Re: [gentoo-user] ALSA wizard...

[Jorge Almeida <jjalmeida@gmail.com>]

On Thu, Apr 23, 2020 at 5:54 PM Michael <confabulate@kintzios.com> wrote:
>

>
> > > > > The setup:
> > > > > -- a microphone connected to an audio interface, which connects to an
> > > > > USB port in the computer. The interface works like a USB sound card,
> > > > > at least regarding sound capture. It works: I can record my voice with

> >
> > Yes, and the device works for recording; the playing together with the
> > other card (for output) is the problem, which I believe is a matter of
> > having an appropriate .asoundrc (the syntax of which beats me)
>
> OK, have a look at the end of this message for an example.
>
>
> > > If an application like vlc allows you to get audio output by
> > > switching devices, then you know you will have to change the order of your
> > > cards as they are detected by the kernel.
> >

> Not relevant, but if the RCA is detected as a serial modem or what not, you
> may need to also be in dialup group.

I checked the kernel messages, nothing seems relevant.
>
>



> OK, I believe you need to use the "asym" alsa plugin to combine input from one
> card and output through another.  I have not used this before - I'd probably
> opt for jackd instead.  Some experimentation may be necessary to get the
> manual setup as you want it.  Have a look at this page:
>
> https://github.com/opensrc/alsa/blob/master/lib/md/Asym.md

Good link, I didn't knw this one.

>
> Essentially, you define two cards, for two different functions, then use the
> asym plugin to combine them.  Something like this?
>
> # Specify the MoBo card as the default
> pcm.!default {
>         type hw
>         card PCH
> }
>
> # Retain controls on this card for alsamixer and applications
> ctl.!default {
>         type hw
>         card PCH
> }
>
> # Now the USB device
> ctl.!USB{
>         type hw
>         card CODEC
>         format "S16_LE"
>         channels 1
>         rate 44100
>         #more options here
> }
>
> # Join the I/O devices
> pcm.duplex{
>         type asym
>         playback.pcm "default"
>         capture.pcm "USB"
> }
>
> See how the above works and consult the asym page for further tweakerage.

I need the "virtual" card to be the default, so I did this:

pcm.mbcard{
type hw
card PCH
device 1
}
ctl.mbcard{
type hw
card 0
}
pcm.usbcard{
type hw
card CODEC
device 0
}
pcm.output{
type plug
slave.pcm "mbcard"
}
pcm.input{
type plug
slave {
pcm "usbcard"
channels 1
}
}
pcm.!default{
type asym
playback.pcm "output"
capture.pcm "input"
}

(The microphone is mono, hence the channels entry. I'm not sure it is needed.)

I think this sets the defaults, because:
--I can record with "arecord -fdat test.wav"
--I can playback with "aplay test.wav"

What I cannot do is to coax discord into working. Maybe discord
doesn't expect ALSA's defaults after all?
Anyone familiar with discord? (No gamers?)

Thanks

Jorge