WIP: add support for multistreams.

[smimram]

No description provided.

[smimram]

I have improved the binding but it seems that we still have some more testing to do (a simple 5.1 file does not work here)... You can find lots of small multichanels examples here for testing: https://people.xiph.org/~greg/opus_multichannel_examples/

[smimram]

Ok, here is the magic function VLC is using to get the decoding parameters from the header. We need this since current function always returns two channels...

int opus_header_parse(const unsigned char *packet, int len, OpusHeader *h)
{
    char str[9];
    ROPacket p;
    unsigned char ch;
    ogg_uint16_t shortval;

    p.data = packet;
    p.maxlen = len;
    p.pos = 0;
    str[8] = 0;
    if (len<19)return 0;
    read_chars(&p, (unsigned char*)str, 8);
    if (memcmp(str, "OpusHead", 8)!=0)
        return 0;

    if (!read_chars(&p, &ch, 1))
        return 0;
    h->version = ch;
    if((h->version&240) != 0) /* Only major version 0 supported. */
        return 0;

    if (!read_chars(&p, &ch, 1))
        return 0;
    h->channels = ch;
    if (h->channels == 0)
        return 0;

    if (!read_uint16(&p, &shortval))
        return 0;
    h->preskip = shortval;

    if (!read_uint32(&p, &h->input_sample_rate))
        return 0;

    if (!read_uint16(&p, &shortval))
        return 0;
    h->gain = (short)shortval;

    if (!read_chars(&p, &ch, 1))
        return 0;
    h->channel_mapping = ch;

    if (h->channel_mapping != 0)
    {
        if (!read_chars(&p, &ch, 1))
            return 0;

        if (ch<1)
            return 0;
        h->nb_streams = ch;

        if (!read_chars(&p, &ch, 1))
            return 0;

        if (ch>h->nb_streams || (ch+h->nb_streams)>255)
            return 0;
        h->nb_coupled = ch;

        /* Multi-stream support */
        for (int i=0;i<h->channels;i++)
        {
            if (!read_chars(&p, &h->stream_map[i], 1))
                return 0;
            if (h->stream_map[i]>(h->nb_streams+h->nb_coupled) && h->stream_map[i]!=255)
                return 0;
        }
    } else {
        if(h->channels>2)
            return 0;
        h->nb_streams = 1;
        h->nb_coupled = h->channels>1;
        h->stream_map[0]=0;
        h->stream_map[1]=1;
    }
    /*For version 0/1 we know there won't be any more data
      so reject any that have data past the end.*/
    if ((h->version==0 || h->version==1) && p.pos != len)
        return 0;
    return 1;
}