content: /*
   * Copyright (C) 2020 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.mediacodec;
  
  import static java.lang.Math.max;
  
  import com.google.android.exoplayer2.C;
  import com.google.android.exoplayer2.Format;
  import com.google.android.exoplayer2.audio.MpegAudioUtil;
  import com.google.android.exoplayer2.decoder.DecoderInputBuffer;
  import com.google.android.exoplayer2.util.Assertions;
  import com.google.android.exoplayer2.util.Log;
  import java.nio.ByteBuffer;
  
  /**
   * Tracks the number of processed samples to calculate an accurate current timestamp, matching the
   * calculations made in the Codec2 Mp3 decoder.
   */
  /* package */ final class C2Mp3TimestampTracker {
  
    private static final long DECODER_DELAY_FRAMES = 529;
    private static final String TAG = "C2Mp3TimestampTracker";
  
    private long anchorTimestampUs;
    private long processedFrames;
    private boolean seenInvalidMpegAudioHeader;
  
    /**
     * Resets the timestamp tracker.
     *
     * <p>This should be done when the codec is flushed.
     */
    public void reset() {
      anchorTimestampUs = 0;
      processedFrames = 0;
      seenInvalidMpegAudioHeader = false;
    }
  
    /**
     * Updates the tracker with the given input buffer and returns the expected output timestamp.
     *
     * @param format The format associated with the buffer.
     * @param buffer The current input buffer.
     * @return The expected output presentation time, in microseconds.
     */
    public long updateAndGetPresentationTimeUs(Format format, DecoderInputBuffer buffer) {
      if (processedFrames == 0) {
        anchorTimestampUs = buffer.timeUs;
      }
  
      if (seenInvalidMpegAudioHeader) {
        return buffer.timeUs;
      }
  
      ByteBuffer data = Assertions.checkNotNull(buffer.data);
      int sampleHeaderData = 0;
      for (int i = 0; i < 4; i++) {
        sampleHeaderData <<= 8;
        sampleHeaderData |= data.get(i) & 0xFF;
      }
  
      int frameCount = MpegAudioUtil.parseMpegAudioFrameSampleCount(sampleHeaderData);
      if (frameCount == C.LENGTH_UNSET) {
        seenInvalidMpegAudioHeader = true;
        processedFrames = 0;
        anchorTimestampUs = buffer.timeUs;
        Log.w(TAG, "MPEG audio header is invalid.");
        return buffer.timeUs;
      }
      long currentBufferTimestampUs = getBufferTimestampUs(format.sampleRate);
      processedFrames += frameCount;
      return currentBufferTimestampUs;
    }
  
    /**
     * Returns the timestamp of the last buffer that will be produced if the stream ends at the
     * current position, in microseconds.
     *
     * @param format The format associated with input buffers.
     * @return The timestamp of the last buffer that will be produced if the stream ends at the
     *     current position, in microseconds.
     */
    public long getLastOutputBufferPresentationTimeUs(Format format) {
      return getBufferTimestampUs(format.sampleRate);
    }
  
    private long getBufferTimestampUs(long sampleRate) {
      // This calculation matches the timestamp calculation in the Codec2 Mp3 Decoder.
      // https://cs.android.com/android/platform/superproject/+/main:frameworks/av/media/codec2/components/mp3/C2SoftMp3Dec.cpp;l=464;drc=ed134640332fea70ca4b05694289d91a5265bb46
      return anchorTimestampUs
          + max(0, (processedFrames - DECODER_DELAY_FRAMES) * C.MICROS_PER_SECOND / sampleRate);
    }
  }
  