snd_uaudio multichannel problems

[Hans Petter Selasky]

On 10/10/16 19:31, Goran Mekić wrote:
> Hello,
>
> I own 2 18ch audio interfaces, and both have the same symptoms described in https://lists.freebsd.org/pipermail/freebsd-questions/2016-October/273960.html. Since I wrote that mail, I did a little research. My hypotesis is that audio is 9 times faster as driver is handling 18 channels like they are 2. Also, if something for stereo stream is sent to all outputs, you expect to get some small and very high pitched output on all out jack, and I do. Also, playing with http://manuals.opensound.com/developer/singen.c.html revealed to me that if SNDCTL_DSP_CHANNELS is set to number different than the number of actual channels in a working stack (laptop and it's internal audio interface, in my case), you get difference in pitch and volume.
>
> I didn't poke snd_uaudio code, yet, as I didn't do any kernel development before, but I'm affraid the number of kernel developers with multichannel audio interfaces is quite low, so I don't mind getting my hands dirty, but I'd love to get some advice before I attack this problem. Thank you!
>
> Regards,
> meka
>

Hi,

Up to 127 channels are supported using USB audio.

Which version of FreeBSD are you using?

What does dmesg say about your audio device.

Channel numbers above 8, are only supported through bitperfect modes. 
Then you'll need something like virtual_oss, to subdivide the audio 
device into several 2-channel or 1-channel DSP devices.

svn --username anonsvn --password anonsvn \
       checkout svn://svn.turbocat.net/i4b/trunk/virtual_oss

cd virtual_oss
make all install
man virtual_oss

--HPS