Deinterlacing chroma errors, help!

[koopa]

Finally, I caught the bugger, I've been having some colour deinterlacing errors, and I've never quite been able to put my finger on it... finally this clip has made it obvious.

http://www.2shared.com/file/5225725/3e159251/Colour_Errors.html

I always deinterlace to 50/60fps (normally 50 because I live in PAL region), and for less important material I use YADIF, otherwise TEMPGAUSSMC. But there are always colour errors. It's like the luminance is TFF, but the colour is BFF, so I can't have both smooth?

It doesn't matter what source it is (commercial, DVB, DVD, my handycam, VHS@CANOPUS300), same problem.

It doesn't matter what Avisynth import I use, mpeg2dec, avisource, directshowsource.

And yet, by using TMPGenc with "Double Framerate via Interpolated-Adjusted", it comes out fine... so it's not my directshow filters?

Any help would be much appreciated (and I'll clean up my post immediately if I'm breaking some upload rule, I tried to use just 20 frames (less than a second) of my source in the most obvious part).

Cheers!

[koopa]

Oh and here's the MPEG2 original source (nearest I frame cuts)

http://www.2shared.com/file/5225868/2f946cd5/Colour_Errors_Original.html

[Didée]

Compare to see what you did wrong:
mpeg2source("Colour Errors Original.d2v")
v1 = crop(8,2,-8,-2) .bob()
v2 = bob() .crop(8,2,-8,-2)
stackhorizontal(v1,v2)

IF you are cropping an interlaced YV12 clip before (bob-) deinterlacing, then the vertical crop numbers must be mod4 (modulo-4, evenly divisible by four). When you crop the top border by [2,6,10,14,...] before deinterlacing, then the top/bottom fields are swapped to bottom/top. Cropping vertically by [4,8,12,16,...] pixels is OK.
In case of doubt, don't crop (vertically) before deinterlacing.

[koopa]

That completely fixed it, thanks very much Didée!