Comment 36 for bug 1481170

Reviewing the above discussion and thinking about this more, I think the original proposal to cut off input when the enable switch is turned off and stop processing when the output gets below a threshold is the best approach. Depending on each effect to implement its own way of shutting itself off cannot work for external effects, but this approach will. I don't think it's necessary for Mixxx to automatically fade out effects like the Bitcrusher that stop producing output when their input is cut off. Suddenly switching those kinds of effects on and off can be used in a musical way. If Mixxx automatically faded out such effects, there would need to be an additional parameter to control how long that takes, but the chain dry/wet knob can already serve that purpose.

I will implement this by moving the enable state onto the GroupFeatureState. For effects that would keep producing output indefinitely, it would be up to the effect to set the enable state to fully disabled from the intermediate disabling state.

Any approach that complicates the user experience with more COs or preference options is a non-starter for me.