annotate ffmpeg/libavformat/h264dec.c @ 13:844d341cf643 tip

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/*
 * RAW H.264 video demuxer
 * Copyright (c) 2008 Michael Niedermayer <[e-mail]>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "avformat.h"
#include "rawdec.h"

static int h264_probe(AVProbeData *p)
{
    uint32_t code= -1;
    int sps=0, pps=0, idr=0, res=0, sli=0;
    int i;

    for(i=0; i<p->buf_size; i++){
        code = (code<<8) + p->buf[i];
        if ((code & 0xffffff00) == 0x100) {
            int ref_idc= (code>>5)&3;
            int type   = code & 0x1F;
            static const int8_t ref_zero[32]={
                2, 0, 0, 0, 0,-1, 1,-1,
               -1, 1, 1, 1, 1,-1, 2, 2,
                2, 2, 2, 0, 2, 2, 2, 2,
                2, 2, 2, 2, 2, 2, 2, 2
            };

            if(code & 0x80) //forbidden bit
                return 0;

            if(ref_zero[type] == 1 && ref_idc)
                return 0;
            if(ref_zero[type] ==-1 && !ref_idc)
                return 0;
            if(ref_zero[type] == 2)
                res++;

            switch(type){
            case     1:   sli++; break;
            case     5:   idr++; break;
            case     7:
                if (p->buf[i + 2] & 0x03)
                    return 0;
                sps++;
                break;
            case     8:   pps++; break;
            }
        }
    }
    if(sps && pps && (idr||sli>3) && res<(sps+pps+idr))
        return AVPROBE_SCORE_MAX/2+1; // +1 for .mpg
    return 0;
}

FF_DEF_RAWVIDEO_DEMUXER(h264 , "raw H.264 video", h264_probe, "h26l,h264,264", AV_CODEC_ID_H264)