libavcodec/mpeg4video_parser.c

   1 /*
   2  * MPEG4 Video frame extraction
   3  * Copyright (c) 2003 Fabrice Bellard
   4  * Copyright (c) 2003 Michael Niedermayer
   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 #include "parser.h"
  24 #include "mpegvideo.h"
  25 #include "mpeg4video_parser.h"
  26
  27
  28 int ff_mpeg4_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size){
  29     int vop_found, i;
  30     uint32_t state;
  31
  32     vop_found= pc->frame_start_found;
  33     state= pc->state;
  34
  35     i=0;
  36     if(!vop_found){
  37         for(i=0; i<buf_size; i++){
  38             state= (state<<8) | buf[i];
  39             if(state == 0x1B6){
  40                 i++;
  41                 vop_found=1;
  42                 break;
  43             }
  44         }
  45     }
  46
  47     if(vop_found){
  48         /* EOF considered as end of frame */
  49         if (buf_size == 0)
  50             return 0;
  51         for(; i<buf_size; i++){
  52             state= (state<<8) | buf[i];
  53             if((state&0xFFFFFF00) == 0x100){
  54                 pc->frame_start_found=0;
  55                 pc->state=-1;
  56                 return i-3;
  57             }
  58         }
  59     }
  60     pc->frame_start_found= vop_found;
  61     pc->state= state;
  62     return END_NOT_FOUND;
  63 }
  64
  65 /* XXX: make it use less memory */
  66 static int av_mpeg4_decode_header(AVCodecParserContext *s1,
  67                                   AVCodecContext *avctx,
  68                                   const uint8_t *buf, int buf_size)
  69 {
  70     ParseContext1 *pc = s1->priv_data;
  71     MpegEncContext *s = pc->enc;
  72     GetBitContext gb1, *gb = &gb1;
  73     int ret;
  74
  75     s->avctx = avctx;
  76     s->current_picture_ptr = &s->current_picture;
  77
  78     if (avctx->extradata_size && pc->first_picture){
  79         init_get_bits(gb, avctx->extradata, avctx->extradata_size*8);
  80         ret = ff_mpeg4_decode_picture_header(s, gb);
  81     }
  82
  83     init_get_bits(gb, buf, 8 * buf_size);
  84     ret = ff_mpeg4_decode_picture_header(s, gb);
  85     if (s->width) {
  86         avcodec_set_dimensions(avctx, s->width, s->height);
  87     }
  88     s1->pict_type= s->pict_type;
  89     pc->first_picture = 0;
  90     return ret;
  91 }
  92
  93 static av_cold int mpeg4video_parse_init(AVCodecParserContext *s)
  94 {
  95     ParseContext1 *pc = s->priv_data;
  96
  97     pc->enc = av_mallocz(sizeof(MpegEncContext));
  98     if (!pc->enc)
  99         return -1;
 100     pc->first_picture = 1;
 101     return 0;
 102 }
 103
 104 static int mpeg4video_parse(AVCodecParserContext *s,
 105                            AVCodecContext *avctx,
 106                            const uint8_t **poutbuf, int *poutbuf_size,
 107                            const uint8_t *buf, int buf_size)
 108 {
 109     ParseContext *pc = s->priv_data;
 110     int next;
 111
 112     if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
 113         next= buf_size;
 114     }else{
 115         next= ff_mpeg4_find_frame_end(pc, buf, buf_size);
 116
 117         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
 118             *poutbuf = NULL;
 119             *poutbuf_size = 0;
 120             return buf_size;
 121         }
 122     }
 123     av_mpeg4_decode_header(s, avctx, buf, buf_size);
 124
 125     *poutbuf = buf;
 126     *poutbuf_size = buf_size;
 127     return next;
 128 }
 129
 130
 131 AVCodecParser mpeg4video_parser = {
 132     { CODEC_ID_MPEG4 },
 133     sizeof(ParseContext1),
 134     mpeg4video_parse_init,
 135     mpeg4video_parse,
 136     ff_parse1_close,
 137     ff_mpeg4video_split,
 138 };