[mythtv-users] Help with xorg.conf
Michael T. Dean
mtdean at thirdcontact.com
Thu Dec 22 16:18:47 EST 2005
Allan Wilson wrote:
> I do have a VGA input on my TV but it will not take up the full screen
> if you use it.
It will accept a signal over VGA, but because *all* TV's (including
LCD's/DLP's/SXRD's/...) have been designed to include overscan (i.e. if
you display 1920x1080 pixels in a 1:1 pixel-for-pixel format, part of
the image will be displayed "off-screen"), the manufacturer probably
took this into account for their setup. Here, I'm guessing your TV is
like mine: because loss of the top/bottom/sides of a computer screen
(which contains Start bars/Quick-Launch toolbars/Dock's/Task
bars/whatever your WM calls them) makes using a typical computer
difficult (and annoying), the manufacturer probably designed all VGA
input to be scaled.
My TV takes any input from the VGA port and scales it to 95% of the
visible display size. So, I just tell the TV to scale the image to take
up the full screen (including overscan since I'm using a Myth box and
not Windows with the Start bar). This means I have very close to 1:1
pixel mapping and full screen/resolution. Only tradeoff is overscan
(but, you can only have 2 out of 3, so you have to choose which to give up).
> Refering to what you where talking about Michael should I get a cable
> to convert the VGA to something else?
Nope. Plain VGA.
> If so what input should I shoot for?
> I do like the idea of using the VGA output anyhow b/c every computer
> already comes with this.
> Even if I use the VGA out won't I still have to tell it the specs for
> my Display with a modeline since it is not standard?
If you plug in a VGA cable (either a cheap one or some high-end ones),
the digital display will be able to transmit EDID informaion, which X
can use to choose the appropriate display size. (Some cables--even some
high-end cables--block the EDID info.) Therefore, you can just plug it
in and it should work--if not, try another VGA cable (if you have one
handy, but don't buy one just for testing) or specify a modeline. If
you're using some fancy Linux distribution, it probably has all the
tools you need to configure X (i.e. just mark the appropriate checkboxes
for the resolutions you want and it computes the modelines).
IIRC, my TV tells the computer it will accept a 1280x1024 or an 800x600
image, but the manual lists several other (normal computer) modes
(including 640x480 and 1024x768) all at 60Hz refresh, so any "standard"
modeline for 1280x1024 at 60Hz would work. However, since I wanted full
1920x1080, I specified my own modeline (technically, John P. Poet's
modeline--thanks, John ;). To find yours, check out that avsforum link
I gave you.
> Steve, I have seen where some people are using different resolutions
> for different content but how do you control this? Also if you are
> using Myth in on a widescreen display what do you use for the theme.
> Thanks for the help I think I am starting to understand a little better.
IMHO, you don't want to use Xrandr. If you use Xrandr, Myth can select
the best available mode (from those you've configured) for use in
displaying your video. Myth changes X to use a different video mode and
it's up to the TV to scale the image--however it decides is
appropriate. I am a big believer in being able to control how things
are scaled (i.e. let Myth recognize a 4:3 video I recorded with my
PVR-x50 and put black bars on the side while allowing me to change the
aspect ratio /through Myth/ when appropriate--i.e. letterboxed video in
4:3 content can be displayed full screen by using 16:9 zoom--instead of
having to set my TV's scaling mode to get the display I want). Power to
the people and all... :)
You may be able to argue for using a component/DVI connection to send
video at the video's native resolution, but doing so means you can't do
1080p60 (since only the VGA port can accept that), so your GUI (and any
1920x854 at 24fps progressive high-def movie trailers) will "suffer" (not
too bad for the GUI--you could use 1280x720 for it, but it will affect
your ability to do the movie trailers justice).
However, based on what I've seen of the abilities of the ATI Xilleon
processor (which my TV uses and yours probably does, too), I still think
you're better off doing your own scaling. The Xilleon is great at
serving it's intended purpose--real-time decoding of high-def video--but
leaves much to be desired in the scaling arena...
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