Outputting to two sound cards with ALSA
 

Hi,
I have a Dell Inspiron 15R laptop. It has two sound cards: one for the internal speakers and headphone jack, and one for the HDMI audio. Originally, the default was the HDMI, but I fixed that with the help of this thread: https://www.linuxquestions.org/quest...er-4175506142/

The configuration that set the internal speaker card as default:
/etc/asound.conf
~/.asoundrc
While that worked, I'd like to be able to use HDMI audio as well, if I connect my laptop to something over HDMI.
Using this guide (http://slack4dummies.blogspot.com/20...ple-sound.html) I came up with this /etc/asound.conf, and no ~/.asoundrc
However, that isn't working. Not only does HDMI audio not work, but the internal speakers aren't doing anything either. When I try to open alsamixer, I get this error:
I had to move my asound.conf out of the way and reboot in order to get this output, but I know that you'd ask for it anyway :D
When I open alsamixer and go to the HDMI sound card, there are no "slider" bars. Instead, there are three "S/PDIF" options that only have the option to mute/unmute. Could that have anything to do with why it failed?

I apologize if there's some ridiculously stupid mistake in there. I'm still having trouble wrapping my head around the syntax of these files.

At first glance, there seem to be several things in that asound.conf that reference things not defined anywhere.

First off, there are certain difficulties with merging two sound cards. From my work on jackd I learned that, unless the two cards are sample-synchronized, there is a very good chance it will just not work reliably.

It may work well enough for the desktop pops and clicks, or for watching a movie, but may well fail after a few hours, when one of the dmix buffers underflows.

That said, when using type hw, card must be numeric, not a name. Refer to your aplay -l output for these numbers. In your case, the HDMI audio port is port 0 and the analog is port 1.

This gives you:

pcm.onboard {
type hw
card 1
}
ctl.onboard {
type hw
card 1
}

pcm.hdmi {
type hw
card 0
}
ctl.hdmi {
type hw
card 0
}

Now the names "onboard" and "hdmi" are defined.

The next bit is the DMIXers. You need them to allow different programs to set different sample rates.

Here you had "internal", which wasn't defined. Changing this to "onboard", which _is_ defined, makes it look like this:

pcm.internalDmix {
type dmix
ipc_key 1024
slave {
pcm "onboard"
channels 2
}
bindings {
0 0
1 1
}
}

pcm.hdmiDmix {
type dmix
ipc_key 2048
slave {
pcm "hdmi"
channels 2
}
bindings {
0 0
1 1
}
}

Finally, your router:

pcm.both {
type route
slave.pcm {
slaves.a.pcm "internalDmix"
slaves.b.pcm "hdmiDmix"
slaves.a.channels 2
slaves.b.channels 2

bindings.0.slave a
bindings.0.channel 0
bindings.1.slave a
bindings.1.channel 1

bindings.0.slave b
bindings.0.channel 0
bindings.1.slave b
bindings.1.channel 1
}

ttable.0.0 1
ttable.1.1 1
}

Nothing seems to be wrong here.

And your output defaults.

pcm.!default {
type plug
slave {
pcm both
}
}

ctl.!default {
type hw
card 1
}

Note how I changed the CTL default to be a number here again?

Now, I have no way to test this, but it should give you a nudge in the right direction.

- Melanie

Thanks for the reply!

Unfortunately, your suggestion did not help. Just to double-check, here is the latest asound.conf:
If it helps, this /etc/asound.conf makes the internal speakers work (no HDMI):

I think I'm going to leave good enough alone.

Also, I was directed to a "more correct" method on the debian-user mailing lists: https://lists.debian.org/debian-user.../msg00985.html

This has the added benefit of making my internal microphone work. I don't use it often so I didn't even realize that it wasn't working; but it does now. :)