[mythtv-users] DVI connection overscan
Rich.West at wesmo.com
Sun Apr 15 08:48:55 UTC 2007
Alex Malinovich wrote:
> I have my Myth box hooked up to my TV via a DVI-to-HDMI converter cable.
> The video card feeds DVI out, and the TV takes HDMI in. What's strange,
> however, is that I still get a fair amount of overscan on the TV. I had
> thought that in the case of DVI and newer connections the full signal
> resolution is sent to the TV as part of the signal so no overscan is
> I've overcome this with Myth by manually scaling the window, but I'd
> prefer to not have to do that and to instead have the full screen
> properly displayed. I had heard that the nvidia-settings utility has
> overscan compensation, but I'm pretty sure that that's only when using a
> TV-out signal, not a direct DVI signal. (If that setting is still there
> with a DVI connection I certainly can't find it, and the interface
> really isn't all that complex.)
> So anyone know what's causing the overscanning and how to fix it?
Other responses hit on how to fix it, but the answer to your "what's
causing the overscanning" question is simply that it was designed that way.
All of the inputs on the TV, aside from a "PC" connection (be it
designated as PC - VGA or PC - DVI), are pre-configured for some
overscan. It varies per TV, with some brands of plasmas and LCD's
having ~3% overscan, to other TV's having as much as 11% overscan.
The HDMI input is no different in the _type_ of signal than the
component input (of course, the signal is all digital, and it can be
coupled with audio, but you get the point). The "PC" connections on
TV's are the exception to the rule.
A prime example is this plasma that I just got. In the manual, it has a
grid of all of the available resolutions for all of the inputs. The
component connections are hard configured to accept 480i, 480p, 720p,
1080i at a couple of varying Hz (60, 70, 75, etc). The HDMI connection
is the same, except that it can display 1080p. The list for the
resolutions available for the PC connection is huge, allowing for finer
tuning of the picture with absolutely no overscan. Of course, that's
where things get tricky as the configuration can be a pain, with both
the graphics card and the limitations/specifications of the TV.
You might want to check the config on your MythTV system. If you have
an nVidia card, check out the wiki entry for ComponentOut (it applies to
"HDMI in to TV", too). The nVidia drivers (the later ones) have some
pre-configured "modelines" which send 480p, 720p, and 1080i signals
without the need for an actual modeline.
#Option "TVStandard" "HD480p"
#Option "metamodes" "CRT: 720x480 +0+0"
Option "TVStandard" "HD720p"
Option "metamodes" "CRT: 1280x720 +0+0"
#Option "metamodes" "CRT: 1920x1080 +0+0"
#Option "TVStandard" "HD1080i"
Or, you can specify the resolution you want in the Display section, and
the driver will do the rest:
Modes "1920x1080_60" "1280x720_60" "720x480_60"
For 1080p, 720p, 480p respectively....
Not sure if any of this helps you, but I thought I would put it out
there since I've had some pretty good success with it...
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