liveMedia/VP8VideoRTPSource.cpp

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/**********
This library is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the
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This library is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for
more details.

You should have received a copy of the GNU Lesser General Public License
along with this library; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
**********/
// "liveMedia"
// Copyright (c) 1996-2012 Live Networks, Inc.  All rights reserved.
// VP8 Video RTP Sources
// Implementation

#include "VP8VideoRTPSource.hh"

VP8VideoRTPSource*
VP8VideoRTPSource::createNew(UsageEnvironment& env, Groupsock* RTPgs,
                              unsigned char rtpPayloadFormat,
                              unsigned rtpTimestampFrequency) {
  return new VP8VideoRTPSource(env, RTPgs, rtpPayloadFormat,
                               rtpTimestampFrequency);
}

VP8VideoRTPSource
::VP8VideoRTPSource(UsageEnvironment& env, Groupsock* RTPgs,
                     unsigned char rtpPayloadFormat,
                     unsigned rtpTimestampFrequency)
  : MultiFramedRTPSource(env, RTPgs, rtpPayloadFormat, rtpTimestampFrequency) {
}

VP8VideoRTPSource::~VP8VideoRTPSource() {
}

Boolean VP8VideoRTPSource
::processSpecialHeader(BufferedPacket* packet,
                       unsigned& resultSpecialHeaderSize) {
  unsigned char* headerStart = packet->data();
  unsigned packetSize = packet->dataSize();

  // The special header is from 1 to 6 bytes long.
  if (packetSize == 0) return False; // error
  resultSpecialHeaderSize = 1; // unless we learn otherwise

  u_int8_t const byte1 = headerStart[0];
  Boolean const X = (byte1&0x80) != 0;
  Boolean const S = (byte1&0x10) != 0;
  u_int8_t const PartID = byte1&0x0F;

  fCurrentPacketBeginsFrame = S && PartID == 0;
  fCurrentPacketCompletesFrame = packet->rtpMarkerBit(); // RTP header's "M" bit

  if (X) {
    ++resultSpecialHeaderSize;

    u_int8_t const byte2 = headerStart[1];
    Boolean const I = (byte2&0x80) != 0;
    Boolean const L = (byte2&0x40) != 0;
    Boolean const T = (byte2&0x20) != 0;
    Boolean const K = (byte2&0x10) != 0;

    if (I) {
      ++resultSpecialHeaderSize;
      if (headerStart[2]&0x80) { // extension flag in the PictureID is set
        ++resultSpecialHeaderSize;
      }
    }

    if (L) ++resultSpecialHeaderSize;
    if (T||K) ++resultSpecialHeaderSize;
  }
  
  return True;
}

char const* VP8VideoRTPSource::MIMEtype() const {
  return "video/VP8";
}

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