Re: Handling complex matrix mixers in ALSA

[Mark Hills <mark@xxxxxxxx>]

On Mon, 1 Jul 2024, Asahi Lina wrote:

[...]
> The problem is that the device has a 66x34 matrix mixer, with up to 2048
> cross points enabled at once. Exposing each cross point as an ALSA mixer
> control (similar to how mixer_scarlett2.c does it) would mean 2244
> controls just for the mixer... which seems like a bit too much.
> 
> On top of that there is also VU meter feedback for all the
> inputs/outputs, as well as general fader controls for each output and
> global output configs and status. I'm not sure about the VU meters, but
> everything else sounds like it would map fine to normal mixer controls.
> 
> Is there some recommended way to expose this kind of matrix mixer
> interface to userspace?

I don't know if it's recommended practice, but the echo3g driver may be a 
prior art as it has a working matrix mixer for the Layla, and the 
corresponding echomixer in alsa-tools.

> I think for something like this you pretty much have to rely on 
> device-specific tools to make the UX manageable

For a full UX, perhaps. But the concept of a matrix mixer itself is 
general enough.

Perhaps there could be a UI tool which is self contained with one purpose, 
to control a 'standard' matrix mixer. It could be invoked alongside 
alsamixer or other mixer tool, and multiple times if there are multiple 
matrix mixers on a piece of hardware.

-- 
Mark