libavcodec/h263_parser.c

   1 /*
   2  * H.263 parser
   3  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
   4  *
   5  * This file is part of Libav.
   6  *
   7  * Libav 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  * Libav 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 Libav; 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     next= ff_h263_find_frame_end(pc, buf, buf_size);
  74
  75     if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
  76         *poutbuf = NULL;
  77         *poutbuf_size = 0;
  78         return buf_size;
  79     }
  80
  81     *poutbuf = buf;
  82     *poutbuf_size = buf_size;
  83     return next;
  84 }
  85
  86 AVCodecParser ff_h263_parser = {
  87     .codec_ids      = { AV_CODEC_ID_H263 },
  88     .priv_data_size = sizeof(ParseContext),
  89     .parser_parse   = h263_parse,
  90     .parser_close   = ff_parse_close,
  91 };