[MPlayer-users] Feature request: derainbow filter

[John Evans]

Hello,

I don't have a reference image of the effect, but I believe the origional
poster refers to
" cross-luminance interference ", which happens if the processing of the
video information
is not done properly in the studio. Cross-luminance interference is
basically color information
that is mistaken for luminance information. There is high-end studio
hardware that can deal
with reversing this effect but the source must be of good quality ( forget
about properly correcting
a composite signal ;-) ). This high-end equipment / software will split the
color and luminance
information, tweak it, and put it back together.

Credits. ;-) This effect is most visible in the credits sections of movies,
etc. because of the difference
in color information ( white text next to black background or small text on
a black background ). This
effect can also be seen in color images if a person wears clothing that has
fine datails on it ( pin-stripes ).

One quick & dirty way of reducing cross-luminance interference is to blur
the image slightly or change
the chroma range ( say. bumping chroma from +110 IRE to 100 IRE ) but this
effects the picture quality.
Of course, you could always turn off chroma. ;-) I do this for black & white
source that has cross-luminance
interference in it. ;-)

I don't have a non-destructive solution for this problem, just a description
for it. ;-)

John

----- Original Message -----
From: "D Richard Felker III" <dalias at aerifal.cx>
To: "MPlayer user's list." <mplayer-users at mplayerhq.hu>
Sent: Sunday, March 23, 2003 9:26 AM
Subject: Re: [MPlayer-users] Feature request: derainbow filter


> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> 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
>
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