View Full Version : OpenGL screws with my tv... Refresh rate?
05-27-2009, 12:10 PM
I have a rather unusual problem and would be very grateful for any pointers in the right direction.
My Ubuntu machine is hooked up to my tv via dvi-to-hdmi cable. Now while trying out XBMC, a great media media center solution, my tv suddenly looses its signal after a while. This happens quite nondeterministicly. It just goes blue, as if I would have changed the resolution to an unsupported one.
Of course I checked the logs of XBMC, but nothing unusual was happening there. Actually nothing at all happened at the moment the screen would go blue...
The thing is, it seams to be related to OpenGL. Glxgears would produce the same effect!
That's where I'm stuck, I'm afraid ;-) What could OpenGL be doing that would cause my TV to protest? It isn't the resolution that's being changed, but the effect is the same (tv goes blue on me). Would it be possible that the refresh rate is being changed on the fly? How would I go about to confirm something like that?
It's a long shot, I know ;-)
Thanks a bunch!
PS: My setup, http://pastebin.ca/1436510
05-27-2009, 12:26 PM
Screensaver or standby/suspend mode can disable video output, check that first.
Graphic card overheating ?
Do you have same results when using a classic monitor ?
Does it happend after a few seconds, minutes, hours ?
glxgears in fullscreen, or small window ?
How do you get out of the blue ? reset ? restart X server (Ctrl-Alt-Backspace) ? Plug a different screen ?
refresh rate changed on the fly is very improbable, especially with glxgears, or your graphic drivers are severely bugged.
05-27-2009, 02:54 PM
The screensaver and standby/suspend mode where one of the first things I disabled. Sadly that didn't change anything.
I doubt it's a heating problem. I have the card a long time now and I've never run into such problems. Be it on Windows or Linux.
Oh and you're right, I forgot to mention that I don't have these problems whatsoever with a classic monitor. I suspect it's just more tolerable to whatever is going on.
What's also curious is that it happens in both fullscreen and windowed mode, but it *seems* to happen faster in fullscreen mode. All in all it just isn't very consistent, so I can't be too specific here...
When it happens in fullscreen mode, I can change to windowed mode with a key combination (of XBMC). Then I get my screen back, with XBMC windowed again.
Another way to get back the screen is kill the program, be it glxgears or xbmc.
Is there anything other than the refresh rate that could change on the fly?
Thanks for your interest.
05-27-2009, 03:53 PM
1) Does it happend after a few seconds, minutes, hours ?
2) Do you use the same dvi output for a classic monitor ?
It may be the video card having small troubles, amplified by the dvi-to-hdmi cable, something like that...
3) If you switch the TV off then on again, does it gets out of the blue ?
4) if you unplug the dvi-to-hdmi cable from both ends, wait a few seconds to let capacitors discharge, and plug it again ?
5) And what about 3 and 4 combined ?
Out of ideas now ... can you try with another TV ?
05-28-2009, 01:21 AM
>Does it happend after a few seconds, minutes, hours ?
Sometimes just a couple of seconds, sometimes a few minutes. I've been able to use xbmc in full screen mode for up to (about) 5 min at a time without the problem. But then, as soon as I think it's ok, bang! ;-)
>2) Do you use the same dvi output for a classic monitor ?
The classic monitor was connected to the same dvi output, but with a dvi-to-vga adapter. Could that be filtering out something?
>3) If you switch the TV off then on again, does it gets out of the blue ?
No, that doesn't work either...
> 4) if you unplug the dvi-to-hdmi cable from both ends, wait a few seconds to let capacitors discharge, and plug it again ?
This I haven't tried, but I'll give it a shot as soon as I get home.
>Out of ideas now ... can you try with another TV ?
I guess it's worth a shot, maybe there might be some descriptive output on that one, even if it works.
The next step I'm going to try is to crank up log verbosity on Xorg, maybe that could point me in the right direction. Any other logs that could be related / would have OpenGL related stuff?
Other than that, I'm out of ideas, too ;-) I think I'll soon just chuck my ATI card, and get a reasonable nVidia one with good linux support.
05-28-2009, 03:10 AM
Maybe the signal quality of the HDMI connection is bad? And when the graphics chips increases clock speed under load, the signal quality gets a bit worse and fails randomly(DVI/HDMI has no error detection/correction).
I had that kind of problem with my TFT connected via a 5meter long DVI cable: When refresh rate was set to 75Hz, the screen went blank every 30seconds or so under specfifc loads.
Using a shorter cable or 60Hz solved the problem => signal quality was the problem.
So you might try a another/shorter cable.
05-28-2009, 01:49 PM
I didn't think of that! Sounds plausible, eventhough my cable isn't that long (2m).
Thanks, I'll have to look into that this weekend!
06-02-2009, 05:06 AM
It looks like Nighthawk was right. Since I'm running XBMC with 30 Hz, I haven't had a problem!
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