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 Libav.
   7  *
   8  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include "internal.h"
  24 #include "parser.h"
  25 #include "mpegvideo.h"
  26 #include "mpeg4video.h"
  27 #include "mpeg4video_parser.h"
  28
  29 struct Mp4vParseContext {
  30     ParseContext pc;
  31     struct MpegEncContext enc;
  32     int first_picture;
  33 };
  34
  35 int ff_mpeg4_find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size){
  36     int vop_found, i;
  37     uint32_t state;
  38
  39     vop_found= pc->frame_start_found;
  40     state= pc->state;
  41
  42     i=0;
  43     if(!vop_found){
  44         for(i=0; i<buf_size; i++){
  45             state= (state<<8) | buf[i];
  46             if(state == 0x1B6){
  47                 i++;
  48                 vop_found=1;
  49                 break;
  50             }
  51         }
  52     }
  53
  54     if(vop_found){
  55         /* EOF considered as end of frame */
  56         if (buf_size == 0)
  57             return 0;
  58         for(; i<buf_size; i++){
  59             state= (state<<8) | buf[i];
  60             if((state&0xFFFFFF00) == 0x100){
  61                 pc->frame_start_found=0;
  62                 pc->state=-1;
  63                 return i-3;
  64             }
  65         }
  66     }
  67     pc->frame_start_found= vop_found;
  68     pc->state= state;
  69     return END_NOT_FOUND;
  70 }
  71
  72 /* XXX: make it use less memory */
  73 static int av_mpeg4_decode_header(AVCodecParserContext *s1,
  74                                   AVCodecContext *avctx,
  75                                   const uint8_t *buf, int buf_size)
  76 {
  77     struct Mp4vParseContext *pc = s1->priv_data;
  78     MpegEncContext *s = &pc->enc;
  79     GetBitContext gb1, *gb = &gb1;
  80     int ret;
  81
  82     s->avctx = avctx;
  83     s->current_picture_ptr = &s->current_picture;
  84
  85     if (avctx->extradata_size && pc->first_picture){
  86         init_get_bits(gb, avctx->extradata, avctx->extradata_size*8);
  87         ret = ff_mpeg4_decode_picture_header(s, gb);
  88     }
  89
  90     init_get_bits(gb, buf, 8 * buf_size);
  91     ret = ff_mpeg4_decode_picture_header(s, gb);
  92     if (s->width && (!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height)) {
  93         ret = ff_set_dimensions(avctx, s->width, s->height);
  94         if (ret < 0)
  95             return ret;
  96     }
  97     s1->pict_type= s->pict_type;
  98     pc->first_picture = 0;
  99     return ret;
 100 }
 101
 102 static av_cold int mpeg4video_parse_init(AVCodecParserContext *s)
 103 {
 104     struct Mp4vParseContext *pc = s->priv_data;
 105
 106     pc->first_picture = 1;
 107     pc->enc.slice_context_count = 1;
 108     return 0;
 109 }
 110
 111 static int mpeg4video_parse(AVCodecParserContext *s,
 112                            AVCodecContext *avctx,
 113                            const uint8_t **poutbuf, int *poutbuf_size,
 114                            const uint8_t *buf, int buf_size)
 115 {
 116     ParseContext *pc = s->priv_data;
 117     int next;
 118
 119     if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
 120         next= buf_size;
 121     }else{
 122         next= ff_mpeg4_find_frame_end(pc, buf, buf_size);
 123
 124         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
 125             *poutbuf = NULL;
 126             *poutbuf_size = 0;
 127             return buf_size;
 128         }
 129     }
 130     av_mpeg4_decode_header(s, avctx, buf, buf_size);
 131
 132     *poutbuf = buf;
 133     *poutbuf_size = buf_size;
 134     return next;
 135 }
 136
 137
 138 AVCodecParser ff_mpeg4video_parser = {
 139     .codec_ids      = { AV_CODEC_ID_MPEG4 },
 140     .priv_data_size = sizeof(struct Mp4vParseContext),
 141     .parser_init    = mpeg4video_parse_init,
 142     .parser_parse   = mpeg4video_parse,
 143     .parser_close   = ff_parse_close,
 144     .split          = ff_mpeg4video_split,
 145 };