Witness protection not working correctly on interlaced footage

Avid 2018.12.11
Mac OS 10.13.6
8 core Mac Pro Late 2013, 32GB RAM, AMD FirePro D500 3072MB
Project settings: 1080/50i

Applying witness protection and tracking car numberplates etc I am finding that on field 2 the effect is acting as if it was already on field 1 of the next frame i.e it is jumping ahead to the next field therefore not covering the full license plate on field 2 of the previous frame. I have fields set to “Quality Optimised” in the general menu.

Is there some way to fix this so the effect respects the correct field?

Ok, it turns out that if I flip the project to 25p, then re-render as P then flip back, that works. Does Mocha only work in progressive?

Hi Andi, I tested on Win with the released BCC 14.0.3 in Avid with both 25p/50i & 29.97p/59.94i projs setups & I see no drift in i projs. Possible to send your proj & sys specs plus BCC vers you are running etc? If possible please send a scrrencap showing the drift. This may help repro the problem.


  • Mukesh Shah
    Boris FX/QA

Thanks for testing Mukesh. Unfortunately I’m not at that facility anymore for a while now. They were running a slightly older version I think. The effect was essentially offset on field 2. Doesn’t show up in the Avid UI but on a connected monitor displaying an interlace signal it’s there. Possibly it’s been fixed in a newer release I guess. Never mind though, was fixed by rendering in progressive so I worked around it.