[ubuntu-studio-devel] Re: PipeWire/JACK Findings (Was: Ubuntu Studio on Gnome (23.04))

[Erich Eickmeyer]

On Wednesday, July 12, 2023 12:15:42 PM PDT Ross Gammon wrote:
> On 7/12/23 19:49, Ross Gammon wrote:
> > On 7/12/23 19:46, Ross Gammon wrote:
> >> qpwgraph is a QT GUI interface to wireplumber which is in Lunar.
> > 
> > Correction - qpwgraph depends on pipewire itself and not wireplumber.
> > That was a wrong assumption on my part.
> > 
> > Ross
> 
> Well I had a play with qpwgraph and pipwire, and the some of the Ubuntu
> Studio audio tools with 23.04 (Lunar) on Gnome - and you can do stuff!
> 
> But I see what everyone means about pro-studios. It is all a bit clunky.
> and latency is a problem without an easy way to get in and fiddle with
> the settings. At least - one that I know of.
> 
> Apparently you can use some pipewire command line tools. But the manpage
> is light on information. I suppose your Ubuntu Studio Audio Config tool
> will help here - now I understand better what you were saying about the
> PIPEWIRE_QUANTUM variable.
> 
> With qpwgraph, I could make all of the connections that I used to make
> with The patch section of Carla. But everytime I clicked on another
> window, and then clicked back to qpwgraph, its window was un-maximised.
> 
> Hydrogen works.
> 
> I recorded an extra track into a previous Ardour project. Latency!
> 
> I recorded my electric guitar into an extra track via Guitarix. Same
> problem - naturally.
> 
> I played FluidSynth via the Virtual Keyboard without going into Ardour -
> there wasn't much point recording my virtual keyboard playing skills :-)
> No problems.
> 
> I didn't bother with any other effect/EQ plugins.
> 
> So. I didn't confirm what sample rate settings were being used. But if
> you can deal with the latency issue, you can do some rough/basic audio
> work on pipewire. For a true amateur like me - it would be OK after the
> latency is fixed.
> 
> Cheers,
> 
> Ross

Hi Ross,

I experimented today with bridging PipeWire/JACK using Studio Controls and 
QJackControl.

I could get JACK started with QJackControl, but there appeared to be no automatic 
bridging of JACK to PipeWire. In fact, all PulseAudio emulation of PipeWire seemed 
to be killed when JACK was started as indicated by a lack of audio device as shown 
by both Plasma and pavucontrol.

Studio Controls, however, would not cooperate as Autojack would crash if it couldn't 
stop PulseAudio via systemd (if systemd returned an error). This indicates that 
PulseAudio is a hard dependency of Studio Controls and I need to adjust the 
packaging as such.

However, this much I did discover: It seems as though the PipeWire JACK emulation 
(pipewire-jack) can be started/stopped on the fly by removing the symlink the 
ubuntustudio-pipewire-config package creates and running ldconfig. This might be 
good for people who want to simply run JACK without PulseAudio as I could simply 
write a piece of the Ubuntu Studio Audio Configuration app to include a part to 
enable or disable pipewire-jack.

Honestly, this is great as now the professional audio people don't have to 
completely rip-out PipeWire anymore unless they want to bridge system audio to 
their JACK setup, in which case we can still leave ubuntustudio-pulseaudio-config 
around (doesn't solve the ubuntu-desktop hard dependency issue, I know, but I'll 
address that with them in a bug report). Simply unchecking a box in Ubuntu Studio 
Audio Configuration to turn-off pipewire-jack and starting JACK via QJackControl 
would leave people with a professional way to do what they need to do, so long as 
they know what they're doing (I still feel as though QJackControl doesn't have the 
best UX).

In an IRC channel, I saw some tips on how to reduce PipeWire's latency with ALSA, 
so if those items can be implemented in a systemwide config, I might  implement 
that as well.

-- 
Erich Eickmeyer
Project Leader - Ubuntu Studio
Technical Lead - Edubuntu
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