libavcodec/mjpeg_parser.c

   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 mjpeg_parser.c
  26  * MJPEG parser.
  27  */
  28
  29 #include "parser.h"
  30
  31
  32 /**
  33  * finds the end of the current frame in the bitstream.
  34  * @return the position of the first byte of the next frame, or -1
  35  */
  36 static int find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size){
  37     int vop_found, i;
  38     uint16_t state;
  39
  40     vop_found= pc->frame_start_found;
  41     state= pc->state;
  42
  43     i=0;
  44     if(!vop_found){
  45         for(i=0; i<buf_size; i++){
  46             state= (state<<8) | buf[i];
  47             if(state == 0xFFD8){
  48                 i++;
  49                 vop_found=1;
  50                 break;
  51             }
  52         }
  53     }
  54
  55     if(vop_found){
  56         /* EOF considered as end of frame */
  57         if (buf_size == 0)
  58             return 0;
  59         for(; i<buf_size; i++){
  60             state= (state<<8) | buf[i];
  61             if(state == 0xFFD8){
  62                 pc->frame_start_found=0;
  63                 pc->state=0;
  64                 return i-1;
  65             }
  66         }
  67     }
  68     pc->frame_start_found= vop_found;
  69     pc->state= state;
  70     return END_NOT_FOUND;
  71 }
  72
  73 static int jpeg_parse(AVCodecParserContext *s,
  74                            AVCodecContext *avctx,
  75                            const uint8_t **poutbuf, int *poutbuf_size,
  76                            const uint8_t *buf, int buf_size)
  77 {
  78     ParseContext *pc = s->priv_data;
  79     int next;
  80
  81     next= find_frame_end(pc, buf, buf_size);
  82
  83     if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
  84         *poutbuf = NULL;
  85         *poutbuf_size = 0;
  86         return buf_size;
  87     }
  88
  89     *poutbuf = buf;
  90     *poutbuf_size = buf_size;
  91     return next;
  92 }
  93
  94
  95 AVCodecParser mjpeg_parser = {
  96     { CODEC_ID_MJPEG },
  97     sizeof(ParseContext),
  98     NULL,
  99     jpeg_parse,
 100     ff_parse_close,
 101 };