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  1. /*
  2.  * MJPEG parser
  3.  * Copyright (c) 2000, 2001 Fabrice Bellard
  4.  * Copyright (c) 2003 Alex Beregszaszi
  5.  * Copyright (c) 2003-2004 Michael Niedermayer
  6.  *
  7.  * This file is part of FFmpeg.
  8.  *
  9.  * FFmpeg is free software; you can redistribute it and/or
  10.  * modify it under the terms of the GNU Lesser General Public
  11.  * License as published by the Free Software Foundation; either
  12.  * version 2.1 of the License, or (at your option) any later version.
  13.  *
  14.  * FFmpeg is distributed in the hope that it will be useful,
  15.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17.  * Lesser General Public License for more details.
  18.  *
  19.  * You should have received a copy of the GNU Lesser General Public
  20.  * License along with FFmpeg; if not, write to the Free Software
  21.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22.  */
  23.  
  24. /**
  25.  * @file
  26.  * MJPEG parser.
  27.  */
  28.  
  29. #include "parser.h"
  30.  
  31. typedef struct MJPEGParserContext{
  32.     ParseContext pc;
  33.     int size;
  34. }MJPEGParserContext;
  35.  
  36. /**
  37.  * Find the end of the current frame in the bitstream.
  38.  * @return the position of the first byte of the next frame, or -1
  39.  */
  40. static int find_frame_end(MJPEGParserContext *m, const uint8_t *buf, int buf_size){
  41.     ParseContext *pc= &m->pc;
  42.     int vop_found, i;
  43.     uint32_t state;
  44.  
  45.     vop_found= pc->frame_start_found;
  46.     state= pc->state;
  47.  
  48.     i=0;
  49.     if(!vop_found){
  50.         for(i=0; i<buf_size;){
  51.             state= (state<<8) | buf[i];
  52.             if(state>=0xFFC00000 && state<=0xFFFEFFFF){
  53.                 if(state>=0xFFD80000 && state<=0xFFD8FFFF){
  54.                     i++;
  55.                     vop_found=1;
  56.                     break;
  57.                 }else if(state<0xFFD00000 || state>0xFFD9FFFF){
  58.                     m->size= (state&0xFFFF)-1;
  59.                 }
  60.             }
  61.             if(m->size>0){
  62.                 int size= FFMIN(buf_size-i, m->size);
  63.                 i+=size;
  64.                 m->size-=size;
  65.                 state=0;
  66.                 continue;
  67.             }else
  68.                 i++;
  69.         }
  70.     }
  71.  
  72.     if(vop_found){
  73.         /* EOF considered as end of frame */
  74.         if (buf_size == 0)
  75.             return 0;
  76.         for(; i<buf_size;){
  77.             state= (state<<8) | buf[i];
  78.             if(state>=0xFFC00000 && state<=0xFFFEFFFF){
  79.                 if(state>=0xFFD80000 && state<=0xFFD8FFFF){
  80.                     pc->frame_start_found=0;
  81.                     pc->state=0;
  82.                     return i-3;
  83.                 } else if(state<0xFFD00000 || state>0xFFD9FFFF){
  84.                     m->size= (state&0xFFFF)-1;
  85.                 }
  86.             }
  87.             if(m->size>0){
  88.                 int size= FFMIN(buf_size-i, m->size);
  89.                 i+=size;
  90.                 m->size-=size;
  91.                 state=0;
  92.                 continue;
  93.             }else
  94.                 i++;
  95.         }
  96.     }
  97.     pc->frame_start_found= vop_found;
  98.     pc->state= state;
  99.     return END_NOT_FOUND;
  100. }
  101.  
  102. static int jpeg_parse(AVCodecParserContext *s,
  103.                       AVCodecContext *avctx,
  104.                       const uint8_t **poutbuf, int *poutbuf_size,
  105.                       const uint8_t *buf, int buf_size)
  106. {
  107.     MJPEGParserContext *m = s->priv_data;
  108.     ParseContext *pc = &m->pc;
  109.     int next;
  110.  
  111.     if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
  112.         next= buf_size;
  113.     }else{
  114.         next= find_frame_end(m, buf, buf_size);
  115.  
  116.         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
  117.             *poutbuf = NULL;
  118.             *poutbuf_size = 0;
  119.             return buf_size;
  120.         }
  121.     }
  122.  
  123.     *poutbuf = buf;
  124.     *poutbuf_size = buf_size;
  125.     return next;
  126. }
  127.  
  128.  
  129. AVCodecParser ff_mjpeg_parser = {
  130.     .codec_ids      = { AV_CODEC_ID_MJPEG },
  131.     .priv_data_size = sizeof(MJPEGParserContext),
  132.     .parser_parse   = jpeg_parse,
  133.     .parser_close   = ff_parse_close,
  134. };
  135.