[mythtv-users] Problem: 4:3 content always fills my 15:9 screen. Consequently, the aspect ratio is incorrect.

Christopher David Petersen christopher.david.petersen at gmail.com
Thu Oct 11 02:59:46 UTC 2007

On 10/10/07, Alex Halovanic <halovanic at gmail.com> wrote:
> Under mythfrontend's setup menu->appearance, check to see if there's a
> setting that says 'monitor aspect ratio.'  It's only there if you have
> a newer version of Xorg or have xinerama enabled.  I'm betting it's
> currently set to 4:3.  Try setting it to 16:9 (there's no 15:9) and
> seeing if that improves it to be a slightly squished picture in myth.
> If that does help, then I think I may be able to figure out how to get
> it working at 15:9.
> Alex
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Thanks for the suggestion. Unfortunately, I don't have the 'monitor aspect
ratio' setting available.

I think I've determined the source of the problem, and arrived at a suitable
(although not entirely satisfactory) work-around.

I believe (although I cannot confirm) that my TV (a Olevia by Syntax
LT26HVE) is providing improper EDID information to the SiS X driver.

Regardless of what I set the screens DisplaySize to in xorg.conf, xdpyinfo
reports that my screen is 40x30 mm (apparently my 26" TV is actually a iPod
Nano screen :).

I believe that MythTV looks at the screen size as reported by Xserver to
determine the aspect ratio of the screen. MythTV thinks my screen is a 4:3
aspect ratio and therefore fills the whole screen. This is correct behavior
on the part of MythTV.

Having been unable to figure out a way to tell the SiS driver to ignore the
EDID information (some nVidia drivers accept a 'Option "IgnoreEDID" "true" '
option in the xorg.conf), I have a couple of work arounds:

Work around 1:
Tell MythTV to display the GUI and playback in separate windows. Have both
windows set to 1280x768 at 60Hz, but indicate that the aspect ratio for TV
playback is 16:9.
There are two problems with this work around: a) 16:9 isn't quite 15:9 b) as
Myth creates the new windows my TV losses the signal and flashes it's "no
signal" screen. Twice for about a quarter of a second. It's very annoying
and strikes me as bad for the TV.

Work around 2:
Tell MythTV to have a horizontal overscan of -8 percent, and a vertical
overscan of 1 percent (to get rid of the embedded signal info at the top).
This gives a picture that is very close to 4:3 (within a pixel or two).

I'm pretty happy with Workaround #2.
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