libavcodec/h261_parser.c

   1 /*
   2  * H261 parser
   3  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
   4  * Copyright (c) 2004 Maarten Daniels
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 /**
  24  * @file h261_parser.c
  25  * h261codec.
  26  */
  27
  28 #include "parser.h"
  29
  30
  31 static int h261_find_frame_end(ParseContext *pc, AVCodecContext* avctx, const uint8_t *buf, int buf_size){
  32     int vop_found, i, j;
  33     uint32_t state;
  34
  35     vop_found= pc->frame_start_found;
  36     state= pc->state;
  37
  38     for(i=0; i<buf_size && !vop_found; i++){
  39         state= (state<<8) | buf[i];
  40         for(j=0; j<8; j++){
  41             if(((state>>j)&0xFFFFF0) == 0x000100){
  42                 vop_found=1;
  43                 break;
  44             }
  45         }
  46     }
  47     if(vop_found){
  48         for(; i<buf_size; i++){
  49             state= (state<<8) | buf[i];
  50             for(j=0; j<8; j++){
  51                 if(((state>>j)&0xFFFFF0) == 0x000100){
  52                     pc->frame_start_found=0;
  53                     pc->state= (state>>(3*8))+0xFF00;
  54                     return i-2;
  55                 }
  56             }
  57         }
  58     }
  59
  60     pc->frame_start_found= vop_found;
  61     pc->state= state;
  62     return END_NOT_FOUND;
  63 }
  64
  65 static int h261_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= h261_find_frame_end(pc,avctx, buf, buf_size);
  74     if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
  75         *poutbuf = NULL;
  76         *poutbuf_size = 0;
  77         return buf_size;
  78     }
  79     *poutbuf = buf;
  80     *poutbuf_size = buf_size;
  81     return next;
  82 }
  83
  84 AVCodecParser h261_parser = {
  85     { CODEC_ID_H261 },
  86     sizeof(ParseContext),
  87     NULL,
  88     h261_parse,
  89     ff_parse_close,
  90 };