mplayer > avisynth > mencoder ?

Because mencoder cannot convert fps (or resample fps ... call it whatever you want) and just drop frames and then sync i wanted to make it in avisynth, but don't want to use avisynth loadavi (i don't know if source will be avi) neither loaddirectshow - i don't want to use directshow input because it require decoders etc.

So is there a way how to pass video output from mplayer to avisynth and then encdoce it's output with mencoder?

... or some other way to resample fps/convert fps in mencoder?

AFAIK you can not import a script from mplayer to avisynth. I can't say I'm familiar with mencoder but avisynth. I use directshow input and there are very few times when ffdshow can't playback a video for me.