Ghosting Problem

[SameSelf]

I have two different NTSC caps with slightly different proc settings that I am filtering with the latest version of Average. However, for certain portions of the video where there is significant motion, severe ghosting is introduced. I tried de-interlacing the caps prior to averaging but it doesn't make any difference (plus de-interlacing two vids instead of one is quite cumbersome). As soon as I turn off the Average filter the ghosting is gone, so I know it is the Average filter introducing the ghosting.

Has anyone else seen this problem or know a solution? Maybe I need to post a bug report? I just don't understand why averaging two fields/frames would be so hard?

[poisondeathray]

Are you sure they are aligned during those parts ? For example if one cap has dropped frames or duplicates, they aren't really aligned properly => ghosting

What kind of "different proc settings ?" Because if one is oversharpened , or has overbright edges, and the other doesn't you can get ghosting too

[johnmeyer]

I first did multiple capture averaging (to reduce noise from VHS tapes) over fifteen years ago. While the theory is great, and the results can sometimes be spectacular, in actual practice the alignment issues are very difficult to deal with. The problem is that captures can very easily get off by a field, simply due to timing issues (the time base for the analog video has to be perfect, and of course, it is not). Since there is no concept of "upper" and "lower" field in analog NTSC video (it is just a series of scanning lines), that concept gets introduced during the capture (A/D conversion) process. It is very easy to have one capture suddenly be off by a field or two. This will create temporal ghosting. In addition, unless you have a commercial TBC, you can also get time base offsets which will give you spatial ghosting.

Both of these things will result in ghosting (offsets) that come and go.

The solution is to line up both captures on your NLE timeline and, where the ghosting happens, split one of the videos and offset it in time until the two align. You might end up with a duplicate or drop at that point, but if you are clever you can mitigate that so you'll never notice it. For the spatial offsets, you have to move one capture up/down/left/right until it perfectly aligns with the other one. This is a lot of work, but if you're willing to do it, you can fix the problem.

[SameSelf]

OK, after closer inspection, the caps had slightly different starting points in my NLE which is why I didn't catch it. User error on my part as they say. Other than that, there is very minimal duplicate/dropped frames throughout the caps thankfully.

Thanks for the insights guys.