Wrong Chroma Problem

[phe]

Hello

I'm doing some capture and found a weird chroma problem

It happens that in some interlaced frames the chroma is swapped between the fields: the field A have the field B chroma and viceversa

Here is a example:



The fields:


Deinterlaced:


I've captured some scenes several times and always happens in the same frame
I'm using virtualdub to capture at 29.9700 wiith M-JPEG but i've tried with Lagarith and it keep happening



Here is a small video sample: http://www.sendspace.com/file/kjh02h

I have no clue what to do now, any advice would be appreciated.

Thanks

[jagabo]

You can fix it by shifting the luma up a line -- that reverses the field order of the luma. But it looks like it needs to be shift up by three lines to get the luma and chroma to line up.

 MergeChroma(Crop(0,3,0,0).AddBorders(0,0,0,3), last)

Or, as a compromise, you could shift the luma up by one line, and the chroma down by 2.

 MergeChroma(Crop(0,1,0,0).AddBorders(0,0,0,1), Crop(0,0,0,-2).AddBorders(0,2,0,0))

Something's not right with the capture process.

[pandy]

Chroma belong to opposite fields? swap chroma between fields - interlace it looks OK so seem that something went wrong later.

[jagabo]

I was concentrating the frame pictured above and didn't notice the chroma is switching randomly (?) between in-phase and out-of-phase. So you have to determine whether to swap it on a frame by frame basis. Much more difficult.