[tsp]

hartford: function is like the function to the buildt in filter scriptclip. So it can be an internal(build-in) or external(plugin) filter or a function that is defined in an AVS file. just remember the quotes(or triple quotes) because it's a string. So your example would be like this:

Avisource("d:\test-mt.avi").ConvertToYV12

Telecide(order=1,Post=0,Guide=1)
Decimate(Cycle=5,Mode=0,Quality=3)
mt("fft3dgpu(sigma=4.0,bw=32,bh=32,bt=3,plane=0,mode=2)")

But fft3dgpu doesn't work well with MT because only one thread at a time can acces fft3dgpu (Directx really hates multithreading)

you can also use it like this:

Telecide(order=1,Post=0,Guide=1)
Decimate(Cycle=5,Mode=0,Quality=3)
MT("fft3d()")

function fft3d(clip c)
{
c
fft3dfilter(plane=0)
fft3dfilter(plane=1)
fft3dfilter(plane=2)
}