Clips at zero alpha should bypass mixer (and audio at zero volume)

[silverbacknet]

One of the largest problems I have in large projects is that clips that are completely zeroed out still hit the CPU hard. During transitions, it's expected, but not for all 20 clips that are in the timeline -- but only 2-3 with an alpha other than zero -- to make playback stutter and exports take forever.

As an example of one of my use-cases, I may add a single longer clip 4-5 times, shifting each one, to pull different segments from and blend between. Having to cut it down before even editing to decide where to put the cuts is painful, but it's something I have to do if I want it to play back in real-time. Then likewise for layers on top that I only want a little bit from.

So anything with zero opacity or volume should just bypass the mixer completely, instead of mixing nothing.

I plan to look into the code to see how this might be possible.