Micro Buffer "inputRate" doesn't work because alpha isn't set on persisted 1x1 accumulator buffer.

[gmatters]

Empirically in ISFEditor (macOS 10.12.6, MacBook Pro (Retina, 15-inch, Mid 2015)), "inputRate" doesn't work and the buffer chain is advanced every frame. I could fix this by setting adding the following to pass 0:

srcPixel.a = 1.0; // Without this values don't persist (pre-multiplied away?)

after which the accumulator implemented in pass 0 works, the buffer chain can update less often than every frame, and the buffer chain allows access to further in the past.

Probably Micro Buffer RGB has the same problem.