content: /*
   * Copyright 2022 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.source.rtsp.reader;
  
  import static com.google.android.exoplayer2.source.rtsp.reader.RtpReaderUtils.toSampleTimeUs;
  import static com.google.android.exoplayer2.util.Assertions.checkArgument;
  import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
  import static com.google.android.exoplayer2.util.Assertions.checkStateNotNull;
  
  import com.google.android.exoplayer2.C;
  import com.google.android.exoplayer2.extractor.ExtractorOutput;
  import com.google.android.exoplayer2.extractor.TrackOutput;
  import com.google.android.exoplayer2.source.rtsp.RtpPacket;
  import com.google.android.exoplayer2.source.rtsp.RtpPayloadFormat;
  import com.google.android.exoplayer2.util.Log;
  import com.google.android.exoplayer2.util.MimeTypes;
  import com.google.android.exoplayer2.util.ParsableByteArray;
  import com.google.android.exoplayer2.util.Util;
  import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
  
  /**
   * Parses an AMR byte stream carried on RTP packets and extracts individual samples. Interleaving
   * mode is not supported. Refer to RFC4867 for more details.
   */
  /* package */ final class RtpAmrReader implements RtpPayloadReader {
    private static final String TAG = "RtpAmrReader";
    /**
     * The frame size in bytes, including header (1 byte), for each of the 16 frame types for AMR-NB
     * (narrow band). AMR-NB supports eight narrow band speech encoding modes with bit rates between
     * 4.75 and 12.2 kbps defined in RFC4867 Section 3.1. Refer to table 1a in 3GPP TS 26.101 for the
     * mapping definition.
     */
    private static final int[] AMR_NB_FRAME_TYPE_INDEX_TO_FRAME_SIZE = {
      13, // 4.75kbps
      14, // 5.15kbps
      16, // 5.90kbps
      18, // 6.70kbps PDC-EFR
      20, // 7.40kbps TDMA-EFR
      21, // 7.95kbps
      27, // 10.2kbps
      32, // 12.2kbps GSM-EFR
      6, // AMR SID
      7, // GSM-EFR SID
      6, // TDMA-EFR SID
      6, // PDC-EFR SID
      1, // Future use
      1, // Future use
      1, // Future use
      1 // No data
    };
  
    /**
     * The frame size in bytes, including header (1 byte), for each of the 16 frame types for AMR-WB
     * (wide band). AMR-WB supports nine wide band speech encoding modes with bit rates between 6.6 to
     * 23.85 kbps defined in RFC4867 Section 3.2. Refer to table 1a in 3GPP TS 26.201. for the mapping
     * definition.
     */
    private static final int[] AMR_WB_FRAME_TYPE_INDEX_TO_FRAME_SIZE = {
      18, // 6.60kbps
      24, // 8.85kbps
      33, // 12.65kbps
      37, // 14.25kbps
      41, // 15.85kbps
      47, // 18.25kbps
      51, // 19.85kbps
      59, // 23.05kbps
      61, // 23.85kbps
      6, // AMR-WB SID
      1, // Future use
      1, // Future use
      1, // Future use
      1, // Future use
      1, // speech lost
      1 // No data
    };
  
    private final RtpPayloadFormat payloadFormat;
    private final boolean isWideBand;
    private final int sampleRate;
  
    private @MonotonicNonNull TrackOutput trackOutput;
    private long firstReceivedTimestamp;
    private long startTimeOffsetUs;
    private int previousSequenceNumber;
  
    public RtpAmrReader(RtpPayloadFormat payloadFormat) {
      this.payloadFormat = payloadFormat;
      this.isWideBand =
          MimeTypes.AUDIO_AMR_WB.equals(checkNotNull(payloadFormat.format.sampleMimeType));
      this.sampleRate = payloadFormat.clockRate;
      this.firstReceivedTimestamp = C.TIME_UNSET;
      this.previousSequenceNumber = C.INDEX_UNSET;
      // Start time offset must be 0 before the first seek.
      this.startTimeOffsetUs = 0;
    }
  
    // RtpPayloadReader implementation.
  
    @Override
    public void createTracks(ExtractorOutput extractorOutput, int trackId) {
      trackOutput = extractorOutput.track(trackId, C.TRACK_TYPE_AUDIO);
      trackOutput.format(payloadFormat.format);
    }
  
    @Override
    public void onReceivingFirstPacket(long timestamp, int sequenceNumber) {
      this.firstReceivedTimestamp = timestamp;
    }
  
    @Override
    public void consume(
        ParsableByteArray data, long timestamp, int sequenceNumber, boolean rtpMarker) {
      checkStateNotNull(trackOutput);
      // Check that this packet is in the sequence of the previous packet.
      if (previousSequenceNumber != C.INDEX_UNSET) {
        int expectedSequenceNumber = RtpPacket.getNextSequenceNumber(previousSequenceNumber);
        if (sequenceNumber != expectedSequenceNumber) {
          Log.w(
              TAG,
              Util.formatInvariant(
                  "Received RTP packet with unexpected sequence number. Expected: %d; received: %d.",
                  expectedSequenceNumber, sequenceNumber));
        }
      }
      //
      // AMR as RTP payload (RFC4867 Section 4.2).
      //
      // +----------------+-------------------+----------------
      // | payload header | table of contents | speech data ...
      // +----------------+-------------------+----------------
      //
      // Payload header (RFC4867 Section 4.4.1).
      //
      // The header won't contain ILL and ILP, as interleaving is not currently supported.
      // +-+-+-+-+-+-+-+- - - - - - - -
      // | CMR |R|R|R|R| ILL  |  ILP  |
      // +-+-+-+-+-+-+-+- - - - - - - -
      //
      // Skip CMR and reserved bits.
      data.skipBytes(1);
      // Loop over sampleSize to send multiple frames along with appropriate timestamp when compound
      // payload support is added.
      int frameType = (data.peekUnsignedByte() >> 3) & 0x0f;
      int frameSize = getFrameSize(frameType, isWideBand);
      int sampleSize = data.bytesLeft();
      checkArgument(sampleSize == frameSize, "compound payload not supported currently");
      trackOutput.sampleData(data, sampleSize);
      long sampleTimeUs =
          toSampleTimeUs(startTimeOffsetUs, timestamp, firstReceivedTimestamp, sampleRate);
      trackOutput.sampleMetadata(
          sampleTimeUs, C.BUFFER_FLAG_KEY_FRAME, sampleSize, /* offset= */ 0, /* cryptoData= */ null);
  
      previousSequenceNumber = sequenceNumber;
    }
  
    @Override
    public void seek(long nextRtpTimestamp, long timeUs) {
      firstReceivedTimestamp = nextRtpTimestamp;
      startTimeOffsetUs = timeUs;
    }
  
    // Internal methods.
  
    public static int getFrameSize(int frameType, boolean isWideBand) {
      checkArgument(
          // Valid frame types are defined in RFC4867 Section 4.3.1.
          (frameType >= 0 && frameType <= 8) || frameType == 15,
          "Illegal AMR " + (isWideBand ? "WB" : "NB") + " frame type " + frameType);
  
      return isWideBand
          ? AMR_WB_FRAME_TYPE_INDEX_TO_FRAME_SIZE[frameType]
          : AMR_NB_FRAME_TYPE_INDEX_TO_FRAME_SIZE[frameType];
    }
  }
  