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marqs85 / ossc_pro

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[BUG] Blank screen in QHD with VRR #14

Open arncht opened 2 months ago

arncht commented 2 months ago

The VRR mode looks ok in 1920x1080, the display shows correctly the right frequency, and pass through the various DOS frequencies. In 2560x1440, i got just a blank/black screen even with 60Hz input.

marqs85 commented 2 months ago

Which display is that, and do you have another source that works in Freesync mode at 2560x1440? In the latter case, is there any chance you could extract the SPD/vendor infoframe metadata sent by the source? There is no publicly available information which metadata should be sent and I've formatted the Infoframe only based on what information I could gather from a couple online sources.

arncht commented 2 months ago

Samsung G8 OLED is 1440p native (but with 3440x1440), i would be surprised, if they do not support this popular resolution with vrr. The display shows clearly, if it gets an unsupported mode - starting to go suspend, here i got nothing, just a black screen. This is the reason, i thought maybe the ossc send something differently.

arncht commented 2 months ago

Here is a test case:

Input: DOS text @ 70Hz Mode: Scaler Framelock: On VRR Flag: FreeSync

Resolution: 1920x1080 - I get the image correctly. If I switch off VRR, the default display profile does not support 70Hz; there is no image. At this point, if I try to change the resolution, I can see exactly which resolutions support VRR. If there is no support, the display shows a clear "Mode Not Supported" message.

The resolutions where I do not get the "Mode Not Supported" message (so probably the VRR mode is supported):

1280x720: I see the DOS screen. 1920x1080: I see the DOS screen. 2560x1440: Black

Is it not related to the 50-60Hz 1440p limitation?

marqs85 commented 2 months ago

The video signal is identical with VRR setting on and off, only the metadata changes. It might be that the display supports VRR only on certain pixel clock frequencies (usually matching 120Hz or native refresh rate). 2560x1440@70 is on the limits what OSSC Pro can output, thus it's not able to increase pixel clock further without using pixel repetition.