[mythtv-users] Problem with TV resolution after upgrading to 20.04

[Stephen Worthington]

On Fri, 9 Oct 2020 12:11:36 -0500, you wrote:

>I've recently upgraded (fresh install) of Xubuntu 20.04. I'd been
>using Ubuntu (desktop) for almost 10 years, but recently the gnome
>desktop has been giving me fits.  I had Xubuntu on my remote frontend,
>and that installation was a charm, fixing all the problems with menu
>bars.
>
>So, the installation went well with the exception of losing a power
>supply in one of my disk arrays (fixed and the raid arrays are all
>online) but I still have problems with the part that everyone using
>the system looks at: the TV.  I set the display to 3840x2160 in the
>desktop and told it to hide the menu bar and it looked great! Until I
>turned the TV off and back on.  It had changed the resolution to
>1920x1080.
>
>After some digging I found the issue with X.  In the Xorg.log.0 file I
>see this after switching the display to the proper resolution:
>
>[ 52764.156] (--) NVIDIA(GPU-0): DFP-0: disconnected
>[ 52764.156] (--) NVIDIA(GPU-0): DFP-0: Internal TMDS
>[ 52764.156] (--) NVIDIA(GPU-0): DFP-0: 165.0 MHz maximum pixel clock
>[ 52764.156] (--) NVIDIA(GPU-0):
>[ 52764.186] (--) NVIDIA(GPU-0): DENON, Ltd. DENON-AVR (DFP-1): connected
>[ 52764.186] (--) NVIDIA(GPU-0): DENON, Ltd. DENON-AVR (DFP-1): Internal TMDS
>[ 52764.186] (--) NVIDIA(GPU-0): DENON, Ltd. DENON-AVR (DFP-1): 600.0
>MHz maximum pixel clock
>[ 52764.186] (--) NVIDIA(GPU-0):
>[ 52764.241] (II) NVIDIA(0): Setting mode "HDMI-0: 3840x2160
>@3840x2160 +0+0 {ViewPortIn=3840x2160, ViewPortOut=3840x2160+0+0}"
>
>Then after turning the TV off I see this:
>
>[ 52827.478] (--) NVIDIA(GPU-0): DFP-0: disconnected
>[ 52827.478] (--) NVIDIA(GPU-0): DFP-0: Internal TMDS
>[ 52827.478] (--) NVIDIA(GPU-0): DFP-0: 165.0 MHz maximum pixel clock
>[ 52827.478] (--) NVIDIA(GPU-0):
>[ 52827.508] (--) NVIDIA(GPU-0): DENON, Ltd. DENON-AVR (DFP-1): connected
>[ 52827.508] (--) NVIDIA(GPU-0): DENON, Ltd. DENON-AVR (DFP-1): Internal TMDS
>[ 52827.508] (--) NVIDIA(GPU-0): DENON, Ltd. DENON-AVR (DFP-1): 600.0
>MHz maximum pixel clock
>[ 52827.508] (--) NVIDIA(GPU-0):
>[ 52827.543] (II) NVIDIA(0): Setting mode "HDMI-0: nvidia-auto-select
>@1920x1080 +0+0 {ViewPortIn=1920x1080, ViewPortOut=1920x1080+0+0}"
>
>And there it stays until I go back into the display properties and put it back.
>
>I also noticed this declaration in the Xorg.log.0 file:
>
>[ 52762.997] (--) NVIDIA(GPU-0): DFP-0: disconnected
>[ 52762.997] (--) NVIDIA(GPU-0): DFP-0: Internal TMDS
>[ 52762.997] (--) NVIDIA(GPU-0): DFP-0: 165.0 MHz maximum pixel clock
>[ 52762.997] (--) NVIDIA(GPU-0):
>[ 52763.027] (--) NVIDIA(GPU-0): DENON, Ltd. DENON-AVR (DFP-1): connected
>[ 52763.027] (--) NVIDIA(GPU-0): DENON, Ltd. DENON-AVR (DFP-1): Internal TMDS
>[ 52763.027] (--) NVIDIA(GPU-0): DENON, Ltd. DENON-AVR (DFP-1): 600.0
>MHz maximum pixel clock
>[ 52763.027] (--) NVIDIA(GPU-0):
>[ 52763.031] (==) NVIDIA(0):
>[ 52763.032] (==) NVIDIA(0): No modes were requested; the default mode
>"nvidia-auto-select"
>[ 52763.032] (==) NVIDIA(0):     will be used as the requested mode.
>[ 52763.032] (==) NVIDIA(0):
>[ 52763.032] (II) NVIDIA(0): Validated MetaModes:
>[ 52763.032] (II) NVIDIA(0):     "DFP-1:nvidia-auto-select"
>[ 52763.032] (II) NVIDIA(0): Virtual screen size determined to be 1920 x 1080
>[ 52763.039] (--) NVIDIA(0): DPI set to (30, 30); computed from
>"UseEdidDpi" X config
>[ 52763.039] (--) NVIDIA(0):     option
>[ 52763.039] (II) NVIDIA: Using 24576.00 MB of virtual memory for
>indirect memory
>[ 52763.039] (II) NVIDIA:     access.
>[ 52763.059] (II) NVIDIA(0): Setting mode "DFP-1:nvidia-auto-select"
>
>Other people with a 4K monitor must have discovered this issue, but my
>searching has only shown up some older issues fixed with modelines or
>insidious EDID fake files to force X not to ask for what's available.
>I've tried some of these with no success, but thought someone has had
>to have come across this before, so I'm humbly asking for help.
>
>I'm using an NVIDIAGeForce GT1030 card, NVIDIA driver 450.51.06, a
>Denon AVR-X2600H, and an LG OLED65C9PUA 4K HDR TV.
>
>Regards,
>
>Ken Emerson

The standard fix is to use nvidia-settings to download the EDID data
for the TV, then set up xorg.conf to use the downloaded copy of the
EDID data and not to fetch the EDID data from the TV.  This seems to
be a problem that happens with AV amps more often than the TVs
themselves, so it may not happen if you directly connect the TV to the
MythTV box.  I would recommend having it directly connected when you
download its EDID data.

It is likely that you would be able to use an xrandr command to get
the display to switch back to 4k mode again, if you preferred to do
that every time it happens rather than messing around with xorg.conf.