I have noticed an issue in Virtualdub NV ... if there is a black border of less than 16 pixels at the left of the frame, especially a hard edged border, it causes the temporal filter not to clean the left edge of the image. Even a one pixel wide black border disrupts filtration. The right hand edge of the frame is not affected by this issue at all. I suspect the first 16 pixels on the left are affected; perhaps the NV algorithm works on 16x16 pixel blocks.
NV3.0 also has this problem but it seems the demo version of NV2 does not.
Neatvideo 3.1
Virtualdub 1.10.1, 1.7.7
Temporal filter at default threshold, radius = 2
Spatial filtering OFF
I initially thought the problem was due to the edge of the (VHS) frame being noisier than the rest of the image, but cropping 100 pixels from the left (to eliminate this possibility) and adding a thin black border on the left (using the FILL filter in vdub) still leads to the same problem.
I have noticed that turning down the temporal threshold to -100 reveals some kind of spatial filtering in the image (even though I have spatial filtering always set to zero). I presume this to be a pre-temporal filter stage. The improperly filtered left portion of the image, described above, looks just like this spatial filtering.
While cropping the border eliminates the problem, the size of the border on TV shows can vary from one camera shot to the next, thus it is unrealistic to crop every shot. Also I don't want to crop the full 16 pixels from the left of every video I clean.
I have attached a brief raw VHS avi (huffyuv) file (30MB).
http://www.mediafire.com/?ag5k28f22tz57jr
Same clip processed and showing the problem on the left edge :
http://www.mediafire.com/?vgba7cuec2sh2i7
I don't think the problem is related to the noise profile but I have attached one anyway.
http://www.mediafire.com/?qi93du877jvf4mn
I look forward to your reply.
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EDIT - my workaround is to add a 16 pixel black border to the left of the frame in vdub then crop it off after NV cleans the frame.
Left edge black border causes improper filtration
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