[MPlayer-dev-eng] [PATCH] -vf combdetect: crude detection of interlaced sources
Reimar.Doeffinger at gmx.de
Mon Aug 2 18:39:05 CEST 2010
On Mon, Aug 02, 2010 at 03:50:30PM +0100, Christopher Key wrote:
> As mentioned, this is very crude. It works well for my library of PAL
> dvds, which will either be 24fps film sped to to 25fps, or natively
> 50f(ields)ps interlaced TV, but isn't designed to analyse NTSC material
> that may use 3:2 pulldown etc. This is why I've named it combdetect,
> that's all it does, and it leaves room for a more advanced filter than
> can detect a rather broader range of field/frame fiddling techniques.
> Nevertheless, I find this very useful, and suspect that it may be useful
> to others with similar aims.
But even for detecting combing it should be quite simple to do a lot
better, e.g. by comparing C(line i, line i+1) to C(line i, line i+2) where
C is the covariance.
But even without going that far, the property of combing is not that
line i differs a lot from line i+1 but that line i+1 differs _more_ from
line i than line i+2.
Thus your filter only detects a high variance vertically but has not
much to do with combing IMO.
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