[mythtv-users] Running TV out OR DVI out, not both

Allen Edwards allen.p.edwards at gmail.com
Sun Dec 7 05:56:04 UTC 2008

On Sat, Dec 6, 2008 at 8:26 PM, Bill Williamson <bill at bbqninja.com> wrote:
> This is a bit more of a basic Linux question, so please forgive, but has
> specifics that are valid here.  For reference, I am running ubuntu 8.10 and
> myth .21 from mythbuntu packages.
> Basically what I want is a dual headed machine where only 1 head is active
> at a time.  I got a nice new geforce 8400 for future use with VDAPU, and it
> has tv out (going to a smaller PAL tv via component) and dvi out (going to a
> 720p projector via hdmi converter).  I want to be able to run via TV, OR run
> via projector.  I do not care (nor want) dual outputs.
> In the olden days (slackware 1998-ish), before gdm and the like, I'd just
> run "startx" from my first two terminals, and use ctrl-alt-f7 and
> ctrl-alt-f8 for the two x sessions.  I don't want to do something that
> manual, but is there perhaps an easy way to tell GDM to spawn twice, with a
> different xorg config?  Or is there a way to force the nvidia
> I don't mind having to do a key combination (and run blind for 10 seconds if
> it starts in the wrong one), but don't want to be dropping to console/etc
> every login.  I don't mind if technically it's running two x-servers as long
> as mythtv works, and with the correct settings for each (I guess I'd set up
> two different settings names in two different shortcuts?)
> My "ideal" setup would be similar how laptops work in windows.  You hit some
> key combinations to activate TV-Out, then another combo to disable it.
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You have the same setup I have.  Normally I watch myth with S-video
out playing to a CRT TV.  When we want to use the projector, we use
DVI output to a HDMI projector.  I have tried several arrangements but
what I do it to have the projector switched away from the myth box (by
selecting DVD on my DVI switching preamp) and start X so that it
starts up on the TV.  I then do a CTRL-ALT-BS and myth shows up on the
TV.  Turn the projector on and switch to it, CTRL-ALT-BS and in a few
seconds myth is on the projector.  The Xorg.conf setup is key to
making the setup work.  The outputs are assigned single resolutions,
not auto.  I have two displays defined in xorg.  Basically if myth
sees the projector, it starts up there, if not it starts up on the TV.

There are other ways of doing this.  You can start myth on either
display if both display/desktops are there but be sure to close myth
down if you leave a display.  You can switch desktops with the mouse
but the problem is that the remote will operate both instances of myth
if you happen to have one on each desktop/display.  With two instances
running, they will get out of sync and you have no idea what the one
you are not watching is doing.  Since you cannot see a screen that is
turned off, this can be a problem which led to my solution being
easier even though it seems crude.

If I didn't have a preamp that switched the DVI for me, I would
probably just unplug the hdmi cable into the projector so that myth
would not see it when X starts up.

Hope this helps,


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