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
  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>=0xFFD8FFC0 && 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>=0xFFD8FFC0 && state<=0xFFD8FFFF){
  80                     pc->frame_start_found=0;
  81                     pc->state=0;
  82                     return i-3;
  83                 } else if((state>>16)==0xFFD9 && (state&0xFFFF)!=0xFFD8){
  84                     state= 0xFFD900|(state&0xFF);
  85                 } else if(state<0xFFD00000 || state>0xFFD9FFFF){
  86                     m->size= (state&0xFFFF)-1;
  87                 }
  88             }
  89             if(m->size>0){
  90                 int size= FFMIN(buf_size-i, m->size);
  91                 i+=size;
  92                 m->size-=size;
  93                 state=0;
  94                 continue;
  95             }else
  96                 i++;
  97         }
  98     }
  99     pc->frame_start_found= vop_found;
 100     pc->state= state;
 101     return END_NOT_FOUND;
 102 }
 103
 104 static int jpeg_parse(AVCodecParserContext *s,
 105                       AVCodecContext *avctx,
 106                       const uint8_t **poutbuf, int *poutbuf_size,
 107                       const uint8_t *buf, int buf_size)
 108 {
 109     MJPEGParserContext *m = s->priv_data;
 110     ParseContext *pc = &m->pc;
 111     int next;
 112
 113     if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
 114         next= buf_size;
 115     }else{
 116         next= find_frame_end(m, buf, buf_size);
 117
 118         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
 119             *poutbuf = NULL;
 120             *poutbuf_size = 0;
 121             return buf_size;
 122         }
 123     }
 124
 125     *poutbuf = buf;
 126     *poutbuf_size = buf_size;
 127     return next;
 128 }
 129
 130
 131 const AVCodecParser ff_mjpeg_parser = {
 132     .codec_ids      = { AV_CODEC_ID_MJPEG, AV_CODEC_ID_JPEGLS },
 133     .priv_data_size = sizeof(MJPEGParserContext),
 134     .parser_parse   = jpeg_parse,
 135     .parser_close   = ff_parse_close,
 136 };