FFmpeg
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mpegvideodec.c
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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 
28 #define SEQ_START_CODE 0x000001b3
29 #define GOP_START_CODE 0x000001b8
30 #define PICTURE_START_CODE 0x00000100
31 #define SLICE_START_CODE 0x00000101
32 #define PACK_START_CODE 0x000001ba
33 #define VIDEO_ID 0x000001e0
34 #define AUDIO_ID 0x000001c0
35 
37 {
38  uint32_t code= -1;
39  int pic=0, seq=0, slice=0, pspack=0, vpes=0, apes=0, res=0, sicle=0;
40  int i, j;
41  uint32_t last = 0;
42 
43  for(i=0; i<p->buf_size; i++){
44  code = (code<<8) + p->buf[i];
45  if ((code & 0xffffff00) == 0x100) {
46  switch(code){
47  case SEQ_START_CODE:
48  if (!(p->buf[i+1+3+1+2] & 0x20))
49  break;
50  j = i;
51  if (p->buf[j+8] & 2)
52  j+= 64;
53  if (j >= p->buf_size)
54  break;
55  if (p->buf[j+8] & 1)
56  j+= 64;
57  if (j >= p->buf_size)
58  break;
59  if (AV_RB24(p->buf + j + 9) & 0xFFFFFE)
60  break;
61  seq++;
62  break;
63  case PICTURE_START_CODE: pic++; break;
64  case PACK_START_CODE: pspack++; break;
65  case 0x1b6:
66  res++; break;
67  }
68  if (code >= SLICE_START_CODE && code <= 0x1af) {
69  if (last >= SLICE_START_CODE && last <= 0x1af) {
70  if (code >= last) slice++;
71  else sicle++;
72  }else{
73  if (code == SLICE_START_CODE) slice++;
74  else sicle++;
75  }
76  }
77  if ((code & 0x1f0) == VIDEO_ID) vpes++;
78  else if((code & 0x1e0) == AUDIO_ID) apes++;
79  last = code;
80  }
81  }
82  if(seq && seq*9<=pic*10 && pic*9<=slice*10 && !pspack && !apes && !res && slice > sicle) {
83  if(vpes) return AVPROBE_SCORE_EXTENSION / 4;
84  else return pic>1 ? AVPROBE_SCORE_EXTENSION + 1 : AVPROBE_SCORE_EXTENSION / 2; // +1 for .mpg
85  }
86  return 0;
87 }
88