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 h263_parser.c
  24  * H.263 parser
  25  */
  26
  27 #include "parser.h"
  28
  29 int ff_h263_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size){
  30     int vop_found, i;
  31     uint32_t state;
  32
  33     vop_found= pc->frame_start_found;
  34     state= pc->state;
  35
  36     i=0;
  37     if(!vop_found){
  38         for(i=0; i<buf_size; i++){
  39             state= (state<<8) | buf[i];
  40             if(state>>(32-22) == 0x20){
  41                 i++;
  42                 vop_found=1;
  43                 break;
  44             }
  45         }
  46     }
  47
  48     if(vop_found){
  49       for(; i<buf_size; i++){
  50         state= (state<<8) | buf[i];
  51         if(state>>(32-22) == 0x20){
  52             pc->frame_start_found=0;
  53             pc->state=-1;
  54             return i-3;
  55         }
  56       }
  57     }
  58     pc->frame_start_found= vop_found;
  59     pc->state= state;
  60
  61     return END_NOT_FOUND;
  62 }
  63
  64 static int h263_parse(AVCodecParserContext *s,
  65                            AVCodecContext *avctx,
  66                            const uint8_t **poutbuf, int *poutbuf_size,
  67                            const uint8_t *buf, int buf_size)
  68 {
  69     ParseContext *pc = s->priv_data;
  70     int next;
  71
  72     next= ff_h263_find_frame_end(pc, buf, buf_size);
  73
  74     if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
  75         *poutbuf = NULL;
  76         *poutbuf_size = 0;
  77         return buf_size;
  78     }
  79
  80     *poutbuf = buf;
  81     *poutbuf_size = buf_size;
  82     return next;
  83 }
  84
  85 AVCodecParser h263_parser = {
  86     { CODEC_ID_H263 },
  87     sizeof(ParseContext),
  88     NULL,
  89     h263_parse,
  90     ff_parse_close,
  91 };