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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
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) 1996-2005 Live Networks, Inc. All rights reserved.
// An abstract parser for MPEG video streams
// C++ header
#ifndef _MPEG_VIDEO_STREAM_PARSER_HH
#define _MPEG_VIDEO_STREAM_PARSER_HH
#ifndef _STREAM_PARSER_HH
#include "StreamParser.hh"
#endif
#ifndef _MPEG_VIDEO_STREAM_FRAMER_HH
#include "MPEGVideoStreamFramer.hh"
#endif
////////// MPEGVideoStreamParser definition //////////
class MPEGVideoStreamParser: public StreamParser {
public:
MPEGVideoStreamParser(MPEGVideoStreamFramer* usingSource,
FramedSource* inputSource);
virtual ~MPEGVideoStreamParser();
public:
void registerReadInterest(unsigned char* to, unsigned maxSize);
virtual unsigned parse() = 0;
// returns the size of the frame that was acquired, or 0 if none was
// The number of truncated bytes (if any) is given by:
unsigned numTruncatedBytes() const { return fNumTruncatedBytes; }
protected:
void setParseState();
// Record "byte" in the current output frame:
void saveByte(u_int8_t byte) {
if (fTo >= fLimit) { // there's no space left
++fNumTruncatedBytes;
return;
}
*fTo++ = byte;
}
void 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;
}
// Save data until we see a sync word (0x000001xx):
void 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;
}
}
}
// Skip data until we see a sync word (0x000001xx):
void 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;
}
}
}
protected:
MPEGVideoStreamFramer* fUsingSource;
// state of the frame that's currently being read:
unsigned char* fStartOfFrame;
unsigned char* fTo;
unsigned char* fLimit;
unsigned fNumTruncatedBytes;
unsigned curFrameSize() { return fTo - fStartOfFrame; }
unsigned char* fSavedTo;
unsigned fSavedNumTruncatedBytes;
private: // redefined virtual functions
virtual void restoreSavedParserState();
};
#endif
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