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libavcodec/h263_parser.c

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00001 /*
00002  * H.263 parser
00003  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00027 #include "parser.h"
00028 
00029 int ff_h263_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size){
00030     int vop_found, i;
00031     uint32_t state;
00032 
00033     vop_found= pc->frame_start_found;
00034     state= pc->state;
00035 
00036     i=0;
00037     if(!vop_found){
00038         for(i=0; i<buf_size; i++){
00039             state= (state<<8) | buf[i];
00040             if(state>>(32-22) == 0x20){
00041                 i++;
00042                 vop_found=1;
00043                 break;
00044             }
00045         }
00046     }
00047 
00048     if(vop_found){
00049       for(; i<buf_size; i++){
00050         state= (state<<8) | buf[i];
00051         if(state>>(32-22) == 0x20){
00052             pc->frame_start_found=0;
00053             pc->state=-1;
00054             return i-3;
00055         }
00056       }
00057     }
00058     pc->frame_start_found= vop_found;
00059     pc->state= state;
00060 
00061     return END_NOT_FOUND;
00062 }
00063 
00064 static int h263_parse(AVCodecParserContext *s,
00065                            AVCodecContext *avctx,
00066                            const uint8_t **poutbuf, int *poutbuf_size,
00067                            const uint8_t *buf, int buf_size)
00068 {
00069     ParseContext *pc = s->priv_data;
00070     int next;
00071 
00072     next= ff_h263_find_frame_end(pc, buf, buf_size);
00073 
00074     if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
00075         *poutbuf = NULL;
00076         *poutbuf_size = 0;
00077         return buf_size;
00078     }
00079 
00080     *poutbuf = buf;
00081     *poutbuf_size = buf_size;
00082     return next;
00083 }
00084 
00085 AVCodecParser h263_parser = {
00086     { CODEC_ID_H263 },
00087     sizeof(ParseContext),
00088     NULL,
00089     h263_parse,
00090     ff_parse_close,
00091 };

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