[LAU] Jack-hardware bridging issue

Chris Caudle chris at chriscaudle.org
Wed Apr 1 16:36:23 CEST 2020

The cases you described:

On Wed, April 1, 2020 5:00 am, Iain Mott wrote:
> If Jack is already running (with pulseaudio-module-jack
> uninstalled) and configured to use an external USB sound
> card, starting the daemon results in its audio i/o being
> connected with the laptop's internal mic and speaker.

> Jack is not running, the daemon connects with card 1 listed
> by "aplay -l", which happens to be the USB card.

> Jack is running with pulseaudio-module-jack installed and all
> other non-jack audio apps are routed via the sink to the USB
> card, the telephony daemon again connects
> and runs correctly with laptop's internal hardware.

Based on these descriptions it seems that the telephony application only
connects to the first ALSA hardware device it finds, and all of the other
software on your machine will use PulseAudio, either directly or using the
PulseAudio ALSA emulation.

> I don't think ALSA-Jack loopback scripts will work as I think
> pulseaudio-module-jack does this job now.

It is also possible that this unnamed telephony application is for some
reason checking to make sure that the ALSA device is a true hardware
device and not just a software interface.  Hard to tell whether that is
the case, but usually when PulseAudio is running, devices which use the
default ALSA device will find the PulseAudio ALSA interface first.

If it is the case that the software checks whether the ALSA interface is a
true hardware interface or not then using ALSA-jack loopback may not work
for that reason.

Chris Caudle

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