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.checkState;
  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.ParsableByteArray;
  import com.google.android.exoplayer2.util.Util;
  import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
  
  /**
   * Parses a VP9 byte stream carried on RTP packets, and extracts VP9 Access Units. Refer to <a
   * href=https://datatracker.ietf.org/doc/html/draft-ietf-payload-vp9>this draft RFC</a> for more
   * details.
   */
  /* package */ final class RtpVp9Reader implements RtpPayloadReader {
  
    private static final String TAG = "RtpVp9Reader";
  
    private static final int MEDIA_CLOCK_FREQUENCY = 90_000;
    private static final int SCALABILITY_STRUCTURE_SIZE = 4;
  
    private final RtpPayloadFormat payloadFormat;
  
    private @MonotonicNonNull TrackOutput trackOutput;
  
    /**
     * First received RTP timestamp. All RTP timestamps are dimension-less, the time base is defined
     * by {@link #MEDIA_CLOCK_FREQUENCY}.
     */
    private long firstReceivedTimestamp;
  
    private long startTimeOffsetUs;
    private int previousSequenceNumber;
    /** The combined size of a sample that is fragmented into multiple RTP packets. */
    private int fragmentedSampleSizeBytes;
  
    private long fragmentedSampleTimeUs;
  
    private int width;
    private int height;
    /**
     * Whether the first packet of a VP9 frame is received, it mark the start of a VP9 partition. A
     * VP9 frame can be split into multiple RTP packets.
     */
    private boolean gotFirstPacketOfVp9Frame;
  
    private boolean reportedOutputFormat;
    private boolean isKeyFrame;
  
    /** Creates an instance. */
    public RtpVp9Reader(RtpPayloadFormat payloadFormat) {
      this.payloadFormat = payloadFormat;
      firstReceivedTimestamp = C.TIME_UNSET;
      fragmentedSampleSizeBytes = C.LENGTH_UNSET;
      fragmentedSampleTimeUs = C.TIME_UNSET;
      // The start time offset must be 0 until the first seek.
      startTimeOffsetUs = 0;
      previousSequenceNumber = C.INDEX_UNSET;
      width = C.LENGTH_UNSET;
      height = C.LENGTH_UNSET;
    }
  
    @Override
    public void createTracks(ExtractorOutput extractorOutput, int trackId) {
      trackOutput = extractorOutput.track(trackId, C.TRACK_TYPE_VIDEO);
      trackOutput.format(payloadFormat.format);
    }
  
    @Override
    public void onReceivingFirstPacket(long timestamp, int sequenceNumber) {
      checkState(firstReceivedTimestamp == C.TIME_UNSET);
      firstReceivedTimestamp = timestamp;
    }
  
    @Override
    public void consume(
        ParsableByteArray data, long timestamp, int sequenceNumber, boolean rtpMarker) {
      checkStateNotNull(trackOutput);
  
      if (validateVp9Descriptor(data, sequenceNumber)) {
        if (fragmentedSampleSizeBytes == C.LENGTH_UNSET && gotFirstPacketOfVp9Frame) {
          // Parsing the frame_type in VP9 uncompressed header, 0 - key frame, 1 - inter frame.
          // Refer to VP9 Bitstream superframe and uncompressed header, Section 4.1.
          isKeyFrame = (data.peekUnsignedByte() & 0x04) == 0;
        }
  
        if (!reportedOutputFormat && width != C.LENGTH_UNSET && height != C.LENGTH_UNSET) {
          if (width != payloadFormat.format.width || height != payloadFormat.format.height) {
            trackOutput.format(
                payloadFormat.format.buildUpon().setWidth(width).setHeight(height).build());
          }
          reportedOutputFormat = true;
        }
  
        int currentFragmentSizeBytes = data.bytesLeft();
        // Write the video sample.
        trackOutput.sampleData(data, currentFragmentSizeBytes);
        if (fragmentedSampleSizeBytes == C.LENGTH_UNSET) {
          fragmentedSampleSizeBytes = currentFragmentSizeBytes;
        } else {
          fragmentedSampleSizeBytes += currentFragmentSizeBytes;
        }
        fragmentedSampleTimeUs =
            toSampleTimeUs(
                startTimeOffsetUs, timestamp, firstReceivedTimestamp, MEDIA_CLOCK_FREQUENCY);
  
        if (rtpMarker) {
          outputSampleMetadataForFragmentedPackets();
        }
        previousSequenceNumber = sequenceNumber;
      }
    }
  
    @Override
    public void seek(long nextRtpTimestamp, long timeUs) {
      firstReceivedTimestamp = nextRtpTimestamp;
      fragmentedSampleSizeBytes = C.LENGTH_UNSET;
      startTimeOffsetUs = timeUs;
    }
  
    // Internal methods.
    /**
     * Returns {@code true} and sets the {@link ParsableByteArray#getPosition() payload.position} to
     * the end of the descriptor, if a valid VP9 descriptor is present.
     */
    private boolean validateVp9Descriptor(ParsableByteArray payload, int packetSequenceNumber) {
      // VP9 Payload Descriptor, Section 4.2
      //         0 1 2 3 4 5 6 7
      //        +-+-+-+-+-+-+-+-+
      //        |I|P|L|F|B|E|V|Z| (REQUIRED)
      //        +-+-+-+-+-+-+-+-+
      //   I:   |M| PICTURE ID  | (RECOMMENDED)
      //        +-+-+-+-+-+-+-+-+
      //   M:   | EXTENDED PID  | (RECOMMENDED)
      //        +-+-+-+-+-+-+-+-+
      //   L:   | TID |U| SID |D| (Conditionally RECOMMENDED)
      //        +-+-+-+-+-+-+-+-+
      //        |   TL0PICIDX   | (Conditionally REQUIRED)
      //        +-+-+-+-+-+-+-+-+
      //   V:   | SS            |
      //        | ..            |
      //        +-+-+-+-+-+-+-+-+
  
      int header = payload.readUnsignedByte();
      if ((header & 0x08) == 0x08) {
        if (gotFirstPacketOfVp9Frame && fragmentedSampleSizeBytes > 0) {
          // Received new VP9 fragment, output data of previous fragment to decoder.
          outputSampleMetadataForFragmentedPackets();
        }
        gotFirstPacketOfVp9Frame = true;
      } else if (gotFirstPacketOfVp9Frame) {
        // Check that this packet is in the sequence of the previous packet.
        int expectedSequenceNumber = RtpPacket.getNextSequenceNumber(previousSequenceNumber);
        if (packetSequenceNumber < expectedSequenceNumber) {
          Log.w(
              TAG,
              Util.formatInvariant(
                  "Received RTP packet with unexpected sequence number. Expected: %d; received: %d."
                      + " Dropping packet.",
                  expectedSequenceNumber, packetSequenceNumber));
          return false;
        }
      } else {
        Log.w(
            TAG,
            "First payload octet of the RTP packet is not the beginning of a new VP9 partition,"
                + " Dropping current packet.");
        return false;
      }
  
      // Check if optional I header is present.
      if ((header & 0x80) != 0) {
        int optionalHeader = payload.readUnsignedByte();
        // Check M for 15 bits PictureID.
        if ((optionalHeader & 0x80) != 0) {
          if (payload.bytesLeft() < 1) {
            return false;
          }
        }
      }
  
      // Flexible-mode is not implemented.
      checkArgument((header & 0x10) == 0, "VP9 flexible mode is not supported.");
  
      // Check if the optional L header is present.
      if ((header & 0x20) != 0) {
        payload.skipBytes(1);
        if (payload.bytesLeft() < 1) {
          return false;
        }
        // Check if TL0PICIDX header present (non-flexible mode).
        if ((header & 0x10) == 0) {
          payload.skipBytes(1);
        }
      }
  
      // Check if the optional V header is present, Refer to RFC Section 4.2.1.
      if ((header & 0x02) != 0) {
        int scalabilityStructure = payload.readUnsignedByte();
        int spatialLayersCount = (scalabilityStructure >> 5) & 0x7;
  
        // Check Y bit.
        if ((scalabilityStructure & 0x10) != 0) {
          int scalabilityStructureCount = spatialLayersCount + 1;
          if (payload.bytesLeft() < scalabilityStructureCount * SCALABILITY_STRUCTURE_SIZE) {
            return false;
          }
          for (int index = 0; index < scalabilityStructureCount; index++) {
            width = payload.readUnsignedShort();
            height = payload.readUnsignedShort();
          }
        }
  
        // Checks G bit, skips all additional temporal layers.
        if ((scalabilityStructure & 0x08) != 0) {
          // Reads N_G.
          int numOfPicInPictureGroup = payload.readUnsignedByte();
          if (payload.bytesLeft() < numOfPicInPictureGroup) {
            return false;
          }
  
          for (int picIndex = 0; picIndex < numOfPicInPictureGroup; picIndex++) {
            int picture = payload.readUnsignedShort();
            int referenceIndices = (picture & 0x0C) >> 2;
            if (payload.bytesLeft() < referenceIndices) {
              return false;
            }
            // Ignore Reference indices.
            payload.skipBytes(referenceIndices);
          }
        }
      }
      return true;
    }
  
    /**
     * Outputs sample metadata of the received fragmented packets.
     *
     * <p>Call this method only after receiving an end of a VP9 partition.
     */
    private void outputSampleMetadataForFragmentedPackets() {
      checkNotNull(trackOutput)
          .sampleMetadata(
              fragmentedSampleTimeUs,
              isKeyFrame ? C.BUFFER_FLAG_KEY_FRAME : 0,
              fragmentedSampleSizeBytes,
              /* offset= */ 0,
              /* cryptoData= */ null);
      fragmentedSampleSizeBytes = C.LENGTH_UNSET;
      fragmentedSampleTimeUs = C.TIME_UNSET;
      gotFirstPacketOfVp9Frame = false;
    }
  }
  