Need help with pulldown

[videoFred]

Hello everybody,

I'm using Avisynth and VirtualDub for processing my old digitised 8mm films.
I use a 1024x768 machine vision camera for this, frame by frame recording.
The captured AVI's are 1024x768 15fps, Huffyuv codec. But the original films where about 16fps, sometimes 18fps (Fuji Single-8).

For use on DVD, my editing program does the 25fps pulldown (mpeg2), but on some scenes I need a better pulldown. I found this exellent script from Fizick, using his DePan functions. I understand this script creates new frames, more then we need, and than we select the frames we want, right?

But can someone explain me exactly what it does? I don't understand the 'offset=1./3'

Also, is it possible to make a similar script for a 18/25 pulldown? (about 4/3: 18.75/25)



Here's an example clip (divX) 1972, Fuji single-8 film:
ftp://ftp.filmshooting.com/upload/video/avi/videoFred_DivX_Suzuki.avi



Here's the script:

*************************************************************************************
function fps2to3(clipYV12)
{
# change FPS from 2 to 3 (or 16.66 to 25, or 20 to 30 and so on), i.e. with factor=3/2
# uses global motion compensation
# input must be YV12 progressive (or separated fields probably ?)
data = DePanEstimate(clipYV12)
f1_3 = DePan(clipYV12, data, offset=1./3)
b1_3 = DePan(clipYV12, data, offset=-1./3)
Interleave(f1_3, clipYV12, b1_3)
SelectEvery(6, 0, 1, 2)
}

AviSource("001.avi")
assumeFPS(16.666)
LoadPlugin("depan.dll")
ConvertToYV12()
fps2to3()
*************************************************************************************

Thanks in advance,

Fred.