Bug 502764 - Display fractional refresh rates are not listed.
Summary: Display fractional refresh rates are not listed.
Status: ASSIGNED
Alias: None
Product: systemsettings
Classification: Applications
Component: kcm_kscreen (show other bugs)
Version: unspecified
Platform: Other Linux
: NOR normal
Target Milestone: ---
Assignee: kscreen-bugs-null@kde.org
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2025-04-13 22:15 UTC by Adolfo Rodrigues
Modified: 2025-04-16 21:30 UTC (History)
6 users (show)

See Also:
Latest Commit:
Version Fixed In:
Sentry Crash Report:


Attachments
gnome refresh rates. (124.74 KB, image/png)
2025-04-13 22:15 UTC, Adolfo Rodrigues
Details
kscreen-doctor -o (2.30 KB, text/plain)
2025-04-14 22:44 UTC, Adolfo Rodrigues
Details
kscreen-console json (17.45 KB, text/plain)
2025-04-14 22:45 UTC, Adolfo Rodrigues
Details
My test video files (76.29 KB, image/png)
2025-04-14 23:01 UTC, Adolfo Rodrigues
Details
windows refresh rates (91.15 KB, image/jpeg)
2025-04-14 23:12 UTC, Adolfo Rodrigues
Details

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Description Adolfo Rodrigues 2025-04-13 22:15:50 UTC
Created attachment 180238 [details]
gnome refresh rates.

Hi.

Display fractional refresh rates are not listed under display settings, why ? 
I leave Gnome as an example on how it should appear. Windowz does the same FYI.
Comment 1 John Kizer 2025-04-14 06:45:26 UTC
Hi - merging this in with what I believe is the existing bug report for this topic, as also noted on the Discuss thread that was created.

If you could also please note for the future, bug reports submitted via Bugzilla need to contain structured steps to reproduce, observed results and expected results in order to be actionable by KDE developers - https://community.kde.org/Get_Involved/Issue_Reporting#Steps_to_Reproduce is a helpful reference.

Thanks!

*** This bug has been marked as a duplicate of bug 431057 ***
Comment 2 Adolfo Rodrigues 2025-04-14 07:23:17 UTC
(In reply to John Kizer from comment #1)
> Hi - merging this in with what I believe is the existing bug report for this
> topic, as also noted on the Discuss thread that was created.
> 
> If you could also please note for the future, bug reports submitted via
> Bugzilla need to contain structured steps to reproduce, observed results and
> expected results in order to be actionable by KDE developers -
> https://community.kde.org/Get_Involved/Issue_Reporting#Steps_to_Reproduce is
> a helpful reference.
> 
> Thanks!
> 
> *** This bug has been marked as a duplicate of bug 431057 ***

I saw that report but it quickly side tracked to freesync and did not focus clearly on the fractional refresh rates. 
I wanted this one to be dedicated just to the missing refresh rates enumeration. 

I though putting steps to reproduce where silly on this report. Just try to change your monitor/Tv that you know has 23.976Hz or 29.97hz or 59.94Hz using display settings. 

If you have a monitor/TV connected that you know supports fractional refresh rates, kde display settings does not list them. In X11 you can see them with xrandr and in kscreen-doctor json in wayland.
Comment 3 TraceyC 2025-04-14 22:19:08 UTC
Can you please post the output of the following so we have the data about your display's refresh rates?

kscreen-doctor -o

Thanks
Comment 4 Adolfo Rodrigues 2025-04-14 22:44:28 UTC
Created attachment 180271 [details]
kscreen-doctor -o

kscreen-doctor -o  does not list what my screen is capable of.
Comment 5 Adolfo Rodrigues 2025-04-14 22:45:47 UTC
Created attachment 180272 [details]
kscreen-console json

kscreen-console json 
is what I expected to see. The fractional refresh rates are visible.
Comment 6 Adolfo Rodrigues 2025-04-14 23:01:09 UTC
Created attachment 180273 [details]
My test video files

I know my screen is capable of all these refresh rates. NVIDIA has a bug with 24Hz, it uses 23.976Hz which I can fix with an edid override. But that's not important now.  I disabled the edid override to create the files you asked.

Using mpv with the script mpv-kscreen-doctor.lua from https://gitlab.com/smaniottonicola/mpv-kscreen-doctor, mpv changes the screen to the correct refresh rate. The exception is 24Hz (that I fix using edid override) and 30Hz that is also not available, mpv-kscreen-doctor.lua uses 60Hz which is fine since the screen is still in perfect sync.
Comment 7 Adolfo Rodrigues 2025-04-14 23:12:55 UTC
Created attachment 180274 [details]
windows refresh rates

Just for reference, when NVIDIA gets their linux driver in perfect working conditions, the refresh rate list should be what is listed in the windows refresh rate screenshot.
But this is getting side tracked. IMO KDE should list the available fractional refresh rates like gnome and windows, rounded to two decimal places. In my case I do not actually have 30Hz or 24Hz under linux with the nvidia driver but kde incorrectly lists them. GNOME lists correctly the available refresh rates.
Comment 8 TraceyC 2025-04-15 15:02:06 UTC
Thank you for taking the time to add all that additional detail. That does help pinpoint the issue.

I can confirm this on git-master. The bug will only surface if two refresh rates exist that would round up or down to the next whole number refresh rate (like 59.939998626708984 and 60)

I do see in the attached kscreen-doctor output that the fractional refresh rates are being named with the same name as the non-fractional, e.g.

                {
                    "id": "1",
                    "name": "3840x2160@60",
                    "refreshRate": 60,
                    "size": {
                        "height": 2160,
                        "width": 3840
                    }
                },

                {
                    "id": "12",
                    "name": "3840x2160@60",
                    "refreshRate": 59.939998626708984,
                    "size": {
                        "height": 2160,
                        "width": 3840
                    }
                },



On my system, the kscreen-doctor -j output for one monitor shows the following refresh rates for its native resolution. You can see that the fractional refresh rates are rounded up. This doesn't show the bug in the kcm on my system, because there aren't two fractional refresh rates being set to the same "name".
❯ kscreen-doctor -j | rg -A 1 -F 'name": "3440x1440'
                    "name": "3440x1440@85",
                    "refreshRate": 85,
--
                    "name": "3440x1440@50",
                    "refreshRate": 50.000999450683594,
--
                    "name": "3440x1440@60",
                    "refreshRate": 59.972999572753906,
--
                    "name": "3440x1440@144",
                    "refreshRate": 143.92300415039062,
--
                    "name": "3440x1440@120",
                    "refreshRate": 120,
--
                    "name": "3440x1440@100",
                    "refreshRate": 99.98200225830078,
--
                    "name": "3440x1440@75",
                    "refreshRate": 75.05000305175781,


 I'll let the more experienced developers take it from here.
Comment 9 Bug Janitor Service 2025-04-16 21:30:06 UTC
A possibly relevant merge request was started @ https://invent.kde.org/plasma/kscreen/-/merge_requests/372