[ale] Two different audio streams output

Ed Cashin ecashin at noserose.net
Wed Oct 23 12:50:28 EDT 2019


I have gone *way* down the rabbit hole on Linux audio and wanted to share
the gotchas I can remember.

First, jack is the conventional choice for serious audio in Linux.  It is
like a software patchbay with support for "transport" that synchronizes
different things.  To use it, you're best off choosing a "lowlatency"
version of your kernel, but you can try it without.  You also have to
either stop using pulseaudio or get it to play nice with jack, but
pulseaudio should be expected to behave like a bad sport.  To first get
jack to work, I had to find the /etc file where pulseaudio was implicitly
configured to respawn and configure it to NOT respawn.

It's possible to use CLI and scripts to automate jack connections, but I
use Claudia, a GUI that allows connections via drag and drop.  It will
restore connections when the previously connected things reappear.

For MIDI, ALSA's MIDI support is good and jack's is ... not really
conventional yet, so I use "a2j -e" to get the ALSA MIDI stuff to show up
in Claudia, so that I can connect things.

With all that working, you'll be able to route audio in Claudia to your
heart's content.

For USB audio devices, sometimes you'll hear that things don't work and
they really do.  A Scarlett Solo pretty much just works.  My Scarlett 18i8
only works right if Linux is already booted and connected via USB when I
turn it on.  It sometimes (every couple months?) gets confused, and a
reboot sorts things out.

It is often problematic to use two audio devices at the same time.  It's
easier to get jack to use a single audio device that has as many inputs and
outputs as you need.

On Wed, Oct 23, 2019 at 11:34 AM Pete Hardie via Ale <ale at ale.org> wrote:

> G'day all,
> I'd like to have my Linux laptop emit 2 different audio streams to
> different outputs, basically music to one output and sound effects to
> another. What's the latest way to do this? I know I'll need another output
> device, and was considering a USB audio adapter.
> _______________________________________________
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> Ale at ale.org
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  Ed Cashin <ecashin at noserose.net>
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