Avisynth only using 30% of CPU

[Asterra]

For whatever reason, Avisynth (via VirtualDub) is making very poor use of my CPU. I'm using v2.6 MT, and all four of the cores are being used more or less equally, but the average CPU usage is about 25 or 30%. It fluctuates wildly between 15% and 40% (with some cores spiking to ~85% on rare occasion).

I have caught hints that there are supposed to be ways to force Avisynth to more fully utilize the CPU, but those hints are really all I've been able to find. You'd better believe I'd rather have these encodes done in 12 hours vs. 36.

If it matters, here is an example script:

Import("c:\Program Files (x86)\AviSynth 2.5\plugins\DeStripe.avs")
AVISource("file.avi")
AssumeTFF
ConvertToYV12(interlaced=true)
QTGMC(preset="Very Slow", sharpness=0.5)
DeStripe(rad=2, offset=1, thr=16)

(No comments on the efficacy of using something besides "very slow", please. As it happens, with the footage in question, anything faster generates unwanted artifacts in the output.)

[Baldrick]

One similar thread is enough. COntiune in https://forum.videohelp.com/threads/334045-Ways-to-speed-up-rendering-with-VirtualDub-A...30#post2072430 .