Fix extension FLAC decoder to correctly handle non-16-bit depths

PiperOrigin-RevId: 288860159

RELEASENOTES.md

@@ -32,6 +32,10 @@
   ([#4078](https://github.com/google/ExoPlayer/issues/4078)).
 * Don't use notification chronometer if playback speed is != 1.0
   ([#6816](https://github.com/google/ExoPlayer/issues/6816)).
+* FLAC extension: Fix handling of bit depths other than 16 in `FLACDecoder`.
+  This issue caused FLAC streams with other bit depths to sound like white noise
+  on earlier releases, but only when embedded in a non-FLAC container such as
+  Matroska or MP4.
 
 ### 2.11.1 (2019-12-20) ###
 
@@ -198,7 +202,7 @@
     `C.MSG_SET_OUTPUT_BUFFER_RENDERER`.
   * Use `VideoDecoderRenderer` as an implementation of
     `VideoDecoderOutputBufferRenderer`, instead of `VideoDecoderSurfaceView`.
-* Flac extension: Update to use NDK r20.
+* FLAC extension: Update to use NDK r20.
 * Opus extension: Update to use NDK r20.
 * FFmpeg extension:
   * Update to use NDK r20.
@@ -335,7 +339,7 @@
   ([#6241](https://github.com/google/ExoPlayer/issues/6241)).
 * MP3: Use CBR header bitrate, not calculated bitrate. This reverts a change
   from 2.9.3 ([#6238](https://github.com/google/ExoPlayer/issues/6238)).
-* Flac extension: Parse `VORBIS_COMMENT` and `PICTURE` metadata
+* FLAC extension: Parse `VORBIS_COMMENT` and `PICTURE` metadata
   ([#5527](https://github.com/google/ExoPlayer/issues/5527)).
 * Fix issue where initial seek positions get ignored when playing a preroll ad
   ([#6201](https://github.com/google/ExoPlayer/issues/6201)).
@@ -344,7 +348,7 @@
   ([#6153](https://github.com/google/ExoPlayer/issues/6153)).
 * Fix `DataSchemeDataSource` re-opening and range requests
   ([#6192](https://github.com/google/ExoPlayer/issues/6192)).
-* Fix Flac and ALAC playback on some LG devices
+* Fix FLAC and ALAC playback on some LG devices
   ([#5938](https://github.com/google/ExoPlayer/issues/5938)).
 * Fix issue when calling `performClick` on `PlayerView` without
   `PlayerControlView`

extensions/flac/src/main/java/com/google/android/exoplayer2/ext/flac/FlacDecoder.java

@@ -33,7 +33,7 @@ import java.util.List;
 /* package */ final class FlacDecoder extends
     SimpleDecoder<DecoderInputBuffer, SimpleOutputBuffer, FlacDecoderException> {
 
-  private final int maxOutputBufferSize;
+  private final FlacStreamMetadata streamMetadata;
   private final FlacDecoderJni decoderJni;
 
   /**
@@ -59,7 +59,6 @@ import java.util.List;
     }
     decoderJni = new FlacDecoderJni();
     decoderJni.setData(ByteBuffer.wrap(initializationData.get(0)));
-    FlacStreamMetadata streamMetadata;
     try {
       streamMetadata = decoderJni.decodeStreamMetadata();
     } catch (ParserException e) {
@@ -72,7 +71,6 @@ import java.util.List;
     int initialInputBufferSize =
         maxInputBufferSize != Format.NO_VALUE ? maxInputBufferSize : streamMetadata.maxFrameSize;
     setInitialInputBufferSize(initialInputBufferSize);
-    maxOutputBufferSize = streamMetadata.getMaxDecodedFrameSize();
   }
 
   @Override
@@ -103,7 +101,8 @@ import java.util.List;
       decoderJni.flush();
     }
     decoderJni.setData(Util.castNonNull(inputBuffer.data));
-    ByteBuffer outputData = outputBuffer.init(inputBuffer.timeUs, maxOutputBufferSize);
+    ByteBuffer outputData =
+        outputBuffer.init(inputBuffer.timeUs, streamMetadata.getMaxDecodedFrameSize());
     try {
       decoderJni.decodeSample(outputData);
     } catch (FlacDecoderJni.FlacFrameDecodeException e) {
@@ -121,4 +120,8 @@ import java.util.List;
     decoderJni.release();
   }
 
+  /** Returns the {@link FlacStreamMetadata} decoded from the initialization data. */
+  public FlacStreamMetadata getStreamMetadata() {
+    return streamMetadata;
+  }
 }

extensions/flac/src/main/java/com/google/android/exoplayer2/ext/flac/LibflacAudioRenderer.java

@@ -24,15 +24,20 @@ import com.google.android.exoplayer2.audio.AudioRendererEventListener;
 import com.google.android.exoplayer2.audio.SimpleDecoderAudioRenderer;
 import com.google.android.exoplayer2.drm.DrmSessionManager;
 import com.google.android.exoplayer2.drm.ExoMediaCrypto;
+import com.google.android.exoplayer2.util.Assertions;
+import com.google.android.exoplayer2.util.FlacConstants;
+import com.google.android.exoplayer2.util.FlacStreamMetadata;
 import com.google.android.exoplayer2.util.MimeTypes;
+import com.google.android.exoplayer2.util.Util;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
-/**
- * Decodes and renders audio using the native Flac decoder.
- */
-public class LibflacAudioRenderer extends SimpleDecoderAudioRenderer {
+/** Decodes and renders audio using the native Flac decoder. */
+public final class LibflacAudioRenderer extends SimpleDecoderAudioRenderer {
 
   private static final int NUM_BUFFERS = 16;
 
+  @MonotonicNonNull private FlacStreamMetadata streamMetadata;
+
   public LibflacAudioRenderer() {
     this(/* eventHandler= */ null, /* eventListener= */ null);
   }
@@ -57,7 +62,23 @@ public class LibflacAudioRenderer extends SimpleDecoderAudioRenderer {
     if (!FlacLibrary.isAvailable()
         || !MimeTypes.AUDIO_FLAC.equalsIgnoreCase(format.sampleMimeType)) {
       return FORMAT_UNSUPPORTED_TYPE;
-    } else if (!supportsOutput(format.channelCount, C.ENCODING_PCM_16BIT)) {
+    }
+    // Compute the PCM encoding that the FLAC decoder will output.
+    @C.PcmEncoding int pcmEncoding;
+    if (format.initializationData.isEmpty()) {
+      // The initialization data might not be set if the format was obtained from a manifest (e.g.
+      // for DASH playbacks) rather than directly from the media. In this case we assume
+      // ENCODING_PCM_16BIT. If the actual encoding is different, playback will still succeed as
+      // long as the AudioSink supports it (which will always be true when using DefaultAudioSink).
+      pcmEncoding = C.ENCODING_PCM_16BIT;
+    } else {
+      int streamMetadataOffset =
+          FlacConstants.STREAM_MARKER_SIZE + FlacConstants.METADATA_BLOCK_HEADER_SIZE;
+      FlacStreamMetadata streamMetadata =
+          new FlacStreamMetadata(format.initializationData.get(0), streamMetadataOffset);
+      pcmEncoding = Util.getPcmEncoding(streamMetadata.bitsPerSample);
+    }
+    if (!supportsOutput(format.channelCount, pcmEncoding)) {
       return FORMAT_UNSUPPORTED_SUBTYPE;
     } else if (!supportsFormatDrm(drmSessionManager, format.drmInitData)) {
       return FORMAT_UNSUPPORTED_DRM;
@@ -69,8 +90,27 @@ public class LibflacAudioRenderer extends SimpleDecoderAudioRenderer {
   @Override
   protected FlacDecoder createDecoder(Format format, @Nullable ExoMediaCrypto mediaCrypto)
       throws FlacDecoderException {
-    return new FlacDecoder(
-        NUM_BUFFERS, NUM_BUFFERS, format.maxInputSize, format.initializationData);
+    FlacDecoder decoder =
+        new FlacDecoder(NUM_BUFFERS, NUM_BUFFERS, format.maxInputSize, format.initializationData);
+    streamMetadata = decoder.getStreamMetadata();
+    return decoder;
   }
 
+  @Override
+  protected Format getOutputFormat() {
+    Assertions.checkNotNull(streamMetadata);
+    return Format.createAudioSampleFormat(
+        /* id= */ null,
+        MimeTypes.AUDIO_RAW,
+        /* codecs= */ null,
+        /* bitrate= */ Format.NO_VALUE,
+        /* maxInputSize= */ Format.NO_VALUE,
+        streamMetadata.channels,
+        streamMetadata.sampleRate,
+        Util.getPcmEncoding(streamMetadata.bitsPerSample),
+        /* initializationData= */ null,
+        /* drmInitData= */ null,
+        /* selectionFlags= */ 0,
+        /* language= */ null);
+  }
 }

library/core/src/main/java/com/google/android/exoplayer2/audio/SimpleDecoderAudioRenderer.java

@@ -351,15 +351,8 @@ public abstract class SimpleDecoderAudioRenderer extends BaseRenderer implements
   /**
    * Returns the format of audio buffers output by the decoder. Will not be called until the first
    * output buffer has been dequeued, so the decoder may use input data to determine the format.
-   * <p>
-   * The default implementation returns a 16-bit PCM format with the same channel count and sample
-   * rate as the input.
    */
-  protected Format getOutputFormat() {
-    return Format.createAudioSampleFormat(null, MimeTypes.AUDIO_RAW, null, Format.NO_VALUE,
-        Format.NO_VALUE, inputFormat.channelCount, inputFormat.sampleRate, C.ENCODING_PCM_16BIT,
-        null, null, 0, null);
-  }
+  protected abstract Format getOutputFormat();
 
   /**
    * Returns whether the existing decoder can be kept for a new format.

library/core/src/main/java/com/google/android/exoplayer2/util/FlacStreamMetadata.java

@@ -102,8 +102,9 @@ public final class FlacStreamMetadata {
   /**
    * Parses binary FLAC stream info metadata.
    *
-   * @param data An array containing binary FLAC stream info block (with or without header).
-   * @param offset The offset of the stream info block in {@code data} (header excluded).
+   * @param data An array containing binary FLAC stream info block.
+   * @param offset The offset of the stream info block in {@code data}, excluding the header (i.e.
+   *     the offset points to the first byte of the minimum block size).
    */
   public FlacStreamMetadata(byte[] data, int offset) {
     ParsableBitArray scratch = new ParsableBitArray(data);

library/core/src/test/java/com/google/android/exoplayer2/audio/SimpleDecoderAudioRendererTest.java

@@ -67,10 +67,14 @@ public class SimpleDecoderAudioRendererTest {
           @Override
           protected SimpleDecoder<
                   DecoderInputBuffer, ? extends SimpleOutputBuffer, ? extends AudioDecoderException>
-              createDecoder(Format format, @Nullable ExoMediaCrypto mediaCrypto)
-                  throws AudioDecoderException {
+              createDecoder(Format format, @Nullable ExoMediaCrypto mediaCrypto) {
             return new FakeDecoder();
           }
+
+          @Override
+          protected Format getOutputFormat() {
+            return FORMAT;
+          }
         };
   }