libavformat/mpegvideodec.c

   1 /*
   2  * RAW MPEG video demuxer
   3  * Copyright (c) 2002-2003 Fabrice Bellard
   4  * Copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
   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 "avformat.h"
  24 #include "rawdec.h"
  25
  26 #include "libavutil/intreadwrite.h"
  27 #include "libavcodec/startcode.h"
  28
  29 #define SEQ_START_CODE          0x000001b3
  30 #define GOP_START_CODE          0x000001b8
  31 #define PICTURE_START_CODE      0x00000100
  32 #define SLICE_START_CODE        0x00000101
  33 #define PACK_START_CODE         0x000001ba
  34 #define VIDEO_ID                0x000001e0
  35 #define AUDIO_ID                0x000001c0
  36
  37 static int mpegvideo_probe(const AVProbeData *p)
  38 {
  39     uint32_t code= -1;
  40     int pic=0, seq=0, slice=0, pspack=0, vpes=0, apes=0, res=0, sicle=0;
  41     const uint8_t *ptr = p->buf, *end = ptr + p->buf_size;
  42     uint32_t last = 0;
  43     int j;
  44
  45     while (ptr < end) {
  46         ptr = avpriv_find_start_code(ptr, end, &code);
  47         if ((code & 0xffffff00) == 0x100) {
  48             switch(code){
  49             case     SEQ_START_CODE:
  50                 if (!(ptr[3 + 1 + 2] & 0x20))
  51                     break;
  52                 j = -1;
  53                 if (ptr[j + 8] & 2)
  54                     j+= 64;
  55                 if (j >= end - ptr)
  56                     break;
  57                 if (ptr[j + 8] & 1)
  58                     j+= 64;
  59                 if (j >= end - ptr)
  60                     break;
  61                 if (AV_RB24(ptr + j + 9) & 0xFFFFFE)
  62                     break;
  63                 seq++;
  64             break;
  65             case PICTURE_START_CODE:   pic++; break;
  66             case    PACK_START_CODE: pspack++; break;
  67             case              0x1b6:
  68                                         res++; break;
  69             }
  70             if (code >= SLICE_START_CODE && code <= 0x1af) {
  71                 if (last >= SLICE_START_CODE && last <= 0x1af) {
  72                     if (code >= last) slice++;
  73                     else              sicle++;
  74                 }else{
  75                     if (code == SLICE_START_CODE) slice++;
  76                     else                          sicle++;
  77                 }
  78             }
  79             if     ((code & 0x1f0) == VIDEO_ID)   vpes++;
  80             else if((code & 0x1e0) == AUDIO_ID)   apes++;
  81             last = code;
  82         }
  83     }
  84     if(seq && seq*9<=pic*10 && pic*9<=slice*10 && !pspack && !apes && !res && slice > sicle) {
  85         if(vpes) return AVPROBE_SCORE_EXTENSION / 4;
  86         else     return pic>1 ? AVPROBE_SCORE_EXTENSION + 1 : AVPROBE_SCORE_EXTENSION / 2; // +1 for .mpg
  87     }
  88     return 0;
  89 }
  90
  91 FF_DEF_RAWVIDEO_DEMUXER(mpegvideo, "raw MPEG video", mpegvideo_probe, NULL, AV_CODEC_ID_MPEG1VIDEO)