• Main Page
  • Related Pages
  • Modules
  • Data Structures
  • Files
  • File List
  • Globals

libavcodec/h261_parser.c

Go to the documentation of this file.
00001 /*
00002  * H261 parser
00003  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
00004  * Copyright (c) 2004 Maarten Daniels
00005  *
00006  * This file is part of FFmpeg.
00007  *
00008  * FFmpeg is free software; you can redistribute it and/or
00009  * modify it under the terms of the GNU Lesser General Public
00010  * License as published by the Free Software Foundation; either
00011  * version 2.1 of the License, or (at your option) any later version.
00012  *
00013  * FFmpeg is distributed in the hope that it will be useful,
00014  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00015  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00016  * Lesser General Public License for more details.
00017  *
00018  * You should have received a copy of the GNU Lesser General Public
00019  * License along with FFmpeg; if not, write to the Free Software
00020  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00021  */
00022 
00028 #include "parser.h"
00029 
00030 
00031 static int h261_find_frame_end(ParseContext *pc, AVCodecContext* avctx, const uint8_t *buf, int buf_size){
00032     int vop_found, i, j;
00033     uint32_t state;
00034 
00035     vop_found= pc->frame_start_found;
00036     state= pc->state;
00037 
00038     for(i=0; i<buf_size && !vop_found; i++){
00039         state= (state<<8) | buf[i];
00040         for(j=0; j<8; j++){
00041             if(((state>>j)&0xFFFFF0) == 0x000100){
00042                 vop_found=1;
00043                 break;
00044             }
00045         }
00046     }
00047     if(vop_found){
00048         for(; i<buf_size; i++){
00049             state= (state<<8) | buf[i];
00050             for(j=0; j<8; j++){
00051                 if(((state>>j)&0xFFFFF0) == 0x000100){
00052                     pc->frame_start_found=0;
00053                     pc->state= (state>>(3*8))+0xFF00;
00054                     return i-2;
00055                 }
00056             }
00057         }
00058     }
00059 
00060     pc->frame_start_found= vop_found;
00061     pc->state= state;
00062     return END_NOT_FOUND;
00063 }
00064 
00065 static int h261_parse(AVCodecParserContext *s,
00066                       AVCodecContext *avctx,
00067                       const uint8_t **poutbuf, int *poutbuf_size,
00068                       const uint8_t *buf, int buf_size)
00069 {
00070     ParseContext *pc = s->priv_data;
00071     int next;
00072 
00073     next= h261_find_frame_end(pc,avctx, buf, buf_size);
00074     if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
00075         *poutbuf = NULL;
00076         *poutbuf_size = 0;
00077         return buf_size;
00078     }
00079     *poutbuf = buf;
00080     *poutbuf_size = buf_size;
00081     return next;
00082 }
00083 
00084 AVCodecParser h261_parser = {
00085     { CODEC_ID_H261 },
00086     sizeof(ParseContext),
00087     NULL,
00088     h261_parse,
00089     ff_parse_close,
00090 };

Generated on Fri Sep 16 2011 17:17:36 for FFmpeg by  doxygen 1.7.1