Posted by Jukka Aho on 08/28/06 09:49

joe murphy wrote:

> On some of my DVD there is a shimmering effect. This appears to be
> mostly older DVDs. The is mostly evident wgere tgere is a lot of
> detail. What is this.

The shimmering effect you see is caused by the interlaced nature of
(traditional) video signal and the interlaced scanning of the tv set.
This makes thin, contrasty horizontal details flicker on the screen.

The reason why you see the effect more clearly on old discs is that
newer (better authored) DVD releases do away with the problem by having
applied (adaptive) vertical filtering to the material, smoothing out the
problematic details a bit.

See the animated illustration on this page:

<http://en.wikipedia.org/wiki/Interlace>

You can get rid of the problem by purchasing a tv set and a DVD player
that support progressive scan:

<http://hometheater.about.com/od/beforeyoubuy/a/progressivescan.htm>

--
znark

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