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 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 "parser_internal.h"
  29
  30 static int h263_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size)
  31 {
  32     int vop_found, i;
  33     uint32_t state;
  34
  35     vop_found= pc->frame_start_found;
  36     state= pc->state;
  37
  38     i=0;
  39     if(!vop_found){
  40         for(i=0; i<buf_size; i++){
  41             state= (state<<8) | buf[i];
  42             if(state>>(32-22) == 0x20){
  43                 i++;
  44                 vop_found=1;
  45                 break;
  46             }
  47         }
  48     }
  49
  50     if(vop_found){
  51       for(; i<buf_size; i++){
  52         state= (state<<8) | buf[i];
  53         if(state>>(32-22) == 0x20){
  54             pc->frame_start_found=0;
  55             pc->state=-1;
  56             return i-3;
  57         }
  58       }
  59     }
  60     pc->frame_start_found= vop_found;
  61     pc->state= state;
  62
  63     return END_NOT_FOUND;
  64 }
  65
  66 static int h263_parse(AVCodecParserContext *s,
  67                            AVCodecContext *avctx,
  68                            const uint8_t **poutbuf, int *poutbuf_size,
  69                            const uint8_t *buf, int buf_size)
  70 {
  71     ParseContext *pc = s->priv_data;
  72     int next;
  73
  74     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
  75         next = buf_size;
  76     } else {
  77         next = h263_find_frame_end(pc, buf, buf_size);
  78
  79         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
  80             *poutbuf = NULL;
  81             *poutbuf_size = 0;
  82             return buf_size;
  83         }
  84     }
  85
  86     *poutbuf = buf;
  87     *poutbuf_size = buf_size;
  88     return next;
  89 }
  90
  91 const FFCodecParser ff_h263_parser = {
  92     PARSER_CODEC_LIST(AV_CODEC_ID_H263),
  93     .priv_data_size = sizeof(ParseContext),
  94     .parse          = h263_parse,
  95     .close          = ff_parse_close,
  96 };