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.ogg;
  
  import com.google.android.exoplayer2.C;
  import com.google.android.exoplayer2.Format;
  import com.google.android.exoplayer2.util.MimeTypes;
  import com.google.android.exoplayer2.util.ParsableByteArray;
  import com.google.android.exoplayer2.util.Util;
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.ByteOrder;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  
  /**
   * {@link StreamReader} to extract Opus data out of Ogg byte stream.
   */
  /* package */ final class OpusReader extends StreamReader {
  
    private static final int DEFAULT_SEEK_PRE_ROLL_SAMPLES = 3840;
  
    /**
     * Opus streams are always decoded at 48000 Hz.
     */
    private static final int SAMPLE_RATE = 48000;
  
    private static final int OPUS_CODE = Util.getIntegerCodeForString("Opus");
    private static final byte[] OPUS_SIGNATURE = {'O', 'p', 'u', 's', 'H', 'e', 'a', 'd'};
  
    private boolean headerRead;
  
    public static boolean verifyBitstreamType(ParsableByteArray data) {
      if (data.bytesLeft() < OPUS_SIGNATURE.length) {
        return false;
      }
      byte[] header = new byte[OPUS_SIGNATURE.length];
      data.readBytes(header, 0, OPUS_SIGNATURE.length);
      return Arrays.equals(header, OPUS_SIGNATURE);
    }
  
    @Override
    protected void reset(boolean headerData) {
      super.reset(headerData);
      if (headerData) {
        headerRead = false;
      }
    }
  
    @Override
    protected long preparePayload(ParsableByteArray packet) {
      return convertTimeToGranule(getPacketDurationUs(packet.data));
    }
  
    @Override
    protected boolean readHeaders(ParsableByteArray packet, long position, SetupData setupData)
        throws IOException, InterruptedException {
      if (!headerRead) {
        byte[] metadata = Arrays.copyOf(packet.data, packet.limit());
        int channelCount = metadata[9] & 0xFF;
        int preskip = ((metadata[11] & 0xFF) << 8) | (metadata[10] & 0xFF);
  
        List<byte[]> initializationData = new ArrayList<>(3);
        initializationData.add(metadata);
        putNativeOrderLong(initializationData, preskip);
        putNativeOrderLong(initializationData, DEFAULT_SEEK_PRE_ROLL_SAMPLES);
  
        setupData.format = Format.createAudioSampleFormat(null, MimeTypes.AUDIO_OPUS, null,
            Format.NO_VALUE, Format.NO_VALUE, channelCount, SAMPLE_RATE, initializationData, null, 0,
            null);
        headerRead = true;
      } else {
        boolean headerPacket = packet.readInt() == OPUS_CODE;
        packet.setPosition(0);
        return headerPacket;
      }
      return true;
    }
  
    private void putNativeOrderLong(List<byte[]> initializationData, int samples) {
      long ns = (samples * C.NANOS_PER_SECOND) / SAMPLE_RATE;
      byte[] array = ByteBuffer.allocate(8).order(ByteOrder.nativeOrder()).putLong(ns).array();
      initializationData.add(array);
    }
  
    /**
     * Returns the duration of the given audio packet.
     *
     * @param packet Contains audio data.
     * @return Returns the duration of the given audio packet.
     */
    private long getPacketDurationUs(byte[] packet) {
      int toc = packet[0] & 0xFF;
      int frames;
      switch (toc & 0x3) {
        case 0:
          frames = 1;
          break;
        case 1:
        case 2:
          frames = 2;
          break;
        default:
          frames = packet[1] & 0x3F;
          break;
      }
  
      int config = toc >> 3;
      int length = config & 0x3;
      if (config >= 16) {
        length = 2500 << length;
      } else if (config >= 12) {
        length = 10000 << (length & 0x1);
      } else if (length == 3) {
        length = 60000;
      } else {
        length = 10000 << length;
      }
      return frames * length;
    }
  }
  