fix: Qodo on #135 — oversized frames and silent decoders fall back to software, size walks the markers, no restart after stop, surface swaps not fatal, stack trace logged

Author: compot-dev

android/app/src/main/java/com/openipc/decoder/Decoder.java

@@ -1607,22 +1607,24 @@ private int dp(float dp) {
      * with BitmapFactory (into the previous bitmap when the size is the same) and drawn over
      * the whole surface; the view's fit transform keeps the aspect ratio, as for video.
      */
-    private void drawJpeg(Frame frame) {
+    private void drawJpeg(Frame frame, int gen) {
         Surface s = mVideoSurface;
-        if (s == null || !s.isValid()) return;
+        if (s == null || !s.isValid() || gen != listenerGen) return;
         // The hardware JPEG decoder first, where there is one (#132)
         if (!hwJpegFailed && !jpegDrawn && JpegCodec.candidate() != null) {
             int[] size = JpegAssembler.size(frame.data(), frame.length());
             if (size != null) {
                 try {
-                    if (jpegCodec.decode(frame, s, size[0], size[1])) {
+                    if (jpegCodec.decode(frame, s, size[0], size[1],
+                            () -> gen == listenerGen && s == mVideoSurface)) {
                         jpegShown(size[0], size[1]);
                     }
                     return;
                 } catch (Exception e) {
-                    Log.w(TAG, "Hardware MJPEG decoder failed, decoding in software: "
-                            + e.getMessage());
                     jpegCodec.release();
+                    // The surface was replaced meanwhile: not the decoder's fault, try again
+                    if (s != mVideoSurface || gen != listenerGen) return;
+                    Log.w(TAG, "Hardware MJPEG decoder failed, decoding in software", e);
                     hwJpegFailed = true;
                 }
             }
@@ -1703,7 +1705,7 @@ private void startListener() {
                 try {
                     Frame buffer = nalQueue.poll(5, TimeUnit.MILLISECONDS);
                     if (buffer != null && rtspClient.isJpeg()) {
-                        drawJpeg(buffer);
+                        drawJpeg(buffer, gen);
                         framePool.recycle(buffer);
                     } else if (buffer != null && surfacePending) {
                         // Waiting for a fresh surface after MJPEG; the next key frame follows
@@ -1781,7 +1783,6 @@ public void run() {
 
     private void stopStreams() {
         lastJpegFrameMs = 0;
-        jpegCodec.release();
         mSurface.removeCallbacks(singleUdpCheck);
         // The single view's stream ends here: it is no longer "connected" for the debug page
         singleState = "disconnected";
@@ -1803,6 +1804,9 @@ private void stopStreams() {
         // for on the UI thread (#32: this used to block it for seconds)
         audioManager.setEnabled(false);
         stopExecutor();
+        // After the worker's generation is gone: a frame still in flight sees that and can no
+        // longer create the JPEG decoder again (Qodo on #135)
+        jpegCodec.release();
         nalQueue.clear();
     }
 

android/app/src/main/java/com/openipc/decoder/JpegAssembler.java

@@ -222,12 +222,21 @@ private void drop(String reason) {
 
     /** {width, height} from the SOF0 header of a JPEG, or null (#132). */
     static int[] size(byte[] d, int length) {
-        for (int i = 2; i + 8 < length; i++) {
-            if ((d[i] & 0xFF) == 0xFF && (d[i + 1] & 0xFF) == 0xC0) {
+        // Walk the marker segments by their lengths: table bytes may contain FF C0 (Qodo on #135)
+        int i = 2;
+        while (i + 4 <= length) {
+            if ((d[i] & 0xFF) != 0xFF) return null;
+            int marker = d[i + 1] & 0xFF;
+            if (marker == 0xDA || marker == 0xD9) return null; // scan or end before any SOF
+            int len = ((d[i + 2] & 0xFF) << 8) | (d[i + 3] & 0xFF);
+            if (len < 2) return null;
+            if (marker == 0xC0) {
+                if (i + 9 > length) return null;
                 int h = ((d[i + 5] & 0xFF) << 8) | (d[i + 6] & 0xFF);
                 int w = ((d[i + 7] & 0xFF) << 8) | (d[i + 8] & 0xFF);
                 return new int[] {w, h};
             }
+            i += 2 + len;
         }
         return null;
     }

android/app/src/main/java/com/openipc/decoder/JpegCodec.java

@@ -98,7 +98,18 @@ static String[] candidate() {
         return byNameTried ? null : BY_NAME[0];
     }
 
-    synchronized boolean decode(Frame frame, Surface target, int w, int h) throws Exception {
+    /** Frames queued in a row without any output: the decoder is not working (Qodo on #135). */
+    static final int MAX_SILENT_FRAMES = 15;
+    private int silentFrames;
+
+    /** Checked under the lock: false once the stream that called decode() has stopped. */
+    interface Current {
+        boolean holds();
+    }
+
+    synchronized boolean decode(Frame frame, Surface target, int w, int h, Current current)
+            throws Exception {
+        if (!current.holds()) return false;
         String[] dec = chosen != null ? chosen : find();
         if (dec == null) {
             if (byNameTried) throw new IllegalStateException("no JPEG decoder");
@@ -120,6 +131,7 @@ synchronized boolean decode(Frame frame, Surface target, int w, int h) throws Ex
             }
             codec = c;
             chosen = dec;
+            silentFrames = 0;
             surface = target;
             width = w;
             height = h;
@@ -128,13 +140,15 @@ synchronized boolean decode(Frame frame, Surface target, int w, int h) throws Ex
         int in = codec.dequeueInputBuffer(40_000);
         if (in >= 0) {
             ByteBuffer b = codec.getInputBuffer(in);
-            if (b != null && b.capacity() >= frame.length()) {
-                b.clear();
-                b.put(frame.data(), 0, frame.length());
-                codec.queueInputBuffer(in, 0, frame.length(), System.nanoTime() / 1000, 0);
-            } else {
+            if (b == null || b.capacity() < frame.length()) {
+                // A frame larger than the decoder's input buffers: let the software path have it
                 codec.queueInputBuffer(in, 0, 0, 0, 0);
+                throw new IllegalStateException("JPEG frame of " + frame.length()
+                        + " bytes does not fit the input buffer");
             }
+            b.clear();
+            b.put(frame.data(), 0, frame.length());
+            codec.queueInputBuffer(in, 0, frame.length(), System.nanoTime() / 1000, 0);
         }
         boolean rendered = false;
         int out;
@@ -146,6 +160,10 @@ synchronized boolean decode(Frame frame, Surface target, int w, int h) throws Ex
             }
             in = -1; // after the first output, only take what is ready
         }
+        silentFrames = rendered ? 0 : silentFrames + 1;
+        if (silentFrames > MAX_SILENT_FRAMES) {
+            throw new IllegalStateException(MAX_SILENT_FRAMES + " frames without output");
+        }
         return rendered;
     }
 

android/app/src/test/java/com/openipc/decoder/JpegAssemblerTest.java

@@ -179,4 +179,17 @@ public void sizeFromTheFrameHeader() throws Exception {
         assertEquals(64, size[0]);
         assertEquals(32, size[1]);
     }
+
+    @Test
+    public void sizeSkipsTableBytesThatLookLikeSof() {
+        // A DQT whose table contains FF C0 before the real SOF0 (64x32)
+        byte[] tables = new byte[128];
+        tables[10] = (byte) 0xFF;
+        tables[11] = (byte) 0xC0;
+        byte[] h = JpegAssembler.headers(0, 64, 32, tables, 0);
+        int[] size = JpegAssembler.size(h, h.length);
+        assertNotNull(size);
+        assertEquals(64, size[0]);
+        assertEquals(32, size[1]);
+    }
 }