libvpx integration

app/src/main/java/com/foxx/androidcast/media/CodecNegotiator.java

@@ -82,4 +82,9 @@ public final class CodecNegotiator {
     public static boolean isHevc(String mime) {
         return MediaFormat.MIMETYPE_VIDEO_HEVC.equals(mime);
     }
+
+    public static boolean isVpx(String mime) {
+        return MediaFormat.MIMETYPE_VIDEO_VP8.equals(mime)
+                || MediaFormat.MIMETYPE_VIDEO_VP9.equals(mime);
+    }
 }

app/src/main/java/com/foxx/androidcast/media/RgbToYuv420.java

@@ -1,6 +1,7 @@
 package com.foxx.androidcast.media;
 
 import android.graphics.Bitmap;
+import android.media.Image;
 
 /**
  * ARGB to YUV420 planar (I420) or semi-planar (NV12) for MediaCodec buffer input.
@@ -32,6 +33,35 @@ public final class RgbToYuv420 {
         return width * height + (width * height) / 2;
     }
 
+    /** Fills {@code scratch} with I420 from an RGBA {@link Image} (reuses scratch when large enough). */
+    public static byte[] fromRgbaImage(Image image, byte[] scratch) {
+        if (image == null) {
+            return null;
+        }
+        int width = image.getWidth();
+        int height = image.getHeight();
+        int need = bufferSize(width, height);
+        byte[] out = scratch != null && scratch.length >= need ? scratch : new byte[need];
+        Image.Plane plane = image.getPlanes()[0];
+        java.nio.ByteBuffer buffer = plane.getBuffer();
+        int rowStride = plane.getRowStride();
+        int pixelStride = plane.getPixelStride();
+        int[] argb = new int[width * height];
+        int offset = 0;
+        for (int row = 0; row < height; row++) {
+            int rowStart = row * rowStride;
+            for (int col = 0; col < width; col++) {
+                int pixel = buffer.getInt(rowStart + col * pixelStride);
+                argb[offset++] = pixel;
+            }
+        }
+        byte[] i420 = toI420(argb, width, height);
+        if (out != i420) {
+            System.arraycopy(i420, 0, out, 0, i420.length);
+        }
+        return out;
+    }
+
     private static byte[] toI420(int[] argb, int width, int height) {
         int frameSize = width * height;
         int chromaW = (width + 1) / 2;

app/src/main/java/com/foxx/androidcast/media/codec/LibvpxCapableVideoDecoder.java

@@ -0,0 +1,52 @@
+package com.foxx.androidcast.media.codec;
+
+import android.util.Log;
+import android.view.Surface;
+
+import com.foxx.androidcast.media.CodecNegotiator;
+import com.foxx.androidcast.receiver.LibvpxVideoDecoder;
+import com.foxx.androidcast.receiver.VideoDecoder;
+
+import java.io.IOException;
+
+/**
+ * Uses libvpx for VP8/VP9 when linked; otherwise or on failure falls back to {@link VideoDecoder}.
+ */
+public final class LibvpxCapableVideoDecoder implements VideoDecoderSink {
+    private static final String TAG = "LibvpxCapableVideoDecoder";
+
+    private final VideoDecoder hwDecoder = new VideoDecoder();
+    private final LibvpxVideoDecoder libvpxDecoder = new LibvpxVideoDecoder();
+    private VideoDecoderSink active;
+
+    @Override
+    public void configure(String mime, int width, int height, byte[] csd0, byte[] csd1, Surface surface,
+            Listener listener) throws IOException {
+        if (CodecNegotiator.isVpx(mime)) {
+            try {
+                libvpxDecoder.configure(mime, width, height, csd0, csd1, surface, listener);
+                active = libvpxDecoder;
+                Log.i(TAG, "Using libvpx for " + mime);
+                return;
+            } catch (IOException e) {
+                Log.w(TAG, "libvpx decode unavailable, trying MediaCodec: " + e.getMessage());
+            }
+        }
+        hwDecoder.configure(mime, width, height, csd0, csd1, surface, listener);
+        active = hwDecoder;
+    }
+
+    @Override
+    public void queueFrame(long ptsUs, boolean keyFrame, byte[] data) {
+        if (active != null) {
+            active.queueFrame(ptsUs, keyFrame, data);
+        }
+    }
+
+    @Override
+    public void release() {
+        hwDecoder.release();
+        libvpxDecoder.release();
+        active = null;
+    }
+}

app/src/main/java/com/foxx/androidcast/media/codec/LibvpxVideoEncoderSink.java

@@ -1,22 +1,31 @@
 package com.foxx.androidcast.media.codec;
 
 import android.graphics.Bitmap;
+import android.graphics.PixelFormat;
+import android.media.Image;
+import android.media.ImageReader;
 import android.media.MediaFormat;
+import android.os.Handler;
+import android.os.HandlerThread;
+import android.util.Log;
 import android.view.Surface;
 
 import com.foxx.androidcast.CastSettings;
 import com.foxx.androidcast.CastTuningEngine;
 import com.foxx.androidcast.media.RgbToYuv420;
 import com.foxx.androidcast.media.codec.jni.NativeCodecBridge;
+import com.foxx.androidcast.media.codec.jni.VpxEncodedFrame;
 import com.foxx.androidcast.sender.VideoEncoder;
 
 import java.io.IOException;
 
 /**
  * Software VP8/VP9 via libvpx when {@link NativeCodecBridge#isLibvpxAvailable()}.
- * Surface capture still uses hardware {@link VideoEncoder} (libvpx is buffer-input only today).
+ * Screen capture uses an {@link ImageReader} surface; calibration may use buffer or GLES paths.
  */
 public final class LibvpxVideoEncoderSink implements VideoEncoderSink {
+    private static final String TAG = "LibvpxVideoEncoder";
+
     private final CastSettings.VideoCodec preference;
     private final VideoEncoder hwFallback = new VideoEncoder();
 
@@ -29,12 +38,19 @@ public final class LibvpxVideoEncoderSink implements VideoEncoderSink {
     private byte[] yuvScratch;
     private boolean forceKeyframe;
 
+    private HandlerThread captureThread;
+    private Handler captureHandler;
+    private ImageReader imageReader;
+
     public LibvpxVideoEncoderSink(CastSettings.VideoCodec preference) {
         this.preference = preference;
     }
 
     @Override
     public Surface getInputSurface() {
+        if (nativeActive && imageReader != null) {
+            return imageReader.getSurface();
+        }
         return hwFallback.getInputSurface();
     }
 
@@ -51,14 +67,37 @@ public final class LibvpxVideoEncoderSink implements VideoEncoderSink {
     @Override
     public Surface prepare(int width, int height, String mime, CastTuningEngine.EffectiveParams params,
             Callback callback) throws IOException {
-        nativeActive = false;
+        releaseCapture();
+        this.callback = callback;
+        this.width = width;
+        this.height = height;
+        this.mime = mime;
+        yuvScratch = new byte[RgbToYuv420.bufferSize(width, height)];
+
+        int bitrateKbps = Math.max(500, params.videoBitrate / 1000);
+        nativeHandle = NativeCodecBridge.vpxEncoderCreate(mime, width, height, bitrateKbps);
+        nativeActive = nativeHandle != 0L;
+        if (!nativeActive) {
+            Log.w(TAG, "libvpx encoder init failed; using MediaCodec for surface capture");
             CodecSessionRegistry.setVideoBackend(VideoCodecBackend.MEDIA_CODEC_HW, mime);
             return hwFallback.prepare(width, height, mime, params, callback);
         }
 
+        CodecSessionRegistry.setVideoBackend(VideoCodecBackend.LIBVPX_NATIVE, mime);
+        captureThread = new HandlerThread("libvpx-capture");
+        captureThread.start();
+        captureHandler = new Handler(captureThread.getLooper());
+        imageReader = ImageReader.newInstance(width, height, PixelFormat.RGBA_8888, 2);
+        imageReader.setOnImageAvailableListener(this::onImageAvailable, captureHandler);
+        callback.onConfig(width, height, null, null);
+        Log.i(TAG, "libvpx surface encoder " + width + "x" + height + " mime=" + mime);
+        return imageReader.getSurface();
+    }
+
     @Override
     public void prepareBufferInput(int width, int height, String mime, CastTuningEngine.EffectiveParams params,
             Callback callback) throws IOException {
+        releaseCapture();
         this.width = width;
         this.height = height;
         this.mime = mime;
@@ -76,6 +115,33 @@ public final class LibvpxVideoEncoderSink implements VideoEncoderSink {
         hwFallback.prepareBufferInput(width, height, mime, params, callback);
     }
 
+    private void onImageAvailable(ImageReader reader) {
+        if (!nativeActive || callback == null) {
+            return;
+        }
+        try (Image image = reader.acquireLatestImage()) {
+            if (image == null) {
+                return;
+            }
+            byte[] yuv = RgbToYuv420.fromRgbaImage(image, yuvScratch);
+            if (yuv == null) {
+                return;
+            }
+            long ptsUs = image.getTimestamp() / 1000L;
+            emitEncodedFrame(yuv, ptsUs);
+        } catch (Exception e) {
+            Log.w(TAG, "Capture frame skipped: " + e.getMessage());
+        }
+    }
+
+    private void emitEncodedFrame(byte[] yuv, long ptsUs) {
+        VpxEncodedFrame frame = NativeCodecBridge.vpxEncodeYuvFrame(nativeHandle, yuv, ptsUs, forceKeyframe);
+        forceKeyframe = false;
+        if (frame != null && frame.data != null && callback != null) {
+            callback.onEncodedFrame(ptsUs, frame.keyFrame, frame.data);
+        }
+    }
+
     @Override
     public void queueBitmapFrame(Bitmap bitmap, long ptsUs) {
         if (!nativeActive) {
@@ -83,7 +149,7 @@ public final class LibvpxVideoEncoderSink implements VideoEncoderSink {
             return;
         }
         byte[] yuv = RgbToYuv420.fromBitmap(bitmap, RgbToYuv420.Layout.I420);
-        queueYuvFrame(yuv, ptsUs);
+        emitEncodedFrame(yuv, ptsUs);
     }
 
     @Override
@@ -92,12 +158,7 @@ public final class LibvpxVideoEncoderSink implements VideoEncoderSink {
             hwFallback.queueYuvFrame(yuv, ptsUs);
             return;
         }
-        byte[] frame = NativeCodecBridge.vpxEncodeYuv(nativeHandle, yuv, ptsUs, forceKeyframe);
+        emitEncodedFrame(yuv, ptsUs);
-        forceKeyframe = false;
-        if (frame != null && callback != null) {
-            boolean key = frame.length > 0 && (frame[0] & 0x01) == 0;
-            callback.onEncodedFrame(ptsUs, key, frame);
-        }
     }
 
     @Override
@@ -107,9 +168,22 @@ public final class LibvpxVideoEncoderSink implements VideoEncoderSink {
             nativeHandle = 0L;
             nativeActive = false;
         }
+        releaseCapture();
         hwFallback.stop();
     }
 
+    private void releaseCapture() {
+        if (imageReader != null) {
+            imageReader.close();
+            imageReader = null;
+        }
+        if (captureThread != null) {
+            captureThread.quitSafely();
+            captureThread = null;
+            captureHandler = null;
+        }
+    }
+
     static String mimeFor(CastSettings.VideoCodec preference) {
         if (preference == CastSettings.VideoCodec.LIBVPX_VP9) {
             return MediaFormat.MIMETYPE_VIDEO_VP9;

app/src/main/java/com/foxx/androidcast/media/codec/PassthroughCodecPolicy.java

@@ -4,6 +4,7 @@ import android.media.MediaFormat;
 
 import com.foxx.androidcast.CastSettings;
 import com.foxx.androidcast.media.CodecNegotiator;
+import com.foxx.androidcast.media.codec.jni.NativeCodecBridge;
 
 /**
  * Maps UI / future software codec choices to wire negotiation and HW backends.
@@ -30,7 +31,8 @@ public final class PassthroughCodecPolicy {
     public static VideoCodecBackend videoBackendFor(CastSettings.VideoCodec preference) {
         if (preference == CastSettings.VideoCodec.LIBVPX_VP8
                 || preference == CastSettings.VideoCodec.LIBVPX_VP9) {
-            return VideoCodecBackend.LIBVPX_STUB;
+            return NativeCodecBridge.isLibvpxAvailable()
+                    ? VideoCodecBackend.LIBVPX_NATIVE : VideoCodecBackend.LIBVPX_STUB;
         }
         if (preference == CastSettings.VideoCodec.PASSTHROUGH) {
             return VideoCodecBackend.PASSTHROUGH;

app/src/main/java/com/foxx/androidcast/media/codec/VideoDecoderFactory.java

@@ -1,5 +1,6 @@
 package com.foxx.androidcast.media.codec;
 
+import com.foxx.androidcast.media.codec.jni.NativeCodecBridge;
 import com.foxx.androidcast.receiver.VideoDecoder;
 
 /** Creates video decoder sinks. */
@@ -7,6 +8,9 @@ public final class VideoDecoderFactory {
     private VideoDecoderFactory() {}
 
     public static VideoDecoderSink createDecoder() {
+        if (NativeCodecBridge.isLibvpxAvailable()) {
+            return new LibvpxCapableVideoDecoder();
+        }
         return new VideoDecoder();
     }
 }

app/src/main/java/com/foxx/androidcast/media/codec/jni/NativeCodecBridge.java

@@ -1,6 +1,7 @@
 package com.foxx.androidcast.media.codec.jni;
 
 import android.util.Log;
+import android.view.Surface;
 
 /** JNI probes for third-party codecs built from {@code ndk/} + {@code third-party/}. */
 public final class NativeCodecBridge {
@@ -47,10 +48,36 @@ public final class NativeCodecBridge {
     }
 
     public static byte[] vpxEncodeYuv(long handle, byte[] i420, long ptsUs, boolean forceKeyframe) {
+        VpxEncodedFrame frame = vpxEncodeYuvFrame(handle, i420, ptsUs, forceKeyframe);
+        return frame != null ? frame.data : null;
+    }
+
+    public static VpxEncodedFrame vpxEncodeYuvFrame(long handle, byte[] i420, long ptsUs,
+            boolean forceKeyframe) {
         if (handle == 0L || i420 == null) {
             return null;
         }
-        return nativeVpxEncodeYuv(handle, i420, ptsUs, forceKeyframe);
+        return nativeVpxEncodeYuvFrame(handle, i420, ptsUs, forceKeyframe);
+    }
+
+    public static long vpxDecoderCreate(String mime) {
+        if (!isLibvpxAvailable()) {
+            return 0L;
+        }
+        return nativeVpxDecoderCreate(mime);
+    }
+
+    public static boolean vpxDecodeFrame(long handle, byte[] data, long ptsUs, Surface surface) {
+        if (handle == 0L || data == null || surface == null) {
+            return false;
+        }
+        return nativeVpxDecodeFrame(handle, data, ptsUs, surface);
+    }
+
+    public static void vpxDecoderRelease(long handle) {
+        if (handle != 0L) {
+            nativeVpxDecoderRelease(handle);
+        }
     }
 
     public static void vpxEncoderRelease(long handle) {
@@ -75,7 +102,16 @@ public final class NativeCodecBridge {
 
     private static native byte[] nativeVpxEncodeYuv(long handle, byte[] yuv, long ptsUs, boolean forceKeyframe);
 
+    private static native VpxEncodedFrame nativeVpxEncodeYuvFrame(long handle, byte[] yuv, long ptsUs,
+            boolean forceKeyframe);
+
     private static native void nativeVpxEncoderRelease(long handle);
 
     private static native void nativeVpxRequestKeyframe(long handle);
+
+    private static native long nativeVpxDecoderCreate(String mime);
+
+    private static native boolean nativeVpxDecodeFrame(long handle, byte[] data, long ptsUs, Surface surface);
+
+    private static native void nativeVpxDecoderRelease(long handle);
 }

app/src/main/java/com/foxx/androidcast/media/codec/jni/VpxEncodedFrame.java

@@ -0,0 +1,12 @@
+package com.foxx.androidcast.media.codec.jni;
+
+/** One compressed VP8/VP9 frame from libvpx. */
+public final class VpxEncodedFrame {
+    public final byte[] data;
+    public final boolean keyFrame;
+
+    public VpxEncodedFrame(byte[] data, boolean keyFrame) {
+        this.data = data;
+        this.keyFrame = keyFrame;
+    }
+}

app/src/main/java/com/foxx/androidcast/receiver/LibvpxVideoDecoder.java

@@ -0,0 +1,85 @@
+package com.foxx.androidcast.receiver;
+
+import android.util.Log;
+import android.view.Surface;
+
+import com.foxx.androidcast.media.codec.VideoDecoderSink;
+import com.foxx.androidcast.media.codec.jni.NativeCodecBridge;
+
+import java.io.IOException;
+
+/** Software VP8/VP9 decode via libvpx, rendering to a {@link Surface}. */
+public final class LibvpxVideoDecoder implements VideoDecoderSink {
+    private static final String TAG = "LibvpxVideoDecoder";
+
+    private final Object lock = new Object();
+    private long nativeHandle;
+    private Surface outputSurface;
+    private Listener listener;
+    private boolean released;
+    private boolean firstFrameNotified;
+
+    @Override
+    public void configure(String mime, int width, int height, byte[] csd0, byte[] csd1, Surface surface,
+            Listener listener) throws IOException {
+        synchronized (lock) {
+            releaseLocked();
+            if (!NativeCodecBridge.isLibvpxAvailable()) {
+                throw new IOException("libvpx not available");
+            }
+            nativeHandle = NativeCodecBridge.vpxDecoderCreate(mime);
+            if (nativeHandle == 0L) {
+                throw new IOException("libvpx decoder init failed for " + mime);
+            }
+            this.outputSurface = surface;
+            this.listener = listener;
+            this.released = false;
+            this.firstFrameNotified = false;
+            Log.i(TAG, "Configured libvpx decoder " + mime + " " + width + "x" + height);
+        }
+    }
+
+    @Override
+    public void queueFrame(long ptsUs, boolean keyFrame, byte[] data) {
+        synchronized (lock) {
+            if (released || nativeHandle == 0L || outputSurface == null || data == null || data.length == 0) {
+                return;
+            }
+            if (NativeCodecBridge.vpxDecodeFrame(nativeHandle, data, ptsUs, outputSurface)) {
+                notifyRenderedLocked();
+            }
+        }
+    }
+
+    @Override
+    public void release() {
+        synchronized (lock) {
+            releaseLocked();
+        }
+    }
+
+    private void releaseLocked() {
+        released = true;
+        listener = null;
+        outputSurface = null;
+        firstFrameNotified = false;
+        if (nativeHandle != 0L) {
+            NativeCodecBridge.vpxDecoderRelease(nativeHandle);
+            nativeHandle = 0L;
+        }
+    }
+
+    private void notifyRenderedLocked() {
+        Listener cb = listener;
+        if (cb == null) {
+            return;
+        }
+        if (!firstFrameNotified) {
+            firstFrameNotified = true;
+            Log.i(TAG, "First frame rendered (libvpx)");
+            cb.onFirstFrameRendered();
+        } else {
+            cb.onFrameRendered();
+        }
+    }
+}

app/src/main/java/com/foxx/androidcast/sender/CodecCatalog.java

@@ -6,6 +6,7 @@ import android.media.MediaFormat;
 import android.os.Build;
 
 import com.foxx.androidcast.CastSettings;
+import com.foxx.androidcast.media.codec.jni.NativeCodecBridge;
 
 import java.util.ArrayList;
 import java.util.LinkedHashSet;
@@ -121,6 +122,10 @@ public final class CodecCatalog {
         if (out.isEmpty()) {
             out.add(MediaFormat.MIMETYPE_VIDEO_AVC);
         }
+        if (NativeCodecBridge.isLibvpxAvailable()) {
+            out.add(MediaFormat.MIMETYPE_VIDEO_VP8);
+            out.add(MediaFormat.MIMETYPE_VIDEO_VP9);
+        }
         return new ArrayList<>(out);
     }
 }

app/src/main/java/com/foxx/androidcast/sender/ScreenCastService.java

@@ -475,8 +475,6 @@ public class ScreenCastService extends Service implements
         }
 
         videoEncoder = VideoCodecFactory.createEncoder(settings.getVideoCodec());
-        CodecSessionRegistry.setVideoBackend(
-                PassthroughCodecPolicy.videoBackendFor(settings.getVideoCodec()), mime);
         CodecSessionRegistry.setProtectionSummary(PassthroughCodecPolicy.protectionDescription(
                 settings.getStreamProtection(), settings.getTransport(), settings.getAudioCodec()));
         VideoEncoderSink.Callback videoCb = buildVideoEncoderCallback(mime);

docs/ROADMAP.md

@@ -22,10 +22,11 @@ Enable in **Settings → Stream protection (UDP)** on both sender and receiver,
 | Item | Status |
 |------|--------|
 | `libandroidcast_codecs.so` + JNI probes | Done |
-| Cross-compile `libvpx.a` (`scripts/build-native-codecs.sh`) | Script ready (needs submodule + NDK build) |
+| Cross-compile `libvpx.a` (`scripts/build-native-codecs.sh`) | Done |
-| JNI encode in `libvpx_bridge.c` | Done (when `ANDROIDCAST_LIBVPX_LIB` set) |
+| JNI encode/decode in `libvpx_bridge.c` | Done (when `libvpx.a` linked per ABI) |
-| `LibvpxVideoEncoderSink` (buffer / calibration path) | Done |
+| `LibvpxVideoEncoderSink` (surface + buffer) | Done |
-| libvpx decoder on receiver | TODO |
+| libvpx decoder on receiver (`LibvpxCapableVideoDecoder`) | Done |
+| Surface → libvpx without MediaCodec passthrough on cast | Done (ImageReader) |
 | Opus / Speex build + sinks | TODO |
 
 See [ndk/README.md](../ndk/README.md).

ndk/CMakeLists.txt

@@ -46,4 +46,5 @@ else()
 endif()
 
 find_library(log-lib log)
-target_link_libraries(androidcast_codecs ${log-lib})
+find_library(android-lib android)
+target_link_libraries(androidcast_codecs ${log-lib} ${android-lib})

ndk/README.md

@@ -8,13 +8,16 @@ The app loads `libandroidcast_codecs.so` for availability probes and future soft
 |-----------|------|--------|-------|
 | FEC 3/4 + RS | Yes | — | v2 **per-shard** on wire (`FecShardWire`); v1 monolithic decode still accepted |
 | NACK + retransmit cache | Yes | — | UDP `MSG_NACK`, combined with FEC when enabled |
-| libvpx VP8/VP9 | Stub | Probe only | HW passthrough until `ANDROIDCAST_LIBVPX_LIB` is linked |
+| libvpx VP8/VP9 | Native | Encode + decode | Screen cast via ImageReader; receiver libvpx or MediaCodec fallback |
 | Opus / Speex | Stub | Probe only | Submodules under `third-party/` |
 
 ## Enable libvpx (developer)
 
 1. `git submodule update --init third-party/libvpx`
-2. Build `libvpx.a` for your ABI: `./scripts/build-native-codecs.sh arm64-v8a`  
+2. Build `libvpx.a` per ABI (NDK is auto-detected; see `scripts/android-ndk.sh`):
+
+   `./scripts/build-native-codecs.sh arm64-v8a`
+
    (If the repo path has **spaces**, the script uses `/tmp/androidcast-libvpx-$USER` automatically.)
 3. Build **each ABI** you ship (Gradle links `build/native/<abi>/libvpx.a` automatically):
 

ndk/jni/libvpx_bridge.c

@@ -1,4 +1,6 @@
 #include <jni.h>
+#include <android/native_window.h>
+#include <android/native_window_jni.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -14,6 +16,7 @@
 #endif
 
 #define VPX_ENC_MAGIC 0x56505845L /* VPXE */
+#define VPX_DEC_MAGIC 0x56505844L /* VPXD */
 
 #if ANDROIDCAST_HAVE_LIBVPX
 
@@ -34,6 +37,13 @@ static vpx_codec_iface_t *pick_encoder_iface(const char *mime) {
     return vpx_codec_vp8_cx();
 }
 
+static vpx_codec_iface_t *pick_decoder_iface(const char *mime) {
+    if (mime != NULL && strstr(mime, "VP9") != NULL) {
+        return vpx_codec_vp9_dx();
+    }
+    return vpx_codec_vp8_dx();
+}
+
 static vpx_img_fmt_t img_fmt(void) {
     return VPX_IMG_FMT_I420;
 }
@@ -63,6 +73,75 @@ static VpxEncoderCtx *enc_from_handle(jlong handle) {
     return ctx;
 }
 
+typedef struct {
+    unsigned long magic;
+    vpx_codec_ctx_t codec;
+} VpxDecoderCtx;
+
+static VpxDecoderCtx *dec_from_handle(jlong handle) {
+    VpxDecoderCtx *ctx = (VpxDecoderCtx *) (intptr_t) handle;
+    if (ctx == NULL || ctx->magic != VPX_DEC_MAGIC) {
+        return NULL;
+    }
+    return ctx;
+}
+
+static void render_i420_to_window(ANativeWindow *window, const vpx_image_t *img) {
+    if (window == NULL || img == NULL) {
+        return;
+    }
+    const int width = (int) img->d_w;
+    const int height = (int) img->d_h;
+    if (width <= 0 || height <= 0) {
+        return;
+    }
+    ANativeWindow_setBuffersGeometry(window, width, height, WINDOW_FORMAT_RGBA_8888);
+    ANativeWindow_Buffer buffer;
+    if (ANativeWindow_lock(window, &buffer, NULL) != 0) {
+        return;
+    }
+    uint8_t *dst = (uint8_t *) buffer.bits;
+    const int dst_stride = buffer.stride * 4;
+    const uint8_t *y_plane = img->planes[VPX_PLANE_Y];
+    const uint8_t *u_plane = img->planes[VPX_PLANE_U];
+    const uint8_t *v_plane = img->planes[VPX_PLANE_V];
+    const int y_stride = img->stride[VPX_PLANE_Y];
+    const int u_stride = img->stride[VPX_PLANE_U];
+    const int v_stride = img->stride[VPX_PLANE_V];
+
+    for (int row = 0; row < height; row++) {
+        uint8_t *row_dst = dst + row * dst_stride;
+        for (int col = 0; col < width; col++) {
+            int y = y_plane[row * y_stride + col];
+            int u = u_plane[(row / 2) * u_stride + (col / 2)] - 128;
+            int v = v_plane[(row / 2) * v_stride + (col / 2)] - 128;
+            int r = y + ((351 * v) >> 8);
+            int g = y - ((179 * v + 86 * u) >> 8);
+            int b = y + ((443 * u) >> 8);
+            if (r < 0) {
+                r = 0;
+            } else if (r > 255) {
+                r = 255;
+            }
+            if (g < 0) {
+                g = 0;
+            } else if (g > 255) {
+                g = 255;
+            }
+            if (b < 0) {
+                b = 0;
+            } else if (b > 255) {
+                b = 255;
+            }
+            row_dst[col * 4] = (uint8_t) r;
+            row_dst[col * 4 + 1] = (uint8_t) g;
+            row_dst[col * 4 + 2] = (uint8_t) b;
+            row_dst[col * 4 + 3] = 255;
+        }
+    }
+    ANativeWindow_unlockAndPost(window);
+}
+
 #endif /* ANDROIDCAST_HAVE_LIBVPX */
 
 JNIEXPORT jboolean JNICALL
@@ -132,8 +211,8 @@ Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeVpxEncoderCrea
 #endif
 }
 
-JNIEXPORT jbyteArray JNICALL
+JNIEXPORT jobject JNICALL
-Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeVpxEncodeYuv(
+Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeVpxEncodeYuvFrame(
         JNIEnv *env, jclass clazz, jlong handle, jbyteArray yuv, jlong ptsUs, jboolean forceKeyframe) {
     (void) clazz;
 #if !ANDROIDCAST_HAVE_LIBVPX
@@ -176,18 +255,47 @@ Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeVpxEncodeYuv(
     while ((pkt = vpx_codec_get_cx_data(&ctx->codec, &iter)) != NULL) {
         if (pkt->kind == VPX_CODEC_CX_FRAME_PKT) {
             jbyteArray out = (*env)->NewByteArray(env, (jsize) pkt->data.frame.sz);
-            if (out != NULL) {
+            if (out == NULL) {
+                return NULL;
+            }
             (*env)->SetByteArrayRegion(env, out, 0, (jsize) pkt->data.frame.sz,
                                        (const jbyte *) pkt->data.frame.buf);
-            }
+            jboolean key = (pkt->data.frame.flags & VPX_FRAME_IS_KEY) ? JNI_TRUE : JNI_FALSE;
+            jclass frame_cls = (*env)->FindClass(
+                    env, "com/foxx/androidcast/media/codec/jni/VpxEncodedFrame");
+            jmethodID ctor = (*env)->GetMethodID(env, frame_cls, "<init>", "([BZ)V");
+            jobject frame = (*env)->NewObject(env, frame_cls, ctor, out, key);
             ctx->frame_count++;
-            return out;
+            return frame;
         }
     }
     return NULL;
 #endif
 }
 
+JNIEXPORT jbyteArray JNICALL
+Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeVpxEncodeYuv(
+        JNIEnv *env, jclass clazz, jlong handle, jbyteArray yuv, jlong ptsUs, jboolean forceKeyframe) {
+#if !ANDROIDCAST_HAVE_LIBVPX
+    (void) env;
+    (void) clazz;
+    (void) handle;
+    (void) yuv;
+    (void) ptsUs;
+    (void) forceKeyframe;
+    return NULL;
+#else
+    jobject frame = Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeVpxEncodeYuvFrame(
+            env, clazz, handle, yuv, ptsUs, forceKeyframe);
+    if (frame == NULL) {
+        return NULL;
+    }
+    jclass frame_cls = (*env)->GetObjectClass(env, frame);
+    jfieldID data_f = (*env)->GetFieldID(env, frame_cls, "data", "[B");
+    return (jbyteArray) (*env)->GetObjectField(env, frame, data_f);
+#endif
+}
+
 JNIEXPORT void JNICALL
 Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeVpxEncoderRelease(
         JNIEnv *env, jclass clazz, jlong handle) {
@@ -217,3 +325,95 @@ Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeVpxRequestKeyf
     }
 #endif
 }
+
+JNIEXPORT jlong JNICALL
+Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeVpxDecoderCreate(
+        JNIEnv *env, jclass clazz, jstring mime) {
+    (void) clazz;
+#if !ANDROIDCAST_HAVE_LIBVPX
+    (void) env;
+    (void) mime;
+    return 0L;
+#else
+    const char *mime_utf = (*env)->GetStringUTFChars(env, mime, NULL);
+    VpxDecoderCtx *ctx = (VpxDecoderCtx *) calloc(1, sizeof(VpxDecoderCtx));
+    if (ctx == NULL) {
+        (*env)->ReleaseStringUTFChars(env, mime, mime_utf);
+        return 0L;
+    }
+    ctx->magic = VPX_DEC_MAGIC;
+    vpx_codec_dec_cfg_t cfg = {0};
+    cfg.threads = 1;
+    if (vpx_codec_dec_init(&ctx->codec, pick_decoder_iface(mime_utf), &cfg, 0) != VPX_CODEC_OK) {
+        free(ctx);
+        (*env)->ReleaseStringUTFChars(env, mime, mime_utf);
+        return 0L;
+    }
+    (*env)->ReleaseStringUTFChars(env, mime, mime_utf);
+    return (jlong) (intptr_t) ctx;
+#endif
+}
+
+JNIEXPORT jboolean JNICALL
+Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeVpxDecodeFrame(
+        JNIEnv *env, jclass clazz, jlong handle, jbyteArray data, jlong ptsUs, jobject surface) {
+    (void) clazz;
+    (void) ptsUs;
+#if !ANDROIDCAST_HAVE_LIBVPX
+    (void) env;
+    (void) handle;
+    (void) data;
+    (void) surface;
+    return JNI_FALSE;
+#else
+    VpxDecoderCtx *ctx = dec_from_handle(handle);
+    if (ctx == NULL || data == NULL || surface == NULL) {
+        return JNI_FALSE;
+    }
+    jsize len = (*env)->GetArrayLength(env, data);
+    if (len <= 0) {
+        return JNI_FALSE;
+    }
+    jbyte *bytes = (*env)->GetByteArrayElements(env, data, NULL);
+    if (bytes == NULL) {
+        return JNI_FALSE;
+    }
+    vpx_codec_err_t err = vpx_codec_decode(&ctx->codec, (const uint8_t *) bytes, (unsigned int) len,
+                                            NULL, 0);
+    (*env)->ReleaseByteArrayElements(env, data, bytes, JNI_ABORT);
+    if (err != VPX_CODEC_OK) {
+        return JNI_FALSE;
+    }
+
+    ANativeWindow *window = ANativeWindow_fromSurface(env, surface);
+    if (window == NULL) {
+        return JNI_FALSE;
+    }
+
+    vpx_codec_iter_t iter = NULL;
+    vpx_image_t *img;
+    jboolean rendered = JNI_FALSE;
+    while ((img = vpx_codec_get_frame(&ctx->codec, &iter)) != NULL) {
+        render_i420_to_window(window, img);
+        rendered = JNI_TRUE;
+    }
+    ANativeWindow_release(window);
+    return rendered;
+#endif
+}
+
+JNIEXPORT void JNICALL
+Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeVpxDecoderRelease(
+        JNIEnv *env, jclass clazz, jlong handle) {
+    (void) env;
+    (void) clazz;
+#if ANDROIDCAST_HAVE_LIBVPX
+    VpxDecoderCtx *ctx = dec_from_handle(handle);
+    if (ctx == NULL) {
+        return;
+    }
+    ctx->magic = 0;
+    vpx_codec_destroy(&ctx->codec);
+    free(ctx);
+#endif
+}

rebuild.sh

@@ -107,9 +107,9 @@ reconnect_known_devices() {
   adb devices -l
 }
 
-# shellcheck source=android_find_latest_ndk.sh
+# shellcheck source=scripts/android-ndk.sh
-source "$ROOT/android_find_latest_ndk.sh"
+source "$ROOT/scripts/android-ndk.sh"
-export ANDROID_NDK_HOME="$(android_find_ndk_root "$ROOT")"
+export ANDROID_NDK_HOME="$(androidcast_find_ndk_root "$ROOT")"
 export ANDROID_NDK_ROOT="$ANDROID_NDK_HOME"
 echo "==> Using NDK: $ANDROID_NDK_HOME"
 

scripts/android-ndk.sh

@@ -0,0 +1,91 @@
+#!/usr/bin/env bash
+# Android NDK discovery for AndroidCast build scripts.
+# Source this file:  source "$(dirname "$0")/android-ndk.sh"
+#
+# Optional env:
+#   ANDROIDCAST_NDK_VERSION  — pin a version under $HOME/Android/Sdk/ndk (e.g. 29.0.14206865)
+#   ANDROID_NDK_HOME / ANDROID_NDK_ROOT — used when valid
+#
+set -euo pipefail
+
+_androidcast_sdk_base() {
+  printf '%s\n' "${ANDROIDCAST_SDK_BASE:-${ANDROID_HOME:-${ANDROID_SDK_ROOT:-$HOME/Android/Sdk}}}"
+}
+
+# Print absolute NDK root (directory containing ndk-build). Errors on stderr.
+androidcast_find_ndk_root() {
+  local project_root="${1:-}"
+  local ndk="" ndk_root ndk_ver parent pinned
+
+  if [[ -n "$project_root" && -f "$project_root/local.properties" ]]; then
+    ndk="$(sed -n 's/^[[:space:]]*ndk\.dir=//p' "$project_root/local.properties" | tr -d '\r' | head -1)"
+    ndk="${ndk%/}"
+    while [[ -n "$ndk" ]]; do
+      if [[ -x "$ndk/ndk-build" ]]; then
+        realpath "$ndk"
+        return 0
+      fi
+      parent="$(dirname "$ndk")"
+      [[ "$parent" == "$ndk" ]] && break
+      ndk="$parent"
+    done
+  fi
+
+  for ndk in "${ANDROID_NDK_HOME:-}" "${ANDROID_NDK_ROOT:-}"; do
+    ndk="${ndk%/}"
+    if [[ -n "$ndk" && -x "$ndk/ndk-build" ]]; then
+      realpath "$ndk"
+      return 0
+    fi
+  done
+
+  ndk_root="$(_androidcast_sdk_base)/ndk"
+  if [[ ! -d "$ndk_root" ]]; then
+    echo "ERROR: No Android NDK found. Install via SDK Manager ($ndk_root) or set ANDROID_NDK_HOME." >&2
+    return 1
+  fi
+
+  pinned="${ANDROIDCAST_NDK_VERSION:-}"
+  if [[ -n "$pinned" ]]; then
+    if [[ -d "$ndk_root/$pinned" ]]; then
+      ndk_ver="$pinned"
+    else
+      echo "ERROR: ANDROIDCAST_NDK_VERSION=$pinned not found under $ndk_root" >&2
+      return 1
+    fi
+  else
+    ndk_ver="$(ls -1 "$ndk_root" 2>/dev/null | sort -V | tail -n 1 || true)"
+    if [[ -z "$ndk_ver" ]]; then
+      echo "ERROR: No NDK versions under $ndk_root" >&2
+      return 1
+    fi
+  fi
+
+  ndk="$ndk_root/$ndk_ver"
+  if [[ ! -x "$ndk/ndk-build" ]]; then
+    echo "ERROR: ndk-build missing under $ndk" >&2
+    return 1
+  fi
+  realpath "$ndk"
+}
+
+# Print llvm prebuilt bin directory for the current host.
+androidcast_ndk_host_bin() {
+  local ndk_root="${1:?NDK root required}"
+  local os arch host_tag
+  case "$(uname -s)" in
+    Linux) os=linux ;;
+    Darwin) os=darwin ;;
+    *) os="$(uname -s | tr '[:upper:]' '[:lower:]')" ;;
+  esac
+  arch="$(uname -m)"
+  case "$arch" in
+    x86_64 | amd64) arch=x86_64 ;;
+    aarch64 | arm64) arch=aarch64 ;;
+  esac
+  host_tag="${os}-${arch}"
+  if [[ ! -d "$ndk_root/toolchains/llvm/prebuilt/${host_tag}/bin" ]]; then
+    host_tag="linux-x86_64"
+  fi
+  realpath "$ndk_root/toolchains/llvm/prebuilt/${host_tag}/bin"
+}

scripts/build-native-codecs.sh

@@ -6,7 +6,7 @@
 #
 # Prerequisites:
 #   git submodule update --init third-party/libvpx
-#   Android NDK (ndk.dir in local.properties or ANDROID_NDK_HOME)
+#   Android NDK (auto-detected via scripts/android-ndk.sh)
 #
 # Usage:
 #   ./scripts/build-native-codecs.sh arm64-v8a
@@ -27,12 +27,12 @@ if [[ ! -d "$VPX_SRC_REAL" ]]; then
   exit 1
 fi
 
-# shellcheck source=android_find_latest_ndk.sh
+# shellcheck source=android-ndk.sh
-source "$ROOT/android_find_latest_ndk.sh"
+source "$ROOT/scripts/android-ndk.sh"
-if ! NDK="$(android_find_ndk_root "$ROOT")"; then
+if ! NDK="$(androidcast_find_ndk_root "$ROOT")"; then
   exit 1
 fi
-NDK_HOST_BIN="$(android_ndk_host_prebuilt_bin "$NDK")"
+NDK_HOST_BIN="$(androidcast_ndk_host_bin "$NDK")"
 if [[ ! -d "$NDK_HOST_BIN" ]]; then
   echo "ERROR: NDK host toolchain bin not found under $NDK"
   exit 1