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 android.support.annotation.IntDef;
  import com.google.android.exoplayer2.C;
  import com.google.android.exoplayer2.Format;
  import com.google.android.exoplayer2.audio.Ac3Util;
  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.ParsableBitArray;
  import com.google.android.exoplayer2.util.ParsableByteArray;
  import java.lang.annotation.Retention;
  import java.lang.annotation.RetentionPolicy;
  
  /**
   * Parses a continuous (E-)AC-3 byte stream and extracts individual samples.
   */
  public final class Ac3Reader implements ElementaryStreamReader {
  
    @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 static final int HEADER_SIZE = 128;
  
    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 lastByteWas0B;
  
    // 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 (E-)AC-3 elementary streams.
     */
    public Ac3Reader() {
      this(null);
    }
  
    /**
     * Constructs a new reader for (E-)AC-3 elementary streams.
     *
     * @param language Track language.
     */
    public Ac3Reader(String language) {
      headerScratchBits = new ParsableBitArray(new byte[HEADER_SIZE]);
      headerScratchBytes = new ParsableByteArray(headerScratchBits.data);
      state = STATE_FINDING_SYNC;
      this.language = language;
    }
  
    @Override
    public void seek() {
      state = STATE_FINDING_SYNC;
      bytesRead = 0;
      lastByteWas0B = 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, boolean dataAlignmentIndicator) {
      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] = 0x0B;
              headerScratchBytes.data[1] = 0x77;
              bytesRead = 2;
            }
            break;
          case STATE_READING_HEADER:
            if (continueRead(data, headerScratchBytes.data, HEADER_SIZE)) {
              parseHeader();
              headerScratchBytes.setPosition(0);
              output.sampleData(headerScratchBytes, HEADER_SIZE);
              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 (!lastByteWas0B) {
          lastByteWas0B = pesBuffer.readUnsignedByte() == 0x0B;
          continue;
        }
        int secondByte = pesBuffer.readUnsignedByte();
        if (secondByte == 0x77) {
          lastByteWas0B = false;
          return true;
        } else {
          lastByteWas0B = secondByte == 0x0B;
        }
      }
      return false;
    }
  
    /**
     * Parses the sample header.
     */
    @SuppressWarnings("ReferenceEquality")
    private void parseHeader() {
      headerScratchBits.setPosition(0);
      Ac3Util.Ac3SyncFrameInfo frameInfo = Ac3Util.parseAc3SyncframeInfo(headerScratchBits);
      if (format == null || frameInfo.channelCount != format.channelCount
          || frameInfo.sampleRate != format.sampleRate
          || frameInfo.mimeType != format.sampleMimeType) {
        format = Format.createAudioSampleFormat(trackFormatId, frameInfo.mimeType, null,
            Format.NO_VALUE, Format.NO_VALUE, frameInfo.channelCount, frameInfo.sampleRate, null,
            null, 0, language);
        output.format(format);
      }
      sampleSize = frameInfo.frameSize;
      // In this class a sample is an access unit (syncframe in AC-3), but the MediaFormat sample rate
      // specifies the number of PCM audio samples per second.
      sampleDurationUs = C.MICROS_PER_SECOND * frameInfo.sampleCount / format.sampleRate;
    }
  
  }
  