auxilliary send bus

[Be]

As discussed in https://github.com/mixxxdj/mixxx/pull/1254#issuecomment-346853954 , it is not technically possible to implement send/return loops for hardware effects in our effects system that supports switching signal paths during a performance. However, external effects could be used with Mixxx by implementing an auxiliary send bus. Every EngineChannel would have a binary ControlPushbutton added to it to send to this new auxiliary bus and the whole bus mixed together would have an output gain knob.

To interface with hardware effects, a sound card output could be configured for the auxiliary send bus. The output of the hardware effects would have to be mixed in hardware with Mixxx's other outputs without going back into Mixxx to avoid introducing a latency offset between the hardware effect's output and Mixxx's other outputs. This could be done either by running the output of the hardware effects to a dedicated hardware mixer or running the hardware effect's output back to a sound card input and using direct monitoring.

We may consider making the sends to the auxiliary bus configurable between prefader and postfader positions in Mixxx's signal chain. Prefader sends would allow taking the channel out of Mixxx's Master output and having only the effected signal heard by the audience like an insert effect. Postfader sends would be like Mixxx's effect chains in send mode (as described in Bug #1662049).

This auxiliary send bus may also serve other use cases we have not thought of yet.

[Daniel Schürmann (daschuer)]

Related: bug #1097070 bug #1430464

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/9020