Add support for Dolby TrueHD passthrough

Issue: #2147

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=180678595

RELEASENOTES.md

@@ -39,6 +39,8 @@
 * DefaultTrackSelector: Support disabling of individual text track selection
   flags.
 * New Cast extension: Simplifies toggling between local and Cast playbacks.
+* Audio: Support TrueHD passthrough for rechunked samples in Matroska files
+  ([#2147](https://github.com/google/ExoPlayer/issues/2147)).
 
 ### 2.6.1 ###
 

library/core/src/main/java/com/google/android/exoplayer2/C.java

@@ -122,13 +122,22 @@ public final class C {
    */
   public static final int AUDIO_SESSION_ID_UNSET = AudioManager.AUDIO_SESSION_ID_GENERATE;
 
-  /**
-   * Represents an audio encoding, or an invalid or unset value.
-   */
+  /** Represents an audio encoding, or an invalid or unset value. */
   @Retention(RetentionPolicy.SOURCE)
-  @IntDef({Format.NO_VALUE, ENCODING_INVALID, ENCODING_PCM_8BIT, ENCODING_PCM_16BIT,
-      ENCODING_PCM_24BIT, ENCODING_PCM_32BIT, ENCODING_PCM_FLOAT, ENCODING_AC3, ENCODING_E_AC3,
-      ENCODING_DTS, ENCODING_DTS_HD})
+  @IntDef({
+    Format.NO_VALUE,
+    ENCODING_INVALID,
+    ENCODING_PCM_8BIT,
+    ENCODING_PCM_16BIT,
+    ENCODING_PCM_24BIT,
+    ENCODING_PCM_32BIT,
+    ENCODING_PCM_FLOAT,
+    ENCODING_AC3,
+    ENCODING_E_AC3,
+    ENCODING_DTS,
+    ENCODING_DTS_HD,
+    ENCODING_DOLBY_TRUEHD
+  })
   public @interface Encoding {}
 
   /**
@@ -138,46 +147,28 @@ public final class C {
   @IntDef({Format.NO_VALUE, ENCODING_INVALID, ENCODING_PCM_8BIT, ENCODING_PCM_16BIT,
       ENCODING_PCM_24BIT, ENCODING_PCM_32BIT, ENCODING_PCM_FLOAT})
   public @interface PcmEncoding {}
-  /**
-   * @see AudioFormat#ENCODING_INVALID
-   */
+  /** @see AudioFormat#ENCODING_INVALID */
   public static final int ENCODING_INVALID = AudioFormat.ENCODING_INVALID;
-  /**
-   * @see AudioFormat#ENCODING_PCM_8BIT
-   */
+  /** @see AudioFormat#ENCODING_PCM_8BIT */
   public static final int ENCODING_PCM_8BIT = AudioFormat.ENCODING_PCM_8BIT;
-  /**
-   * @see AudioFormat#ENCODING_PCM_16BIT
-   */
+  /** @see AudioFormat#ENCODING_PCM_16BIT */
   public static final int ENCODING_PCM_16BIT = AudioFormat.ENCODING_PCM_16BIT;
-  /**
-   * PCM encoding with 24 bits per sample.
-   */
+  /** PCM encoding with 24 bits per sample. */
   public static final int ENCODING_PCM_24BIT = 0x80000000;
-  /**
-   * PCM encoding with 32 bits per sample.
-   */
+  /** PCM encoding with 32 bits per sample. */
   public static final int ENCODING_PCM_32BIT = 0x40000000;
-  /**
-   * @see AudioFormat#ENCODING_PCM_FLOAT
-   */
+  /** @see AudioFormat#ENCODING_PCM_FLOAT */
   public static final int ENCODING_PCM_FLOAT = AudioFormat.ENCODING_PCM_FLOAT;
-  /**
-   * @see AudioFormat#ENCODING_AC3
-   */
+  /** @see AudioFormat#ENCODING_AC3 */
   public static final int ENCODING_AC3 = AudioFormat.ENCODING_AC3;
-  /**
-   * @see AudioFormat#ENCODING_E_AC3
-   */
+  /** @see AudioFormat#ENCODING_E_AC3 */
   public static final int ENCODING_E_AC3 = AudioFormat.ENCODING_E_AC3;
-  /**
-   * @see AudioFormat#ENCODING_DTS
-   */
+  /** @see AudioFormat#ENCODING_DTS */
   public static final int ENCODING_DTS = AudioFormat.ENCODING_DTS;
-  /**
-   * @see AudioFormat#ENCODING_DTS_HD
-   */
+  /** @see AudioFormat#ENCODING_DTS_HD */
   public static final int ENCODING_DTS_HD = AudioFormat.ENCODING_DTS_HD;
+  /** @see AudioFormat#ENCODING_DOLBY_TRUEHD */
+  public static final int ENCODING_DOLBY_TRUEHD = AudioFormat.ENCODING_DOLBY_TRUEHD;
 
   /**
    * @see AudioFormat#CHANNEL_OUT_7POINT1_SURROUND

library/core/src/main/java/com/google/android/exoplayer2/audio/Ac3Util.java

@@ -27,9 +27,7 @@ import com.google.android.exoplayer2.util.ParsableBitArray;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import java.nio.ByteBuffer;
 
-/**
- * Utility methods for parsing (E-)AC-3 syncframes, which are access units in (E-)AC-3 bitstreams.
- */
+/** Utility methods for parsing Dolby TrueHD and (E-)AC3 syncframes. */
 public final class Ac3Util {
 
   /**
@@ -94,6 +92,17 @@ public final class Ac3Util {
   }
 
   /**
+   * The number of samples to store in each output chunk when rechunking TrueHD streams. The number
+   * of samples extracted from the container corresponding to one syncframe must be an integer
+   * multiple of this value.
+   */
+  public static final int TRUEHD_RECHUNK_SAMPLE_COUNT = 8;
+  /**
+   * The number of bytes that must be parsed from a TrueHD syncframe to calculate the sample count.
+   */
+  public static final int TRUEHD_SYNCFRAME_PREFIX_LENGTH = 12;
+
+  /**
    * The number of new samples per (E-)AC-3 audio block.
    */
   private static final int AUDIO_SAMPLES_PER_AUDIO_BLOCK = 256;
@@ -441,6 +450,43 @@ public final class Ac3Util {
         : BLOCKS_PER_SYNCFRAME_BY_NUMBLKSCOD[(buffer.get(buffer.position() + 4) & 0x30) >> 4]);
   }
 
+  /**
+   * Returns the number of audio samples represented by the given TrueHD syncframe, or 0 if the
+   * buffer is not the start of a syncframe.
+   *
+   * @param syncframe The bytes from which to read the syncframe. Must be at least {@link
+   *     #TRUEHD_SYNCFRAME_PREFIX_LENGTH} bytes long.
+   * @return The number of audio samples represented by the syncframe, or 0 if the buffer doesn't
+   *     contain the start of a syncframe.
+   */
+  public static int parseTrueHdSyncframeAudioSampleCount(byte[] syncframe) {
+    // TODO: Link to specification if available.
+    if (syncframe[4] != (byte) 0xF8
+        || syncframe[5] != (byte) 0x72
+        || syncframe[6] != (byte) 0x6F
+        || syncframe[7] != (byte) 0xBA) {
+      return 0;
+    }
+    return 40 << (syncframe[8] & 7);
+  }
+
+  /**
+   * Reads the number of audio samples represented by the given TrueHD syncframe, or 0 if the buffer
+   * is not the start of a syncframe. The buffer's position is not modified.
+   *
+   * @param buffer The {@link ByteBuffer} from which to read the syncframe. Must have at least
+   *     {@link #TRUEHD_SYNCFRAME_PREFIX_LENGTH} bytes remaining.
+   * @return The number of audio samples represented by the syncframe, or 0 if the buffer is not the
+   *     start of a syncframe.
+   */
+  public static int parseTrueHdSyncframeAudioSampleCount(ByteBuffer buffer) {
+    // TODO: Link to specification if available.
+    if (buffer.getInt(buffer.position() + 4) != 0xBA6F72F8) {
+      return 0;
+    }
+    return 40 << (buffer.get(buffer.position() + 8) & 0x07);
+  }
+
   private static int getAc3SyncframeSize(int fscod, int frmsizecod) {
     int halfFrmsizecod = frmsizecod / 2;
     if (fscod < 0 || fscod >= SAMPLE_RATE_BY_FSCOD.length || frmsizecod < 0

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

@@ -446,9 +446,12 @@ public final class DefaultAudioSink implements AudioSink {
       if (outputEncoding == C.ENCODING_AC3 || outputEncoding == C.ENCODING_E_AC3) {
         // AC-3 allows bitrates up to 640 kbit/s.
         bufferSize = (int) (PASSTHROUGH_BUFFER_DURATION_US * 80 * 1024 / C.MICROS_PER_SECOND);
-      } else /* (outputEncoding == C.ENCODING_DTS || outputEncoding == C.ENCODING_DTS_HD */ {
+      } else if (outputEncoding == C.ENCODING_DTS) {
         // DTS allows an 'open' bitrate, but we assume the maximum listed value: 1536 kbit/s.
         bufferSize = (int) (PASSTHROUGH_BUFFER_DURATION_US * 192 * 1024 / C.MICROS_PER_SECOND);
+      } else /* outputEncoding == C.ENCODING_DTS_HD || outputEncoding == C.ENCODING_DOLBY_TRUEHD*/ {
+        // HD passthrough requires a larger buffer to avoid underrun.
+        bufferSize = (int) (PASSTHROUGH_BUFFER_DURATION_US * 192 * 6 * 1024 / C.MICROS_PER_SECOND);
       }
     }
     bufferSizeUs =
@@ -580,6 +583,13 @@ public final class DefaultAudioSink implements AudioSink {
       if (!isInputPcm && framesPerEncodedSample == 0) {
         // If this is the first encoded sample, calculate the sample size in frames.
         framesPerEncodedSample = getFramesPerEncodedSample(outputEncoding, buffer);
+        if (framesPerEncodedSample == 0) {
+          // We still don't know the number of frames per sample, so drop the buffer.
+          // For TrueHD this can occur after some seek operations, as not every sample starts with
+          // a syncframe header. If we chunked samples together so the extracted samples always
+          // started with a syncframe header, the chunks would be too large.
+          return true;
+        }
       }
 
       if (drainingPlaybackParameters != null) {
@@ -1225,6 +1235,9 @@ public final class DefaultAudioSink implements AudioSink {
       return Ac3Util.getAc3SyncframeAudioSampleCount();
     } else if (encoding == C.ENCODING_E_AC3) {
       return Ac3Util.parseEAc3SyncframeAudioSampleCount(buffer);
+    } else if (encoding == C.ENCODING_DOLBY_TRUEHD) {
+      return Ac3Util.parseTrueHdSyncframeAudioSampleCount(buffer)
+          * Ac3Util.TRUEHD_RECHUNK_SAMPLE_COUNT;
     } else {
       throw new IllegalStateException("Unexpected audio encoding: " + encoding);
     }

library/core/src/main/java/com/google/android/exoplayer2/extractor/mkv/MatroskaExtractor.java

@@ -16,11 +16,13 @@
 package com.google.android.exoplayer2.extractor.mkv;
 
 import android.support.annotation.IntDef;
+import android.support.annotation.Nullable;
 import android.util.Log;
 import android.util.SparseArray;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.ParserException;
+import com.google.android.exoplayer2.audio.Ac3Util;
 import com.google.android.exoplayer2.drm.DrmInitData;
 import com.google.android.exoplayer2.drm.DrmInitData.SchemeData;
 import com.google.android.exoplayer2.extractor.ChunkIndex;
@@ -32,6 +34,7 @@ import com.google.android.exoplayer2.extractor.MpegAudioHeader;
 import com.google.android.exoplayer2.extractor.PositionHolder;
 import com.google.android.exoplayer2.extractor.SeekMap;
 import com.google.android.exoplayer2.extractor.TrackOutput;
+import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.LongArray;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.NalUnitUtil;
@@ -413,6 +416,9 @@ public final class MatroskaExtractor implements Extractor {
     reader.reset();
     varintReader.reset();
     resetSample();
+    for (int i = 0; i < tracks.size(); i++) {
+      tracks.valueAt(i).reset();
+    }
   }
 
   @Override
@@ -431,7 +437,13 @@ public final class MatroskaExtractor implements Extractor {
         return Extractor.RESULT_SEEK;
       }
     }
-    return continueReading ? Extractor.RESULT_CONTINUE : Extractor.RESULT_END_OF_INPUT;
+    if (!continueReading) {
+      for (int i = 0; i < tracks.size(); i++) {
+        tracks.valueAt(i).outputPendingSampleMetadata();
+      }
+      return Extractor.RESULT_END_OF_INPUT;
+    }
+    return Extractor.RESULT_CONTINUE;
   }
 
   /* package */ int getElementType(int id) {
@@ -1077,14 +1089,26 @@ public final class MatroskaExtractor implements Extractor {
   }
 
   private void commitSampleToOutput(Track track, long timeUs) {
-    if (CODEC_ID_SUBRIP.equals(track.codecId)) {
-      commitSubtitleSample(track, SUBRIP_TIMECODE_FORMAT, SUBRIP_PREFIX_END_TIMECODE_OFFSET,
-          SUBRIP_TIMECODE_LAST_VALUE_SCALING_FACTOR, SUBRIP_TIMECODE_EMPTY);
-    } else if (CODEC_ID_ASS.equals(track.codecId)) {
-      commitSubtitleSample(track, SSA_TIMECODE_FORMAT, SSA_PREFIX_END_TIMECODE_OFFSET,
-          SSA_TIMECODE_LAST_VALUE_SCALING_FACTOR, SSA_TIMECODE_EMPTY);
+    if (track.trueHdSampleRechunker != null) {
+      track.trueHdSampleRechunker.sampleMetadata(track, timeUs);
+    } else {
+      if (CODEC_ID_SUBRIP.equals(track.codecId)) {
+        commitSubtitleSample(
+            track,
+            SUBRIP_TIMECODE_FORMAT,
+            SUBRIP_PREFIX_END_TIMECODE_OFFSET,
+            SUBRIP_TIMECODE_LAST_VALUE_SCALING_FACTOR,
+            SUBRIP_TIMECODE_EMPTY);
+      } else if (CODEC_ID_ASS.equals(track.codecId)) {
+        commitSubtitleSample(
+            track,
+            SSA_TIMECODE_FORMAT,
+            SSA_PREFIX_END_TIMECODE_OFFSET,
+            SSA_TIMECODE_LAST_VALUE_SCALING_FACTOR,
+            SSA_TIMECODE_EMPTY);
+      }
+      track.output.sampleMetadata(timeUs, blockFlags, sampleBytesWritten, 0, track.cryptoData);
     }
-    track.output.sampleMetadata(timeUs, blockFlags, sampleBytesWritten, 0, track.cryptoData);
     sampleRead = true;
     resetSample();
   }
@@ -1251,6 +1275,10 @@ public final class MatroskaExtractor implements Extractor {
         }
       }
     } else {
+      if (track.trueHdSampleRechunker != null) {
+        Assertions.checkState(sampleStrippedBytes.limit() == 0);
+        track.trueHdSampleRechunker.startSample(input, blockFlags, size);
+      }
       while (sampleBytesRead < size) {
         readToOutput(input, output, size - sampleBytesRead);
       }
@@ -1510,7 +1538,70 @@ public final class MatroskaExtractor implements Extractor {
         throws IOException, InterruptedException {
       MatroskaExtractor.this.binaryElement(id, contentsSize, input);
     }
+  }
+
+  /**
+   * Rechunks TrueHD sample data into groups of {@link Ac3Util#TRUEHD_RECHUNK_SAMPLE_COUNT} samples.
+   */
+  private static final class TrueHdSampleRechunker {
+
+    private final byte[] syncframePrefix;
+
+    private boolean foundSyncframe;
+    private int sampleCount;
+    private int chunkSize;
+    private long timeUs;
+    private @C.BufferFlags int blockFlags;
+
+    public TrueHdSampleRechunker() {
+      syncframePrefix = new byte[Ac3Util.TRUEHD_SYNCFRAME_PREFIX_LENGTH];
+    }
+
+    public void reset() {
+      foundSyncframe = false;
+    }
+
+    public void startSample(ExtractorInput input, @C.BufferFlags int blockFlags, int size)
+        throws IOException, InterruptedException {
+      if (!foundSyncframe) {
+        input.peekFully(syncframePrefix, 0, Ac3Util.TRUEHD_SYNCFRAME_PREFIX_LENGTH);
+        input.resetPeekPosition();
+        if ((Ac3Util.parseTrueHdSyncframeAudioSampleCount(syncframePrefix) == C.INDEX_UNSET)) {
+          return;
+        }
+        foundSyncframe = true;
+        sampleCount = 0;
+      }
+      if (sampleCount == 0) {
+        // This is the first sample in the chunk, so reset the block flags and chunk size.
+        this.blockFlags = blockFlags;
+        chunkSize = 0;
+      }
+      chunkSize += size;
+    }
 
+    public void sampleMetadata(Track track, long timeUs) {
+      if (!foundSyncframe) {
+        return;
+      }
+      if (sampleCount++ == 0) {
+        // This is the first sample in the chunk, so update the timestamp.
+        this.timeUs = timeUs;
+      }
+      if (sampleCount < Ac3Util.TRUEHD_RECHUNK_SAMPLE_COUNT) {
+        // We haven't read enough samples to output a chunk.
+        return;
+      }
+      track.output.sampleMetadata(this.timeUs, blockFlags, chunkSize, 0, track.cryptoData);
+      sampleCount = 0;
+    }
+
+    public void outputPendingSampleMetadata(Track track) {
+      if (foundSyncframe && sampleCount > 0) {
+        track.output.sampleMetadata(this.timeUs, blockFlags, chunkSize, 0, track.cryptoData);
+        sampleCount = 0;
+      }
+    }
   }
 
   private static final class Track {
@@ -1573,6 +1664,7 @@ public final class MatroskaExtractor implements Extractor {
     public int sampleRate = 8000;
     public long codecDelayNs = 0;
     public long seekPreRollNs = 0;
+    @Nullable public TrueHdSampleRechunker trueHdSampleRechunker;
 
     // Text elements.
     public boolean flagForced;
@@ -1583,9 +1675,7 @@ public final class MatroskaExtractor implements Extractor {
     public TrackOutput output;
     public int nalUnitLengthFieldLength;
 
-    /**
-     * Initializes the track with an output.
-     */
+    /** Initializes the track with an output. */
     public void initializeOutput(ExtractorOutput output, int trackId) throws ParserException {
       String mimeType;
       int maxInputSize = Format.NO_VALUE;
@@ -1669,6 +1759,7 @@ public final class MatroskaExtractor implements Extractor {
           break;
         case CODEC_ID_TRUEHD:
           mimeType = MimeTypes.AUDIO_TRUEHD;
+          trueHdSampleRechunker = new TrueHdSampleRechunker();
           break;
         case CODEC_ID_DTS:
         case CODEC_ID_DTS_EXPRESS:
@@ -1786,9 +1877,21 @@ public final class MatroskaExtractor implements Extractor {
       this.output.format(format);
     }
 
-    /**
-     * Returns the HDR Static Info as defined in CTA-861.3.
-     */
+    /** Forces any pending sample metadata to be flushed to the output. */
+    public void outputPendingSampleMetadata() {
+      if (trueHdSampleRechunker != null) {
+        trueHdSampleRechunker.outputPendingSampleMetadata(this);
+      }
+    }
+
+    /** Resets any state stored in the track in response to a seek. */
+    public void reset() {
+      if (trueHdSampleRechunker != null) {
+        trueHdSampleRechunker.reset();
+      }
+    }
+
+    /** Returns the HDR Static Info as defined in CTA-861.3. */
     private byte[] getHdrStaticInfo() {
       // Are all fields present.
       if (primaryRChromaticityX == Format.NO_VALUE || primaryRChromaticityY == Format.NO_VALUE

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

@@ -264,6 +264,8 @@ public final class MimeTypes {
         return C.ENCODING_DTS;
       case MimeTypes.AUDIO_DTS_HD:
         return C.ENCODING_DTS_HD;
+      case MimeTypes.AUDIO_TRUEHD:
+        return C.ENCODING_DOLBY_TRUEHD;
       default:
         return C.ENCODING_INVALID;
     }