[mythtv-users] Weird HDMI problem

[Calvin Harrigan]

On 4/3/2012 5:20 AM, Simon Hobson wrote:
> Igor Cicimov wrote:
>
>> When I switch on the TV first and then the Mythtv all is fine. But the
>> other way around I get a black screen. Same happens if I leave the
>> Mythtv box idle for some time: when I switch back to it I get black
>> screen. It is like due to some power savings, I assume on the TV side,
>> the HDMI gets switched off.
>
> I have the same issue (0.24, MythBuntu, Samsung TV, Intel chipset)
>
> What I'm guessing is happening is ...
>
> If the TV is not powered up when the <the graphics system starts>*, then
> there is no feedback from the TV and so the HDMI port is not enabled for
> output - looking in the xorg log, it's clear it's auto-detecting
> displays for all the ports. Thus when you switch on the TV, you get a
> blank screen because nothing was detected and the output was not enabled.
>
> * This seems to be not only when the system starts, but also when waking
> from (at least some) sleep mode.
>
>
> I have tried fiddling around with xorg.conf, but not really knowing what
> I'm doing it does seem a lot like you need to configure loads of stuff
> to add a fixed modeline - and I've never managed to get anything other
> than a broken system.
>
> If my TV supported it, I'd be tempted to get an HDMI-CEC adapter and try
> re-configuring the system to turn the TV off/on instead of activating a
> screen saver. I've disabled all the screen saver options in the control
> panel but it still seems to do it.
>


I've had similar problems related to this chicken, egg issue.  I even 
had a problem with getting the audio over the HDMI cable because of an 
errant edid. Both were fixed with the same solution.  Extract the edid 
from your tv, save it to a file.  Instruct xorg to use the file for the 
TV info, negating the need to ask the TV directly.  If the TV is off 
this will return nothing, which will result in a blank screen when you 
finally turn on the TV.  Detailed instructions can be found here:
http://analogbit.com/fix_nvidia_edid
Luckily for you, you won't have to edit the edid data, recalculate 
checksums and the like. I had to do this to strip away the audio 
information provided by the TV, which prevented me using the TV the way 
I wanted to.