I need to clarify when I refer to TDecimate I'm referring to both TDecimate and VDecimate (which is a port of it to VapourSynth)
Time and time again I see people using this function to decimate for inverse-telecine purposes but I implore you to continue reading this and use an alternative decimation method.
Simply put, it's far too inaccurate and it is ruining a lot of encodes.
