PeerStreamer

/*

 * RAW H.261 video demuxer

 * Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>

 *

 * This file is part of Libav.

 *

 * Libav 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.

 *

 * Libav 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 Libav; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include "libavcodec/get_bits.h"

#include "avformat.h"

#include "rawdec.h"

static int h261_probe(AVProbeData *p)

{

    uint32_t code= -1;

    int i;

    int valid_psc=0;

    int invalid_psc=0;

    int next_gn=0;

    int src_fmt=0;

    GetBitContext gb;

    init_get_bits(&gb, p->buf, p->buf_size*8);

    for(i=0; i<p->buf_size*8; i++){

        if ((code & 0x01ff0000) || !(code & 0xff00)) {

            code = (code<<8) + get_bits(&gb, 8);

            i += 7;

        } else

            code = (code<<1) + get_bits1(&gb);

        if ((code & 0xffff0000) == 0x10000) {

            int gn= (code>>12)&0xf;

            if(!gn)

                src_fmt= code&8;

            if(gn != next_gn) invalid_psc++;

            else              valid_psc++;

            if(src_fmt){ // CIF

                next_gn= (gn+1     )%13;

            }else{       //QCIF

                next_gn= (gn+1+!!gn)% 7;

            }

        }

    }

    if(valid_psc > 2*invalid_psc + 6){

        return 50;

    }else if(valid_psc > 2*invalid_psc + 2)

        return 25;

    return 0;

}

AVInputFormat ff_h261_demuxer = {

    "h261",

    NULL_IF_CONFIG_SMALL("raw H.261"),

    0,

    h261_probe,

    ff_raw_video_read_header,

    ff_raw_read_partial_packet,

    .flags= AVFMT_GENERIC_INDEX,

    .extensions = "h261",

    .value = CODEC_ID_H261,

};