mtv.c

mediastreamer2是开源的网络传输媒体流的库

/*
 * mtv demuxer
 * Copyright (c) 2006 Reynaldo H. Verdejo Pinochet
 *
 * 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
 */

/**
 * @file mtv.c
 * MTV demuxer.
 */

#include "avformat.h"
#include "bswap.h"

#define MTV_ASUBCHUNK_DATA_SIZE 500
#define MTV_HEADER_SIZE 512
#define MTV_AUDIO_PADDING_SIZE 12
#define AUDIO_SAMPLING_RATE 44100
#define VIDEO_SID 0
#define AUDIO_SID 1

typedef struct MTVDemuxContext {

    unsigned int        file_size;         ///< filesize, not always right
    unsigned int        segments;          ///< number of 512 byte segments
    unsigned int        audio_identifier;  ///< 'MP3' on all files I have seen
    unsigned int        audio_br;          ///< bitrate of audio chanel (mp3)
    unsigned int        img_colorfmt;      ///< frame colorfmt rgb 565/555
    unsigned int        img_bpp;           ///< frame bits per pixel
    unsigned int        img_width;         //
    unsigned int        img_height;        //
    unsigned int        img_segment_size;  ///< size of image segment
    unsigned int        video_fps;         //
    unsigned int        audio_subsegments; ///< audio subsegments on one segment

    uint8_t             audio_packet_count;

} MTVDemuxContext;

static int mtv_probe(AVProbeData *p)
{
    /* Magic is 'AMV' */

    if(*(p->buf) != 'A' || *(p->buf+1) != 'M' || *(p->buf+2) != 'V')
        return 0;

    return AVPROBE_SCORE_MAX;
}

static int mtv_read_header(AVFormatContext *s, AVFormatParameters *ap)
{
    MTVDemuxContext    *mtv = s->priv_data;
    ByteIOContext      *pb  = s->pb;
    AVStream           *st;


    url_fskip(pb, 3);
    mtv->file_size         = get_le32(pb);
    mtv->segments          = get_le32(pb);
    url_fskip(pb, 32);
    mtv->audio_identifier  = get_le24(pb);
    mtv->audio_br          = get_le16(pb);
    mtv->img_colorfmt      = get_le24(pb);
    mtv->img_bpp           = get_byte(pb);
    mtv->img_width         = get_le16(pb);
    mtv->img_height        = get_le16(pb);
    mtv->img_segment_size  = get_le16(pb);
    url_fskip(pb, 4);
    mtv->audio_subsegments = get_le16(pb);
    mtv->video_fps         = (mtv->audio_br / 4) / mtv->audio_subsegments;

    /* FIXME Add sanity check here */

    /* first packet is always audio*/

    mtv->audio_packet_count = 1;

    /* all systems go! init decoders */

    /* video - raw rgb565 */

    st = av_new_stream(s, VIDEO_SID);
    if(!st)
        return AVERROR(ENOMEM);

    av_set_pts_info(st, 64, 1, mtv->video_fps);
    st->codec->codec_type      = CODEC_TYPE_VIDEO;
    st->codec->codec_id        = CODEC_ID_RAWVIDEO;
    st->codec->codec_tag       = MKTAG('R', 'G', 'B', mtv->img_bpp);
    st->codec->width           = mtv->img_width;
    st->codec->height          = mtv->img_height;
    st->codec->bits_per_sample = mtv->img_bpp;
    st->codec->sample_rate     = mtv->video_fps;

    /* audio - mp3 */

    st = av_new_stream(s, AUDIO_SID);
    if(!st)
        return AVERROR(ENOMEM);

    av_set_pts_info(st, 64, 1, AUDIO_SAMPLING_RATE);
    st->codec->codec_type      = CODEC_TYPE_AUDIO;
    st->codec->codec_id        = CODEC_ID_MP3;
    st->codec->bit_rate        = mtv->audio_br;
    st->need_parsing           = AVSTREAM_PARSE_FULL;

    /* Jump over header */

    if(url_fseek(pb, MTV_HEADER_SIZE, SEEK_SET) != MTV_HEADER_SIZE)
        return AVERROR(EIO);

    return(0);

}

static int mtv_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    MTVDemuxContext *mtv = s->priv_data;
    ByteIOContext *pb = s->pb;
    int ret;
#ifndef WORDS_BIGENDIAN
    int i;
#endif

    ret = 0;

    if(mtv->audio_subsegments >= mtv->audio_packet_count)
    {
        url_fskip(pb, MTV_AUDIO_PADDING_SIZE);

        ret = av_get_packet(pb, pkt, MTV_ASUBCHUNK_DATA_SIZE);
        if(ret != MTV_ASUBCHUNK_DATA_SIZE)
            return AVERROR(EIO);

        mtv->audio_packet_count++;
        pkt->stream_index = AUDIO_SID;

    }else
    {
        ret = av_get_packet(pb, pkt, mtv->img_segment_size);
        if(ret != mtv->img_segment_size)
            return AVERROR(EIO);

#ifndef WORDS_BIGENDIAN

        /* pkt->data is GGGRRRR BBBBBGGG
         * and we need RRRRRGGG GGGBBBBB
         * for PIX_FMT_RGB565 so here we
         * just swap bytes as they come
         */

        for(i=0;i<mtv->img_segment_size/2;i++)
            *((uint16_t *)pkt->data+i) = bswap_16(*((uint16_t *)pkt->data+i));
#endif
        mtv->audio_packet_count = 1;
        pkt->stream_index = VIDEO_SID;
    }

    return(ret);
}

AVInputFormat mtv_demuxer = {
    "MTV",
    "MTV format",
    sizeof(MTVDemuxContext),
    mtv_probe,
    mtv_read_header,
    mtv_read_packet,
};