The free Canopus DV Codec v1.00 upsamples the chroma channels incorrectly (although newer non-free versions appear to work fine). Chroma is duplicated from the other field, resulting in the famous Chroma Upsampling Error ....
FixBrokenChromaUpsampling filter compensates for it. You should put this after AviSource if you're using the above Canopus DV codec. Old versions of the DirectShow based MS DV codec also might have this problem (the one that comes with DirectX7 (but i need to check this), the one that comes with DirectX8/9 works fine).
The Canopus DV codec swaps the chroma of the middle 2 for each group of 4 lines:
|line 1||line 1|
|line 2||line 3|
|line 3||line 2|
|line 4||line 4|
|line 5||line 5|
|line 6||line 7|
|line 7||line 6|
|line 8||line 8|
For each group of 4 lines FixBrokenChromaUpsampling corrects this by swapping the chroma back.