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 != packet_size)
        return AVERROR(EIO);

    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;
}