[mythtv-users] HDMI: No signal if TV is swichted on after Myth box

James Crow james at ultratans.com
Mon Jan 12 13:22:47 UTC 2009


On Mon, 2009-01-12 at 12:15 +0100, Kilian wrote:
> Hi!
> 
> I found some posts in other forums but not on this list, and I don't
> have a satisfying solution yet:
> 
> I connected my Myth box to the TV via HDMI which worked well out of
> the box. But I always have to switch on the TV *before* the Myth box
> to get a picture. If the Myth box is already running and I then switch
> on the TV, it does not display any picture on the HDMI input channel.
> If I reboot the Myth box then, everything is fine.
> 
> TV: Panasonic 37LZD85F (37" LCD, Full HD)
> Graphics: Asus M3N78 mainboard with on-board nVidia Geforce 8200 and
> on-board HDMI
> System: Mythbuntu 8.10
> 
> I found some information that the HDMI interface only sends a signal
> after it has confirmed that there is a capable display at the other
> end. If the TV is off, this is not possible.
> Is there some way to manually initiate this check?
> How can I get a picture out of an already running Myth box if the TV
> is switched on afterwards?
> 
> Thanks in advance!
> Kilian

My HDMI capable TV is hooked up to the DVI port on video card. Even if
the TV is off it is still communicating through HDMI. X will see the TV
just fine even if it is technically off (which is just a lower power
state than "on"). What you may want to try is forcing the X server to
output HDMI/DVI and force the resolution. 

With older version of X and the binary nvidia driver I had to do this.
The newest drivers have fixed my problem. I do not know what video card
and driver you are using, but the only one I have experience with is the
nvidia binary.

If you start up X and use the nvidia-settings program you can grab a
copy of the EDID from your TV. That is what the driver uses to decide
what resolution to send a signal at. Save the EDID to a file and then
add it to you xorg.conf file.

The first Google result when I looked for the correct line was from this
list:

http://www.gossamer-threads.com/lists/mythtv/users/362432?page=last

Cheers,
James




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