Custom Resolution Utility (CRU)

[ToastyX]

(02-12-2024 10:25 PM)speedstyle Wrote:  I have a Vega 56 (HDMI 2.0b) and a TV supporting 4k120 (over HDMI 2.1). On older AMD drivers (until late 2020) I could select 4k120 in Windows, and it would switch to 8bpc YCbCr 4:2:0. I think this was a bug, as 2.1 had only recently come out, and it would take the TV's report of 4k120 without realizing it couldn't do it with HDMI 2.0. On more recent driver versions this was 'fixed' and I can only select 4k60.

Is there any way to re-enable 4k120 at 4:2:0? By adding a resolution somewhere (anything over 600MHz gets ignored), by spoofing the supported pixel clock (CRU can only change the 'monitor-reported' max, AMD PCP doesn't seem to handle the 600MHz limit), by saying it supports 5bpc or something? Aren't there TVs that *only* support YUV/YCbCr, where it would be nonsensical to interpret it as requiring timing+resolution*24 Hz by default?

I searched around this thread for similar queries, but the answer is usually that HDMI 2.0 just doesn't support this. So it's frustrating that I *know* it would work, even now if I download an old driver it works fine (other than some applications refusing to run), but I can't tell it to do it.

HDMI 2.0 has enough bandwidth for 3840x2160 @ 120 Hz with YCbCr 4:2:0. Even though this wasn't officially specified until HDMI 2.1, I don't see anything in the HDMI 2.0 specification that forbids this, so I would say this is an AMD driver bug or an intentional limitation for some reason. If you export a file and post it here, I can check if YCbCr 4:2:0 support is defined correctly.