/**********
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This library is free software; you can redistribute it and/or modify it under
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the terms of the GNU Lesser General Public License as published by the
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Free Software Foundation; either version 3 of the License, or (at your
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option) any later version. (See <http://www.gnu.org/copyleft/lesser.html>.)
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This library is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
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more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this library; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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**********/
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// "liveMedia"
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// Copyright (c) 1996-2017 Live Networks, Inc. All rights reserved.
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// An abstract parser for MPEG video streams
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// C++ header
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#ifndef _MPEG_VIDEO_STREAM_PARSER_HH
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#define _MPEG_VIDEO_STREAM_PARSER_HH
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#ifndef _STREAM_PARSER_HH
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#include "StreamParser.hh"
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#endif
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#ifndef _MPEG_VIDEO_STREAM_FRAMER_HH
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#include "MPEGVideoStreamFramer.hh"
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#endif
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////////// MPEGVideoStreamParser definition //////////
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class MPEGVideoStreamParser: public StreamParser {
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public:
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MPEGVideoStreamParser(MPEGVideoStreamFramer* usingSource,
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FramedSource* inputSource);
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virtual ~MPEGVideoStreamParser();
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public:
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void registerReadInterest(unsigned char* to, unsigned maxSize);
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virtual unsigned parse() = 0;
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// returns the size of the frame that was acquired, or 0 if none was
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// The number of truncated bytes (if any) is given by:
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unsigned numTruncatedBytes() const { return fNumTruncatedBytes; }
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protected:
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void setParseState() {
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fSavedTo = fTo;
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fSavedNumTruncatedBytes = fNumTruncatedBytes;
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saveParserState();
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}
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// Record "byte" in the current output frame:
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void saveByte(u_int8_t byte) {
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if (fTo >= fLimit) { // there's no space left
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++fNumTruncatedBytes;
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return;
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}
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*fTo++ = byte;
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}
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void save4Bytes(u_int32_t word) {
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if (fTo+4 > fLimit) { // there's no space left
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fNumTruncatedBytes += 4;
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return;
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}
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*fTo++ = word>>24; *fTo++ = word>>16; *fTo++ = word>>8; *fTo++ = word;
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}
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// Save data until we see a sync word (0x000001xx):
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void saveToNextCode(u_int32_t& curWord) {
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saveByte(curWord>>24);
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curWord = (curWord<<8)|get1Byte();
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while ((curWord&0xFFFFFF00) != 0x00000100) {
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if ((unsigned)(curWord&0xFF) > 1) {
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// a sync word definitely doesn't begin anywhere in "curWord"
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save4Bytes(curWord);
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curWord = get4Bytes();
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} else {
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// a sync word might begin in "curWord", although not at its start
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saveByte(curWord>>24);
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unsigned char newByte = get1Byte();
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curWord = (curWord<<8)|newByte;
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}
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}
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}
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// Skip data until we see a sync word (0x000001xx):
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void skipToNextCode(u_int32_t& curWord) {
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curWord = (curWord<<8)|get1Byte();
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while ((curWord&0xFFFFFF00) != 0x00000100) {
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if ((unsigned)(curWord&0xFF) > 1) {
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// a sync word definitely doesn't begin anywhere in "curWord"
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curWord = get4Bytes();
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} else {
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// a sync word might begin in "curWord", although not at its start
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unsigned char newByte = get1Byte();
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curWord = (curWord<<8)|newByte;
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}
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}
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}
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protected:
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MPEGVideoStreamFramer* fUsingSource;
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// state of the frame that's currently being read:
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unsigned char* fStartOfFrame;
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unsigned char* fTo;
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unsigned char* fLimit;
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unsigned fNumTruncatedBytes;
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unsigned curFrameSize() { return fTo - fStartOfFrame; }
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unsigned char* fSavedTo;
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unsigned fSavedNumTruncatedBytes;
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private: // redefined virtual functions
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virtual void restoreSavedParserState();
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};
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#endif
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