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Re: Playing Cinema DVDs problem



On Tue, 2009-07-28 at 13:30 +0100, Marko Vojinovic wrote:
> AFAIK, playing NTSC content on a PAL system is not an easy thing to 
> do. The computer has to perform appropriate conversion, and this might
> get CPU-intensive.

Unless you're connecting video out from a computer to an ordinary
television set, then NTSC or PAL (colour encoding schemes for composite-
or S-video) don't come into the equation.  

It's only scan rates that are a problem, where people think of NTSC or
PAL issues, and that's probably the case for any computer, no matter
what your local television standards are.  Films are 24 frames per
second, video is usually 25 or 30 frames per second (PAL or NTSC can be
either), computer displays are typically anywhere from 60 to 100 frames
per second.  So frames need showing more than once, and often not by
*exact* multiples.  This gives you flickers, during frame repeats, and
annoying flashes if a frame changes part way down the picture.

If you can change your display frequency, and that's probably not
possible with most LCD displays, then you can minimise those visual
annoyances, and change the workload of your PC.

Likewise, the display resolution is an issue.  DVDs are usually either
720 by 576 or 720 by 486.  If your screen is something else, it needs to
be scaled.  This nearly always looks bad, particularly with LCDs, and
even more so if scaled by integer amounts (e.g. exactly double, or
triple, etc.), and is CPU intensive.

Decoding of the MPEG data is also intensive.  Computer systems that can
do hardware decoding are generally better at it than those that have to
do it all in software.

-- 
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