[vlc-devel] [RFC 0/8] Ambisonics channels support

[Adrien Maglo]

On 24/02/2017 16:40, Francois Cartegnie wrote:
> Le 24/02/2017 à 16:14, Adrien Maglo a écrit :
>> we quickly reach the hard coded limit of VLC on the number of audio
> channels (AOUT_CHAN_MAX=9). It will probably need to be increased.
>
> I don't see the need of increasing the number of channels limited by
> AOUT_CHAN_MAX as, in my understanding, does not belong to the same code
> path:
>
> The ambisonic channels will never be reordered, and you have no aout
> which will support that high number of ambisonic channels, or will just
> support it by ambisonic passthrough. The only ambisonic -> regular
> channels conversion needs to be aware of ambisonic channels count, and
> can still mix output to a mapping within AOUT_CHAN_MAX.

AOUT_CHAN_MAX is also used by the audio decoders.
When trying to decode order 3 Ambisonics raw samples (16 channels), I 
had issue with AOUT_CHAN_MAX, which is currently 9, being to low for the 
raw decoder.

araw.c line 247

if( p_dec->fmt_in.audio.i_channels == 0 ||
     p_dec->fmt_in.audio.i_channels > AOUT_CHAN_MAX )
{
     msg_Err( p_dec, "bad channels count (1-%i): %i",
              AOUT_CHAN_MAX, p_dec->fmt_in.audio.i_channels );
     return VLC_EGENERIC;
}

It may not be the right solution but a simple fix here was to increase 
AOUT_CHAN_MAX. I think this is currently also a problem for other audio 
decoders.

Best regards,


-- 
MagSoft