Exemplo n.º 1
0
/**
 * A depacketizer from VP8. See {@link "http://tools.ietf.org/html/draft-ietf-payload-vp8-11"}
 *
 * @author Boris Grozev
 * @author George Politis
 */
public class DePacketizer extends AbstractCodec2 {
  /**
   * The <tt>Logger</tt> used by the <tt>DePacketizer</tt> class and its instances for logging
   * output.
   */
  private static final Logger logger = Logger.getLogger(DePacketizer.class);

  /** Whether trace logging is enabled. */
  private static final boolean TRACE = logger.isTraceEnabled();

  /**
   * A <tt>Comparator</tt> implementation for RTP sequence numbers. Compares <tt>a</tt> and
   * <tt>b</tt>, taking into account the wrap at 2^16.
   *
   * <p>IMPORTANT: This is a valid <tt>Comparator</tt> implementation only if used for subsets of
   * [0, 2^16) which don't span more than 2^15 elements.
   *
   * <p>E.g. it works for: [0, 2^15-1] and ([50000, 2^16) u [0, 10000]) Doesn't work for: [0, 2^15]
   * and ([0, 2^15-1] u {2^16-1}) and [0, 2^16)
   *
   * <p>NOTE: An identical implementation for Integers can be found in the class SeqNumComparator.
   * Sequence numbers are 16 bits and unsigned, so an Integer should be sufficient to hold that.
   */
  private static final Comparator<? super Long> seqNumComparator =
      new Comparator<Long>() {
        @Override
        public int compare(Long a, Long b) {
          if (a.equals(b)) return 0;
          else if (a > b) {
            if (a - b < 32768) return 1;
            else return -1;
          } else // a < b
          {
            if (b - a < 32768) return -1;
            else return 1;
          }
        }
      };

  /**
   * Stores the RTP payloads (VP8 payload descriptor stripped) from RTP packets belonging to a
   * single VP8 compressed frame.
   */
  private SortedMap<Long, Container> data = new TreeMap<Long, Container>(seqNumComparator);

  /** Stores unused <tt>Container</tt>'s. */
  private Queue<Container> free = new ArrayBlockingQueue<Container>(100);

  /**
   * Stores the first (earliest) sequence number stored in <tt>data</tt>, or -1 if <tt>data</tt> is
   * empty.
   */
  private long firstSeq = -1;

  /**
   * Stores the last (latest) sequence number stored in <tt>data</tt>, or -1 if <tt>data</tt> is
   * empty.
   */
  private long lastSeq = -1;

  /**
   * Stores the value of the <tt>PictureID</tt> field for the VP8 compressed frame, parts of which
   * are currently stored in <tt>data</tt>, or -1 if the <tt>PictureID</tt> field is not in use or
   * <tt>data</tt> is empty.
   */
  private int pictureId = -1;

  /**
   * Stores the RTP timestamp of the packets stored in <tt>data</tt>, or -1 if they don't have a
   * timestamp set.
   */
  private long timestamp = -1;

  /** Whether we have stored any packets in <tt>data</tt>. Equivalent to <tt>data.isEmpty()</tt>. */
  private boolean empty = true;

  /**
   * Whether we have stored in <tt>data</tt> the last RTP packet of the VP8 compressed frame, parts
   * of which are currently stored in <tt>data</tt>.
   */
  private boolean haveEnd = false;

  /**
   * Whether we have stored in <tt>data</tt> the first RTP packet of the VP8 compressed frame, parts
   * of which are currently stored in <tt>data</tt>.
   */
  private boolean haveStart = false;

  /**
   * Stores the sum of the lengths of the data stored in <tt>data</tt>, that is the total length of
   * the VP8 compressed frame to be constructed.
   */
  private int frameLength = 0;

  /** The sequence number of the last RTP packet, which was included in the output. */
  private long lastSentSeq = -1;

  /** Initializes a new <tt>JNIEncoder</tt> instance. */
  public DePacketizer() {
    super(
        "VP8 RTP DePacketizer",
        VideoFormat.class,
        new VideoFormat[] {new VideoFormat(Constants.VP8)});
    inputFormats = new VideoFormat[] {new VideoFormat(Constants.VP8_RTP)};
  }

  /** {@inheritDoc} */
  @Override
  protected void doClose() {}

  /** {@inheritDoc} */
  @Override
  protected void doOpen() throws ResourceUnavailableException {
    if (logger.isInfoEnabled()) logger.info("Opened VP8 depacketizer");
  }

  /**
   * Re-initializes the fields which store information about the currently held data. Empties
   * <tt>data</tt>.
   */
  private void reinit() {
    firstSeq = lastSeq = timestamp = -1;
    pictureId = -1;
    empty = true;
    haveEnd = haveStart = false;
    frameLength = 0;

    Iterator<Map.Entry<Long, Container>> it = data.entrySet().iterator();
    Map.Entry<Long, Container> e;
    while (it.hasNext()) {
      e = it.next();
      free.offer(e.getValue());
      it.remove();
    }
  }

  /**
   * Checks whether the currently held VP8 compressed frame is complete (e.g all its packets are
   * stored in <tt>data</tt>).
   *
   * @return <tt>true</tt> if the currently help VP8 compressed frame is complete, <tt>false</tt>
   *     otherwise.
   */
  private boolean frameComplete() {
    return haveStart && haveEnd && !haveMissing();
  }

  /**
   * Checks whether there are packets with sequence numbers between <tt>firstSeq</tt> and
   * <tt>lastSeq</tt> which are *not* stored in <tt>data</tt>.
   *
   * @return <tt>true</tt> if there are packets with sequence numbers between <tt>firstSeq</tt> and
   *     <tt>lastSeq</tt> which are *not* stored in <tt>data</tt>.
   */
  private boolean haveMissing() {
    Set<Long> seqs = data.keySet();
    long s = firstSeq;
    while (s != lastSeq) {
      if (!seqs.contains(s)) return true;
      s = (s + 1) % (1 << 16);
    }
    return false;
  }

  /** {@inheritDoc} */
  @Override
  protected int doProcess(Buffer inBuffer, Buffer outBuffer) {
    byte[] inData = (byte[]) inBuffer.getData();
    int inOffset = inBuffer.getOffset();

    if (!VP8PayloadDescriptor.isValid(inData, inOffset)) {
      logger.warn("Invalid RTP/VP8 packet discarded.");
      outBuffer.setDiscard(true);
      return BUFFER_PROCESSED_FAILED; // XXX: FAILED or OK?
    }

    long inSeq = inBuffer.getSequenceNumber();
    long inRtpTimestamp = inBuffer.getRtpTimeStamp();
    int inPictureId = VP8PayloadDescriptor.getPictureId(inData, inOffset);
    boolean inMarker = (inBuffer.getFlags() & Buffer.FLAG_RTP_MARKER) != 0;
    boolean inIsStartOfFrame = VP8PayloadDescriptor.isStartOfFrame(inData, inOffset);
    int inLength = inBuffer.getLength();
    int inPdSize = VP8PayloadDescriptor.getSize(inData, inOffset);
    int inPayloadLength = inLength - inPdSize;

    if (empty && lastSentSeq != -1 && seqNumComparator.compare(inSeq, lastSentSeq) != 1) {
      if (logger.isInfoEnabled()) logger.info("Discarding old packet (while empty) " + inSeq);
      outBuffer.setDiscard(true);
      return BUFFER_PROCESSED_OK;
    }

    if (!empty) {
      // if the incoming packet has a different PictureID or timestamp
      // than those of the current frame, then it belongs to a different
      // frame.
      if ((inPictureId != -1 && pictureId != -1 && inPictureId != pictureId)
          | (timestamp != -1 && inRtpTimestamp != -1 && inRtpTimestamp != timestamp)) {
        if (seqNumComparator.compare(inSeq, firstSeq) != 1) // inSeq <= firstSeq
        {
          // the packet belongs to a previous frame. discard it
          if (logger.isInfoEnabled()) logger.info("Discarding old packet " + inSeq);
          outBuffer.setDiscard(true);
          return BUFFER_PROCESSED_OK;
        } else // inSeq > firstSeq (and also presumably isSeq > lastSeq)
        {
          // the packet belongs to a subsequent frame (to the one
          // currently being held). Drop the current frame.

          if (logger.isInfoEnabled())
            logger.info(
                "Discarding saved packets on arrival of"
                    + " a packet for a subsequent frame: "
                    + inSeq);

          // TODO: this would be the place to complain about the
          // not-well-received PictureID by sending a RTCP SLI or NACK.
          reinit();
        }
      }
    }

    // a whole frame in a single packet. avoid the extra copy to
    // this.data and output it immediately.
    if (empty && inMarker && inIsStartOfFrame) {
      byte[] outData = validateByteArraySize(outBuffer, inPayloadLength, false);
      System.arraycopy(inData, inOffset + inPdSize, outData, 0, inPayloadLength);
      outBuffer.setOffset(0);
      outBuffer.setLength(inPayloadLength);
      outBuffer.setRtpTimeStamp(inBuffer.getRtpTimeStamp());

      if (TRACE) logger.trace("Out PictureID=" + inPictureId);

      lastSentSeq = inSeq;

      return BUFFER_PROCESSED_OK;
    }

    // add to this.data
    Container container = free.poll();
    if (container == null) container = new Container();
    if (container.buf == null || container.buf.length < inPayloadLength)
      container.buf = new byte[inPayloadLength];

    if (data.get(inSeq) != null) {
      if (logger.isInfoEnabled())
        logger.info("(Probable) duplicate packet detected, discarding " + inSeq);
      outBuffer.setDiscard(true);
      return BUFFER_PROCESSED_OK;
    }

    System.arraycopy(inData, inOffset + inPdSize, container.buf, 0, inPayloadLength);
    container.len = inPayloadLength;
    data.put(inSeq, container);

    // update fields
    frameLength += inPayloadLength;
    if (firstSeq == -1 || (seqNumComparator.compare(firstSeq, inSeq) == 1)) firstSeq = inSeq;
    if (lastSeq == -1 || (seqNumComparator.compare(inSeq, lastSeq) == 1)) lastSeq = inSeq;

    if (empty) {
      // the first received packet for the current frame was just added
      empty = false;
      timestamp = inRtpTimestamp;
      pictureId = inPictureId;
    }

    if (inMarker) haveEnd = true;
    if (inIsStartOfFrame) haveStart = true;

    // check if we have a full frame
    if (frameComplete()) {
      byte[] outData = validateByteArraySize(outBuffer, frameLength, false);
      int ptr = 0;
      Container b;
      for (Map.Entry<Long, Container> entry : data.entrySet()) {
        b = entry.getValue();
        System.arraycopy(b.buf, 0, outData, ptr, b.len);
        ptr += b.len;
      }

      outBuffer.setOffset(0);
      outBuffer.setLength(frameLength);
      outBuffer.setRtpTimeStamp(inBuffer.getRtpTimeStamp());

      if (TRACE) logger.trace("Out PictureID=" + inPictureId);
      lastSentSeq = lastSeq;

      // prepare for the next frame
      reinit();

      return BUFFER_PROCESSED_OK;
    } else {
      // frame not complete yet
      outBuffer.setDiscard(true);
      return OUTPUT_BUFFER_NOT_FILLED;
    }
  }

  /**
   * Returns true if the buffer contains a VP8 key frame at offset <tt>offset</tt>.
   *
   * @param buff the byte buffer to check
   * @param off the offset in the byte buffer where the actual data starts
   * @param len the length of the data in the byte buffer
   * @return true if the buffer contains a VP8 key frame at offset <tt>offset</tt>.
   */
  public static boolean isKeyFrame(byte[] buff, int off, int len) {
    if (buff == null || buff.length < off + len || len < RawPacket.FIXED_HEADER_SIZE) {
      return false;
    }

    // Check if this is the start of a VP8 partition in the payload
    // descriptor.
    if (!DePacketizer.VP8PayloadDescriptor.isValid(buff, off)) {
      return false;
    }

    if (!DePacketizer.VP8PayloadDescriptor.isStartOfFrame(buff, off)) {
      return false;
    }

    int szVP8PayloadDescriptor = DePacketizer.VP8PayloadDescriptor.getSize(buff, off);

    return DePacketizer.VP8PayloadHeader.isKeyFrame(buff, off + szVP8PayloadDescriptor);
  }

  /**
   * A class that represents the VP8 Payload Descriptor structure defined in {@link
   * "http://tools.ietf.org/html/draft-ietf-payload-vp8-10"}
   */
  public static class VP8PayloadDescriptor {
    /** I bit from the X byte of the Payload Descriptor. */
    private static final byte I_BIT = (byte) 0x80;

    /** K bit from the X byte of the Payload Descriptor. */
    private static final byte K_BIT = (byte) 0x10;
    /** L bit from the X byte of the Payload Descriptor. */
    private static final byte L_BIT = (byte) 0x40;

    /** I bit from the I byte of the Payload Descriptor. */
    private static final byte M_BIT = (byte) 0x80;
    /** Maximum length of a VP8 Payload Descriptor. */
    public static final int MAX_LENGTH = 6;
    /** S bit from the first byte of the Payload Descriptor. */
    private static final byte S_BIT = (byte) 0x10;
    /** T bit from the X byte of the Payload Descriptor. */
    private static final byte T_BIT = (byte) 0x20;

    /** X bit from the first byte of the Payload Descriptor. */
    private static final byte X_BIT = (byte) 0x80;

    /**
     * Gets the temporal layer index (TID), if that's set.
     *
     * @param buf the byte buffer that holds the VP8 packet.
     * @param off the offset in the byte buffer where the VP8 packet starts.
     * @param len the length of the VP8 packet.
     * @return the temporal layer index (TID), if that's set, -1 otherwise.
     */
    public static int getTemporalLayerIndex(byte[] buf, int off, int len) {
      if (buf == null || buf.length < off + len || len < 2) {
        return -1;
      }

      if ((buf[off] & X_BIT) == 0 || (buf[off + 1] & T_BIT) == 0) {
        return -1;
      }

      int sz = getSize(buf, off);
      if (buf.length < off + sz || sz < 1) {
        return -1;
      }

      return (buf[off + sz - 1] & 0xc0) >> 6;
    }

    /**
     * Returns a simple Payload Descriptor, with PartID = 0, the 'start of partition' bit set
     * according to <tt>startOfPartition</tt>, and all other bits set to 0.
     *
     * @param startOfPartition whether to 'start of partition' bit should be set
     * @return a simple Payload Descriptor, with PartID = 0, the 'start of partition' bit set
     *     according to <tt>startOfPartition</tt>, and all other bits set to 0.
     */
    public static byte[] create(boolean startOfPartition) {
      byte[] pd = new byte[1];
      pd[0] = startOfPartition ? (byte) 0x10 : 0;
      return pd;
    }

    /**
     * The size in bytes of the Payload Descriptor at offset <tt>offset</tt> in <tt>input</tt>. The
     * size is between 1 and 6.
     *
     * @param input input
     * @param offset offset
     * @return The size in bytes of the Payload Descriptor at offset <tt>offset</tt> in
     *     <tt>input</tt>, or -1 if the input is not a valid VP8 Payload Descriptor. The size is
     *     between 1 and 6.
     */
    public static int getSize(byte[] input, int offset) {
      if (!isValid(input, offset)) return -1;

      if ((input[offset] & X_BIT) == 0) return 1;

      int size = 2;
      if ((input[offset + 1] & I_BIT) != 0) {
        size++;
        if ((input[offset + 2] & M_BIT) != 0) size++;
      }
      if ((input[offset + 1] & L_BIT) != 0) size++;
      if ((input[offset + 1] & (T_BIT | K_BIT)) != 0) size++;

      return size;
    }

    /**
     * Gets the value of the PictureID field of a VP8 Payload Descriptor.
     *
     * @param input
     * @param offset
     * @return the value of the PictureID field of a VP8 Payload Descriptor, or -1 if the fields is
     *     not present.
     */
    private static int getPictureId(byte[] input, int offset) {
      if (!isValid(input, offset)) return -1;

      if ((input[offset] & X_BIT) == 0 || (input[offset + 1] & I_BIT) == 0) return -1;

      boolean isLong = (input[offset + 2] & M_BIT) != 0;
      if (isLong) return (input[offset + 2] & 0x7f) << 8 | (input[offset + 3] & 0xff);
      else return input[offset + 2] & 0x7f;
    }

    public static boolean isValid(byte[] input, int offset) {
      return true;
    }

    /**
     * Checks whether the '<tt>start of partition</tt>' bit is set in the VP8 Payload Descriptor at
     * offset <tt>offset</tt> in <tt>input</tt>.
     *
     * @param input input
     * @param offset offset
     * @return <tt>true</tt> if the '<tt>start of partition</tt>' bit is set, <tt>false</tt>
     *     otherwise.
     */
    public static boolean isStartOfPartition(byte[] input, int offset) {
      return (input[offset] & S_BIT) != 0;
    }

    /**
     * Returns <tt>true</tt> if both the '<tt>start of partition</tt>' bit is set and the
     * <tt>PID</tt> fields has value 0 in the VP8 Payload Descriptor at offset <tt>offset</tt> in
     * <tt>input</tt>.
     *
     * @param input
     * @param offset
     * @return <tt>true</tt> if both the '<tt>start of partition</tt>' bit is set and the
     *     <tt>PID</tt> fields has value 0 in the VP8 Payload Descriptor at offset <tt>offset</tt>
     *     in <tt>input</tt>.
     */
    public static boolean isStartOfFrame(byte[] input, int offset) {
      return isStartOfPartition(input, offset) && getPartitionId(input, offset) == 0;
    }

    /**
     * Returns the value of the <tt>PID</tt> (partition ID) field of the VP8 Payload Descriptor at
     * offset <tt>offset</tt> in <tt>input</tt>.
     *
     * @param input
     * @param offset
     * @return the value of the <tt>PID</tt> (partition ID) field of the VP8 Payload Descriptor at
     *     offset <tt>offset</tt> in <tt>input</tt>.
     */
    public static int getPartitionId(byte[] input, int offset) {
      return input[offset] & 0x07;
    }
  }

  /**
   * A class that represents the VP8 Payload Header structure defined in {@link
   * "http://tools.ietf.org/html/draft-ietf-payload-vp8-10"}
   */
  public static class VP8PayloadHeader {
    /** S bit of the Payload Descriptor. */
    private static final byte S_BIT = (byte) 0x01;

    /**
     * Returns true if the <tt>P</tt> (inverse key frame flag) field of the VP8 Payload Header at
     * offset <tt>offset</tt> in <tt>input</tt> is 0.
     *
     * @return true if the <tt>P</tt> (inverse key frame flag) field of the VP8 Payload Header at
     *     offset <tt>offset</tt> in <tt>input</tt> is 0, false otherwise.
     */
    public static boolean isKeyFrame(byte[] input, int offset) {
      // When set to 0 the current frame is a key frame.  When set to 1
      // the current frame is an interframe. Defined in [RFC6386]

      return (input[offset] & S_BIT) == 0;
    }
  }

  /** A simple container for a <tt>byte[]</tt> and an integer. */
  private static class Container {
    /** This <tt>Container</tt>'s data. */
    private byte[] buf;

    /** Length used. */
    private int len = 0;
  }
}
  /**
   * Notifies this instance that a <tt>DatagramPacket</tt> packet received on the data
   * <tt>DatagramSocket</tt> of this <tt>Channel</tt> has been accepted for further processing
   * within Jitsi Videobridge.
   *
   * @param pkt the accepted <tt>RawPacket</tt>.
   */
  public void accepted(RawPacket pkt) {
    // With native simulcast we don't have a notification when a stream
    // has started/stopped. The simulcast manager implements a timeout
    // for the high quality stream and it needs to be notified when
    // the channel has accepted a datagram packet for the timeout to
    // function correctly.

    if (!hasLayers() || pkt == null) {
      return;
    }

    // Find the layer that corresponds to this packet.
    int acceptedSSRC = pkt.getSSRC();
    SimulcastLayer[] layers = getSimulcastLayers();
    SimulcastLayer acceptedLayer = null;
    for (SimulcastLayer layer : layers) {
      // We only care about the primary SSRC and not the RTX ssrc (or
      // future FEC ssrc).
      if ((int) layer.getPrimarySSRC() == acceptedSSRC) {
        acceptedLayer = layer;
        break;
      }
    }

    // If this is not an RTP packet or if we can't find an accepted
    // layer, log and return as it makes no sense to continue in this
    // situation.
    if (acceptedLayer == null) {
      return;
    }

    // There are sequences of packets with increasing timestamps but without
    // the marker bit set. Supposedly, they are probes to detect whether the
    // bandwidth may increase. We think that they should cause neither the
    // start nor the stop of any SimulcastLayer.

    // XXX There's RawPacket#getPayloadLength() but the implementation
    // includes pkt.paddingSize at the time of this writing and we do not
    // know whether that's going to stay that way.
    int pktPayloadLength = pkt.getLength() - pkt.getHeaderLength();
    int pktPaddingSize = pkt.getPaddingSize();

    if (pktPayloadLength <= pktPaddingSize) {
      if (logger.isTraceEnabled()) {
        logger.trace(
            "pkt.payloadLength= "
                + pktPayloadLength
                + " <= pkt.paddingSize= "
                + pktPaddingSize
                + "("
                + pkt.getSequenceNumber()
                + ")");
      }
      return;
    }

    // NOTE(gp) we expect the base layer to be always on, so we never touch
    // it or starve it.

    // XXX Refer to the implementation of
    // SimulcastLayer#touch(boolean, RawPacket) for an explanation of why we
    // chose to use a return value.
    boolean frameStarted = acceptedLayer.touch(pkt);
    if (frameStarted) simulcastLayerFrameStarted(acceptedLayer, pkt, layers);
  }