Merge pull request #5303 from DolbyLaboratories:dev-v2-ac4

PiperOrigin-RevId: 239957730

RELEASENOTES.md

@@ -49,6 +49,8 @@
   * Fix an issue that caused audio to be truncated at the end of a period
     when switching to a new period where gapless playback information was newly
     present or newly absent.
+  * Add support for reading AC-4 streams
+    ([#5303](https://github.com/google/ExoPlayer/pull/5303)).
 * Add support for SHOUTcast ICY metadata
   ([#3735](https://github.com/google/ExoPlayer/issues/3735)).
 * CEA-608: Improved conformance to the specification

extensions/flac/src/test/java/com/google/android/exoplayer2/ext/flac/DefaultExtractorsFactoryTest.java

@@ -28,6 +28,7 @@ import com.google.android.exoplayer2.extractor.mp4.FragmentedMp4Extractor;
 import com.google.android.exoplayer2.extractor.mp4.Mp4Extractor;
 import com.google.android.exoplayer2.extractor.ogg.OggExtractor;
 import com.google.android.exoplayer2.extractor.ts.Ac3Extractor;
+import com.google.android.exoplayer2.extractor.ts.Ac4Extractor;
 import com.google.android.exoplayer2.extractor.ts.AdtsExtractor;
 import com.google.android.exoplayer2.extractor.ts.PsExtractor;
 import com.google.android.exoplayer2.extractor.ts.TsExtractor;
@@ -59,6 +60,7 @@ public final class DefaultExtractorsFactoryTest {
           Mp3Extractor.class,
           AdtsExtractor.class,
           Ac3Extractor.class,
+          Ac4Extractor.class,
           TsExtractor.class,
           FlvExtractor.class,
           OggExtractor.class,

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

@@ -146,8 +146,8 @@ public final class C {
    * {@link #ENCODING_INVALID}, {@link #ENCODING_PCM_8BIT}, {@link #ENCODING_PCM_16BIT}, {@link
    * #ENCODING_PCM_24BIT}, {@link #ENCODING_PCM_32BIT}, {@link #ENCODING_PCM_FLOAT}, {@link
    * #ENCODING_PCM_MU_LAW}, {@link #ENCODING_PCM_A_LAW}, {@link #ENCODING_AC3}, {@link
-   * #ENCODING_E_AC3}, {@link #ENCODING_DTS}, {@link #ENCODING_DTS_HD} or {@link
+   * #ENCODING_E_AC3}, {@link #ENCODING_AC4}, {@link #ENCODING_DTS}, {@link #ENCODING_DTS_HD} or
-   * #ENCODING_DOLBY_TRUEHD}.
+   * {@link #ENCODING_DOLBY_TRUEHD}.
    */
   @Documented
   @Retention(RetentionPolicy.SOURCE)
@@ -163,9 +163,10 @@ public final class C {
     ENCODING_PCM_A_LAW,
     ENCODING_AC3,
     ENCODING_E_AC3,
+    ENCODING_AC4,
     ENCODING_DTS,
     ENCODING_DTS_HD,
-    ENCODING_DOLBY_TRUEHD
+    ENCODING_DOLBY_TRUEHD,
   })
   public @interface Encoding {}
 
@@ -209,6 +210,8 @@ public final class C {
   public static final int ENCODING_AC3 = AudioFormat.ENCODING_AC3;
   /** @see AudioFormat#ENCODING_E_AC3 */
   public static final int ENCODING_E_AC3 = AudioFormat.ENCODING_E_AC3;
+  /** @see AudioFormat#ENCODING_AC4 */
+  public static final int ENCODING_AC4 = AudioFormat.ENCODING_AC4;
   /** @see AudioFormat#ENCODING_DTS */
   public static final int ENCODING_DTS = AudioFormat.ENCODING_DTS;
   /** @see AudioFormat#ENCODING_DTS_HD */

library/core/src/main/java/com/google/android/exoplayer2/audio/Ac4Util.java

@@ -0,0 +1,244 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.audio;
+
+import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.Format;
+import com.google.android.exoplayer2.drm.DrmInitData;
+import com.google.android.exoplayer2.util.MimeTypes;
+import com.google.android.exoplayer2.util.ParsableBitArray;
+import com.google.android.exoplayer2.util.ParsableByteArray;
+import java.nio.ByteBuffer;
+
+/** Utility methods for parsing AC-4 frames, which are access units in AC-4 bitstreams. */
+public final class Ac4Util {
+
+  /** Holds sample format information as presented by a syncframe header. */
+  public static final class SyncFrameInfo {
+
+    /** The bitstream version. */
+    public final int bitstreamVersion;
+    /** The audio sampling rate in Hz. */
+    public final int sampleRate;
+    /** The number of audio channels */
+    public final int channelCount;
+    /** The size of the frame. */
+    public final int frameSize;
+    /** Number of audio samples in the frame. */
+    public final int sampleCount;
+
+    private SyncFrameInfo(
+        int bitstreamVersion, int channelCount, int sampleRate, int frameSize, int sampleCount) {
+      this.bitstreamVersion = bitstreamVersion;
+      this.channelCount = channelCount;
+      this.sampleRate = sampleRate;
+      this.frameSize = frameSize;
+      this.sampleCount = sampleCount;
+    }
+  }
+
+  public static final int AC40_SYNCWORD = 0xAC40;
+  public static final int AC41_SYNCWORD = 0xAC41;
+
+  /** The channel count of AC-4 stream. */
+  // TODO: Parse AC-4 stream channel count.
+  private static final int CHANNEL_COUNT_2 = 2;
+  /**
+   * The header size for AC-4 parser. Only needs to be as big as we need to read, not the full
+   * header size.
+   */
+  public static final int HEADER_SIZE_FOR_PARSER = 16;
+  /**
+   * Number of audio samples in the frame. Defined in IEC61937-14:2017 table 5 and 6. This table
+   * provides the number of samples per frame at the playback sampling frequency of 48 kHz. For 44.1
+   * kHz, only frame_rate_index(13) is valid and corresponding sample count is 2048.
+   */
+  private static final int[] SAMPLE_COUNT =
+      new int[] {
+        /* [ 0]  23.976 fps */ 2002,
+        /* [ 1]  24     fps */ 2000,
+        /* [ 2]  25     fps */ 1920,
+        /* [ 3]  29.97  fps */ 1601, // 1601 | 1602 | 1601 | 1602 | 1602
+        /* [ 4]  30     fps */ 1600,
+        /* [ 5]  47.95  fps */ 1001,
+        /* [ 6]  48     fps */ 1000,
+        /* [ 7]  50     fps */ 960,
+        /* [ 8]  59.94  fps */ 800, //  800 |  801 |  801 |  801 |  801
+        /* [ 9]  60     fps */ 800,
+        /* [10] 100     fps */ 480,
+        /* [11] 119.88  fps */ 400, //  400 |  400 |  401 |  400 |  401
+        /* [12] 120     fps */ 400,
+        /* [13]  23.438 fps */ 2048
+      };
+
+  /**
+   * Returns the AC-4 format given {@code data} containing the AC4SpecificBox according to ETSI TS
+   * 103 190-1 Annex E. The reading position of {@code data} will be modified.
+   *
+   * @param data The AC4SpecificBox to parse.
+   * @param trackId The track identifier to set on the format.
+   * @param language The language to set on the format.
+   * @param drmInitData {@link DrmInitData} to be included in the format.
+   * @return The AC-4 format parsed from data in the header.
+   */
+  public static Format parseAc4AnnexEFormat(
+      ParsableByteArray data, String trackId, String language, DrmInitData drmInitData) {
+    data.skipBytes(1); // ac4_dsi_version, bitstream_version[0:5]
+    int sampleRate = ((data.readUnsignedByte() & 0x20) >> 5 == 1) ? 48000 : 44100;
+    return Format.createAudioSampleFormat(
+        trackId,
+        MimeTypes.AUDIO_AC4,
+        /* codecs= */ null,
+        /* bitrate= */ Format.NO_VALUE,
+        /* maxInputSize= */ Format.NO_VALUE,
+        CHANNEL_COUNT_2,
+        sampleRate,
+        /* initializationData= */ null,
+        drmInitData,
+        /* selectionFlags= */ 0,
+        language);
+  }
+
+  /**
+   * Returns AC-4 format information given {@code data} containing a syncframe. The reading position
+   * of {@code data} will be modified.
+   *
+   * @param data The data to parse, positioned at the start of the syncframe.
+   * @return The AC-4 format data parsed from the header.
+   */
+  public static SyncFrameInfo parseAc4SyncframeInfo(ParsableBitArray data) {
+    int headerSize = 0;
+    int syncWord = data.readBits(16);
+    headerSize += 2;
+    int frameSize = data.readBits(16);
+    headerSize += 2;
+    if (frameSize == 0xFFFF) {
+      frameSize = data.readBits(24);
+      headerSize += 3; // Extended frame_size
+    }
+    frameSize += headerSize;
+    if (syncWord == AC41_SYNCWORD) {
+      frameSize += 2; // crc_word
+    }
+    int bitstreamVersion = data.readBits(2);
+    if (bitstreamVersion == 3) {
+      bitstreamVersion += readVariableBits(data, /* bitsPerRead= */ 2);
+    }
+    int sequenceCounter = data.readBits(10);
+    if (data.readBit()) { // b_wait_frames
+      if (data.readBits(3) > 0) { // wait_frames
+        data.skipBits(2); // reserved
+      }
+    }
+    int sampleRate = data.readBit() ? 48000 : 44100;
+    int frameRateIndex = data.readBits(4);
+    int sampleCount = 0;
+    if (sampleRate == 44100 && frameRateIndex == 13) {
+      sampleCount = SAMPLE_COUNT[frameRateIndex];
+    } else if (sampleRate == 48000 && frameRateIndex < SAMPLE_COUNT.length) {
+      sampleCount = SAMPLE_COUNT[frameRateIndex];
+      switch (sequenceCounter % 5) {
+        case 1: // fall through
+        case 3:
+          if (frameRateIndex == 3 || frameRateIndex == 8) {
+            sampleCount++;
+          }
+          break;
+        case 2:
+          if (frameRateIndex == 8 || frameRateIndex == 11) {
+            sampleCount++;
+          }
+          break;
+        case 4:
+          if (frameRateIndex == 3 || frameRateIndex == 8 || frameRateIndex == 11) {
+            sampleCount++;
+          }
+          break;
+        default:
+          break;
+      }
+    }
+    return new SyncFrameInfo(bitstreamVersion, CHANNEL_COUNT_2, sampleRate, frameSize, sampleCount);
+  }
+
+  /**
+   * Returns the size in bytes of the given AC-4 syncframe.
+   *
+   * @param data The syncframe to parse.
+   * @param syncword The syncword value for the syncframe.
+   * @return The syncframe size in bytes, or {@link C#LENGTH_UNSET} if the input is invalid.
+   */
+  public static int parseAc4SyncframeSize(byte[] data, int syncword) {
+    if (data.length < 7) {
+      return C.LENGTH_UNSET;
+    }
+    int headerSize = 2; // syncword
+    int frameSize = ((data[2] & 0xFF) << 8) | (data[3] & 0xFF);
+    headerSize += 2;
+    if (frameSize == 0xFFFF) {
+      frameSize = ((data[4] & 0xFF) << 16) | ((data[5] & 0xFF) << 8) | (data[6] & 0xFF);
+      headerSize += 3;
+    }
+    if (syncword == AC41_SYNCWORD) {
+      headerSize += 2;
+    }
+    frameSize += headerSize;
+    return frameSize;
+  }
+
+  /**
+   * Reads the number of audio samples represented by the given AC-4 syncframe. The buffer's
+   * position is not modified.
+   *
+   * @param buffer The {@link ByteBuffer} from which to read the syncframe.
+   * @return The number of audio samples represented by the syncframe.
+   */
+  public static int parseAc4SyncframeAudioSampleCount(ByteBuffer buffer) {
+    byte[] bufferBytes = new byte[HEADER_SIZE_FOR_PARSER];
+    int position = buffer.position();
+    buffer.get(bufferBytes);
+    buffer.position(position);
+    return parseAc4SyncframeInfo(new ParsableBitArray(bufferBytes)).sampleCount;
+  }
+
+  /** Populates {@code buffer} with an AC-4 sample header for a sample of the specified size. */
+  public static void getAc4SampleHeader(int size, ParsableByteArray buffer) {
+    // See ETSI TS 103 190-1 V1.3.1, Annex G.
+    buffer.reset(/* limit= */ 7);
+    buffer.data[0] = (byte) 0xAC;
+    buffer.data[1] = 0x40;
+    buffer.data[2] = (byte) 0xFF;
+    buffer.data[3] = (byte) 0xFF;
+    buffer.data[4] = (byte) ((size >> 16) & 0xFF);
+    buffer.data[5] = (byte) ((size >> 8) & 0xFF);
+    buffer.data[6] = (byte) (size & 0xFF);
+  }
+
+  private static int readVariableBits(ParsableBitArray data, int bitsPerRead) {
+    int value = 0;
+    while (true) {
+      value += data.readBits(bitsPerRead);
+      if (!data.readBit()) {
+        break;
+      }
+      value++;
+      value <<= bitsPerRead;
+    }
+    return value;
+  }
+
+  private Ac4Util() {}
+}

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

@@ -1126,6 +1126,8 @@ public final class DefaultAudioSink implements AudioSink {
         return 640 * 1000 / 8;
       case C.ENCODING_E_AC3:
         return 6144 * 1000 / 8;
+      case C.ENCODING_AC4:
+        return 2688 * 1000 / 8;
       case C.ENCODING_DTS:
         // DTS allows an 'open' bitrate, but we assume the maximum listed value: 1536 kbit/s.
         return 1536 * 1000 / 8;
@@ -1154,6 +1156,8 @@ 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_AC4) {
+      return Ac4Util.parseAc4SyncframeAudioSampleCount(buffer);
     } else if (encoding == C.ENCODING_DOLBY_TRUEHD) {
       int syncframeOffset = Ac3Util.findTrueHdSyncframeOffset(buffer);
       return syncframeOffset == C.INDEX_UNSET

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

@@ -784,6 +784,11 @@ public class MediaCodecAudioRenderer extends MediaCodecRenderer implements Media
         mediaFormat.setFloat(MediaFormat.KEY_OPERATING_RATE, codecOperatingRate);
       }
     }
+    if (Util.SDK_INT <= 28 && MimeTypes.AUDIO_AC4.equals(format.sampleMimeType)) {
+      // On some older builds, the AC-4 decoder expects to receive samples formatted as raw frames
+      // not sync frames. Set a format key to override this.
+      mediaFormat.setInteger("ac4-is-sync", 1);
+    }
     return mediaFormat;
   }
 

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

@@ -23,6 +23,7 @@ import com.google.android.exoplayer2.extractor.mp4.FragmentedMp4Extractor;
 import com.google.android.exoplayer2.extractor.mp4.Mp4Extractor;
 import com.google.android.exoplayer2.extractor.ogg.OggExtractor;
 import com.google.android.exoplayer2.extractor.ts.Ac3Extractor;
+import com.google.android.exoplayer2.extractor.ts.Ac4Extractor;
 import com.google.android.exoplayer2.extractor.ts.AdtsExtractor;
 import com.google.android.exoplayer2.extractor.ts.DefaultTsPayloadReaderFactory;
 import com.google.android.exoplayer2.extractor.ts.PsExtractor;
@@ -47,6 +48,7 @@ import java.lang.reflect.Constructor;
  *   <li>FLV ({@link FlvExtractor})
  *   <li>WAV ({@link WavExtractor})
  *   <li>AC3 ({@link Ac3Extractor})
+ *   <li>AC4 ({@link Ac4Extractor})
  *   <li>AMR ({@link AmrExtractor})
  *   <li>FLAC (only available if the FLAC extension is built and included)
  * </ul>
@@ -206,7 +208,7 @@ public final class DefaultExtractorsFactory implements ExtractorsFactory {
 
   @Override
   public synchronized Extractor[] createExtractors() {
-    Extractor[] extractors = new Extractor[FLAC_EXTRACTOR_CONSTRUCTOR == null ? 12 : 13];
+    Extractor[] extractors = new Extractor[FLAC_EXTRACTOR_CONSTRUCTOR == null ? 13 : 14];
     extractors[0] = new MatroskaExtractor(matroskaFlags);
     extractors[1] = new FragmentedMp4Extractor(fragmentedMp4Flags);
     extractors[2] = new Mp4Extractor(mp4Flags);
@@ -235,9 +237,10 @@ public final class DefaultExtractorsFactory implements ExtractorsFactory {
                 | (constantBitrateSeekingEnabled
                     ? AmrExtractor.FLAG_ENABLE_CONSTANT_BITRATE_SEEKING
                     : 0));
+    extractors[12] = new Ac4Extractor();
     if (FLAC_EXTRACTOR_CONSTRUCTOR != null) {
       try {
-        extractors[12] = FLAC_EXTRACTOR_CONSTRUCTOR.newInstance();
+        extractors[13] = FLAC_EXTRACTOR_CONSTRUCTOR.newInstance();
       } catch (Exception e) {
         // Should never happen.
         throw new IllegalStateException("Unexpected error creating FLAC extractor", e);

library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/Atom.java

@@ -80,6 +80,8 @@ import java.util.List;
   public static final int TYPE_dac3 = Util.getIntegerCodeForString("dac3");
   public static final int TYPE_ec_3 = Util.getIntegerCodeForString("ec-3");
   public static final int TYPE_dec3 = Util.getIntegerCodeForString("dec3");
+  public static final int TYPE_ac_4 = Util.getIntegerCodeForString("ac-4");
+  public static final int TYPE_dac4 = Util.getIntegerCodeForString("dac4");
   public static final int TYPE_dtsc = Util.getIntegerCodeForString("dtsc");
   public static final int TYPE_dtsh = Util.getIntegerCodeForString("dtsh");
   public static final int TYPE_dtsl = Util.getIntegerCodeForString("dtsl");

library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/AtomParsers.java

@@ -23,6 +23,7 @@ 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.audio.Ac4Util;
 import com.google.android.exoplayer2.drm.DrmInitData;
 import com.google.android.exoplayer2.extractor.GaplessInfoHolder;
 import com.google.android.exoplayer2.metadata.Metadata;
@@ -756,6 +757,7 @@ import java.util.List;
           || childAtomType == Atom.TYPE_enca
           || childAtomType == Atom.TYPE_ac_3
           || childAtomType == Atom.TYPE_ec_3
+          || childAtomType == Atom.TYPE_ac_4
           || childAtomType == Atom.TYPE_dtsc
           || childAtomType == Atom.TYPE_dtse
           || childAtomType == Atom.TYPE_dtsh
@@ -1071,6 +1073,8 @@ import java.util.List;
       mimeType = MimeTypes.AUDIO_AC3;
     } else if (atomType == Atom.TYPE_ec_3) {
       mimeType = MimeTypes.AUDIO_E_AC3;
+    } else if (atomType == Atom.TYPE_ac_4) {
+      mimeType = MimeTypes.AUDIO_AC4;
     } else if (atomType == Atom.TYPE_dtsc) {
       mimeType = MimeTypes.AUDIO_DTS;
     } else if (atomType == Atom.TYPE_dtsh || atomType == Atom.TYPE_dtsl) {
@@ -1128,6 +1132,10 @@ import java.util.List;
         parent.setPosition(Atom.HEADER_SIZE + childPosition);
         out.format = Ac3Util.parseEAc3AnnexFFormat(parent, Integer.toString(trackId), language,
             drmInitData);
+      } else if (childAtomType == Atom.TYPE_dac4) {
+        parent.setPosition(Atom.HEADER_SIZE + childPosition);
+        out.format =
+            Ac4Util.parseAc4AnnexEFormat(parent, Integer.toString(trackId), language, drmInitData);
       } else if (childAtomType == Atom.TYPE_ddts) {
         out.format = Format.createAudioSampleFormat(Integer.toString(trackId), mimeType, null,
             Format.NO_VALUE, Format.NO_VALUE, channelCount, sampleRate, null, drmInitData, 0,

library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/FragmentedMp4Extractor.java

@@ -22,6 +22,7 @@ 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.Ac4Util;
 import com.google.android.exoplayer2.drm.DrmInitData;
 import com.google.android.exoplayer2.drm.DrmInitData.SchemeData;
 import com.google.android.exoplayer2.extractor.ChunkIndex;
@@ -133,13 +134,14 @@ public class FragmentedMp4Extractor implements Extractor {
   private final ParsableByteArray nalStartCode;
   private final ParsableByteArray nalPrefix;
   private final ParsableByteArray nalBuffer;
+  private final byte[] scratchBytes;
+  private final ParsableByteArray scratch;
 
   // Adjusts sample timestamps.
   private final @Nullable TimestampAdjuster timestampAdjuster;
 
   // Parser state.
   private final ParsableByteArray atomHeader;
-  private final byte[] extendedTypeScratch;
   private final ArrayDeque<ContainerAtom> containerAtoms;
   private final ArrayDeque<MetadataSampleInfo> pendingMetadataSampleInfos;
   private final @Nullable TrackOutput additionalEmsgTrackOutput;
@@ -160,6 +162,7 @@ public class FragmentedMp4Extractor implements Extractor {
   private int sampleBytesWritten;
   private int sampleCurrentNalBytesRemaining;
   private boolean processSeiNalUnitPayload;
+  private boolean isAc4HeaderRequired;
 
   // Extractor output.
   private ExtractorOutput extractorOutput;
@@ -254,7 +257,8 @@ public class FragmentedMp4Extractor implements Extractor {
     nalStartCode = new ParsableByteArray(NalUnitUtil.NAL_START_CODE);
     nalPrefix = new ParsableByteArray(5);
     nalBuffer = new ParsableByteArray();
-    extendedTypeScratch = new byte[16];
+    scratchBytes = new byte[16];
+    scratch = new ParsableByteArray(scratchBytes);
     containerAtoms = new ArrayDeque<>();
     pendingMetadataSampleInfos = new ArrayDeque<>();
     trackBundles = new SparseArray<>();
@@ -291,6 +295,7 @@ public class FragmentedMp4Extractor implements Extractor {
     pendingMetadataSampleBytes = 0;
     pendingSeekTimeUs = timeUs;
     containerAtoms.clear();
+    isAc4HeaderRequired = false;
     enterReadingAtomHeaderState();
   }
 
@@ -538,7 +543,7 @@ public class FragmentedMp4Extractor implements Extractor {
   }
 
   private void onMoofContainerAtomRead(ContainerAtom moof) throws ParserException {
-    parseMoof(moof, trackBundles, flags, extendedTypeScratch);
+    parseMoof(moof, trackBundles, flags, scratchBytes);
     // If drm init data is sideloaded, we ignore pssh boxes.
     DrmInitData drmInitData = sideloadedDrmInitData != null ? null
         : getDrmInitDataFromAtoms(moof.leafChildren);
@@ -1224,6 +1229,8 @@ public class FragmentedMp4Extractor implements Extractor {
       sampleSize += sampleBytesWritten;
       parserState = STATE_READING_SAMPLE_CONTINUE;
       sampleCurrentNalBytesRemaining = 0;
+      isAc4HeaderRequired =
+          MimeTypes.AUDIO_AC4.equals(currentTrackBundle.track.format.sampleMimeType);
     }
 
     TrackFragment fragment = currentTrackBundle.fragment;
@@ -1288,6 +1295,14 @@ public class FragmentedMp4Extractor implements Extractor {
         }
       }
     } else {
+      if (isAc4HeaderRequired) {
+        Ac4Util.getAc4SampleHeader(sampleSize, scratch);
+        int length = scratch.limit();
+        output.sampleData(scratch, length);
+        sampleSize += length;
+        sampleBytesWritten += length;
+        isAc4HeaderRequired = false;
+      }
       while (sampleBytesWritten < sampleSize) {
         int writtenBytes = output.sampleData(input, sampleSize - sampleBytesWritten, false);
         sampleBytesWritten += writtenBytes;

library/core/src/main/java/com/google/android/exoplayer2/extractor/mp4/Mp4Extractor.java

@@ -19,6 +19,7 @@ import androidx.annotation.IntDef;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.ParserException;
+import com.google.android.exoplayer2.audio.Ac4Util;
 import com.google.android.exoplayer2.extractor.Extractor;
 import com.google.android.exoplayer2.extractor.ExtractorInput;
 import com.google.android.exoplayer2.extractor.ExtractorOutput;
@@ -31,6 +32,7 @@ import com.google.android.exoplayer2.extractor.TrackOutput;
 import com.google.android.exoplayer2.extractor.mp4.Atom.ContainerAtom;
 import com.google.android.exoplayer2.metadata.Metadata;
 import com.google.android.exoplayer2.util.Assertions;
+import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.NalUnitUtil;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import com.google.android.exoplayer2.util.Util;
@@ -95,6 +97,7 @@ public final class Mp4Extractor implements Extractor, SeekMap {
   // Temporary arrays.
   private final ParsableByteArray nalStartCode;
   private final ParsableByteArray nalLength;
+  private final ParsableByteArray scratch;
 
   private final ParsableByteArray atomHeader;
   private final ArrayDeque<ContainerAtom> containerAtoms;
@@ -108,6 +111,7 @@ public final class Mp4Extractor implements Extractor, SeekMap {
   private int sampleTrackIndex;
   private int sampleBytesWritten;
   private int sampleCurrentNalBytesRemaining;
+  private boolean isAc4HeaderRequired;
 
   // Extractor outputs.
   private ExtractorOutput extractorOutput;
@@ -136,6 +140,7 @@ public final class Mp4Extractor implements Extractor, SeekMap {
     containerAtoms = new ArrayDeque<>();
     nalStartCode = new ParsableByteArray(NalUnitUtil.NAL_START_CODE);
     nalLength = new ParsableByteArray(4);
+    scratch = new ParsableByteArray();
     sampleTrackIndex = C.INDEX_UNSET;
   }
 
@@ -156,6 +161,7 @@ public final class Mp4Extractor implements Extractor, SeekMap {
     sampleTrackIndex = C.INDEX_UNSET;
     sampleBytesWritten = 0;
     sampleCurrentNalBytesRemaining = 0;
+    isAc4HeaderRequired = false;
     if (position == 0) {
       enterReadingAtomHeaderState();
     } else if (tracks != null) {
@@ -493,6 +499,8 @@ public final class Mp4Extractor implements Extractor, SeekMap {
       if (sampleTrackIndex == C.INDEX_UNSET) {
         return RESULT_END_OF_INPUT;
       }
+      isAc4HeaderRequired =
+          MimeTypes.AUDIO_AC4.equals(tracks[sampleTrackIndex].track.format.sampleMimeType);
     }
     Mp4Track track = tracks[sampleTrackIndex];
     TrackOutput trackOutput = track.trackOutput;
@@ -546,6 +554,14 @@ public final class Mp4Extractor implements Extractor, SeekMap {
         }
       }
     } else {
+      if (isAc4HeaderRequired) {
+        Ac4Util.getAc4SampleHeader(sampleSize, scratch);
+        int length = scratch.limit();
+        trackOutput.sampleData(scratch, length);
+        sampleSize += length;
+        sampleBytesWritten += length;
+        isAc4HeaderRequired = false;
+      }
       while (sampleBytesWritten < sampleSize) {
         int writtenBytes = trackOutput.sampleData(input, sampleSize - sampleBytesWritten, false);
         sampleBytesWritten += writtenBytes;

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

@@ -76,7 +76,7 @@ public final class Ac3Extractor implements Extractor {
       if (scratch.readUnsignedInt24() != ID3_TAG) {
         break;
       }
-      scratch.skipBytes(3);
+      scratch.skipBytes(3); // version, flags
       int length = scratch.readSynchSafeInt();
       startPosition += 10 + length;
       input.advancePeekPosition(length);

library/core/src/main/java/com/google/android/exoplayer2/extractor/ts/Ac4Extractor.java

@@ -0,0 +1,164 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.extractor.ts;
+
+import static com.google.android.exoplayer2.audio.Ac4Util.AC40_SYNCWORD;
+import static com.google.android.exoplayer2.audio.Ac4Util.AC41_SYNCWORD;
+import static com.google.android.exoplayer2.extractor.ts.TsPayloadReader.FLAG_DATA_ALIGNMENT_INDICATOR;
+
+import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.audio.Ac4Util;
+import com.google.android.exoplayer2.extractor.Extractor;
+import com.google.android.exoplayer2.extractor.ExtractorInput;
+import com.google.android.exoplayer2.extractor.ExtractorOutput;
+import com.google.android.exoplayer2.extractor.ExtractorsFactory;
+import com.google.android.exoplayer2.extractor.PositionHolder;
+import com.google.android.exoplayer2.extractor.SeekMap;
+import com.google.android.exoplayer2.extractor.ts.TsPayloadReader.TrackIdGenerator;
+import com.google.android.exoplayer2.util.ParsableByteArray;
+import com.google.android.exoplayer2.util.Util;
+import java.io.IOException;
+
+/** Extracts data from AC-4 bitstreams. */
+public final class Ac4Extractor implements Extractor {
+
+  /** Factory for {@link Ac4Extractor} instances. */
+  public static final ExtractorsFactory FACTORY = () -> new Extractor[] {new Ac4Extractor()};
+
+  /**
+   * The maximum number of bytes to search when sniffing, excluding ID3 information, before giving
+   * up.
+   */
+  private static final int MAX_SNIFF_BYTES = 8 * 1024;
+
+  /**
+   * The size of the reading buffer, in bytes. This value is determined based on the maximum frame
+   * size used in broadcast applications.
+   */
+  private static final int READ_BUFFER_SIZE = 16384;
+
+  /** The size of the frame header, in bytes. */
+  private static final int FRAME_HEADER_SIZE = 7;
+
+  private static final int ID3_TAG = Util.getIntegerCodeForString("ID3");
+
+  private final long firstSampleTimestampUs;
+  private final Ac4Reader reader;
+  private final ParsableByteArray sampleData;
+
+  private boolean startedPacket;
+
+  /** Creates a new extractor for AC-4 bitstreams. */
+  public Ac4Extractor() {
+    this(/* firstSampleTimestampUs= */ 0);
+  }
+
+  /** Creates a new extractor for AC-4 bitstreams, using the specified first sample timestamp. */
+  public Ac4Extractor(long firstSampleTimestampUs) {
+    this.firstSampleTimestampUs = firstSampleTimestampUs;
+    reader = new Ac4Reader();
+    sampleData = new ParsableByteArray(READ_BUFFER_SIZE);
+  }
+
+  // Extractor implementation.
+
+  @Override
+  public boolean sniff(ExtractorInput input) throws IOException, InterruptedException {
+    // Skip any ID3 headers.
+    ParsableByteArray scratch = new ParsableByteArray(10);
+    int startPosition = 0;
+    while (true) {
+      input.peekFully(scratch.data, /* offset= */ 0, /* length= */ 10);
+      scratch.setPosition(0);
+      if (scratch.readUnsignedInt24() != ID3_TAG) {
+        break;
+      }
+      scratch.skipBytes(3); // version, flags
+      int length = scratch.readSynchSafeInt();
+      startPosition += 10 + length;
+      input.advancePeekPosition(length);
+    }
+    input.resetPeekPosition();
+    input.advancePeekPosition(startPosition);
+
+    int headerPosition = startPosition;
+    int validFramesCount = 0;
+    while (true) {
+      input.peekFully(scratch.data, /* offset= */ 0, /* length= */ FRAME_HEADER_SIZE);
+      scratch.setPosition(0);
+      int syncBytes = scratch.readUnsignedShort();
+      if (syncBytes != AC40_SYNCWORD && syncBytes != AC41_SYNCWORD) {
+        validFramesCount = 0;
+        input.resetPeekPosition();
+        if (++headerPosition - startPosition >= MAX_SNIFF_BYTES) {
+          return false;
+        }
+        input.advancePeekPosition(headerPosition);
+      } else {
+        if (++validFramesCount >= 4) {
+          return true;
+        }
+        int frameSize = Ac4Util.parseAc4SyncframeSize(scratch.data, syncBytes);
+        if (frameSize == C.LENGTH_UNSET) {
+          return false;
+        }
+        input.advancePeekPosition(frameSize - FRAME_HEADER_SIZE);
+      }
+    }
+  }
+
+  @Override
+  public void init(ExtractorOutput output) {
+    reader.createTracks(
+        output, new TrackIdGenerator(/* firstTrackId= */ 0, /* trackIdIncrement= */ 1));
+    output.endTracks();
+    output.seekMap(new SeekMap.Unseekable(/* durationUs= */ C.TIME_UNSET));
+  }
+
+  @Override
+  public void seek(long position, long timeUs) {
+    startedPacket = false;
+    reader.seek();
+  }
+
+  @Override
+  public void release() {
+    // Do nothing.
+  }
+
+  @Override
+  public int read(ExtractorInput input, PositionHolder seekPosition)
+      throws IOException, InterruptedException {
+    int bytesRead = input.read(sampleData.data, /* offset= */ 0, /* length= */ READ_BUFFER_SIZE);
+    if (bytesRead == C.RESULT_END_OF_INPUT) {
+      return RESULT_END_OF_INPUT;
+    }
+
+    // Feed whatever data we have to the reader, regardless of whether the read finished or not.
+    sampleData.setPosition(0);
+    sampleData.setLimit(bytesRead);
+
+    if (!startedPacket) {
+      // Pass data to the reader as though it's contained within a single infinitely long packet.
+      reader.packetStarted(firstSampleTimestampUs, FLAG_DATA_ALIGNMENT_INDICATOR);
+      startedPacket = true;
+    }
+    // TODO: Make it possible for the reader to consume the dataSource directly, so that it becomes
+    // unnecessary to copy the data through packetBuffer.
+    reader.consume(sampleData);
+    return RESULT_CONTINUE;
+  }
+}

library/core/src/main/java/com/google/android/exoplayer2/extractor/ts/Ac4Reader.java

@@ -0,0 +1,216 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.extractor.ts;
+
+import androidx.annotation.IntDef;
+import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.Format;
+import com.google.android.exoplayer2.audio.Ac4Util;
+import com.google.android.exoplayer2.audio.Ac4Util.SyncFrameInfo;
+import com.google.android.exoplayer2.extractor.ExtractorOutput;
+import com.google.android.exoplayer2.extractor.TrackOutput;
+import com.google.android.exoplayer2.extractor.ts.TsPayloadReader.TrackIdGenerator;
+import com.google.android.exoplayer2.util.MimeTypes;
+import com.google.android.exoplayer2.util.ParsableBitArray;
+import com.google.android.exoplayer2.util.ParsableByteArray;
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/** Parses a continuous AC-4 byte stream and extracts individual samples. */
+public final class Ac4Reader implements ElementaryStreamReader {
+
+  @Documented
+  @Retention(RetentionPolicy.SOURCE)
+  @IntDef({STATE_FINDING_SYNC, STATE_READING_HEADER, STATE_READING_SAMPLE})
+  private @interface State {}
+
+  private static final int STATE_FINDING_SYNC = 0;
+  private static final int STATE_READING_HEADER = 1;
+  private static final int STATE_READING_SAMPLE = 2;
+
+  private final ParsableBitArray headerScratchBits;
+  private final ParsableByteArray headerScratchBytes;
+  private final String language;
+
+  private String trackFormatId;
+  private TrackOutput output;
+
+  @State private int state;
+  private int bytesRead;
+
+  // Used to find the header.
+  private boolean lastByteWasAC;
+  private boolean hasCRC;
+
+  // Used when parsing the header.
+  private long sampleDurationUs;
+  private Format format;
+  private int sampleSize;
+
+  // Used when reading the samples.
+  private long timeUs;
+
+  /** Constructs a new reader for AC-4 elementary streams. */
+  public Ac4Reader() {
+    this(null);
+  }
+
+  /**
+   * Constructs a new reader for AC-4 elementary streams.
+   *
+   * @param language Track language.
+   */
+  public Ac4Reader(String language) {
+    headerScratchBits = new ParsableBitArray(new byte[Ac4Util.HEADER_SIZE_FOR_PARSER]);
+    headerScratchBytes = new ParsableByteArray(headerScratchBits.data);
+    state = STATE_FINDING_SYNC;
+    bytesRead = 0;
+    lastByteWasAC = false;
+    hasCRC = false;
+    this.language = language;
+  }
+
+  @Override
+  public void seek() {
+    state = STATE_FINDING_SYNC;
+    bytesRead = 0;
+    lastByteWasAC = false;
+    hasCRC = false;
+  }
+
+  @Override
+  public void createTracks(ExtractorOutput extractorOutput, TrackIdGenerator generator) {
+    generator.generateNewId();
+    trackFormatId = generator.getFormatId();
+    output = extractorOutput.track(generator.getTrackId(), C.TRACK_TYPE_AUDIO);
+  }
+
+  @Override
+  public void packetStarted(long pesTimeUs, @TsPayloadReader.Flags int flags) {
+    timeUs = pesTimeUs;
+  }
+
+  @Override
+  public void consume(ParsableByteArray data) {
+    while (data.bytesLeft() > 0) {
+      switch (state) {
+        case STATE_FINDING_SYNC:
+          if (skipToNextSync(data)) {
+            state = STATE_READING_HEADER;
+            headerScratchBytes.data[0] = (byte) 0xAC;
+            headerScratchBytes.data[1] = (byte) (hasCRC ? 0x41 : 0x40);
+            bytesRead = 2;
+          }
+          break;
+        case STATE_READING_HEADER:
+          if (continueRead(data, headerScratchBytes.data, Ac4Util.HEADER_SIZE_FOR_PARSER)) {
+            parseHeader();
+            headerScratchBytes.setPosition(0);
+            output.sampleData(headerScratchBytes, Ac4Util.HEADER_SIZE_FOR_PARSER);
+            state = STATE_READING_SAMPLE;
+          }
+          break;
+        case STATE_READING_SAMPLE:
+          int bytesToRead = Math.min(data.bytesLeft(), sampleSize - bytesRead);
+          output.sampleData(data, bytesToRead);
+          bytesRead += bytesToRead;
+          if (bytesRead == sampleSize) {
+            output.sampleMetadata(timeUs, C.BUFFER_FLAG_KEY_FRAME, sampleSize, 0, null);
+            timeUs += sampleDurationUs;
+            state = STATE_FINDING_SYNC;
+          }
+          break;
+        default:
+          break;
+      }
+    }
+  }
+
+  @Override
+  public void packetFinished() {
+    // Do nothing.
+  }
+
+  /**
+   * Continues a read from the provided {@code source} into a given {@code target}. It's assumed
+   * that the data should be written into {@code target} starting from an offset of zero.
+   *
+   * @param source The source from which to read.
+   * @param target The target into which data is to be read.
+   * @param targetLength The target length of the read.
+   * @return Whether the target length was reached.
+   */
+  private boolean continueRead(ParsableByteArray source, byte[] target, int targetLength) {
+    int bytesToRead = Math.min(source.bytesLeft(), targetLength - bytesRead);
+    source.readBytes(target, bytesRead, bytesToRead);
+    bytesRead += bytesToRead;
+    return bytesRead == targetLength;
+  }
+
+  /**
+   * Locates the next syncword, advancing the position to the byte that immediately follows it. If a
+   * syncword was not located, the position is advanced to the limit.
+   *
+   * @param pesBuffer The buffer whose position should be advanced.
+   * @return Whether a syncword position was found.
+   */
+  private boolean skipToNextSync(ParsableByteArray pesBuffer) {
+    while (pesBuffer.bytesLeft() > 0) {
+      if (!lastByteWasAC) {
+        lastByteWasAC = (pesBuffer.readUnsignedByte() == 0xAC);
+        continue;
+      }
+      int secondByte = pesBuffer.readUnsignedByte();
+      lastByteWasAC = secondByte == 0xAC;
+      if (secondByte == 0x40 || secondByte == 0x41) {
+        hasCRC = secondByte == 0x41;
+        return true;
+      }
+    }
+    return false;
+  }
+
+  /** Parses the sample header. */
+  @SuppressWarnings("ReferenceEquality")
+  private void parseHeader() {
+    headerScratchBits.setPosition(0);
+    SyncFrameInfo frameInfo = Ac4Util.parseAc4SyncframeInfo(headerScratchBits);
+    if (format == null
+        || frameInfo.channelCount != format.channelCount
+        || frameInfo.sampleRate != format.sampleRate
+        || !MimeTypes.AUDIO_AC4.equals(format.sampleMimeType)) {
+      format =
+          Format.createAudioSampleFormat(
+              trackFormatId,
+              MimeTypes.AUDIO_AC4,
+              /* codecs= */ null,
+              /* bitrate= */ Format.NO_VALUE,
+              /* maxInputSize= */ Format.NO_VALUE,
+              frameInfo.channelCount,
+              frameInfo.sampleRate,
+              /* initializationData= */ null,
+              /* drmInitData= */ null,
+              /* selectionFlags= */ 0,
+              language);
+      output.format(format);
+    }
+    sampleSize = frameInfo.frameSize;
+    // In this class a sample is an AC-4 sync frame, but Format#sampleRate specifies the number of
+    // PCM audio samples per second.
+    sampleDurationUs = C.MICROS_PER_SECOND * frameInfo.sampleCount / format.sampleRate;
+  }
+}

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

@@ -149,6 +149,8 @@ public final class DefaultTsPayloadReaderFactory implements TsPayloadReader.Fact
       case TsExtractor.TS_STREAM_TYPE_AC3:
       case TsExtractor.TS_STREAM_TYPE_E_AC3:
         return new PesReader(new Ac3Reader(esInfo.language));
+      case TsExtractor.TS_STREAM_TYPE_AC4:
+        return new PesReader(new Ac4Reader(esInfo.language));
       case TsExtractor.TS_STREAM_TYPE_HDMV_DTS:
         if (isSet(FLAG_IGNORE_HDMV_DTS_STREAM)) {
           return null;

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

@@ -87,6 +87,7 @@ public final class TsExtractor implements Extractor {
   public static final int TS_STREAM_TYPE_DTS = 0x8A;
   public static final int TS_STREAM_TYPE_HDMV_DTS = 0x82;
   public static final int TS_STREAM_TYPE_E_AC3 = 0x87;
+  public static final int TS_STREAM_TYPE_AC4 = 0xAC; // DVB/ATSC AC-4 Descriptor
   public static final int TS_STREAM_TYPE_H262 = 0x02;
   public static final int TS_STREAM_TYPE_H264 = 0x1B;
   public static final int TS_STREAM_TYPE_H265 = 0x24;
@@ -102,6 +103,7 @@ public final class TsExtractor implements Extractor {
 
   private static final long AC3_FORMAT_IDENTIFIER = Util.getIntegerCodeForString("AC-3");
   private static final long E_AC3_FORMAT_IDENTIFIER = Util.getIntegerCodeForString("EAC3");
+  private static final long AC4_FORMAT_IDENTIFIER = Util.getIntegerCodeForString("AC-4");
   private static final long HEVC_FORMAT_IDENTIFIER = Util.getIntegerCodeForString("HEVC");
 
   private static final int BUFFER_SIZE = TS_PACKET_SIZE * 50;
@@ -494,8 +496,11 @@ public final class TsExtractor implements Extractor {
     private static final int TS_PMT_DESC_AC3 = 0x6A;
     private static final int TS_PMT_DESC_EAC3 = 0x7A;
     private static final int TS_PMT_DESC_DTS = 0x7B;
+    private static final int TS_PMT_DESC_DVB_EXT = 0x7F;
     private static final int TS_PMT_DESC_DVBSUBS = 0x59;
 
+    private static final int TS_PMT_DESC_DVB_EXT_AC4 = 0x15;
+
     private final ParsableBitArray pmtScratch;
     private final SparseArray<TsPayloadReader> trackIdToReaderScratch;
     private final SparseIntArray trackIdToPidScratch;
@@ -648,6 +653,8 @@ public final class TsExtractor implements Extractor {
             streamType = TS_STREAM_TYPE_AC3;
           } else if (formatIdentifier == E_AC3_FORMAT_IDENTIFIER) {
             streamType = TS_STREAM_TYPE_E_AC3;
+          } else if (formatIdentifier == AC4_FORMAT_IDENTIFIER) {
+            streamType = TS_STREAM_TYPE_AC4;
           } else if (formatIdentifier == HEVC_FORMAT_IDENTIFIER) {
             streamType = TS_STREAM_TYPE_H265;
           }
@@ -655,6 +662,13 @@ public final class TsExtractor implements Extractor {
           streamType = TS_STREAM_TYPE_AC3;
         } else if (descriptorTag == TS_PMT_DESC_EAC3) { // enhanced_AC-3_descriptor
           streamType = TS_STREAM_TYPE_E_AC3;
+        } else if (descriptorTag == TS_PMT_DESC_DVB_EXT) {
+          // Extension descriptor in DVB (ETSI EN 300 468).
+          int descriptorTagExt = data.readUnsignedByte();
+          if (descriptorTagExt == TS_PMT_DESC_DVB_EXT_AC4) {
+            // AC-4_descriptor in DVB (ETSI EN 300 468).
+            streamType = TS_STREAM_TYPE_AC4;
+          }
         } else if (descriptorTag == TS_PMT_DESC_DTS) { // DTS_descriptor
           streamType = TS_STREAM_TYPE_DTS;
         } else if (descriptorTag == TS_PMT_DESC_ISO639_LANG) {

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

@@ -58,6 +58,7 @@ public final class MimeTypes {
   public static final String AUDIO_AC3 = BASE_TYPE_AUDIO + "/ac3";
   public static final String AUDIO_E_AC3 = BASE_TYPE_AUDIO + "/eac3";
   public static final String AUDIO_E_AC3_JOC = BASE_TYPE_AUDIO + "/eac3-joc";
+  public static final String AUDIO_AC4 = BASE_TYPE_AUDIO + "/ac4";
   public static final String AUDIO_TRUEHD = BASE_TYPE_AUDIO + "/true-hd";
   public static final String AUDIO_DTS = BASE_TYPE_AUDIO + "/vnd.dts";
   public static final String AUDIO_DTS_HD = BASE_TYPE_AUDIO + "/vnd.dts.hd";
@@ -228,6 +229,8 @@ public final class MimeTypes {
       return MimeTypes.AUDIO_E_AC3;
     } else if (codec.startsWith("ec+3")) {
       return MimeTypes.AUDIO_E_AC3_JOC;
+    } else if (codec.startsWith("ac-4") || codec.startsWith("dac4")) {
+      return MimeTypes.AUDIO_AC4;
     } else if (codec.startsWith("dtsc") || codec.startsWith("dtse")) {
       return MimeTypes.AUDIO_DTS;
     } else if (codec.startsWith("dtsh") || codec.startsWith("dtsl")) {
@@ -292,6 +295,8 @@ public final class MimeTypes {
         return MimeTypes.AUDIO_DTS_HD;
       case 0xAD:
         return MimeTypes.AUDIO_OPUS;
+      case 0xAE:
+        return MimeTypes.AUDIO_AC4;
       default:
         return null;
     }
@@ -345,6 +350,8 @@ public final class MimeTypes {
       case MimeTypes.AUDIO_E_AC3:
       case MimeTypes.AUDIO_E_AC3_JOC:
         return C.ENCODING_E_AC3;
+      case MimeTypes.AUDIO_AC4:
+        return C.ENCODING_AC4;
       case MimeTypes.AUDIO_DTS:
         return C.ENCODING_DTS;
       case MimeTypes.AUDIO_DTS_HD:

library/core/src/test/assets/ts/sample.ac4.0.dump

@@ -0,0 +1,106 @@
+seekMap:
+  isSeekable = false
+  duration = UNSET TIME
+  getPosition(0) = [[timeUs=0, position=0]]
+numberOfTracks = 1
+track 0:
+  format:
+    bitrate = -1
+    id = 0
+    containerMimeType = null
+    sampleMimeType = audio/ac4
+    maxInputSize = -1
+    width = -1
+    height = -1
+    frameRate = -1.0
+    rotationDegrees = 0
+    pixelWidthHeightRatio = 1.0
+    channelCount = 2
+    sampleRate = 48000
+    pcmEncoding = -1
+    encoderDelay = 0
+    encoderPadding = 0
+    subsampleOffsetUs = 9223372036854775807
+    selectionFlags = 0
+    language = null
+    drmInitData = -
+    initializationData:
+  total output bytes = 7594
+  sample count = 19
+  sample 0:
+    time = 0
+    flags = 1
+    data = length 366, hash B4277F9E
+  sample 1:
+    time = 40000
+    flags = 1
+    data = length 366, hash E8E0A142
+  sample 2:
+    time = 80000
+    flags = 1
+    data = length 366, hash 2E5073D0
+  sample 3:
+    time = 120000
+    flags = 1
+    data = length 366, hash 850E71D8
+  sample 4:
+    time = 160000
+    flags = 1
+    data = length 366, hash 69CD444E
+  sample 5:
+    time = 200000
+    flags = 1
+    data = length 366, hash BD24F36D
+  sample 6:
+    time = 240000
+    flags = 1
+    data = length 366, hash E24F2490
+  sample 7:
+    time = 280000
+    flags = 1
+    data = length 366, hash EE6F1F06
+  sample 8:
+    time = 320000
+    flags = 1
+    data = length 366, hash 2DAB000F
+  sample 9:
+    time = 360000
+    flags = 1
+    data = length 366, hash 8102B7EC
+  sample 10:
+    time = 400000
+    flags = 1
+    data = length 366, hash 55BF59AC
+  sample 11:
+    time = 440000
+    flags = 1
+    data = length 494, hash CBC2E09F
+  sample 12:
+    time = 480000
+    flags = 1
+    data = length 519, hash 9DAF56E9
+  sample 13:
+    time = 520000
+    flags = 1
+    data = length 598, hash 8169EE2
+  sample 14:
+    time = 560000
+    flags = 1
+    data = length 435, hash 28C21246
+  sample 15:
+    time = 600000
+    flags = 1
+    data = length 365, hash FF14716D
+  sample 16:
+    time = 640000
+    flags = 1
+    data = length 392, hash 4CC96B29
+  sample 17:
+    time = 680000
+    flags = 1
+    data = length 373, hash D7AC6D4E
+  sample 18:
+    time = 720000
+    flags = 1
+    data = length 392, hash 99F2511F
+tracksEnded = true

library/core/src/test/java/com/google/android/exoplayer2/extractor/DefaultExtractorsFactoryTest.java

@@ -26,6 +26,7 @@ import com.google.android.exoplayer2.extractor.mp4.FragmentedMp4Extractor;
 import com.google.android.exoplayer2.extractor.mp4.Mp4Extractor;
 import com.google.android.exoplayer2.extractor.ogg.OggExtractor;
 import com.google.android.exoplayer2.extractor.ts.Ac3Extractor;
+import com.google.android.exoplayer2.extractor.ts.Ac4Extractor;
 import com.google.android.exoplayer2.extractor.ts.AdtsExtractor;
 import com.google.android.exoplayer2.extractor.ts.PsExtractor;
 import com.google.android.exoplayer2.extractor.ts.TsExtractor;
@@ -62,7 +63,8 @@ public final class DefaultExtractorsFactoryTest {
           OggExtractor.class,
           PsExtractor.class,
           WavExtractor.class,
-          AmrExtractor.class
+          AmrExtractor.class,
+          Ac4Extractor.class
         };
 
     assertThat(listCreatedExtractorClasses).containsNoDuplicates();

library/core/src/test/java/com/google/android/exoplayer2/extractor/ts/Ac4ExtractorTest.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2.extractor.ts;
+
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import com.google.android.exoplayer2.testutil.ExtractorAsserts;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/** Unit test for {@link Ac4Extractor}. */
+@RunWith(AndroidJUnit4.class)
+public final class Ac4ExtractorTest {
+
+  @Test
+  public void testAc4Sample() throws Exception {
+    ExtractorAsserts.assertBehavior(Ac4Extractor::new, "ts/sample.ac4");
+  }
+}

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/DefaultHlsExtractorFactory.java

@@ -24,6 +24,7 @@ import com.google.android.exoplayer2.extractor.ExtractorInput;
 import com.google.android.exoplayer2.extractor.mp3.Mp3Extractor;
 import com.google.android.exoplayer2.extractor.mp4.FragmentedMp4Extractor;
 import com.google.android.exoplayer2.extractor.ts.Ac3Extractor;
+import com.google.android.exoplayer2.extractor.ts.Ac4Extractor;
 import com.google.android.exoplayer2.extractor.ts.AdtsExtractor;
 import com.google.android.exoplayer2.extractor.ts.DefaultTsPayloadReaderFactory;
 import com.google.android.exoplayer2.extractor.ts.TsExtractor;
@@ -43,6 +44,7 @@ public final class DefaultHlsExtractorFactory implements HlsExtractorFactory {
   public static final String AAC_FILE_EXTENSION = ".aac";
   public static final String AC3_FILE_EXTENSION = ".ac3";
   public static final String EC3_FILE_EXTENSION = ".ec3";
+  public static final String AC4_FILE_EXTENSION = ".ac4";
   public static final String MP3_FILE_EXTENSION = ".mp3";
   public static final String MP4_FILE_EXTENSION = ".mp4";
   public static final String M4_FILE_EXTENSION_PREFIX = ".m4";
@@ -128,6 +130,13 @@ public final class DefaultHlsExtractorFactory implements HlsExtractorFactory {
       }
     }
 
+    if (!(extractorByFileExtension instanceof Ac4Extractor)) {
+      Ac4Extractor ac4Extractor = new Ac4Extractor();
+      if (sniffQuietly(ac4Extractor, extractorInput)) {
+        return buildResult(ac4Extractor);
+      }
+    }
+
     if (!(extractorByFileExtension instanceof Mp3Extractor)) {
       Mp3Extractor mp3Extractor =
           new Mp3Extractor(/* flags= */ 0, /* forcedFirstSampleTimestampUs= */ 0);
@@ -181,6 +190,8 @@ public final class DefaultHlsExtractorFactory implements HlsExtractorFactory {
     } else if (lastPathSegment.endsWith(AC3_FILE_EXTENSION)
         || lastPathSegment.endsWith(EC3_FILE_EXTENSION)) {
       return new Ac3Extractor();
+    } else if (lastPathSegment.endsWith(AC4_FILE_EXTENSION)) {
+      return new Ac4Extractor();
     } else if (lastPathSegment.endsWith(MP3_FILE_EXTENSION)) {
       return new Mp3Extractor(/* flags= */ 0, /* forcedFirstSampleTimestampUs= */ 0);
     } else if (lastPathSegment.endsWith(MP4_FILE_EXTENSION)
@@ -250,6 +261,8 @@ public final class DefaultHlsExtractorFactory implements HlsExtractorFactory {
       return buildResult(new AdtsExtractor());
     } else if (previousExtractor instanceof Ac3Extractor) {
       return buildResult(new Ac3Extractor());
+    } else if (previousExtractor instanceof Ac4Extractor) {
+      return buildResult(new Ac4Extractor());
     } else if (previousExtractor instanceof Mp3Extractor) {
       return buildResult(new Mp3Extractor());
     } else {
@@ -262,6 +275,7 @@ public final class DefaultHlsExtractorFactory implements HlsExtractorFactory {
         extractor,
         extractor instanceof AdtsExtractor
             || extractor instanceof Ac3Extractor
+            || extractor instanceof Ac4Extractor
             || extractor instanceof Mp3Extractor,
         isReusable(extractor));
   }