How can I optimize this code?

I was trying to make a 60i->24p+simulated motion blur script for half an hour, and I could only get it to work like this: loadcplugin("c:\program files\avisynth 2.5\plugins\yadif.dll") loadplugin("c:\program files\avisynth 2.5\plugins\mvtools2.dll") source = AviSource("Tape 2 - Clip 012.avi").ConvertToYV12().AssumeBFF().Yadif(1).RemoveGrain().Blur(0.16) super = source.MSuper() mvbw = MAnalyse(super,isb=true) mvfw = MAnalyse(super,isb=false) source.MFlowFps(super,mvbw,mvfw,num=24000,den=1001) super2 = last.MSuper() bv = MAnalyse(super,isb=true) fv = MAnalyse(super,isb=false) last.MFlowBlur(super2,bv,fv,blur=20) I'm getting ~6 fps output. Is there any way I can make it faster? Also, if the original footage was filmed with 1/60 shutter speed, what blur value should I input into MFlowBlur if I want it to look like it was filmed with 1/48 shutter speed?

If you have a dual core cpu, you could use MT Avisynth.

How would I run MFlowFps and MFlowBlur multithreaded? SetMTMode?

There's not much you can do. Unless you're willing to sacrifice some quality, you can't really make it faster. Edit: Yes, you would use SetMTMode if you want to use MT. MVtools 2 supports multithreading nicely with SetMTMode, unlike the last (depreciated) version. Be sure to put your SMM() call ALL the way at the top of your script.

Yeah, I'm sticking with simple Yadif() 30p, because the crazy slow speed and artifacts of MFlowFps and MFlowBlur just aren't worth it.

I'm not surprised at all you're getting artifacts like that: You're doing frame rate conversion on an -interlaced- source. No good! I didn't notice this at first. I thought it was 60p -> 24p. Try doing yadif -> 24p + motion blur instead.