FFmpeg
h264dec.c
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1 /*
2  * RAW H.264 video demuxer
3  * Copyright (c) 2008 Michael Niedermayer <michaelni@gmx.at>
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #include "libavcodec/get_bits.h"
23 #include "libavcodec/golomb.h"
24 #include "avformat.h"
25 #include "rawdec.h"
26 
27 #define MAX_SPS_COUNT 32
28 #define MAX_PPS_COUNT 256
29 
30 static int h264_probe(const AVProbeData *p)
31 {
32  uint32_t code = -1;
33  int sps = 0, pps = 0, idr = 0, res = 0, sli = 0;
34  int i, ret;
35  int pps_ids[MAX_PPS_COUNT+1] = {0};
36  int sps_ids[MAX_SPS_COUNT+1] = {0};
37  unsigned pps_id, sps_id;
38  GetBitContext gb;
39 
40  for (i = 0; i + 2 < p->buf_size; i++) {
41  code = (code << 8) + p->buf[i];
42  if ((code & 0xffffff00) == 0x100) {
43  int ref_idc = (code >> 5) & 3;
44  int type = code & 0x1F;
45  static const int8_t ref_zero[] = {
46  2, 0, 0, 0, 0, -1, 1, -1,
47  -1, 1, 1, 1, 1, -1, 2, 2,
48  2, 2, 2, 0, 2, 2, 2, 2,
49  2, 2, 2, 2, 2, 2, 2, 2
50  };
51 
52  if (code & 0x80) // forbidden_bit
53  return 0;
54 
55  if (ref_zero[type] == 1 && ref_idc)
56  return 0;
57  if (ref_zero[type] == -1 && !ref_idc)
58  return 0;
59  if (ref_zero[type] == 2) {
60  if (!(code == 0x100 && !p->buf[i + 1] && !p->buf[i + 2]))
61  res++;
62  }
63 
64  ret = init_get_bits8(&gb, p->buf + i + 1, p->buf_size - i - 1);
65  if (ret < 0)
66  return 0;
67 
68  switch (type) {
69  case 1:
70  case 5:
71  get_ue_golomb_long(&gb);
72  if (get_ue_golomb_long(&gb) > 9U)
73  return 0;
74  pps_id = get_ue_golomb_long(&gb);
75  if (pps_id > MAX_PPS_COUNT)
76  return 0;
77  if (!pps_ids[pps_id])
78  break;
79 
80  if (type == 1)
81  sli++;
82  else
83  idr++;
84  break;
85  case 7:
86  skip_bits(&gb, 14);
87  if (get_bits(&gb, 2))
88  return 0;
89  skip_bits(&gb, 8);
90  sps_id = get_ue_golomb_long(&gb);
91  if (sps_id > MAX_SPS_COUNT)
92  return 0;
93  sps_ids[sps_id] = 1;
94  sps++;
95  break;
96  case 8:
97  pps_id = get_ue_golomb_long(&gb);
98  if (pps_id > MAX_PPS_COUNT)
99  return 0;
100  sps_id = get_ue_golomb_long(&gb);
101  if (sps_id > MAX_SPS_COUNT)
102  return 0;
103  if (!sps_ids[sps_id])
104  break;
105  pps_ids[pps_id] = 1;
106  pps++;
107  break;
108  }
109  }
110  }
111  ff_tlog(NULL, "sps:%d pps:%d idr:%d sli:%d res:%d\n", sps, pps, idr, sli, res);
112 
113  if (sps && pps && (idr || sli > 3) && res < (sps + pps + idr))
114  return AVPROBE_SCORE_EXTENSION + 1; // 1 more than .mpg
115 
116  return 0;
117 }
118 
119 FF_DEF_RAWVIDEO_DEMUXER(h264, "raw H.264 video", h264_probe, "h26l,h264,264,avc", AV_CODEC_ID_H264)
idr
static void idr(H264Context *h)
instantaneous decoder refresh.
Definition: h264dec.c:432
AVProbeData::buf_size
int buf_size
Size of buf except extra allocated bytes.
Definition: avformat.h:456
skip_bits
static void skip_bits(GetBitContext *s, int n)
Definition: get_bits.h:468
golomb.h
exp golomb vlc stuff
get_bits
static unsigned int get_bits(GetBitContext *s, int n)
Read 1-25 bits.
Definition: get_bits.h:380
U
#define U(x)
Definition: vp56_arith.h:37
GetBitContext
Definition: get_bits.h:62
type
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf type
Definition: writing_filters.txt:86
init_get_bits8
static int init_get_bits8(GetBitContext *s, const uint8_t *buffer, int byte_size)
Initialize GetBitContext.
Definition: get_bits.h:678
AVProbeData::buf
unsigned char * buf
Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero.
Definition: avformat.h:455
MAX_PPS_COUNT
#define MAX_PPS_COUNT
Definition: h264dec.c:28
get_bits.h
h264_probe
static int h264_probe(const AVProbeData *p)
Definition: h264dec.c:30
AV_CODEC_ID_H264
@ AV_CODEC_ID_H264
Definition: codec_id.h:77
if
if(ret)
Definition: filter_design.txt:179
FF_DEF_RAWVIDEO_DEMUXER
#define FF_DEF_RAWVIDEO_DEMUXER(shortname, longname, probe, ext, id)
Definition: rawdec.h:66
NULL
#define NULL
Definition: coverity.c:32
rawdec.h
AVProbeData
This structure contains the data a format has to probe a file.
Definition: avformat.h:453
AVPROBE_SCORE_EXTENSION
#define AVPROBE_SCORE_EXTENSION
score for file extension
Definition: avformat.h:463
pps
static int FUNC() pps(CodedBitstreamContext *ctx, RWContext *rw, H264RawPPS *current)
Definition: cbs_h264_syntax_template.c:404
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:271
code
and forward the test the status of outputs and forward it to the corresponding return FFERROR_NOT_READY If the filters stores internally one or a few frame for some it can consider them to be part of the FIFO and delay acknowledging a status change accordingly Example code
Definition: filter_design.txt:178
ret
ret
Definition: filter_design.txt:187
sps
static int FUNC() sps(CodedBitstreamContext *ctx, RWContext *rw, H264RawSPS *current)
Definition: cbs_h264_syntax_template.c:260
avformat.h
MAX_SPS_COUNT
#define MAX_SPS_COUNT
Definition: h264dec.c:27
get_ue_golomb_long
static unsigned get_ue_golomb_long(GetBitContext *gb)
Read an unsigned Exp-Golomb code in the range 0 to UINT32_MAX-1.
Definition: golomb.h:104
ff_tlog
#define ff_tlog(ctx,...)
Definition: internal.h:204