Documentation for "Video filter process-ahead"

[benwaggoner]

I'm using VirtualDub 1.10.2 on a 12-core workstation. I am pained to see it running mainly on a single thread when reading from an .avs file (only filter applied is GradFun2DBmod). It is depressing to see CPU in Task Manager sit there bouncing between 4-5%...

I've got Preferences>Threading set up as

Video compression threads=1
Video filter threading=Auto
Video filter process-ahead=1

I know that Video compression threads=1 allows the encoder to run in a separate thread.

Video Filter Threading=Auto would speed things up if I was using multiple filters, which I'm not

However, I've not been able to find ANY documentation on "Video filter process ahead." My best guess is that, ala After Effects, it'll request multiple future frames when they're non-deterministic, so they can be rendered in parallel. Which is exactly what I'd like to be happening.

However, different values don't seem to show meaningful differences in rendering speed. Could be that the .AVS file (or AVISynth overall) only renders frames serialized.

So, anyone know what this option really does, or have any other suggestions for how to speed things up?