[MPlayer-users] Feature request: derainbow filter

[D Richard Felker III]

On Sun, Mar 23, 2003 at 02:38:45AM -0800, Corey Hickey wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> James Bostick Crowson wrote:
> >[Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> >Lots of times, anime DVDs will have odd "rainbows" or odd changing colors
> >on edges.  I've been using a chroma gaussian blur (-vop scale -ssf cgb=1)
> >to get rid of them, but this only deals satisfactory with mild rainbowing.
> >For the more severe ones a blur radius of 3-4 works well, but degrades
> >image quality unacceptable on everything else.  It would be nice if
> >mplayer/mencoder had some sort of adaptive chroma gaussian blur, which
> >could take two radii and a threshold, and use the first (smaller) blur
> >radius for each pixel where the chroma change from the last frame is below
> >the threshold, and the larger radius for each pixel where the chroma
> >change is above the threshold, or something similar.
> >
> 
> I don't have any idea what you're describing. :) ...and probably others
> on this list don't either. Perhaps post a screenshot (use mplayer -vo
> jpeg) or upload a video sample to mplayerhq.hu.

It's very visible in the intro credits text of SE Lain. Apparently the
material passed through analog equipment at one or more points in the
making of the video, and because NTSC sucks, the high-frequency luma
content from fine details in the text bled over into the chroma band,
making the nasty rainbow crap. It's the same effect you get if you use
simple tv-out equipment without a lot of filters and try to display
small white text on a black background on your tv.

Rich