mpeg4esvideortpsink.cpp

流媒体传输协议的实现代码,非常有用.可以支持rtsp mms等流媒体传输协议

/**********
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
Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version. (See <http://www.gnu.org/copyleft/lesser.html>.)

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.,
59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
**********/
// "liveMedia"
// Copyright (c) 1996-2004 Live Networks, Inc.  All rights reserved.
// RTP sink for MPEG-4 Elementary Stream video (RFC 3016)
// Implementation

#include "MPEG4ESVideoRTPSink.hh"
#include "MPEG4VideoStreamFramer.hh"

MPEG4ESVideoRTPSink
::MPEG4ESVideoRTPSink(UsageEnvironment& env, Groupsock* RTPgs,
		      unsigned char rtpPayloadFormat)
  : VideoRTPSink(env, RTPgs, rtpPayloadFormat, 90000, "MP4V-ES"),
    fVOPIsPresent(False), fAuxSDPLine(NULL) {
}

MPEG4ESVideoRTPSink::~MPEG4ESVideoRTPSink() {
  delete[] fAuxSDPLine;
}

MPEG4ESVideoRTPSink*
MPEG4ESVideoRTPSink::createNew(UsageEnvironment& env, Groupsock* RTPgs,
			       unsigned char rtpPayloadFormat) {
  return new MPEG4ESVideoRTPSink(env, RTPgs, rtpPayloadFormat);
}

Boolean MPEG4ESVideoRTPSink::sourceIsCompatibleWithUs(MediaSource& source) {
  // Our source must be an appropriate framer:
  return source.isMPEG4VideoStreamFramer();
}

#define VOP_START_CODE                    0x000001B6

void MPEG4ESVideoRTPSink
::doSpecialFrameHandling(unsigned fragmentationOffset,
			 unsigned char* frameStart,
			 unsigned numBytesInFrame,
			 struct timeval frameTimestamp,
			 unsigned numRemainingBytes) {
  if (fragmentationOffset == 0) {
    // Begin by inspecting the 4-byte code at the start of the frame:
    if (numBytesInFrame < 4) return; // shouldn't happen
    unsigned startCode = (frameStart[0]<<24) | (frameStart[1]<<16)
      | (frameStart[2]<<8) | frameStart[3];

    fVOPIsPresent = startCode == VOP_START_CODE;
  }

  // Set the RTP 'M' (marker) bit iff this frame ends a VOP
  // (and there are no fragments remaining).
  // This relies on the source being a "MPEG4VideoStreamFramer".
  MPEG4VideoStreamFramer* framerSource = (MPEG4VideoStreamFramer*)fSource;
  if (framerSource != NULL && framerSource->pictureEndMarker()
      && numRemainingBytes == 0) {
    setMarkerBit();
    framerSource->pictureEndMarker() = False;
  }

  // Also set the RTP timestamp.  (We do this for each frame
  // in the packet, to ensure that the timestamp of the VOP (if present)
  // gets used.)
  setTimestamp(frameTimestamp);
}

Boolean MPEG4ESVideoRTPSink::allowFragmentationAfterStart() const {
  return True;
}

Boolean MPEG4ESVideoRTPSink
::frameCanAppearAfterPacketStart(unsigned char const* /*frameStart*/,
				 unsigned /*numBytesInFrame*/) const {
  // Once we've packed a VOP into the packet, then no other
  // frame can be packed into it:
  return !fVOPIsPresent;
}

char const* MPEG4ESVideoRTPSink::auxSDPLine() {
  // Generate a new "a=fmtp:" line each time, using parameters from
  // our framer source (in case they've changed since the last time that
  // we were called):
  MPEG4VideoStreamFramer* framerSource = (MPEG4VideoStreamFramer*)fSource;
  if (framerSource == NULL) return NULL; // we don't yet have a source

  u_int8_t profile_level_id = framerSource->profile_and_level_indication();
  if (profile_level_id == 0) return NULL; // our source isn't ready

  unsigned configLength;
  unsigned char* config = framerSource->getConfigBytes(configLength);
  if (config == NULL) return NULL; // our source isn't ready

  char const* fmtpFmt =
    "a=fmtp:%d "
    "profile-level-id=%d;"
    "config=";
  unsigned fmtpFmtSize = strlen(fmtpFmt)
    + 3 /* max char len */
    + 3 /* max char len */
    + 2*configLength /* 2*, because each by prints as 2 chars */
    + 2 /* trailing \r\n */;
  char* fmtp = new char[fmtpFmtSize];
  sprintf(fmtp, fmtpFmt, rtpPayloadType(), profile_level_id);
  char* endPtr = &fmtp[strlen(fmtp)];
  for (unsigned i = 0; i < configLength; ++i) {
    sprintf(endPtr, "%02X", config[i]);
    endPtr += 2;
  }
  sprintf(endPtr, "\r\n");
	  
  delete[] fAuxSDPLine;
  fAuxSDPLine = strDup(fmtp);
  delete[] fmtp;
  return fAuxSDPLine;
}