Has anyone successfully filtered mosaics?

[FredThompson]

I realize they're very different in nature than VHS dropouts because they'll make mosaic smears. Just wonderin if anyone has foudn a way to filter this kinds of impacts. They're usually for one frame only then disappear.

[bb]

If it's just one frame, you could use a painting program to fill the mosaic with a medium grey rectangle. Then use AviSynth and a temporal smoother to average the frame with its predecessor and its successor. Maybe it's even better to use Layer somehow, so that the filtering gets applied in the wanted region only.

If you're looking for a filter doing this automatically, I'm afraid I can't help you.

bb

[FredThompson]

It really needs to be a filter because when this happens, it's going to happen a LOT on the tape. This is really a last-ditch option because the tape is probably screwed once this happens. Can't trust it.

I did get this reply from Konstantin Khlopencov (I just replied asking for settings suggestions):

Hi Fred,


I looked at your sample and my impression is that
SpotRemover can probably clean at least a half of
the artifacts.
But it seems (and you mentioned that) that the video
has already been processed (with Decomb).
I think it would be better if SpotRemover was applied
before Decomb.
I am planning to release a new version (within 3-4 weeks)
that will handle interlaced sources in the appropriate way.


Best regards
Konstantin

[FredThompson]

More:

>> Can you suggest some settings?.
>
>Start from "Aggressive" preset at the "Basic" page.
>Then go to "Spot Removal" and
>play with "Level for detection"
>and "Required perimeter clearance",
>while keeping "Level for clearance" at about
>0.6-0.8 of "Level for detection" and
>keeping "Spot fullness" at 0.
>
>>>I am planning to release a new version (within 3-4 weeks)
>>>that will handle interlaced sources in the appropriate way.
>
>>Do you mean progressive?
>
>No, I meant interlaced.
>Currently, SpotRemover assumes that the source is
>progressive and treats it in that way.
>Your source is interlaced and if you do de-interlacing
>then you will distort the structure of your "mosaic".
>After that, it will be more difficult to clean it.
>
>The next version of SpotRemover will be able
>to process interlaced source on the field-by-field basis.

Oh, I see.

Well, I could make two files, one for each field. Those could be filtered then combined. What do you think?

If you do filtering on known interlaced source it should be a little easier to find these one-frame-one-field problems, yes?

Do you want some test video?


>Currently, it may work too but less efficiently.
>
>
>Konstantin

[FredThompson]

I have examined this some more with AviSynth's SeparateFields().

I have also tried SpotRemover. It has not worked as well as I had hoped. Perhaps it was my settings. In any event, I have a short test segment and will continue to test this with guidance from Konstantin and report the results.

The dropouts appear to be one line only with a little horizontal smear or inappropriate color for one frame. There is usually a similar distortion on the next field.

Some should be easy enough to sense with an appropriate algorithm. My test sample has a Caucasian face with dark hair. As the head turns, there is a hair-colored spot on the check for one frame. The four or five frame before and after it are all skin-colored.

-- breaking news, so to speak ;) --

Reply from Konstantin:

I understand what type of "noise" you are talking about.
Theoretically, SpotRemover can remove any noise "spots" (=blocks of pixels) which conforms to 2 conditions:

1) For a given pixel, there is a distinct spike in time ("distinct" means larger than "level for detection")

2) On a given frame, the spike has a clear surrounding (I call it perimeter clearance).

My impression is that the noise of DV dropout can be also
removed, although it can be tricky.
Current ability of SpotRemover is enough for that.
Except for one thing, - it can not handle interlaced sources.

I am sorry, but right now I am not able to experiment with DV dropout problem.
I am more concerned about releasing the version for handling interlaced sources.