I am trying to configure ALSA to downmix 5.1 surround audio to 2.0 stereo. There is an ALSA output plugin vdownmix
that seems to do exactly this, but I can only seem to use it with my onboard audio instead of my USB soundcard, despite the USB soundcard being set to default. The config in question is /usr/share/alsa/alsa.conf.d/60-vdownmix.conf
(from Debian bullseye libasound2-plugins
):
@args [ SLAVE CHANNELS DELAY ]
@args.SLAVE {
type string
default "plug:hw"
}
@args.CHANNELS {
type integer
default 6
}
@args.DELAY {
type integer
default 0
}
type vdownmix
slave.pcm $SLAVE
hint {
show {
@func refer
name defaults.namehint.basic
}
description "Plugin for channel downmix (stereo) with a simple spacialization"
}
}
The issue seems to be the line default "plug:hw"
, this seems to only let me use my onboard sound instead of USB. What is the proper syntax to tell that to use my USB sound card, or better yet, is it possible for me to modify that to let me use an arbitrary slave device?