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/libavformat/h264dec.c

http://github.com/FFmpeg/FFmpeg
C | 120 lines | 88 code | 12 blank | 20 comment | 33 complexity | 8a9388625ffe2c0e0ca36fc39f6a0463 MD5 | raw file
  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#include "libavcodec/internal.h"
 27
 28#define MAX_SPS_COUNT          32
 29#define MAX_PPS_COUNT         256
 30
 31static int h264_probe(const AVProbeData *p)
 32{
 33    uint32_t code = -1;
 34    int sps = 0, pps = 0, idr = 0, res = 0, sli = 0;
 35    int i, ret;
 36    int pps_ids[MAX_PPS_COUNT+1] = {0};
 37    int sps_ids[MAX_SPS_COUNT+1] = {0};
 38    unsigned pps_id, sps_id;
 39    GetBitContext gb;
 40
 41    for (i = 0; i + 2 < p->buf_size; i++) {
 42        code = (code << 8) + p->buf[i];
 43        if ((code & 0xffffff00) == 0x100) {
 44            int ref_idc = (code >> 5) & 3;
 45            int type    = code & 0x1F;
 46            static const int8_t ref_zero[] = {
 47                 2,  0,  0,  0,  0, -1,  1, -1,
 48                -1,  1,  1,  1,  1, -1,  2,  2,
 49                 2,  2,  2,  0,  2,  2,  2,  2,
 50                 2,  2,  2,  2,  2,  2,  2,  2
 51            };
 52
 53            if (code & 0x80) // forbidden_bit
 54                return 0;
 55
 56            if (ref_zero[type] == 1 && ref_idc)
 57                return 0;
 58            if (ref_zero[type] == -1 && !ref_idc)
 59                return 0;
 60            if (ref_zero[type] == 2) {
 61                if (!(code == 0x100 && !p->buf[i + 1] && !p->buf[i + 2]))
 62                    res++;
 63            }
 64
 65            ret = init_get_bits8(&gb, p->buf + i + 1, p->buf_size - i - 1);
 66            if (ret < 0)
 67                return 0;
 68
 69            switch (type) {
 70            case 1:
 71            case 5:
 72                get_ue_golomb_long(&gb);
 73                if (get_ue_golomb_long(&gb) > 9U)
 74                    return 0;
 75                pps_id = get_ue_golomb_long(&gb);
 76                if (pps_id > MAX_PPS_COUNT)
 77                    return 0;
 78                if (!pps_ids[pps_id])
 79                    break;
 80
 81                if (type == 1)
 82                    sli++;
 83                else
 84                    idr++;
 85                break;
 86            case 7:
 87                skip_bits(&gb, 14);
 88                if (get_bits(&gb, 2))
 89                    return 0;
 90                skip_bits(&gb, 8);
 91                sps_id = get_ue_golomb_long(&gb);
 92                if (sps_id > MAX_SPS_COUNT)
 93                    return 0;
 94                sps_ids[sps_id] = 1;
 95                sps++;
 96                break;
 97            case 8:
 98                pps_id = get_ue_golomb_long(&gb);
 99                if (pps_id > MAX_PPS_COUNT)
100                    return 0;
101                sps_id = get_ue_golomb_long(&gb);
102                if (sps_id > MAX_SPS_COUNT)
103                    return 0;
104                if (!sps_ids[sps_id])
105                    break;
106                pps_ids[pps_id] = 1;
107                pps++;
108                break;
109            }
110        }
111    }
112    ff_tlog(NULL, "sps:%d pps:%d idr:%d sli:%d res:%d\n", sps, pps, idr, sli, res);
113
114    if (sps && pps && (idr || sli > 3) && res < (sps + pps + idr))
115        return AVPROBE_SCORE_EXTENSION + 1;  // 1 more than .mpg
116
117    return 0;
118}
119
120FF_DEF_RAWVIDEO_DEMUXER(h264, "raw H.264 video", h264_probe, "h26l,h264,264,avc", AV_CODEC_ID_H264)