xref: /third_party/ffmpeg/libavformat/m4vdec.c (revision cabdff1a) 
1/*
2 * RAW MPEG-4 video demuxer
3 * Copyright (c) 2006  Thijs Vermeir <thijs.vermeir@barco.com>
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 "avformat.h"
23#include "rawdec.h"
24
25#define VOS_STARTCODE        0x1B0
26#define USER_DATA_STARTCODE  0x1B2
27#define GOP_STARTCODE        0x1B3
28#define VISUAL_OBJ_STARTCODE 0x1B5
29#define VOP_STARTCODE        0x1B6
30#define SLICE_STARTCODE      0x1B7
31#define EXT_STARTCODE        0x1B8
32
33static int mpeg4video_probe(const AVProbeData *probe_packet)
34{
35    uint32_t temp_buffer = -1;
36    int VO = 0, VOL = 0, VOP = 0, VISO = 0, res = 0;
37    int res_main = 0;
38    int i;
39
40    for (i = 0; i < probe_packet->buf_size; i++) {
41        temp_buffer = (temp_buffer << 8) + probe_packet->buf[i];
42        if (temp_buffer & 0xfffffe00)
43            continue;
44        if (temp_buffer < 2)
45            continue;
46
47        if (temp_buffer == VOP_STARTCODE)
48            VOP++;
49        else if (temp_buffer == VISUAL_OBJ_STARTCODE)
50            VISO++;
51        else if (temp_buffer >= 0x100 && temp_buffer < 0x120)
52            VO++;
53        else if (temp_buffer >= 0x120 && temp_buffer < 0x130)
54            VOL++;
55        else if (temp_buffer == SLICE_STARTCODE || temp_buffer == EXT_STARTCODE)
56            res_main++;
57        else if (!(0x1AF < temp_buffer && temp_buffer < 0x1B7) &&
58                 !(0x1B9 < temp_buffer && temp_buffer < 0x1C4))
59            res++;
60    }
61
62    // res_main repesents the reserved codes within the "main" profile, they are
63    // added to the reserved ones if it appears that this is a "main" profile
64    // stream
65    if (res_main && 2*res_main < VOP)
66        res += res_main;
67
68    if (VOP >= VISO && VOP >= VOL && VO >= VOL && VOL > 0 && res == 0)
69        return VOP+VO > 4 ? AVPROBE_SCORE_EXTENSION : AVPROBE_SCORE_EXTENSION/2;
70
71    if (VOP >= VISO && VOP >= VOL && VO >= VOL && VOL > 0 && VOP+VO > 4)
72        return AVPROBE_SCORE_EXTENSION/10;
73    return 0;
74}
75
76FF_DEF_RAWVIDEO_DEMUXER2(m4v, "raw MPEG-4 video", mpeg4video_probe, "m4v",
77                         AV_CODEC_ID_MPEG4, AVFMT_GENERIC_INDEX | AVFMT_TS_DISCONT)
78