Add AC-4 format support

 * Add AC-4 MIME type definition
 * Add AC-4 format support in Mp4Extractor and TsExtractor
 * Add AC-4 Extractor
 * Add AC-4 playback support in MPEG-4, MPEG-DASH, TS and HLS

Author: ybai001

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

@@ -49,6 +49,7 @@
  *   <li>WAV ({@link WavExtractor})
  *   <li>AC3 ({@link Ac3Extractor})
  *   <li>AMR ({@link AmrExtractor})
+ *   <li>AC4 ({@link Ac4Extractor})
  *   <li>FLAC (only available if the FLAC extension is built and included)
  * </ul>
  */

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

@@ -161,6 +161,8 @@ public class FragmentedMp4Extractor implements Extractor {
   private int sampleBytesWritten;
   private int sampleCurrentNalBytesRemaining;
   private boolean processSeiNalUnitPayload;
+  private boolean isAc4HeaderAdded;
+  private int ac4SampleHeaderSize;
 
   // Extractor output.
   private ExtractorOutput extractorOutput;
@@ -262,6 +264,8 @@ public FragmentedMp4Extractor(
     durationUs = C.TIME_UNSET;
     pendingSeekTimeUs = C.TIME_UNSET;
     segmentIndexEarliestPresentationTimeUs = C.TIME_UNSET;
+    isAc4HeaderAdded = false;
+    ac4SampleHeaderSize = 0;
     enterReadingAtomHeaderState();
   }
 
@@ -1217,6 +1221,7 @@ private boolean readSample(ExtractorInput input) throws IOException, Interrupted
       sampleSize += sampleBytesWritten;
       parserState = STATE_READING_SAMPLE_CONTINUE;
       sampleCurrentNalBytesRemaining = 0;
+      isAc4HeaderAdded = false;
     }
 
     TrackFragment fragment = currentTrackBundle.fragment;
@@ -1277,17 +1282,20 @@ private boolean readSample(ExtractorInput input) throws IOException, Interrupted
         }
       }
     } else {
-      int sampleHeaderSize = 0;
-      if (MimeTypes.AUDIO_AC4.equals(track.format.sampleMimeType)) {
+      if (MimeTypes.AUDIO_AC4.equals(track.format.sampleMimeType) && !isAc4HeaderAdded) {
         ParsableByteArray ac4SampleHeaderData = Ac4Util.getAc4SampleHeader(sampleSize);
         output.sampleData(ac4SampleHeaderData, ac4SampleHeaderData.capacity());
-        sampleHeaderSize = ac4SampleHeaderData.capacity();
+        ac4SampleHeaderSize = ac4SampleHeaderData.capacity();
+        isAc4HeaderAdded = true;
       }
       while (sampleBytesWritten < sampleSize) {
         int writtenBytes = output.sampleData(input, sampleSize - sampleBytesWritten, false);
         sampleBytesWritten += writtenBytes;
       }
-      sampleSize += sampleHeaderSize;
+      if (MimeTypes.AUDIO_AC4.equals(track.format.sampleMimeType)) {
+        sampleSize += ac4SampleHeaderSize;
+        isAc4HeaderAdded = false;
+      }
     }
 
     @C.BufferFlags int sampleFlags = fragment.sampleIsSyncFrameTable[sampleIndex]

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

@@ -118,6 +118,8 @@ public final class Mp4Extractor implements Extractor, SeekMap {
   private int firstVideoTrackIndex;
   private long durationUs;
   private boolean isQuickTime;
+  private boolean isAc4HeaderAdded;
+  private int ac4SampleHeaderSize;
 
   /**
    * Creates a new extractor for unfragmented MP4 streams.
@@ -139,6 +141,8 @@ public Mp4Extractor(@Flags int flags) {
     nalStartCode = new ParsableByteArray(NalUnitUtil.NAL_START_CODE);
     nalLength = new ParsableByteArray(4);
     sampleTrackIndex = C.INDEX_UNSET;
+    isAc4HeaderAdded = false;
+    ac4SampleHeaderSize = 0;
   }
 
   @Override
@@ -489,6 +493,7 @@ private int readSample(ExtractorInput input, PositionHolder positionHolder)
       if (sampleTrackIndex == C.INDEX_UNSET) {
         return RESULT_END_OF_INPUT;
       }
+      isAc4HeaderAdded = false;
     }
     Mp4Track track = tracks[sampleTrackIndex];
     TrackOutput trackOutput = track.trackOutput;
@@ -538,18 +543,21 @@ private int readSample(ExtractorInput input, PositionHolder positionHolder)
         }
       }
     } else {
-      int sampleHeaderSize = 0;
-      if (MimeTypes.AUDIO_AC4.equals(track.track.format.sampleMimeType)) {
+      if (MimeTypes.AUDIO_AC4.equals(track.track.format.sampleMimeType) && !isAc4HeaderAdded) {
         ParsableByteArray ac4SampleHeaderData = Ac4Util.getAc4SampleHeader(sampleSize);
         trackOutput.sampleData(ac4SampleHeaderData, ac4SampleHeaderData.capacity());
-        sampleHeaderSize = ac4SampleHeaderData.capacity();
+        ac4SampleHeaderSize = ac4SampleHeaderData.capacity();
+        isAc4HeaderAdded = true;
       }
       while (sampleBytesWritten < sampleSize) {
         int writtenBytes = trackOutput.sampleData(input, sampleSize - sampleBytesWritten, false);
         sampleBytesWritten += writtenBytes;
         sampleCurrentNalBytesRemaining -= writtenBytes;
       }
-      sampleSize += sampleHeaderSize;
+      if (MimeTypes.AUDIO_AC4.equals(track.track.format.sampleMimeType)) {
+        sampleSize += ac4SampleHeaderSize;
+        isAc4HeaderAdded = false;
+      }
     }
     trackOutput.sampleMetadata(track.sampleTable.timestampsUs[sampleIndex],
         track.sampleTable.flags[sampleIndex], sampleSize, 0, null);

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

@@ -115,9 +115,7 @@ public void consume(ParsableByteArray data) {
           if (skipToNextSync(data)) {
             state = STATE_READING_HEADER;
             headerScratchBytes.data[0] = (byte)0xAC;
-            headerScratchBytes.data[1] = 0x40;
-            if (hasCRC)
-              headerScratchBytes.data[1] = 0x41;
+            headerScratchBytes.data[1] = (byte)(hasCRC ? 0x41 : 0x40);
             bytesRead = 2;
           }
           break;

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

@@ -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/assets/ts/sample.ac4.0.dump

@@ -25,6 +25,7 @@
 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 void testCreateExtractors_returnExpectedClasses() {
           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/DefaultExtractorsFactoryTest.java

@@ -0,0 +1,32 @@
+/*
+ * 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 com.google.android.exoplayer2.testutil.ExtractorAsserts;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.RobolectricTestRunner;
+
+/** Unit test for {@link Ac4Extractor}. */
+@RunWith(RobolectricTestRunner.class)
+public final class Ac4ExtractorTest {
+
+  @Test
+  public void testAc4Sample() throws Exception {
+    ExtractorAsserts.assertBehavior(Ac4Extractor::new, "ts/sample.ac4");
+  }
+}
+