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  1. /*
  2.  * H.263 parser
  3.  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
  4.  *
  5.  * This file is part of FFmpeg.
  6.  *
  7.  * FFmpeg is free software; you can redistribute it and/or
  8.  * modify it under the terms of the GNU Lesser General Public
  9.  * License as published by the Free Software Foundation; either
  10.  * version 2.1 of the License, or (at your option) any later version.
  11.  *
  12.  * FFmpeg is distributed in the hope that it will be useful,
  13.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15.  * Lesser General Public License for more details.
  16.  *
  17.  * You should have received a copy of the GNU Lesser General Public
  18.  * License along with FFmpeg; if not, write to the Free Software
  19.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20.  */
  21.  
  22. /**
  23.  * @file
  24.  * H.263 parser
  25.  */
  26.  
  27. #include "parser.h"
  28. #include "h263_parser.h"
  29.  
  30. int ff_h263_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size){
  31.     int vop_found, i;
  32.     uint32_t state;
  33.  
  34.     vop_found= pc->frame_start_found;
  35.     state= pc->state;
  36.  
  37.     i=0;
  38.     if(!vop_found){
  39.         for(i=0; i<buf_size; i++){
  40.             state= (state<<8) | buf[i];
  41.             if(state>>(32-22) == 0x20){
  42.                 i++;
  43.                 vop_found=1;
  44.                 break;
  45.             }
  46.         }
  47.     }
  48.  
  49.     if(vop_found){
  50.       for(; i<buf_size; i++){
  51.         state= (state<<8) | buf[i];
  52.         if(state>>(32-22) == 0x20){
  53.             pc->frame_start_found=0;
  54.             pc->state=-1;
  55.             return i-3;
  56.         }
  57.       }
  58.     }
  59.     pc->frame_start_found= vop_found;
  60.     pc->state= state;
  61.  
  62.     return END_NOT_FOUND;
  63. }
  64.  
  65. static int h263_parse(AVCodecParserContext *s,
  66.                            AVCodecContext *avctx,
  67.                            const uint8_t **poutbuf, int *poutbuf_size,
  68.                            const uint8_t *buf, int buf_size)
  69. {
  70.     ParseContext *pc = s->priv_data;
  71.     int next;
  72.  
  73.     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
  74.         next = buf_size;
  75.     } else {
  76.         next= ff_h263_find_frame_end(pc, buf, buf_size);
  77.  
  78.         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
  79.             *poutbuf = NULL;
  80.             *poutbuf_size = 0;
  81.             return buf_size;
  82.         }
  83.     }
  84.  
  85.     *poutbuf = buf;
  86.     *poutbuf_size = buf_size;
  87.     return next;
  88. }
  89.  
  90. AVCodecParser ff_h263_parser = {
  91.     .codec_ids      = { AV_CODEC_ID_H263 },
  92.     .priv_data_size = sizeof(ParseContext),
  93.     .parser_parse   = h263_parse,
  94.     .parser_close   = ff_parse_close,
  95. };
  96.