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 static java.lang.Math.min;
  
  import androidx.annotation.Nullable;
  import com.google.android.exoplayer2.C;
  import com.google.android.exoplayer2.Format;
  import com.google.android.exoplayer2.audio.DtsUtil;
  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.Assertions;
  import com.google.android.exoplayer2.util.ParsableByteArray;
  import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
  import org.checkerframework.checker.nullness.qual.RequiresNonNull;
  
  /** Parses a continuous DTS byte stream and extracts individual samples. */
  public final class DtsReader implements ElementaryStreamReader {
  
    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 = 18;
  
    private final ParsableByteArray headerScratchBytes;
    @Nullable private final String language;
  
    private @MonotonicNonNull String formatId;
    private @MonotonicNonNull TrackOutput output;
  
    private int state;
    private int bytesRead;
  
    // Used to find the header.
    private int syncBytes;
  
    // Used when parsing the header.
    private long sampleDurationUs;
    private @MonotonicNonNull Format format;
    private int sampleSize;
  
    // Used when reading the samples.
    private long timeUs;
  
    /**
     * Constructs a new reader for DTS elementary streams.
     *
     * @param language Track language.
     */
    public DtsReader(@Nullable String language) {
      headerScratchBytes = new ParsableByteArray(new byte[HEADER_SIZE]);
      state = STATE_FINDING_SYNC;
      timeUs = C.TIME_UNSET;
      this.language = language;
    }
  
    @Override
    public void seek() {
      state = STATE_FINDING_SYNC;
      bytesRead = 0;
      syncBytes = 0;
      timeUs = C.TIME_UNSET;
    }
  
    @Override
    public void createTracks(ExtractorOutput extractorOutput, TrackIdGenerator idGenerator) {
      idGenerator.generateNewId();
      formatId = idGenerator.getFormatId();
      output = extractorOutput.track(idGenerator.getTrackId(), C.TRACK_TYPE_AUDIO);
    }
  
    @Override
    public void packetStarted(long pesTimeUs, @TsPayloadReader.Flags int flags) {
      if (pesTimeUs != C.TIME_UNSET) {
        timeUs = pesTimeUs;
      }
    }
  
    @Override
    public void consume(ParsableByteArray data) {
      Assertions.checkStateNotNull(output); // Asserts that createTracks has been called.
      while (data.bytesLeft() > 0) {
        switch (state) {
          case STATE_FINDING_SYNC:
            if (skipToNextSync(data)) {
              state = STATE_READING_HEADER;
            }
            break;
          case STATE_READING_HEADER:
            if (continueRead(data, headerScratchBytes.getData(), HEADER_SIZE)) {
              parseHeader();
              headerScratchBytes.setPosition(0);
              output.sampleData(headerScratchBytes, HEADER_SIZE);
              state = STATE_READING_SAMPLE;
            }
            break;
          case STATE_READING_SAMPLE:
            int bytesToRead = min(data.bytesLeft(), sampleSize - bytesRead);
            output.sampleData(data, bytesToRead);
            bytesRead += bytesToRead;
            if (bytesRead == sampleSize) {
              if (timeUs != C.TIME_UNSET) {
                output.sampleMetadata(timeUs, C.BUFFER_FLAG_KEY_FRAME, sampleSize, 0, null);
                timeUs += sampleDurationUs;
              }
              state = STATE_FINDING_SYNC;
            }
            break;
          default:
            throw new IllegalStateException();
        }
      }
    }
  
    @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 = min(source.bytesLeft(), targetLength - bytesRead);
      source.readBytes(target, bytesRead, bytesToRead);
      bytesRead += bytesToRead;
      return bytesRead == targetLength;
    }
  
    /**
     * Locates the next SYNC value in the buffer, advancing the position to the byte that immediately
     * follows it. If SYNC was not located, the position is advanced to the limit.
     *
     * @param pesBuffer The buffer whose position should be advanced.
     * @return Whether SYNC was found.
     */
    private boolean skipToNextSync(ParsableByteArray pesBuffer) {
      while (pesBuffer.bytesLeft() > 0) {
        syncBytes <<= 8;
        syncBytes |= pesBuffer.readUnsignedByte();
        if (DtsUtil.isSyncWord(syncBytes)) {
          byte[] headerData = headerScratchBytes.getData();
          headerData[0] = (byte) ((syncBytes >> 24) & 0xFF);
          headerData[1] = (byte) ((syncBytes >> 16) & 0xFF);
          headerData[2] = (byte) ((syncBytes >> 8) & 0xFF);
          headerData[3] = (byte) (syncBytes & 0xFF);
          bytesRead = 4;
          syncBytes = 0;
          return true;
        }
      }
      return false;
    }
  
    /** Parses the sample header. */
    @RequiresNonNull("output")
    private void parseHeader() {
      byte[] frameData = headerScratchBytes.getData();
      if (format == null) {
        format = DtsUtil.parseDtsFormat(frameData, formatId, language, null);
        output.format(format);
      }
      sampleSize = DtsUtil.getDtsFrameSize(frameData);
      // In this class a sample is an access unit (frame in DTS), but the format's sample rate
      // specifies the number of PCM audio samples per second.
      sampleDurationUs =
          (int)
              (C.MICROS_PER_SECOND * DtsUtil.parseDtsAudioSampleCount(frameData) / format.sampleRate);
    }
  }
  