[Bug]: Invalid video scaling on the virtual display using mpc-hc/mpc-be

[momala454]

Which OS?

Win11 Pro

Which release?

24H2

Describe the bug

When I play a 1920x1080 video on a 4k virtual display, and when the video is started on the virtual display, there is always some extra scaling done to the video
see more infos : Aleksoid1978/MPC-BE#669

ps: the streaming using moonlight/sunshine is actually not necessary to reproduce

Steps to reproduce

create a 4k virtual monitor, open mpc-be in that virtual monitor, open a 1080p video, and I can see on the taskbar thumbnails that the video have the invalid scaling.
If I move the window the a real monitor, it has still the scaling, and I can see that the video is resized

Expected behavior

no scaling of the video, the same as when I start a video on my real monitors

Log File (Beta Only)

log_2025-01-03.txt

Contact Details

No response

[bud3699]

You tried setting the resolution you want to be the default(first resolution) or only resolution?

[momala454]

i tried with this config, it does the same (i did "reload driver" after changing config, if that helps)

<?xml version="1.0" encoding="UTF-8"?>
<vdd_settings>
    <monitors>
        <count>1</count>
    </monitors>
    <gpu>
        <friendlyname>default</friendlyname>
    </gpu>
	<global>
		<!--These are global refreshrates, any you add in here, will be replicated to all resolutions-->
		<g_refresh_rate>60</g_refresh_rate>
		<g_refresh_rate>90</g_refresh_rate>
		<g_refresh_rate>120</g_refresh_rate>
		<g_refresh_rate>144</g_refresh_rate>
		<g_refresh_rate>165</g_refresh_rate>
		<g_refresh_rate>244</g_refresh_rate>
	</global>
    <resolutions>
		<resolution>
            <width>3840</width>
            <height>2160</height>
            <refresh_rate>30</refresh_rate>
        </resolution>
        <resolution>
            <width>800</width>
            <height>600</height>
            <refresh_rate>30</refresh_rate>
        </resolution>
        <resolution>
            <width>1366</width>
            <height>768</height>
            <refresh_rate>30</refresh_rate>
        </resolution>
        <resolution>
            <width>1920</width>
            <height>1080</height>
            <refresh_rate>30</refresh_rate>
        </resolution>
        <resolution>
            <width>2560</width>
            <height>1440</height>
            <refresh_rate>30</refresh_rate>
        </resolution>
		<resolution>
            <width>4096</width>
            <height>2160</height>
            <refresh_rate>30</refresh_rate>
        </resolution>
    
        
    </resolutions>
    <options>
		<CustomEdid>false</CustomEdid> <!-- Custom Edid should be named "user_edid.bin"! This does not support emulating resolutions!-->
		<PreventSpoof>false</PreventSpoof> <!--Enable this to prevent manufacturer spoofing when using custom edid. Please only do so if you need to!-->
		<EdidCeaOverride>false</EdidCeaOverride> <!--Enable this to override or add hard coded cea-extension block to custom Edid support allowing you to enable HDR-->
		<HardwareCursor>true</HardwareCursor>
		<SDR10bit>false</SDR10bit>
		<HDRPlus>false</HDRPlus> <!-- If you have SDR10 bit enabled, HDRPlus wont work - there’s a conflict because the display system cannot simultaneously handle both high dynamic range 12-bit and standard dynamic range 10-bit settings. -->
		<logging>false</logging>
        <!-- DEBUG LOGGING FOR EXPERTS ONLY!-->
        <debuglogging>false</debuglogging> 
        <!-- DEBUG LOGS CAN GENERATE 1000+ LINES-->
		<!-- Warning: Leaving logging on too long can lead to excessive filesize. Especially DebugLogging, which should only be used for short periods to log errors. -->
		<!-- Logging: Useful to troubleshoot and determine which GPUs are being used, and if displays are working as intended.-->
		<!-- Debug Logging: Logs local system information with every driver function/event/process. Useful for GitHub Help Tickets.-->
	</options>
</vdd_settings>

[bud3699]

Then despite what the other issue says it's probably how their video player handles the upscaling pixels correctly. Aka if it relies on GPU driver specific features or certain types of gpu hardware acceleration and attaches based off display capabilities, then this is not something we would have to fix. More of the software being able to handle these circumstances

(Id have to take a look at their source but this is most likely something they'd have to change)

[momala454]

changing the "compatibility" settings for the app, settings the scaling to the "application", seems to prevent the problem

[bud3699]

All working then? I'll mark the issue as unrelated and close it

[momala454]

i don't consider as all working if I have to enable application specific "hacks". If it makes that app behave strangely, it can cause the same to others apps/games
maybe there is a bug in the scaling handling in the driver ?

[bud3699]

Like I said before. It's most likely an issue with their app, our driver runs in session0 therefore we're limited by what Microsoft allows, our driver uses iddcx which is built into windows. The only way we'd be able to support everything a real display does would be getting Microsoft to allow for these, since Microsoft won't do that, it relies on external software developer to integrate applications to be able to support these kind of displays making this problem be the video players fault, not the drivers, this is out of our hands

[momala454]

the mpcbe player devs won't do anything about it, they told

[bud3699]

Yes I'm aware but we can't do anything about it, it's out of our hands. So if you need to use that app specifically. Then you're going to have to use that work around you found