I have a TV capture which is sourced from an NTSC broadcast of a film, so it's 30i. When I perform an IVTC, it's restored to 24p (or 23.97), but it plays too fast. I need to slow it down around 74% to get to the right speed, which must mean it was originally a 24p film speeded up for PAL, then converted to NTSC for broadcast in North America.

I'm a little confused with "AssumeFPS" and "ConvertFPS" in Avisynth, not sure which applies in this odd situation. Any help would be appreciated. Thanks!