PeerStreamer

/*

 * Maxis XA (.xa) File Demuxer

 * Copyright (c) 2008 Robert Marston

 *

 * 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

 * Maxis XA File Demuxer

 * by Robert Marston (rmarston@gmail.com)

 * for more information on the XA audio format see

 *   http://wiki.multimedia.cx/index.php?title=Maxis_XA

 */

#include "libavutil/intreadwrite.h"

#include "avformat.h"

#define XA00_TAG MKTAG('X', 'A', 0, 0)

#define XAI0_TAG MKTAG('X', 'A', 'I', 0)

#define XAJ0_TAG MKTAG('X', 'A', 'J', 0)

typedef struct MaxisXADemuxContext {

    uint32_t out_size;

    uint32_t sent_bytes;

    uint32_t audio_frame_counter;

} MaxisXADemuxContext;

static int xa_probe(AVProbeData *p)

{

    int channels, srate, bits_per_sample;

    if (p->buf_size < 24)

        return 0;

    switch(AV_RL32(p->buf)) {

    case XA00_TAG:

    case XAI0_TAG:

    case XAJ0_TAG:

        break;

    default:

        return 0;

    }

    channels        = AV_RL16(p->buf + 10);

    srate           = AV_RL32(p->buf + 12);

    bits_per_sample = AV_RL16(p->buf + 22);

    if (!channels || channels > 8 || !srate || srate > 192000 ||

        bits_per_sample < 4 || bits_per_sample > 32)

        return 0;

    return AVPROBE_SCORE_MAX/2;

}

static int xa_read_header(AVFormatContext *s,

               AVFormatParameters *ap)

{

    MaxisXADemuxContext *xa = s->priv_data;

    ByteIOContext *pb = s->pb;

    AVStream *st;

    /*Set up the XA Audio Decoder*/

    st = av_new_stream(s, 0);

    if (!st)

        return AVERROR(ENOMEM);

    st->codec->codec_type   = AVMEDIA_TYPE_AUDIO;

    st->codec->codec_id     = CODEC_ID_ADPCM_EA_MAXIS_XA;

    url_fskip(pb, 4);       /* Skip the XA ID */

    xa->out_size            =  get_le32(pb);

    url_fskip(pb, 2);       /* Skip the tag */

    st->codec->channels     = get_le16(pb);

    st->codec->sample_rate  = get_le32(pb);

    /* Value in file is average byte rate*/

    st->codec->bit_rate     = get_le32(pb) * 8;

    st->codec->block_align  = get_le16(pb);

    st->codec->bits_per_coded_sample = get_le16(pb);

    av_set_pts_info(st, 64, 1, st->codec->sample_rate);

    return 0;

}

static int xa_read_packet(AVFormatContext *s,

                          AVPacket *pkt)

{

    MaxisXADemuxContext *xa = s->priv_data;

    AVStream *st = s->streams[0];

    ByteIOContext *pb = s->pb;

    unsigned int packet_size;

    int ret;

    if(xa->sent_bytes > xa->out_size)

        return AVERROR(EIO);

    /* 1 byte header and 14 bytes worth of samples * number channels per block */

    packet_size = 15*st->codec->channels;

    ret = av_get_packet(pb, pkt, packet_size);

    if(ret < 0)

        return ret;

    pkt->stream_index = st->index;

    xa->sent_bytes += packet_size;

    pkt->pts = xa->audio_frame_counter;

    /* 14 bytes Samples per channel with 2 samples per byte */

    xa->audio_frame_counter += 28 * st->codec->channels;

    return ret;

}

AVInputFormat xa_demuxer = {

    "xa",

    NULL_IF_CONFIG_SMALL("Maxis XA File Format"),

    sizeof(MaxisXADemuxContext),

    xa_probe,

    xa_read_header,

    xa_read_packet,

};