@Flexy:
My guess is that it crashes because you're using a codec to encode the output of pass 1 that can't handle the extremely small video output (8x8 pixels). It works for me.
@Warp:
Yeah, I guess that could be a useful feature. But it means a lot of work, and I hate programming.
We'll see...
I use all kinds of smoothness values (400-100000). It depends on the clip.