Refactor effect superknob linking

[Daniel Schürmann]

This bug is to continue the discussion at
https://github.com/mixxxdj/mixxx/pull/207

rryan:
Ah, can't we call setParameter(chainParameter) now instead of this log vs. linear logic?

rryan:
Ah, now I see. To get rid of this logic the superknob parameter linking should flow from EffectChainSlot -> EffectSlot -> EffectParameterSlot -> value CO instead of from EffectChainSlot -> EffectChain -> Effect -> EffectParameter::onChainParameterChanged(...).

[Daniel Schürmann (daschuer)]

To be honest, I have not managed to get the new signal and control flow entirely.
A drawing will be really helpful here Bug #1298817

But as far es I get, I got the impression that there is still something weak.
So we should tweak the super knob a little bit.

Controlling two parameter with the superknob feels wrong, because for the desired effect you need a special, probably different scale for the controlled parameters. This is a desired feature, but lets move it to 2.0 to keep things simple.

Idea: (maybe some things are already in place)

SuperKnob:
* One SuperKnob for the each EffectUnit. This is connected to the first parameter of the fist Effect in the Chain.
* Once you work with two effects in a chain, the superknob moves (is focussed) on the last enabled effect
* Add a read only "superknob_focus" CO to reflect this in the GUI
* the superknop linking should be moved one layer up and actually use "setParameter()" of the parameter CO
* For use cases with two or more parameter knobs per effect unit we map the knops in consecutive order to the first parameter of each effects in the effect chain.
* When defining the effect, it is possible to setup an an artificial parameter as first one. In case of the bitchrusher, we may introduce a "LowFi" control, which acts on the bit_dephs and downsampling parameter, in a way that it sounds as desired.

D/W:
* replace the "Mix" control with a "D/W" control on the EffectUnit Layer. Full Stop.
* If a Effect like delay, needs a own "Mix" control to be an end effect "echo" in this case, it should be introduced inside the effect as normal parameter. Preferred: Parameter 2". We may add it in general to all Effects, but introduce correct labeled as "D/W" for Insert effects or "Level" for Send effects.

http://www.reasonexperts.com/video-tutorials/getting-started-with-reason/Send-effects-vs-Insert-Effects.html

Link to the original PL https://github.com/mixxxdj/mixxx/pull/180

This concept can resist even if we introduce 2.0. We only need a Wrapping effect for external VST effect. Which introduces the probably missing Parameter1 and Parameter2 for configurable Superknob mapping with desired scales and "Mix" control.

[RJ Skerry-Ryan (rryan)]

Hi Daniel -- the whole idea behind the superknob is effect parameter linking and this terminology is also found in other software.

I think what you are proposing is virtual parameters or a built-in feature for focus selection with a MIDI Controller. I think that's a separate use case from superknobs.

It will be confusing if we claim something is a superknob and really it's something else.

Focus for MIDI controllers is a problem we face in multiple areas so we should come up with a common solution.

Also, I think I lost you once you started talking about dry/wet. It also sounds like a different bug than this one. Can you clarify what you mean there?

RE: per-effect D/W. Dry/wet calculation is expensive and prevents in-place processing of the buffers. If we really need d/w per effect then it should default to wet. I'm not convinced we need it though. Again this is a separate bug though -- please file?

[RJ Skerry-Ryan (rryan)]

Fix is here:
https://github.com/mixxxdj/mixxx/commit/aecd024fa84bc915e6c80d82d55ed8fa3612938a

Much better!

[Daniel Schürmann (daschuer)]

I have created Bug #1299215 for the remaining issue

[Daniel Schürmann (daschuer)]

> Also, I think I lost you once you started talking about dry/wet. It also sounds like a different bug than this one. Can you clarify what you mean

 Wasn't there a version where the insert type was set from the effect? Just read the Insert code again and it is fine like it is. Sorry.

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/7381