Insert effects via JACK

[egasimus]

Mixxx already has separate outputs for each deck, as well as Aux inputs (which I couldn't quite figure out how they work but I assume they allow you to feed external inputs into the application's mixer). However, last time I tried this still did not allow me to run the signal from a deck through external software FX (such as a Carla rack) and back into the mixer. Is there any way to get that behavior with the current development version of Mixx, or are there any plans to make it possible?

[Be (be.ing)]

I think this should be implemented in a way that does not require involving Mixxx's auxiliary inputs. There should be a straightforward interface in Mixxx for setting a deck to send its signal to a JACK sink and back to Mixxx. Mixxx would automatically create a new JACK sink for the deck when this feature is used.

[Daniel Schürmann (daschuer)]

This bug is somehow blocked by this: Bug #1172299
Mixxx needs to become a native Jack client

Also related:
Bug #1097070
Bug #1370837
www.mixxx.org/wiki/doku.php/extending_the_effects_engine_report_w7
http://www.mixxx.org/forums/viewtopic.php?f=1&t=6590&p=22616&hilit=send+effect#p22616

[Owen Williams (ywwg)]

It's most likely that this bug will get fixed when Mixxx gets support for effects plugins like LADSPA.

[Daniel Schürmann (daschuer)]

Probably not, because we have already a LV2 (LADSPA successor) branch without a Jack interface https://github.com/mixxxdj/mixxx/pull/359.
So if one like to adopt this, fix Bug #1172299 and then introduce an Effect that routs to Jack.

[Owen Williams (ywwg)]

What I meant is, we probably won't do this, instead focusing on bringing effects into mixxx rather than piping audio out to other applications.

[Be (be.ing)]

As discussed in https://github.com/mixxxdj/mixxx/pull/1254#issuecomment-346853954 , external software effects would be supported much better by implementing support for plugin formats designed for this purpose such as LV2 (Bug #1530238) and VST (Bug #1740335). We cannot use Mixxx's controller mapping system to interface with separate programs in a reliable and intuitive way, but we can do that with effect plugins.

As for send/return loops with hardware effects, that is not technically possible because our effect units have switchable inputs and a hardware send/return loop introduces more latency. The extra latency could only be compensated for to keep all channels aligned if the signal path was fixed. Switching the latency of a signal path during playback would create brief gaps of silence and the signal path with added latency would be misaligned in time with the other channels.

[Daniel Schürmann (daschuer)]

We should still consider this use case together with the send / return feature. https://bugs.launchpad.net/mixxx/+bug/1097070

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/7889