content: /*
   * Copyright (C) 2016 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.C;
  import com.google.android.exoplayer2.audio.Ac3Util;
  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 (E-)AC-3 bitstreams.
   */
  public final class Ac3Extractor implements Extractor {
  
    /**
     * Factory for {@link Ac3Extractor} instances.
     */
    public static final ExtractorsFactory FACTORY = new ExtractorsFactory() {
  
      @Override
      public Extractor[] createExtractors() {
        return new Extractor[] {new Ac3Extractor()};
      }
  
    };
  
    /**
     * The maximum number of bytes to search when sniffing, excluding ID3 information, before giving
     * up.
     */
    private static final int MAX_SNIFF_BYTES = 8 * 1024;
    private static final int AC3_SYNC_WORD = 0x0B77;
    private static final int MAX_SYNC_FRAME_SIZE = 2786;
    private static final int ID3_TAG = Util.getIntegerCodeForString("ID3");
  
    private final long firstSampleTimestampUs;
    private final Ac3Reader reader;
    private final ParsableByteArray sampleData;
  
    private boolean startedPacket;
  
    public Ac3Extractor() {
      this(0);
    }
  
    public Ac3Extractor(long firstSampleTimestampUs) {
      this.firstSampleTimestampUs = firstSampleTimestampUs;
      reader = new Ac3Reader();
      sampleData = new ParsableByteArray(MAX_SYNC_FRAME_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, 0, 10);
        scratch.setPosition(0);
        if (scratch.readUnsignedInt24() != ID3_TAG) {
          break;
        }
        scratch.skipBytes(3);
        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, 0, 5);
        scratch.setPosition(0);
        int syncBytes = scratch.readUnsignedShort();
        if (syncBytes != AC3_SYNC_WORD) {
          validFramesCount = 0;
          input.resetPeekPosition();
          if (++headerPosition - startPosition >= MAX_SNIFF_BYTES) {
            return false;
          }
          input.advancePeekPosition(headerPosition);
        } else {
          if (++validFramesCount >= 4) {
            return true;
          }
          int frameSize = Ac3Util.parseAc3SyncframeSize(scratch.data);
          if (frameSize == C.LENGTH_UNSET) {
            return false;
          }
          input.advancePeekPosition(frameSize - 5);
        }
      }
    }
  
    @Override
    public void init(ExtractorOutput output) {
      reader.createTracks(output, new TrackIdGenerator(0, 1));
      output.endTracks();
      output.seekMap(new SeekMap.Unseekable(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, 0, MAX_SYNC_FRAME_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, true);
        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;
    }
  
  }
  