thx but, I'm already doing that:
actually I have a video at 59fps, I apply filters this way:
Resample to PAL or less
Change to 200
Resample to PAL
in this way I can change the first resample value to get more or less speed, but its everytime a try and a waste of time and power.
what I am looking for is exactly like in vdub: before to start the encode I have to know which fps will match the audio duration.