frameData) {
-                    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);
-                }
-            });
-        }
+        startAudioPipeline(settings);
 
         String mode = session.getTransport().getModeLabel();
         updateStatus(getString(R.string.casting_active, mode, captureWidth, captureHeight));
     }
 
     private void setupVideoPipeline(CastResolution.Size size, CastSettings settings) throws IOException {
+        if (settings.isPassthrough()) {
+            throw new IOException("Passthrough video is not implemented yet (debug only)");
+        }
         if (virtualDisplay != null) {
             virtualDisplay.release();
             virtualDisplay = null;
         }
+        if (encoderKeepalive != null) {
+            encoderKeepalive.stop();
+            encoderKeepalive = null;
+        }
         if (videoEncoder != null) {
             videoEncoder.stop();
             videoEncoder = null;
@@ -339,6 +329,16 @@ public class ScreenCastService extends Service {
         captureHeight = size.height;
         captureDensity = size.densityDpi;
 
+        NetworkStatsSnapshot peer = null;
+        if (networkFeedback != null && networkFeedback.getPlane() instanceof PassThroughNetworkControlPlane) {
+            peer = ((PassThroughNetworkControlPlane) networkFeedback.getPlane()).getLastPeerStats();
+        }
+        effectiveParams = CastTuningEngine.resolve(settings, peer);
+        String mime = settings.getNegotiatedVideoMime();
+        if (mime == null || mime.isEmpty()) {
+            throw new IOException("No negotiated video codec");
+        }
+
         videoEncoder = new VideoEncoder();
         VideoEncoder.Callback videoCb = new VideoEncoder.Callback() {
             @Override
@@ -352,13 +352,24 @@ public class ScreenCastService extends Service {
 
             @Override
             public void onEncodedFrame(long ptsUs, boolean keyFrame, byte[] frameData) {
-                if (sendPump != null) {
-                    sendPump.enqueueVideo(ptsUs, keyFrame, frameData);
+                if (sendPump == null || frameData == null) {
+                    return;
                 }
+                boolean tiny = effectiveParams != null && effectiveParams.skipTinyPFrames
+                        && !keyFrame
+                        && frameData.length < CastConfig.MIN_SIGNIFICANT_FRAME_BYTES;
+                if (tiny) {
+                    return;
+                }
+                lastSignificantFrameMs = System.currentTimeMillis();
+                senderMetrics.onEncodedFrame(keyFrame);
+                sendPump.enqueueVideo(ptsUs, keyFrame, frameData);
             }
         };
 
-        Surface surface = videoEncoder.prepare(captureWidth, captureHeight, settings, videoCb);
+        Surface surface = videoEncoder.prepare(captureWidth, captureHeight, mime, effectiveParams, videoCb);
+        encoderKeepalive = new EncoderKeepalive();
+        encoderKeepalive.start(videoEncoder);
         virtualDisplay = projection.createVirtualDisplay(
                 "AndroidCast",
                 captureWidth,
@@ -409,7 +420,7 @@ public class ScreenCastService extends Service {
         DisplayMetrics metrics = new DisplayMetrics();
         WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
         wm.getDefaultDisplay().getRealMetrics(metrics);
-        CastResolution.Size size = CastResolution.compute(metrics, activeSettings);
+        CastResolution.Size size = CastResolution.compute(metrics, activeSettings, getPeerStats());
         if (size.width == captureWidth && size.height == captureHeight) {
             return;
         }
@@ -421,8 +432,125 @@ public class ScreenCastService extends Service {
         }
     }
 
+    private NetworkStatsSnapshot getPeerStats() {
+        if (networkFeedback != null && networkFeedback.getPlane() instanceof PassThroughNetworkControlPlane) {
+            return ((PassThroughNetworkControlPlane) networkFeedback.getPlane()).getLastPeerStats();
+        }
+        return null;
+    }
+
+    private void scheduleTuningTick() {
+        mainHandler.postDelayed(() -> {
+            if (!casting.get() || stopping.get() || activeSettings == null) {
+                return;
+            }
+            NetworkStatsSnapshot peer = getPeerStats();
+            PassThroughNetworkControlPlane plane = networkFeedback != null
+                    && networkFeedback.getPlane() instanceof PassThroughNetworkControlPlane
+                    ? (PassThroughNetworkControlPlane) networkFeedback.getPlane() : null;
+            if (plane != null) {
+                NetworkStatsSnapshot local = plane.buildLocalStats(System.currentTimeMillis());
+                senderMetrics.onNetworkSample(local.sendBitrateKbps,
+                        peer != null ? peer.rttMs : 0);
+            }
+            CastTuningEngine.EffectiveParams next = CastTuningEngine.resolve(activeSettings, peer);
+            long idleMs = lastSignificantFrameMs > 0
+                    ? System.currentTimeMillis() - lastSignificantFrameMs : 0;
+            if (idleMs > CastConfig.KEYFRAME_KEEPALIVE_MS && videoEncoder != null) {
+                videoEncoder.requestKeyframe();
+            }
+            if (effectiveParams != null && next.videoBitrate != effectiveParams.videoBitrate) {
+                Log.d(TAG, "Tuning bitrate " + (next.videoBitrate / 1000) + " kbps (next pipeline)");
+            }
+            effectiveParams = next;
+            maybeAdaptCaptureSize(peer);
+            String mime = activeSettings != null ? activeSettings.getNegotiatedVideoMime() : null;
+            updateStatus(senderMetrics.format(mime, captureWidth, captureHeight, sendPump));
+            scheduleTuningTick();
+        }, 2_000);
+    }
+
+    private void maybeAdaptCaptureSize(NetworkStatsSnapshot peer) {
+        if (activeSettings == null
+                || activeSettings.getResolution() != CastSettings.Resolution.ADAPTIVE) {
+            return;
+        }
+        DisplayMetrics metrics = new DisplayMetrics();
+        WindowManager wm = (WindowManager) getSystemService(WINDOW_SERVICE);
+        wm.getDefaultDisplay().getRealMetrics(metrics);
+        CastResolution.Size size = CastResolution.compute(metrics, activeSettings, peer);
+        int dw = Math.abs(size.width - captureWidth);
+        int dh = Math.abs(size.height - captureHeight);
+        if (dw < Math.max(32, captureWidth / 10) && dh < Math.max(32, captureHeight / 10)) {
+            return;
+        }
+        try {
+            setupVideoPipeline(size, activeSettings);
+            Log.i(TAG, "Adaptive capture " + captureWidth + "x" + captureHeight);
+        } catch (IOException e) {
+            Log.w(TAG, "Adaptive resize failed", e);
+        }
+    }
+
+    private void startAudioPipeline(CastSettings settings) {
+        if (!settings.isAudioEnabled() || Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) {
+            Log.i(TAG, "Audio capture disabled for this session");
+            return;
+        }
+        if (projection == null) {
+            Log.w(TAG, "Audio skipped — no MediaProjection");
+            return;
+        }
+        try {
+            if (audioEncoder != null) {
+                audioEncoder.stop();
+            }
+            if (audioCapture != null) {
+                audioCapture.stop();
+            }
+            audioEncoder = new AudioEncoder();
+            audioEncoder.prepare(new AudioEncoder.Callback() {
+                private boolean configSent;
+
+                @Override
+                public void onConfig(int sampleRate, int channels, byte[] csd0) {
+                    if (configSent || stopping.get()) {
+                        return;
+                    }
+                    configSent = true;
+                    Log.i(TAG, "Sending audio config " + sampleRate + "Hz");
+                    sendSafe(CastProtocol.MSG_AUDIO_CONFIG,
+                            () -> CastProtocol.audioConfigPayload(sampleRate, channels, csd0));
+                }
+
+                @Override
+                public void onEncodedFrame(long ptsUs, byte[] frameData) {
+                    if (frameData == null || frameData.length == 0) {
+                        return;
+                    }
+                    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);
+                }
+            });
+            Log.i(TAG, "Audio pipeline started (playback capture)");
+        } catch (IOException e) {
+            Log.e(TAG, "Audio pipeline failed", e);
+        }
+    }
+
     private void handleAudioConsent(boolean accept) {
-        if (!accept) {
+        if (accept) {
+            if (audioEncoder == null && activeSettings != null) {
+                startAudioPipeline(activeSettings);
+            }
+            Log.i(TAG, "Receiver accepted audio");
+        } else {
             if (audioCapture != null) {
                 audioCapture.stop();
                 audioCapture = null;
@@ -475,6 +603,10 @@ public class ScreenCastService extends Service {
             virtualDisplay.release();
             virtualDisplay = null;
         }
+        if (encoderKeepalive != null) {
+            encoderKeepalive.stop();
+            encoderKeepalive = null;
+        }
         if (videoEncoder != null) {
             videoEncoder.stop();
             videoEncoder = null;
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 10b6e4b..dd30d60 100644
--- a/app/src/main/java/com/foxx/androidcast/sender/SenderActivity.java
+++ b/app/src/main/java/com/foxx/androidcast/sender/SenderActivity.java
@@ -5,12 +5,16 @@ import android.content.Intent;
 import android.media.projection.MediaProjectionManager;
 import android.os.Build;
 import android.os.Bundle;
+import android.os.Handler;
+import android.os.Looper;
 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;
 
@@ -26,13 +30,35 @@ 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 int DEV_TAP_UNLOCK = 7;
 
     private final CastSettings castSettings = new CastSettings();
+    private final Handler handler = new Handler(Looper.getMainLooper());
     private DiscoveryManager discovery;
     private DeviceListAdapter deviceAdapter;
 
-    private EditText pinInput;
     private TextView statusText;
+    private TextView titleText;
+    private ProgressBar discoveryProgress;
+    private View advancedPanel;
+    private EditText pinInput;
+    private EditText manualHostInput;
+    private EditText manualPortInput;
+
+    private int titleTapCount;
+    private long lastTitleTapMs;
+    private boolean useManualConnect;
+
+    private final Runnable discoveryWatchdog = new Runnable() {
+        @Override
+        public void run() {
+            if (discovery != null) {
+                restartDiscoveryInternal(false);
+            }
+            handler.postDelayed(this, DISCOVERY_INTERVAL_MS);
+        }
+    };
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
@@ -41,15 +67,40 @@ public class SenderActivity extends AppCompatActivity {
         PermissionHelper.request(this);
         SettingsUi.bind(this, castSettings);
 
+        titleText = findViewById(R.id.text_sender_title);
         pinInput = findViewById(R.id.edit_pin);
         pinInput.setText(CastConfig.DEFAULT_PIN);
         statusText = findViewById(R.id.text_status);
+        discoveryProgress = findViewById(R.id.progress_discovery);
+        advancedPanel = findViewById(R.id.panel_advanced);
+        manualHostInput = findViewById(R.id.edit_manual_host);
+        manualPortInput = findViewById(R.id.edit_manual_port);
+
+        titleText.setOnClickListener(v -> {
+            long now = System.currentTimeMillis();
+            if (now - lastTitleTapMs > 2000) {
+                titleTapCount = 0;
+            }
+            lastTitleTapMs = now;
+            titleTapCount++;
+            if (titleTapCount >= DEV_TAP_UNLOCK) {
+                titleTapCount = 0;
+                advancedPanel.setVisibility(
+                        advancedPanel.getVisibility() == View.VISIBLE ? View.GONE : View.VISIBLE);
+                Toast.makeText(this,
+                        advancedPanel.getVisibility() == View.VISIBLE
+                                ? R.string.advanced_unlocked : R.string.advanced_hidden,
+                        Toast.LENGTH_SHORT).show();
+            }
+        });
+
         ListView listView = findViewById(R.id.list_devices);
         listView.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
         deviceAdapter = new DeviceListAdapter(this);
         listView.setAdapter(deviceAdapter);
         listView.setOnItemClickListener((parent, view, position, id) -> {
             deviceAdapter.setSelectedPosition(position);
+            useManualConnect = false;
             DiscoveryManager.DiscoveredDevice selected = deviceAdapter.getSelectedDevice();
             if (selected == null) {
                 return;
@@ -63,6 +114,7 @@ public class SenderActivity extends AppCompatActivity {
 
         discovery = new DiscoveryManager(this);
         discovery.setListener(deviceList -> {
+            discoveryProgress.setVisibility(View.GONE);
             deviceAdapter.setDevices(deviceList);
             statusText.setText(deviceList.isEmpty()
                     ? getString(R.string.searching)
@@ -72,16 +124,22 @@ public class SenderActivity extends AppCompatActivity {
         findViewById(R.id.btn_refresh).setOnClickListener(v -> restartDiscovery());
         findViewById(R.id.btn_start_cast).setOnClickListener(v ->
                 PlatformCastSupport.runWithAudioPolicy(this, castSettings, this::startCastFlow));
+        findViewById(R.id.btn_manual_cast).setOnClickListener(v -> {
+            useManualConnect = true;
+            PlatformCastSupport.runWithAudioPolicy(this, castSettings, this::startCastFlow);
+        });
     }
 
     @Override
     protected void onStart() {
         super.onStart();
         restartDiscovery();
+        handler.postDelayed(discoveryWatchdog, DISCOVERY_INTERVAL_MS);
     }
 
     @Override
     protected void onStop() {
+        handler.removeCallbacks(discoveryWatchdog);
         if (discovery != null) {
             discovery.stop();
         }
@@ -89,8 +147,15 @@ public class SenderActivity extends AppCompatActivity {
     }
 
     private void restartDiscovery() {
+        handler.removeCallbacks(discoveryWatchdog);
+        restartDiscoveryInternal(true);
+        handler.postDelayed(discoveryWatchdog, DISCOVERY_INTERVAL_MS);
+    }
+
+    private void restartDiscoveryInternal(boolean userRefresh) {
         deviceAdapter.clearDevices();
-        statusText.setText(R.string.searching);
+        statusText.setText(userRefresh ? R.string.rescanning : R.string.searching);
+        discoveryProgress.setVisibility(View.VISIBLE);
         if (discovery != null) {
             discovery.stop();
             discovery.clearDevices();
@@ -99,13 +164,8 @@ public class SenderActivity extends AppCompatActivity {
     }
 
     private void startCastFlow() {
-        DiscoveryManager.DiscoveredDevice selected = deviceAdapter.getSelectedDevice();
-        if (selected == null) {
-            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 (castSettings.isPassthrough()) {
+            Toast.makeText(this, R.string.codec_passthrough_unavailable, Toast.LENGTH_LONG).show();
             return;
         }
         String pin = pinInput.getText().toString().trim();
@@ -113,12 +173,46 @@ public class SenderActivity extends AppCompatActivity {
             Toast.makeText(this, R.string.enter_pin, Toast.LENGTH_SHORT).show();
             return;
         }
+
+        if (useManualConnect) {
+            String host = manualHostInput.getText().toString().trim();
+            String portStr = manualPortInput.getText().toString().trim();
+            if (TextUtils.isEmpty(host) || TextUtils.isEmpty(portStr)) {
+                Toast.makeText(this, R.string.manual_connect_missing, Toast.LENGTH_SHORT).show();
+                return;
+            }
+            pendingHost = host;
+            try {
+                pendingPort = Integer.parseInt(portStr);
+            } catch (NumberFormatException e) {
+                Toast.makeText(this, R.string.manual_connect_missing, Toast.LENGTH_SHORT).show();
+                return;
+            }
+            pendingDeviceName = host;
+        } else {
+            DiscoveryManager.DiscoveredDevice selected = deviceAdapter.getSelectedDevice();
+            if (selected == null) {
+                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();
+                return;
+            }
+            pendingHost = selected.host;
+            pendingPort = selected.port;
+            pendingDeviceName = selected.name;
+        }
+
         pendingPin = pin;
         MediaProjectionManager mgr = (MediaProjectionManager) getSystemService(MEDIA_PROJECTION_SERVICE);
         startActivityForResult(mgr.createScreenCaptureIntent(), REQUEST_MEDIA_PROJECTION);
     }
 
     private String pendingPin;
+    private String pendingHost;
+    private int pendingPort;
+    private String pendingDeviceName;
 
     @Override
     protected void onActivityResult(int requestCode, int resultCode, Intent data) {
@@ -126,8 +220,7 @@ public class SenderActivity extends AppCompatActivity {
         if (requestCode != REQUEST_MEDIA_PROJECTION) {
             return;
         }
-        DiscoveryManager.DiscoveredDevice selected = deviceAdapter.getSelectedDevice();
-        if (resultCode != Activity.RESULT_OK || data == null || selected == null) {
+        if (resultCode != Activity.RESULT_OK || data == null || pendingHost == null) {
             Toast.makeText(this, R.string.capture_denied, Toast.LENGTH_SHORT).show();
             return;
         }
@@ -139,10 +232,10 @@ public class SenderActivity extends AppCompatActivity {
         Intent serviceIntent = new Intent(this, ScreenCastService.class);
         serviceIntent.putExtra(ScreenCastService.EXTRA_RESULT_CODE, resultCode);
         serviceIntent.putExtra(ScreenCastService.EXTRA_RESULT_DATA, new Intent(data));
-        serviceIntent.putExtra(ScreenCastService.EXTRA_HOST, selected.host);
-        serviceIntent.putExtra(ScreenCastService.EXTRA_PORT, selected.port);
+        serviceIntent.putExtra(ScreenCastService.EXTRA_HOST, pendingHost);
+        serviceIntent.putExtra(ScreenCastService.EXTRA_PORT, pendingPort);
         serviceIntent.putExtra(ScreenCastService.EXTRA_PIN, pendingPin);
-        serviceIntent.putExtra(ScreenCastService.EXTRA_DEVICE_NAME, deviceName);
+        serviceIntent.putExtra(ScreenCastService.EXTRA_DEVICE_NAME, pendingDeviceName != null ? pendingDeviceName : deviceName);
         serviceIntent.putExtra(CastSettings.EXTRA, castSettings);
 
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
diff --git a/app/src/main/java/com/foxx/androidcast/sender/SenderStreamMetrics.java b/app/src/main/java/com/foxx/androidcast/sender/SenderStreamMetrics.java
new file mode 100644
index 0000000..9693656
--- /dev/null
+++ b/app/src/main/java/com/foxx/androidcast/sender/SenderStreamMetrics.java
@@ -0,0 +1,65 @@
+package com.foxx.androidcast.sender;
+
+/** Sender-side encode/send counters for notification diagnostics. */
+public final class SenderStreamMetrics {
+    private long encodedFrames;
+    private long keyFrames;
+    private long windowFrames;
+    private long windowStartMs;
+    private float lastSecondFps;
+    private int lastSendKbps;
+    private int peerRttMs;
+
+    public synchronized void onEncodedFrame(boolean keyFrame) {
+        long now = System.currentTimeMillis();
+        encodedFrames++;
+        if (keyFrame) {
+            keyFrames++;
+        }
+        if (windowStartMs == 0) {
+            windowStartMs = now;
+        }
+        if (now - windowStartMs >= 1000) {
+            lastSecondFps = windowFrames;
+            windowFrames = 0;
+            windowStartMs = now;
+        }
+        windowFrames++;
+    }
+
+    public synchronized void onNetworkSample(int sendKbps, int rttMs) {
+        if (sendKbps > 0) {
+            lastSendKbps = sendKbps;
+        }
+        if (rttMs > 0) {
+            peerRttMs = rttMs;
+        }
+    }
+
+    public synchronized String format(String videoCodec, int captureW, int captureH, CastSendPump pump) {
+        float fps = lastSecondFps > 0 ? lastSecondFps : 0f;
+        StringBuilder sb = new StringBuilder();
+        if (videoCodec != null && !videoCodec.isEmpty()) {
+            sb.append(com.foxx.androidcast.media.CodecNegotiator.displayName(videoCodec)).append(' ');
+        }
+        sb.append(captureW).append('x').append(captureH);
+        sb.append(" · enc ").append(fps > 0 ? String.format("%.0f", fps) : "?").append(" fps");
+        if (lastSendKbps > 0) {
+            sb.append(" · tx ").append(lastSendKbps).append(" kbps");
+        }
+        if (peerRttMs > 0) {
+            sb.append(" · rtt ").append(peerRttMs).append("ms");
+        }
+        if (pump != null) {
+            int dropped = pump.getDroppedPFrames();
+            int q = pump.getQueueDepth();
+            if (dropped > 0 || q > 8) {
+                sb.append(" · q").append(q);
+                if (dropped > 0) {
+                    sb.append(" drop").append(dropped);
+                }
+            }
+        }
+        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 fa1a774..5fa6c34 100644
--- a/app/src/main/java/com/foxx/androidcast/sender/VideoEncoder.java
+++ b/app/src/main/java/com/foxx/androidcast/sender/VideoEncoder.java
@@ -8,16 +8,14 @@ import android.os.Bundle;
 import android.util.Log;
 import android.view.Surface;
 
-import com.foxx.androidcast.CastConfig;
-import com.foxx.androidcast.CastSettings;
+import com.foxx.androidcast.CastTuningEngine;
 
 import java.io.IOException;
 import java.nio.ByteBuffer;
 
-/** H.264 encoder using MediaCodec (AVC), tuned for low-latency screen cast. */
+/** Hardware video encoder (H.264 / H.265) via MediaCodec. */
 public class VideoEncoder {
     private static final String TAG = "VideoEncoder";
-    private static final String MIME = MediaFormat.MIMETYPE_VIDEO_AVC;
 
     public interface Callback {
         void onConfig(int width, int height, byte[] csd0, byte[] csd1);
@@ -32,24 +30,27 @@ public class VideoEncoder {
     private int height;
     private boolean running;
     private Thread drainThread;
+    private String mime;
 
-    public Surface prepare(int width, int height, CastSettings settings, Callback callback) throws IOException {
+    public Surface prepare(int width, int height, String mime, CastTuningEngine.EffectiveParams params,
+            Callback callback) throws IOException {
         this.width = width;
         this.height = height;
+        this.mime = mime;
         this.callback = callback;
 
-        MediaFormat tuned = buildFormat(width, height, settings, true);
-        MediaFormat basic = buildFormat(width, height, settings, false);
+        MediaFormat tuned = buildFormat(width, height, mime, params, true);
+        MediaFormat basic = buildFormat(width, height, mime, params, false);
 
-        codec = MediaCodec.createEncoderByType(MIME);
+        codec = MediaCodec.createEncoderByType(mime);
         if (!tryConfigure(codec, tuned)) {
             Log.w(TAG, "Tuned encoder format rejected; retrying with basic format");
             codec.release();
-            codec = MediaCodec.createEncoderByType(MIME);
+            codec = MediaCodec.createEncoderByType(mime);
             if (!tryConfigure(codec, basic)) {
                 codec.release();
                 codec = null;
-                throw new IOException("H.264 encoder configure failed for " + width + "x" + height);
+                throw new IOException("Encoder configure failed for " + mime + " " + width + "x" + height);
             }
         }
 
@@ -58,18 +59,19 @@ public class VideoEncoder {
         running = true;
         drainThread = new Thread(this::drainLoop, "VideoEncoderDrain");
         drainThread.start();
-        Log.i(TAG, "Encoder " + width + "x" + height + " @ " + settings.getVideoFps() + "fps "
-                + (settings.getVideoBitrate() / 1000) + "kbps");
+        Log.i(TAG, "Encoder " + mime + " " + width + "x" + height + " @ " + params.videoFps + "fps "
+                + (params.videoBitrate / 1000) + "kbps GOP=" + params.keyframeIntervalSec);
         return inputSurface;
     }
 
-    private static MediaFormat buildFormat(int width, int height, CastSettings settings, boolean tuned) {
-        MediaFormat format = MediaFormat.createVideoFormat(MIME, width, height);
+    private static MediaFormat buildFormat(int width, int height, String mime,
+            CastTuningEngine.EffectiveParams params, boolean tuned) {
+        MediaFormat format = MediaFormat.createVideoFormat(mime, width, height);
         format.setInteger(MediaFormat.KEY_COLOR_FORMAT, MediaCodecInfo.CodecCapabilities.COLOR_FormatSurface);
-        format.setInteger(MediaFormat.KEY_BIT_RATE, settings.getVideoBitrate());
-        format.setInteger(MediaFormat.KEY_FRAME_RATE, settings.getVideoFps());
-        format.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, CastConfig.VIDEO_I_FRAME_INTERVAL);
-        if (!tuned) {
+        format.setInteger(MediaFormat.KEY_BIT_RATE, params.videoBitrate);
+        format.setInteger(MediaFormat.KEY_FRAME_RATE, params.videoFps);
+        format.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, params.keyframeIntervalSec);
+        if (!tuned || !params.requestLowLatency) {
             return format;
         }
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
@@ -80,7 +82,7 @@ public class VideoEncoder {
             format.setInteger(MediaFormat.KEY_PRIORITY, 0);
         }
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
-            format.setInteger(MediaFormat.KEY_OPERATING_RATE, settings.getVideoFps());
+            format.setInteger(MediaFormat.KEY_OPERATING_RATE, params.videoFps);
         }
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
             format.setInteger(MediaFormat.KEY_LOW_LATENCY, 1);
diff --git a/app/src/main/res/layout/activity_sender.xml b/app/src/main/res/layout/activity_sender.xml
index 14325b7..9ad839b 100644
--- a/app/src/main/res/layout/activity_sender.xml
+++ b/app/src/main/res/layout/activity_sender.xml
@@ -10,6 +10,7 @@
         android:padding="16dp">
 
         <TextView
+            android:id="@+id/text_sender_title"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:text="@string/sender_title"
@@ -25,6 +26,50 @@
 
         <include layout="@layout/activity_settings_panel" />
 
+        <LinearLayout
+            android:id="@+id/panel_advanced"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="8dp"
+            android:orientation="vertical"
+            android:visibility="gone">
+
+            <TextView
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:text="@string/advanced_connect_title"
+                android:textStyle="bold" />
+
+            <EditText
+                android:id="@+id/edit_manual_host"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:hint="@string/manual_host_hint"
+                android:inputType="text" />
+
+            <EditText
+                android:id="@+id/edit_manual_port"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:hint="@string/manual_port_hint"
+                android:inputType="number"
+                android:text="41235" />
+
+            <EditText
+                android:id="@+id/edit_gateway_url"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:enabled="false"
+                android:hint="@string/gateway_url_hint"
+                android:inputType="textUri" />
+
+            <Button
+                android:id="@+id/btn_manual_cast"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:text="@string/manual_cast" />
+        </LinearLayout>
+
         <EditText
             android:id="@+id/edit_pin"
             android:layout_width="match_parent"
@@ -45,13 +90,27 @@
             android:layout_height="wrap_content"
             android:orientation="horizontal">
 
-            <Button
-                android:id="@+id/btn_refresh"
+            <FrameLayout
                 android:layout_width="0dp"
                 android:layout_height="wrap_content"
                 android:layout_marginEnd="8dp"
-                android:layout_weight="1"
-                android:text="@string/refresh" />
+                android:layout_weight="1">
+
+                <Button
+                    android:id="@+id/btn_refresh"
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:text="@string/refresh" />
+
+                <ProgressBar
+                    android:id="@+id/progress_discovery"
+                    style="?android:attr/progressBarStyleHorizontal"
+                    android:layout_width="match_parent"
+                    android:layout_height="4dp"
+                    android:layout_gravity="bottom"
+                    android:indeterminate="true"
+                    android:visibility="gone" />
+            </FrameLayout>
 
             <Button
                 android:id="@+id/btn_start_cast"
diff --git a/app/src/main/res/layout/activity_settings_panel.xml b/app/src/main/res/layout/activity_settings_panel.xml
index 9c6bc06..b357305 100644
--- a/app/src/main/res/layout/activity_settings_panel.xml
+++ b/app/src/main/res/layout/activity_settings_panel.xml
@@ -22,6 +22,39 @@
         android:layout_width="match_parent"
         android:layout_height="wrap_content" />
 
+    <TextView
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="8dp"
+        android:text="@string/label_video_codec" />
+
+    <Spinner
+        android:id="@+id/spinner_video_codec"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content" />
+
+    <TextView
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="8dp"
+        android:text="@string/label_adjustment_preset" />
+
+    <Spinner
+        android:id="@+id/spinner_adjustment"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content" />
+
+    <TextView
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="8dp"
+        android:text="@string/label_bitrate_mode" />
+
+    <Spinner
+        android:id="@+id/spinner_bitrate_mode"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content" />
+
     <TextView
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
@@ -33,6 +66,17 @@
         android:layout_width="match_parent"
         android:layout_height="wrap_content" />
 
+    <TextView
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_marginTop="8dp"
+        android:text="@string/label_network_adoption" />
+
+    <Spinner
+        android:id="@+id/spinner_network_adoption"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content" />
+
     <TextView
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index 5ee8bca..f0942a7 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -28,7 +28,26 @@
     <string name="resolution_full">Full display</string>
     <string name="resolution_75">75% scale</string>
     <string name="resolution_half">50% scale</string>
-    <string name="resolution_720p">720p (max 1280×720)</string>
+    <string name="resolution_720p">720p height cap (keeps aspect)</string>
+    <string name="resolution_fixed_1080p">Fixed 1080p (fit in 1920×1080)</string>
+    <string name="resolution_fixed_720p">Fixed 720p (fit in 1280×720)</string>
+    <string name="resolution_adaptive">Adaptive (BW estimator, preview)</string>
+    <string name="label_video_codec">Video codec</string>
+    <string name="label_adjustment_preset">Cast adjustment preset</string>
+    <string name="label_bitrate_mode">Bitrate</string>
+    <string name="label_network_adoption">Network adoption</string>
+    <string name="option_auto">AUTO (default)</string>
+    <string name="option_none">None</string>
+    <string name="option_quality">Quality</string>
+    <string name="option_speed">Speed</string>
+    <string name="option_performance">Performance (balanced)</string>
+    <string name="option_balanced">Balanced</string>
+    <string name="option_robust_less">RobustLess (UDP only)</string>
+    <string name="option_estimated">Estimated</string>
+    <string name="codec_h264">H.264 (AVC)</string>
+    <string name="codec_h265">H.265 (HEVC)</string>
+    <string name="codec_passthrough">Passthrough (debug)</string>
+    <string name="codec_passthrough_unavailable">Passthrough video is not implemented yet</string>
     <string name="transport_mismatch">Transport must match the receiver (TCP/UDP)</string>
     <string name="select_receiver">Select a receiver first</string>
     <string name="enter_pin">Enter PIN</string>
@@ -37,6 +56,16 @@
     <string name="found_receivers">Found %1$d receiver(s)</string>
     <string name="receiver_ready">Ready — PIN %1$s · %2$s</string>
     <string name="casting_from">Casting from %1$s</string>
+    <string name="casting_from_codec">Casting from %1$s · %2$s</string>
+    <string name="rescanning">Rescanning for receivers…</string>
+    <string name="advanced_unlocked">Advanced options unlocked</string>
+    <string name="advanced_hidden">Advanced options hidden</string>
+    <string name="advanced_connect_title">Advanced connect (dev)</string>
+    <string name="manual_host_hint">Receiver IP address</string>
+    <string name="manual_port_hint">Port (default 41235)</string>
+    <string name="gateway_url_hint">Relay gateway URL (not implemented)</string>
+    <string name="manual_cast">Connect to IP</string>
+    <string name="manual_connect_missing">Enter host and port</string>
     <string name="playing_resolution">Playing %1$dx%2$d</string>
     <string name="stop">Stop</string>
     <string name="label_receiver_audio">Play incoming cast audio on this device</string>