[mythtv-users] Weird HDMI problem

Nick Rout nick.rout at gmail.com
Tue Apr 3 19:38:18 UTC 2012

On Wed, Apr 4, 2012 at 2:21 AM, Calvin Harrigan
<charriglists at bellsouth.net> wrote:
> 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

Only works on nvidia AFAIK

> 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.
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