[SOLVED] Display turns off during dark scenes (mpv/vlc)

[sdauth]

Hello,
When I watch a movie, if there is a totally dark scene and if it lasts more than 3 seconds, then my display turns off.
Then at soon as the dark scene ends, my display turns back on.
With a laptop and exact same config (xfce / mpv / vlc), the laptop display remains on even during long dark scenes.
So I think this is a power saving feature with this monitor but there is no setting available to turn that off in the monitor settings.
Is there a way to force the monitor to remain active in such case ?

Thanks

[eccerr0r]

I've heard of dynamic backlight control to get darker black colors but wasn't sure if the driver needs to be aware of it, else I'd guess it has to be a monitor setting somewhere. Not a powersave, but look for color control?

Or is it really shutting off versus trying to blacken black pixels further?

[sdauth]

It turns off, with the monitor power led slowly blinking, until some color appears again in the scene (or if a subtitle line shows up)
It is annoying because it needs like 2 seconds to turn back on.

I still have this config block for my monitor :

Code: Select all

/etc/X11/xorg.conf.d/10-monitor.conf 
Section "Monitor"
    Identifier  "Monitor0"
    Option      "DPMS" "true"
EndSection

Section "ServerFlags"
    Option "StandbyTime" "0"
    Option "SuspendTime" "0"
    Option "OffTime" "0"
    Option "BlankTime" "0"
EndSection

And with xfce4-power-manager, I have sleep & shutdown display setting set to "after 60 minutes".
I don't use any screensaver as well.

[sdauth]

Interestingly, I just tried with openbox and the display remains on with my test file.
So it seems xfce is triggering it but I don't find any relevant option.
I will try to create a new user and a fresh xfce config to see if I can reproduce it or not.

edit:
With a new user and fresh xfce config (all default), same problem. It turns off after 3 seconds of a totally dark scene.

[sdauth]

I'd guess it has to be a monitor setting somewhere. Not a powersave, but look for color control?

Not much option available with this old 16/10 IPS monitor except for contrast. I've read a couple of threads online (with the same issue) but not applicable with my monitor unfortunately.

Otherwise, for some reason, I can't reproduce the issue with openbox so I tried to disable xfce dpms in xfce4-power-manager-settings (and killed the daemon too) to let xorg handles dpms itself but the display still turns off.
Well I don't know what else I can try. I don't have an other monitor to test. I don't know if it would make difference to try with dvi instead of hdmi ? Probably not.

[eccerr0r]

So if you completely draw your screen black it will also turn off?

Curious as to make and model of this monitor just to ridicule the manufacturer ...

I would imagine DVI and HDMI go through the same path, and probably monitor firmware unless something fishy with the gpu/driver??

[Hu]

I once saw a television that exhibited similar behavior when used as a display for a computer. Specifically:

• If the video signal is active, and there is at least one non-black pixel, draw the image.
• If the video signal is active, and there are only black pixels, turn off the backlight completely.
• If the video signal is inactive, enable the backlight and show a drifting "Check your cable connection" dialog.

In the case I saw, the backlight on/off was nearly instant, which looked really bad if you managed to get to a virtual terminal where the only non-black pixels were from the blinking underscore indicating text position. When the underscore blinked on, the television would bring the backlight up. When it blinked off, the backlight was turned off. With default parameters, Linux blinks the cursor pretty frequently, so the backlight was cycling very often. Conversely, if you set your screensaver to use a solid black color (as opposed to a picture, or an xscreensaver animation, etc.), then telling the screensaver to blank the screen would turn off the backlight.

[eccerr0r]

So this "feature" would kick in every time a show has a fade to black end scene?

Again I want to bonk whoever thought of this as a smart idea, at least without some sort of timeout before shutting down.

[sdauth]

So if you completely draw your screen black it will also turn off?

Curious as to make and model of this monitor just to ridicule the manufacturer ...

I would imagine DVI and HDMI go through the same path, and probably monitor firmware unless something fishy with the gpu/driver??

Yes! Nice idea. I created a 1920x1200 black png with gimp and displayed it full screen with feh.
If the cursor is visible then the displays stays active. But as soon as I move away the cursor out then the display turns off. (in 5 seconds)
With a single white pixel added to the same png then the displays remains active, cursor visible or not.

Also, I must correct what I said previously, I guess I have not waited enough with openbox and mpv.
Because I just tried also the black image in fullscreen with openbox and the the display turns off too. (feh -F --hide-pointer test.png)

So it seems the monitor (LG 24MB) is the problem here.

edit:

So this "feature" would kick in every time a show has a fade to black end scene?.

Yes, exactly. Crazy stupid isn't ?

[Hu]

So this "feature" would kick in every time a show has a fade to black end scene?

Probably, but it is mitigated by the content providers' obsessive need to put their logo somewhere on screen, so even a show that the director intended to have a completely black frame won't actually be all black.

[eccerr0r]

Also your video card and driver could be suspect but don't know yet...

[sdauth]

It's an iGPU (Radeon HD 8670D) and it uses radeon driver (compiled as module)
To be sure, I just made the same test with a laptop (intel igpu) connected via VGA and it doesn't make any difference. It turns off too after 5s of full black.
In the monitor settings, there is only an auto shutdown feature with a timer (1h / 2h / 3h etc..) but of course it doesn't help.
Maybe it could be somehow "fixed" by forcing mpv to draw a single grey/white pixel in a corner when a >2s full black frame is detected. It sounds a bit ridiculous I know
Maybe it's time to upgrade to a new monitor.

[Anon-E-moose]

Did you emerge xfce with upower use flag, if so check in settings for power instead of monitor.

[sdauth]

Yes upower is enabled system wide (in make.conf)
But it is not the issue here. xfce DPMS works fine with the timer set to 30 minutes for sleep & 60 minutes for shutdown.
The issue is that my monitor turns off itself when a long black frame appears (>5s) and turns back on as soon as color appears again in a scene. Or as said above, even a black image displayed full screen is enough to trigger it.
Disabling xfce own dpms implementation or using xset dpms 0 0 0 to set all timers to 0 doesn't help, the monitor still turns off.
I don't have this issue with my laptop so I assume this is a monitor issue.

[papu]

https://forums.gentoo.org/viewtopic-t-1 ... ight-.html

might be...

[Anon-E-moose]

Yes upower is enabled system wide (in make.conf)
But it is not the issue here. xfce DPMS works fine

It has nothing to do with dpms, per se,
Just like some de's turn off idle for movies, same concept, just not sure what they call it.
Under power, there should be something called presentation... (don't remember full name) there should be a setting under there.

The XFCE Power Manager rather confusingly groups “Blank after” together with “Put to sleep after” and “Switch off after” under the “Display Power Management” main toggle – but that toggle in fact only affects latter two; former is a pure-software thing.

Over here it works to set “Blank after” explicitly to “Never” and disable that main toggle; my screen is then never blanked nor switches off; no “Presentation Mode” needed

(of course also set “Never” on the System tab for “System Power Saving”)

[sdauth]

Yes I tried that already (and also tried "Presentation mode"), it still turns off as soon a long black frame is displayed.
Also it is not specific to xfce; with openbox, I have the same issue. (no xfce4-power-manager is loaded in openbox autostart so it just uses xset values)

I think I still have an old hdmi tv in the basement, I'll try with it later to see if does the same thing or not. Too bad I don't have an other monitor to test.

[Anon-E-moose]

Sounds like it's the monitor then, what's the model I know it's an lg 24mb, but that's not the full model name, ie a lot of 24mb* models all different

[sdauth]

This one : https://www.displayspecifications.com/en/model/0d619e0

Alright so I found the problem...
I was looking at the monitor settings osd by pressing the left button but there are other settings when you press the middle button
When pressed it opens a new osd "Super Energy Saving" with three choices : High / Low / Off
It was set to "off" which is supposed to disable it but it turns out it is buggy. I probably set that a long time ago...
So instead of "off", I set it to "low" then it fully solved the issue. It stays on with full screen black picture (Still on while writing this post... so all good ! )

Code: Select all

Saving Data depends on the Panel. So,those values should be different from each panel and panel vendor
If option of Super Energy Saving is High or Low, monitor luminance become higher or lower depend on source.
LG calculated these values by using “broadcast video signal” (including broadcast video: IEC 62087)
SUPER SAVING refers to how much power can be saved using the SUPER ENERGY SAVING function.
If option of Super Energy Saving is High or Low, Picture Mode will automatically be Custom and Reader Mode will automatically be Reader Off.

I'm really sorry everyone, I totally forgot there was an other round of settings by pressing this button...
I appreciate your help & suggestions nonetheless.

[Hu]

Although this was not a Gentoo problem, your explanation of how it was fixed and citation of model data may yet help someone else who has a 24" LG 24MB65PY-B or similar device. (Yes, I pasted the exact model from your link, just for use as search engine bait. )