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Overscan is back System
I'm not sure when this has been introduced, but probably with 10.2.5. The Displays control panel now has extended options when the computer is connected to a TV. It's now possible to enable overscan, a feature that was available on Mac OS 9, but has been missing on X for a long time. Now, for example, DVD viewing is possible as expected - without a black border around the movie.
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Overscan is back | 5 comments | Create New Account
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Importance of this hint
Authored by: SOX on May 02, '03 01:11:05PM

this hit is potentially way more important than it sounds like.
the issue is that when you play a dvd movie if the screen is not
an integer multiple of the number vertical scan lines in the dvd
then the computer has to interpolate the pixels (horizontal pixels
always get interpolated I believe).

This leads to awful and visible effects on the screen when a
sharply defined edge (say a car door) moves slightly diagonally
across the screen. you can see visible zig-zagging far in excess
of what you might expect from aliasing effects. (I beleive the
reason for this is that the odd and even rows of pixels are stored
in alternate frames slightly delayed in time, the interpolation of
a fast moving object thus has the appearance of two out movies
on top of each other slightly offset).

you can see this effect most clearly on a projector when you
swithch the screen resolution so that it has to interpolate, to a
mode where it does not interpolate (and then re-zoom the
image back to the same size).

anyhow, it turns out that 800x600 screens are just shy by a few
pixels of being an exact multiple of number of scan lines in a
dvd movie. thus being able to forge the screen size to be an
exact multiple by losing just a few pixels on the overscan will
immensley improve the quality of the dvd movie. (interestingly
dvd movies look better on an 800x600 svga screen then they do
on a XGA or SXGA screen because the extra pixels dont give any
more resolution but do cause interploation distortion)

hence to the poster I ask how can I not only just get rid of the
black bars but also make it overscan so that it actually bleeds
off the screen?



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Overscan is back
Authored by: sgi_oh_too on May 03, '03 03:37:12PM

but what about the dimming cycle, repeated dimming and
brightening of the screen (i think as a deterrent to making vhs
copies), that dvd player does when watching a movie full screen
via video out? how does someone get around that?



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Overscan is back
Authored by: Anechoic on May 04, '03 11:57:06AM

Are you connecting your Mac through a VCR or pre-amp, instead
of directly to the TV? If so, try connnecting to the TV and see if
your still getting those effects. My understanding is that the
Macrovision circuitry shouldn't be built into the line-inputs of a
TV, but are likely present in any modern video recording devices
that have line inputs.

I for one am out of luck since my TV doesn't have line-in's, so I
have to connect my Pismo through my VCR.



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Overscan is back
Authored by: Grecy on May 04, '03 10:24:55PM

The constant dimming you are seeing is the macrovision protection that is in a DVD.

When a DVD is played, signals are also sent which control the auto-contrast feature of newer VCR's. This is to prevent people from pluggin a DVD player straight into a VCR and copying all the DVD's they wish.

To avoid this happening, make sure there is no VCR plugged into your system (ie. is your computer connected to your VCR then to the TV?) I would connect the computer directly to the TV and remove all VCR's from the chain.

Hope this helps
-Dan



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Overscan is back
Authored by: czucker on Oct 02, '03 01:00:28PM

Hmmmm. . . Overscan is indeed back. It seems to work differently from the OS 9 overscan though.

I work as a graphic designer for a small new show and we used to use a G4 PB to put up on screen graphics during the taping of the show. I would just use a full screen image in photoshop and send it to the TV. It always worked fine under OS 9. Now when I've tried to do it in 10.2.6 the color looks washed out and the image has space at the top and bottom.

Anyone have any similar experiences? Advice?

Best,
Chris



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