[mythtv-users] Migrating from VGA to HDMI

Matt Doran matt.doran at papercut.biz
Tue Apr 24 08:34:06 UTC 2007


Phill Edwards wrote:
> I bought a 50" Panasonic TH-50PX600A plasma TV a few months ago and
> have had it connected via VGA. The picture has been good but I
> couldn't get X to fill the screen - it leaves quite a large blank
> border on the right and bottom sides, and sometimes these blank areas
> fill with "snow" which doesn't look good and I fear may cause burn-in
> on the plasma screen.
>
> So I recently bought a cable to connect my nVidia card's DVI-D output
> to the HDMI input on my TV. Initially the picture seemed what I can
> only describe as "lairy" - over-vibrant, over-colourful and just
> didn't look as good as with VGA. But it does fill the screen and I
> found that the difference was due to different colour settings on the
> TV for different inputs - doh! So if anyone else has this model TV I
> can recommend HDMI over VGA.
>   
I have exactly this display.   In the picture menu in the display, 
change the color/display(?) mode to "Normal".  The default of "dynamic" 
is way too vibrant.
> I have some questions, though...
>
> 1) The manual says these inputs are acceptable on HDMI:
> 480i (60Hz)
> 480p (60Hz)
> 576i (50Hz)
> 576p (50Hz)
> 720p (60Hz)
> 720p (50Hz)
> 1080i (60Hz)
> 1080i (50Hz)
> What do people recommend I use as TVStandard in xorg.conf? I used to
> use PAL-B. Will picture quality be better if I use something like
> HD1080i or HD720p? I thought (possibly naively!) that if my resolution
> is 1280x720 then using 720p would somehow be a good "match" - is there
> any sense in that or not? To be honest, I haven't found a lot of
> difference no matter which TVStandard setting I use.
>   
> 2) Since using DVI --> HDMI I have found that console windows (when
> you press Shift-Alt-F1) are too big for the screen so that the top,
> bottom and sides seem to be cut off from view. This is a bit of a pain
> as I use the console quite a lot for fiddling around with stuff. Is
> there anything I can do to correct this?
>   

You do get overscan using the 1280x720_60 built-in X modeline ... but 
the output is pretty good.  But it's hard to tell the difference between 
VGA (at the native res) and HDMI at less than native.    I've also 
experimented with the 50Hz modeline, which should be better to display a 
50HZ signal (I assume you're in Aus?).  I honestly had trouble noticing 
the difference.

I also found a mode-line that has no overscan (it's a weird resolution 
though).  I don't have access to it from here, but can post it if you're 
interested.

I think a little bit of overscan is good, because the TV broadcasts seem 
to assume there is some (e.g. the snow you've mentioned).  You can tell 
myth to add 1% overscan so you don't see them.  The option is hidden 
somewhere in the TV playback settings.

-- Matt


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