Add automatic E-AC-3 detection to the Ac3Reader

This is done through the bitstream id field and allows removing
the isEac3 parameter from the constructor.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=131393477

library/src/main/java/com/google/android/exoplayer2/extractor/ts/Ac3Extractor.java

@@ -114,7 +114,7 @@ public final class Ac3Extractor implements Extractor {
 
 
   @Override
   @Override
   public void init(ExtractorOutput output) {
   public void init(ExtractorOutput output) {
-    reader = new Ac3Reader(output.track(0), false); // TODO: Add support for embedded ID3.
+    reader = new Ac3Reader(output.track(0)); // TODO: Add support for embedded ID3.
     output.endTracks();
     output.endTracks();
     output.seekMap(new SeekMap.Unseekable(C.TIME_UNSET));
     output.seekMap(new SeekMap.Unseekable(C.TIME_UNSET));
   }
   }

library/src/main/java/com/google/android/exoplayer2/extractor/ts/Ac3Reader.java

@@ -33,7 +33,6 @@ import com.google.android.exoplayer2.util.ParsableByteArray;
 
 
   private static final int HEADER_SIZE = 8;
   private static final int HEADER_SIZE = 8;
 
 
-  private final boolean isEac3;
   private final ParsableBitArray headerScratchBits;
   private final ParsableBitArray headerScratchBits;
   private final ParsableByteArray headerScratchBytes;
   private final ParsableByteArray headerScratchBytes;
 
 
@@ -47,21 +46,18 @@ import com.google.android.exoplayer2.util.ParsableByteArray;
   private long sampleDurationUs;
   private long sampleDurationUs;
   private Format format;
   private Format format;
   private int sampleSize;
   private int sampleSize;
+  private boolean isEac3;
 
 
   // Used when reading the samples.
   // Used when reading the samples.
   private long timeUs;
   private long timeUs;
 
 
-  // TODO: Remove the isEac3 parameter by reading the BSID field.
   /**
   /**
    * Constructs a new reader for (E-)AC-3 elementary streams.
    * Constructs a new reader for (E-)AC-3 elementary streams.
    *
    *
    * @param output Track output for extracted samples.
    * @param output Track output for extracted samples.
-   * @param isEac3 Whether the stream is E-AC-3 (ETSI TS 102 366 Annex E). Specify {@code false} to
-   *     decode sample headers as AC-3.
    */
    */
-  public Ac3Reader(TrackOutput output, boolean isEac3) {
+  public Ac3Reader(TrackOutput output) {
     super(output);
     super(output);
-    this.isEac3 = isEac3;
     headerScratchBits = new ParsableBitArray(new byte[HEADER_SIZE]);
     headerScratchBits = new ParsableBitArray(new byte[HEADER_SIZE]);
     headerScratchBytes = new ParsableByteArray(headerScratchBits.data);
     headerScratchBytes = new ParsableByteArray(headerScratchBits.data);
     state = STATE_FINDING_SYNC;
     state = STATE_FINDING_SYNC;
@@ -163,6 +159,10 @@ import com.google.android.exoplayer2.util.ParsableByteArray;
    */
    */
   private void parseHeader() {
   private void parseHeader() {
     if (format == null) {
     if (format == null) {
+      // We read ahead to distinguish between AC-3 and E-AC-3.
+      headerScratchBits.skipBits(40);
+      isEac3 = headerScratchBits.readBits(5) == 16;
+      headerScratchBits.setPosition(headerScratchBits.getPosition() - 45);
       format = isEac3 ? Ac3Util.parseEac3SyncframeFormat(headerScratchBits, null, null, null)
       format = isEac3 ? Ac3Util.parseEac3SyncframeFormat(headerScratchBits, null, null, null)
           : Ac3Util.parseAc3SyncframeFormat(headerScratchBits, null, null, null);
           : Ac3Util.parseAc3SyncframeFormat(headerScratchBits, null, null, null);
       output.format(format);
       output.format(format);

library/src/main/java/com/google/android/exoplayer2/extractor/ts/PsExtractor.java

@@ -189,7 +189,7 @@ public final class PsExtractor implements Extractor {
           // Private stream, used for AC3 audio.
           // Private stream, used for AC3 audio.
           // NOTE: This may need further parsing to determine if its DTS, but that's likely only
           // NOTE: This may need further parsing to determine if its DTS, but that's likely only
           // valid for DVDs.
           // valid for DVDs.
-          elementaryStreamReader = new Ac3Reader(output.track(streamId), false);
+          elementaryStreamReader = new Ac3Reader(output.track(streamId));
           foundAudioTrack = true;
           foundAudioTrack = true;
         } else if (!foundAudioTrack && (streamId & AUDIO_STREAM_MASK) == AUDIO_STREAM) {
         } else if (!foundAudioTrack && (streamId & AUDIO_STREAM_MASK) == AUDIO_STREAM) {
           elementaryStreamReader = new MpegAudioReader(output.track(streamId));
           elementaryStreamReader = new MpegAudioReader(output.track(streamId));

library/src/main/java/com/google/android/exoplayer2/extractor/ts/TsExtractor.java

@@ -406,10 +406,8 @@ public final class TsExtractor implements Extractor {
                 : new AdtsReader(output.track(trackId), new DummyTrackOutput());
                 : new AdtsReader(output.track(trackId), new DummyTrackOutput());
             break;
             break;
           case TS_STREAM_TYPE_AC3:
           case TS_STREAM_TYPE_AC3:
-            pesPayloadReader = new Ac3Reader(output.track(trackId), false);
-            break;
           case TS_STREAM_TYPE_E_AC3:
           case TS_STREAM_TYPE_E_AC3:
-            pesPayloadReader = new Ac3Reader(output.track(trackId), true);
+            pesPayloadReader = new Ac3Reader(output.track(trackId));
             break;
             break;
           case TS_STREAM_TYPE_DTS:
           case TS_STREAM_TYPE_DTS:
           case TS_STREAM_TYPE_HDMV_DTS:
           case TS_STREAM_TYPE_HDMV_DTS: