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.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 VP8 byte stream carried on RTP packets, and extracts VP8 individual video frames as
   * defined in RFC7741.
   */
  /* package */ final class RtpVp8Reader implements RtpPayloadReader {
    private static final String TAG = "RtpVP8Reader";
  
    /** VP8 uses a 90 KHz media clock (RFC7741 Section 4.1). */
    private static final int MEDIA_CLOCK_FREQUENCY = 90_000;
  
    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 int previousSequenceNumber;
    /** The combined size of a sample that is fragmented into multiple RTP packets. */
    private int fragmentedSampleSizeBytes;
  
    private long fragmentedSampleTimeUs;
  
    private long startTimeOffsetUs;
    /**
     * Whether the first packet of one VP8 frame is received. A VP8 frame can be split into two RTP
     * packets.
     */
    private boolean gotFirstPacketOfVp8Frame;
  
    private boolean isKeyFrame;
    private boolean isOutputFormatSet;
  
    /** Creates an instance. */
    public RtpVp8Reader(RtpPayloadFormat payloadFormat) {
      this.payloadFormat = payloadFormat;
      firstReceivedTimestamp = C.TIME_UNSET;
      previousSequenceNumber = C.INDEX_UNSET;
      fragmentedSampleSizeBytes = C.LENGTH_UNSET;
      fragmentedSampleTimeUs = C.TIME_UNSET;
      // The start time offset must be 0 until the first seek.
      startTimeOffsetUs = 0;
    }
  
    @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);
  
      boolean isValidVP8Descriptor = validateVp8Descriptor(data, sequenceNumber);
      if (isValidVP8Descriptor) {
        //  VP8 Payload Header is defined in RFC7741 Section 4.3.
        if (fragmentedSampleSizeBytes == C.LENGTH_UNSET && gotFirstPacketOfVp8Frame) {
          isKeyFrame = (data.peekUnsignedByte() & 0x01) == 0;
        }
        if (!isOutputFormatSet) {
          // Parsing frame data to get width and height, RFC6386 Section 19.1.
          int currPosition = data.getPosition();
          // Skips the frame_tag and start_code.
          data.setPosition(currPosition + 6);
          // RFC6386 Section 19.1 specifically uses little endian.
          int width = data.readLittleEndianUnsignedShort() & 0x3fff;
          int height = data.readLittleEndianUnsignedShort() & 0x3fff;
          data.setPosition(currPosition);
  
          if (width != payloadFormat.format.width || height != payloadFormat.format.height) {
            trackOutput.format(
                payloadFormat.format.buildUpon().setWidth(width).setHeight(height).build());
          }
          isOutputFormatSet = true;
        }
  
        int fragmentSize = data.bytesLeft();
        trackOutput.sampleData(data, fragmentSize);
        if (fragmentedSampleSizeBytes == C.LENGTH_UNSET) {
          fragmentedSampleSizeBytes = fragmentSize;
        } else {
          fragmentedSampleSizeBytes += fragmentSize;
        }
  
        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;
    }
  
    /**
     * Returns {@code true} and sets the {@link ParsableByteArray#getPosition() payload.position} to
     * the end of the descriptor, if a valid VP8 descriptor is present.
     */
    private boolean validateVp8Descriptor(ParsableByteArray payload, int packetSequenceNumber) {
      // VP8 Payload Descriptor is defined in RFC7741 Section 4.2.
      int header = payload.readUnsignedByte();
      // TODO(b/198620566) Consider using ParsableBitArray.
      // For start of VP8 partition S=1 and PID=0 as per RFC7741 Section 4.2.
      if ((header & 0x10) == 0x10 && (header & 0x07) == 0) {
        if (gotFirstPacketOfVp8Frame && fragmentedSampleSizeBytes > 0) {
          // Received new VP8 fragment, output data of previous fragment to decoder.
          outputSampleMetadataForFragmentedPackets();
        }
        gotFirstPacketOfVp8Frame = true;
      } else if (gotFirstPacketOfVp8Frame) {
        // 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, "RTP packet is not the start of a new VP8 partition, skipping.");
        return false;
      }
  
      // Check if optional X header is present.
      if ((header & 0x80) != 0) {
        int xHeader = payload.readUnsignedByte();
  
        // Check if optional I header is present.
        if ((xHeader & 0x80) != 0) {
          int iHeader = payload.readUnsignedByte();
          // Check if I header's M bit is present.
          if ((iHeader & 0x80) != 0) {
            payload.skipBytes(1);
          }
        }
  
        // Check if optional L header is present.
        if ((xHeader & 0x40) != 0) {
          payload.skipBytes(1);
        }
  
        // Check if optional T or K header(s) is present.
        if ((xHeader & 0x20) != 0 || (xHeader & 0x10) != 0) {
          payload.skipBytes(1);
        }
      }
      return true;
    }
  
    /**
     * Outputs sample metadata of the received fragmented packets.
     *
     * <p>Call this method only after receiving an end of a VP8 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;
      gotFirstPacketOfVp8Frame = false;
    }
  }
  