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 #if FF_API_FLAG_TRUNCATED
  29 /* Nuke this header when removing FF_API_FLAG_TRUNCATED */
  30 #include "h263_parser.h"
  31
  32 int ff_h263_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size){
  33 #else
  34
  35 static int h263_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size)
  36 {
  37 #endif
  38     int vop_found, i;
  39     uint32_t state;
  40
  41     vop_found= pc->frame_start_found;
  42     state= pc->state;
  43
  44     i=0;
  45     if(!vop_found){
  46         for(i=0; i<buf_size; i++){
  47             state= (state<<8) | buf[i];
  48             if(state>>(32-22) == 0x20){
  49                 i++;
  50                 vop_found=1;
  51                 break;
  52             }
  53         }
  54     }
  55
  56     if(vop_found){
  57       for(; i<buf_size; i++){
  58         state= (state<<8) | buf[i];
  59         if(state>>(32-22) == 0x20){
  60             pc->frame_start_found=0;
  61             pc->state=-1;
  62             return i-3;
  63         }
  64       }
  65     }
  66     pc->frame_start_found= vop_found;
  67     pc->state= state;
  68
  69     return END_NOT_FOUND;
  70 }
  71
  72 static int h263_parse(AVCodecParserContext *s,
  73                            AVCodecContext *avctx,
  74                            const uint8_t **poutbuf, int *poutbuf_size,
  75                            const uint8_t *buf, int buf_size)
  76 {
  77     ParseContext *pc = s->priv_data;
  78     int next;
  79
  80     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
  81         next = buf_size;
  82     } else {
  83 #if FF_API_FLAG_TRUNCATED
  84         next= ff_h263_find_frame_end(pc, buf, buf_size);
  85 #else
  86         next = h263_find_frame_end(pc, buf, buf_size);
  87 #endif
  88
  89         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
  90             *poutbuf = NULL;
  91             *poutbuf_size = 0;
  92             return buf_size;
  93         }
  94     }
  95
  96     *poutbuf = buf;
  97     *poutbuf_size = buf_size;
  98     return next;
  99 }
 100
 101 const AVCodecParser ff_h263_parser = {
 102     .codec_ids      = { AV_CODEC_ID_H263 },
 103     .priv_data_size = sizeof(ParseContext),
 104     .parser_parse   = h263_parse,
 105     .parser_close   = ff_parse_close,
 106 };