1 files changed, 156 insertions, 0 deletions
diff --git a/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/ts/Ac4Extractor.java b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/ts/Ac4Extractor.java
new file mode 100644
index 0000000000..9578d110b7
--- /dev/null
+++ b/mobile/android/exoplayer2/src/main/java/org/mozilla/thirdparty/com/google/android/exoplayer2/extractor/ts/Ac4Extractor.java
@@ -0,0 +1,156 @@
+/*
+ * 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 org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ts;
+
+import static org.mozilla.thirdparty.com.google.android.exoplayer2.audio.Ac4Util.AC40_SYNCWORD;
+import static org.mozilla.thirdparty.com.google.android.exoplayer2.audio.Ac4Util.AC41_SYNCWORD;
+import static org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ts.TsPayloadReader.FLAG_DATA_ALIGNMENT_INDICATOR;
+import static org.mozilla.thirdparty.com.google.android.exoplayer2.metadata.id3.Id3Decoder.ID3_HEADER_LENGTH;
+import static org.mozilla.thirdparty.com.google.android.exoplayer2.metadata.id3.Id3Decoder.ID3_TAG;
+
+import org.mozilla.thirdparty.com.google.android.exoplayer2.C;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.audio.Ac4Util;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.Extractor;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ExtractorInput;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ExtractorOutput;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ExtractorsFactory;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.PositionHolder;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.SeekMap;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.extractor.ts.TsPayloadReader.TrackIdGenerator;
+import org.mozilla.thirdparty.com.google.android.exoplayer2.util.ParsableByteArray;
+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 final Ac4Reader reader;
+  private final ParsableByteArray sampleData;
+
+  private boolean startedPacket;
+
+  /** Creates a new extractor for AC-4 bitstreams. */
+  public Ac4Extractor() {
+    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(ID3_HEADER_LENGTH);
+    int startPosition = 0;
+    while (true) {
+      input.peekFully(scratch.data, /* offset= */ 0, ID3_HEADER_LENGTH);
+      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(/* pesTimeUs= */ 0, 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;
+  }
+}