[mythtv-users] 720p on CRT/overscan

Alex Halovanic halovanic at gmail.com
Wed Mar 21 02:59:12 UTC 2007

None of those overscan options will work, if you're not outputting
using the standard def tv-out (usually s-video) of your graphics card.
 The problem is really that you're feeding the TV the correct signal,
its just been designed or set up to overscan the picture like that.
Its an annoying holdover from standard definition televisions.  In
fact, most networks seem to expect this overscan as I've seen *their*
graphics not totally overlap the action like they're supposed to (CBS
Football for one) or they have annoying white lines or other garbage
at the top of the screen, where they expect you can't see it.

I've found two solutions to overcome this problem:
1) Fix the TV.  In most HDTVs there's a hidden service menu, where
settings affecting the overscan, along with a million other ones are
placed.  There is a reason these are hidden as they're extremely
unfriendly looking and you have the potential to cause damage to your
set if you tweak the wrong settings too far.  If you attempt to do
this yourself, you have to find the service manual for your set (not
the manual that came with it), which gives some info on getting into
the service menu and what some of the things mean.  If you don't do it
yourself, you could pay a tech to adjust the overscan for you, and
this is the method they will use.  I managed to adjust my own as I
found a service manual online, but I found its not perfect.  My CRT
warps the picture as it approaches the edges, which is probably the
reason they were placed off the edge of visible screen so far.

2)Use a screen resolution smaller than the 720p standard of 1280x720
pixels, so that X only draws to a portion of the screen.  If you're
using a component out on your card, this just plain won't work (a
limitation of the cards) but if you're using VGA or DVI it works
pretty well with less risk of breaking something.  For example, I was
running with a resolution of 1144x696 at 720p, which gives you some
idea of just how much horizontal overscan I had.  If you want more
info on this method, I can give you some more on how to do it.

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