live555/liveMedia/MPEGVideoStreamParser.cpp

/**********
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.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
**********/
// "liveMedia"
// Copyright (c) 1996-2015 Live Networks, Inc.  All rights reserved.
// An abstract parser for MPEG video streams
// Implementation

#include "MPEGVideoStreamParser.hh"

MPEGVideoStreamParser
::MPEGVideoStreamParser(MPEGVideoStreamFramer* usingSource,
			FramedSource* inputSource)
  : StreamParser(inputSource, FramedSource::handleClosure, usingSource,
		 &MPEGVideoStreamFramer::continueReadProcessing, usingSource),
  fUsingSource(usingSource) {
}

MPEGVideoStreamParser::~MPEGVideoStreamParser() {
}

void MPEGVideoStreamParser::restoreSavedParserState() {
  StreamParser::restoreSavedParserState();
  fTo = fSavedTo;
  fNumTruncatedBytes = fSavedNumTruncatedBytes;
}

void MPEGVideoStreamParser::registerReadInterest(unsigned char* to,
						 unsigned maxSize) {
  fStartOfFrame = fTo = fSavedTo = to;
  fLimit = to + maxSize;
  fNumTruncatedBytes = fSavedNumTruncatedBytes = 0;
}

void MPEGVideoStreamParser::setParseState() {
  fSavedTo = fTo;
  fSavedNumTruncatedBytes = fNumTruncatedBytes;
  saveParserState();
}

void MPEGVideoStreamParser::saveByte(u_int8_t byte) {
  if (fTo >= fLimit) { // there's no space left
    ++fNumTruncatedBytes;
    return;
  }

  *fTo++ = byte;
}

void MPEGVideoStreamParser::save4Bytes(u_int32_t word) {
  if (fTo+4 > fLimit) { // there's no space left
    fNumTruncatedBytes += 4;
    return;
  }

  *fTo++ = word>>24; *fTo++ = word>>16; *fTo++ = word>>8; *fTo++ = word;
}

void MPEGVideoStreamParser::saveToNextCode(u_int32_t& curWord) {
  saveByte(curWord>>24);
  curWord = (curWord<<8)|get1Byte();
  while ((curWord&0xFFFFFF00) != 0x00000100) {
    if ((unsigned)(curWord&0xFF) > 1) {
  // a sync word definitely doesn't begin anywhere in "curWord"
  save4Bytes(curWord);
  curWord = get4Bytes();
    } else {
  // a sync word might begin in "curWord", although not at its start
  saveByte(curWord>>24);
  unsigned char newByte = get1Byte();
  curWord = (curWord<<8)|newByte;
    }
  }
}

void MPEGVideoStreamParser::skipToNextCode(u_int32_t& curWord) {
  curWord = (curWord<<8)|get1Byte();
  while ((curWord&0xFFFFFF00) != 0x00000100) {
    if ((unsigned)(curWord&0xFF) > 1) {
  // a sync word definitely doesn't begin anywhere in "curWord"
  curWord = get4Bytes();
    } else {
  // a sync word might begin in "curWord", although not at its start
  unsigned char newByte = get1Byte();
  curWord = (curWord<<8)|newByte;
    }
  }
}

unsigned MPEGVideoStreamParser::curFrameSize() {
  return fTo - fStartOfFrame;
}

unsigned MPEGVideoStreamParser::numTruncatedBytes() const {
  return fNumTruncatedBytes;
}