[mythtv-users] Screen blanking issue with NVidia 455 drivers

Stephen Worthington stephen_agent at jsw.gen.nz
Thu Sep 24 14:22:31 UTC 2020

On Thu, 24 Sep 2020 08:44:06 -0500, you wrote:

>I did try pressing remote buttons and keys on the keyboard to try to wake
>it up, but the screen stays blank. In fact, the TV shows what it would show
>for a disconnected input. I am not 100% certain, but while I was having the
>problem, with the screen blank, I could press a button on my remote to
>start playing Live TV. I wouldn't see or hear anything on the TV. But if I
>used the keyboard to CTRL+ALT+F2 out to TTY2, then press CTRL+ALT+F1 to go
>back to X, I could see whatever channel it started playing on and hear the
>audio. The playback is jumpy when I do this, but stopping playback and
>restarting works fine and the system is ok until the next time I turn the
>TV off or stop playing content.
>I did see your suggestion about the Xorg config for DPMS on another thread.
>I didn't have those settings in my config, but I tried them to see and it
>made no difference. On my system, I have mythfrontend started with a small
>script that uses "xset" to disable the screensaver and disable DPMS:
>xset s off -dpms && mythfrontend
>This has worked for me for a few years now to keep the system screensaver
>from kicking in and from DPMS blanking the screen for power savings. My
>Xorg.conf is pretty small, and like I said, it hasn't changed for a number
>of NVidia driver and kernel upgrades.
>I looked briefly on the NVidia forums to see if anyone else was having a
>similar issue, but didn't really find anything. At this point, I'm content
>with leaving my NVidia drivers on 450.66 as it just works with those
>drivers. The 455.23.04 drivers are technically beta drivers, but they are
>the ones ArchLinux has as current. So for now, I'll just pin/hold back
>upgrades on my NVidia drivers. I'll keep checking as NVidia and ArchLinux
>update drivers and see if the problem is resolved down the road, but I have
>a work-around for now.
>With the limited investigation I've done so far, I'd say this is an issue
>with the NVidia drivers, and not likely an issue in MythTV.
>Many thanks,

From your description, the blank screen seems likely to be one done by
the TV because it is seeing a clock rate that is too high.  Just why
switching to Ctrl-Alt-F2 and back again fixes that is unknown but it
certainly sounds like an Nvidia driver bug.  I have had ones like that
before.  The reason for the jumpy playback after going back to
Ctrl-Alt-F1 is likely that mythfrontend does not know the screen mode
has changed to one the TV can cope with and it is playing back at a
different frame rate than the screen is displaying things at.  When
you restart playback, mythfrontend will be querying the screen to find
out the frame rate or setting it to the frame rate it wants and with
everything matching, playback is smooth.

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