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?

[Keiyakusha]

Never noticed that option. Thanks for notifying, will give it a try.
As for your issue, if it works in the way you think, this option will only speed up something when VDub is the bottleneck. But since avisynth is a slowest thing in the Universe, VDub's part of the work on current frame may be finished long before avisynth will even think of preparing next frame. GradFun2DBmod is pretty slow filter (like 10 times slower than flash3kyuu). Does anyone still use it?

[Reel.Deel]

I was also curious on what Video filter process-ahead did, so I did a search and found some relevant information over at the German doom9. (http://forum.gleitz.info/showthread.php?43576-Audio-delay-mit-X6-unter-x264vfw&p=416754&viewfull=1#post416754)
I used google translate and this is my interpretation.

Video filter process-ahead:
These settings only apply to VirtualDub's native filters. If VirtualDub is set to "Video: Fast recompress" than the video filter process-ahead settings are simply ignored.

I agree with Keiyakusha, use flash3kyuu (http://forum.doom9.org/showthread.php?t=161411).
I'm also using Avisynth 2.6 MT which does make a difference, even on my old beat up 4-core.