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ValveSoftware / gamescope

SteamOS session compositing window manager
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Black Frame Insertion (BFI) Support Feasibility #465

Open natek83 opened 2 years ago

natek83 commented 2 years ago

Some newer displays are dropping support for black frame insertion such as the 2022 LG C2 TVs. Would it be possible for Gamescope to support BFI in software as an option?

misyltoad commented 2 years ago

I assume every other frame would just be black?

natek83 commented 2 years ago

It can be that simple which is a 50% duty cycle and halving the effective panel refresh rate or it can be setup with a user defined duty cycle which would have to align with the target frame rate and display refresh rate, for example a target frame rate of 30fps on a 120hz screen can run BFI with a duty cycle of 75% on (single rendered frame repeated 3 times)/25% off (single black frame) as to not lower the screen brightness as much.

ryao commented 2 years ago

I assume every other frame would just be black?

I think that would be ideal given that going black should force the liquid crystals to remove the old frames, which in theory, should eliminate ghosting. Doing anything else would allow ghosting between non-black frames.

This would probably combine nicely with future HDR support, since the brightness would need to be doubled to compensate for the inserted black frames.

Calinou commented 2 years ago

Making every other frame completely black will effectively halve the refresh rate you can see, so it's not a good idea except for games that can only run at half your monitor's refresh rate (60 FPS-locked games on 120 Hz, for instance).

Darkening every other frame by an user-adjustable factor is probably a better idea, so you can still benefit from the full monitor refresh rate in games that can run at arbitrary framerates.

DisplayTalk commented 1 year ago

Calinou, software BFI is FOR halving(or whatever division chosen) your effective refresh rate. That is the intended purpose. Darkening frames would put you in a weird middle ground. Software BFI brings the MPRT of full refresh rate(example: 240hz ~4ms mprt) down to lower virtual refresh rates such as 60hz. That's the entire purpose, to remove duplicate frames and create a lower effective hz while keeping motion resolution the same as max hz. I really hope BFI comes to gamescope someday, it would be an incredible addition, and a huge reason to use linux over windows(there's no compositor-level BFI in windows, always some crappy wrapper with inconsistent timing and drops).