g-force said: Sorry, I've been busy

No apology is necessary. I know the feeling!

The real reason I asked about the YUV version is to circumvent the colorspace conversions. Going to RGB and back once is fine, but the multiple conversions still worry me a bit, which is why I wondered if the existing option to apply the difference between two clips to a third would be one solution.

It's a shame Avisynth is 8-bit only. A 32-bit workflow would help here.

By the way, I don't think I've sent you any e-mails that you haven't replied to. :-)