1650499 - Win7: Wrong Hz display detection

Status: NEW

(Core :: Graphics, defect, P3)

Description

[cholismo]

User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101 Firefox/78.0

Steps to reproduce:

Load this site: https://www.displayhz.com/ or this one: https://www.vsynctester.com/

Actual results:

It shows 64 Hz

Expected results:

It would be 60 Hz instead (my actual display refresh rate).

Comment 1

[cholismo]

Attachment: about:support output

Comment 2

[cholismo]

Attachment: about:support output

Comment 3

[cholismo]

Attachment: about_support.txt

clean profile

Comment 4

[cholismo]

Attachment: vsynctester

Comment 5

[cholismo]

Attachment: displayhz

Comment 6

[cholismo]

I have tried with Brave (Chrome) and IE 11 and the refresh rate is properly detected (60 Hz).

Comment 7

[cholismo]

[Tracking Requested - why for this release]:

Comment 8

[Timothy Nikkel (:tnikkel)]

What happens if you flip the pref gfx.vsync.force-disable-waitforvblank?

Comment 9

[cholismo]

(In reply to Timothy Nikkel (:tnikkel) from comment #8)

What happens if you flip the pref gfx.vsync.force-disable-waitforvblank?

It doesn't change anything, I knew about this switch: https://bugzilla.mozilla.org/show_bug.cgi?id=1628137

I already tried several versions pre-76 and it happens the same. I think that pref is only valid for Windows 8.1 and 10 because on Windows 7 it should be disabled by default: https://bugzilla.mozilla.org/show_bug.cgi?id=1628137#c2

Thanks.

Comment 10

[cholismo]

I have just tested Firefox 68.10 ESR and the behavior is similar but slightly different; At first it detects the display Hz correctly but if you let the test run for a while it turns to 64 Hz eventually.

Comment 11

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:jbonisteel, could you have a look please?

For more information, please visit auto_nag documentation.

Comment 12

[cholismo]

Attachment: Firefox 81 (81.0a1) still affected.

Comment 13

[Kris Taeleman (:ktaeleman)]

@Jamie: you've looked into refresh rate / vsync issues lately. I can't seem to reproduce this on Win 10, so maybe it's a windows 7 only issue. Could you give some insight into what the impact of this is.

Comment 14

[Jamie Nicol [:jnicol]]

I also cannot reproduce on Windows 10. I'm really not familiar at all with the vsync code, but I'm struggling to see where 64 could come from!

@cholismo, would you be able to capture a profile (using https://profiler.firefox.com) when running https://www.vsynctester.com? Thanks.

I have just tested Firefox 68.10 ESR and the behavior is similar but slightly different; At first it detects the display Hz correctly but if you let the test run for a while it turns to 64 Hz eventually.

If you could run mozregression and find out when it changed from working at least for a bit to not working at all, that might give us some useful information!

Comment 15

[cholismo]

(In reply to Jamie Nicol [:jnicol] from comment #14)

I also cannot reproduce on Windows 10. I'm really not familiar at all with the vsync code, but I'm struggling to see where 64 could come from!

@cholismo, would you be able to capture a profile (using https://profiler.firefox.com) when running https://www.vsynctester.com? Thanks.

Sure:
https://share.firefox.dev/3aqHmuS

Sorry for the delay, I haven't had access to this Win7 computer for a few days.

Comment 16

[cholismo]

(In reply to Jamie Nicol [:jnicol] from comment #14)

If you could run mozregression and find out when it changed from working at least for a bit to not working at all, that might give us some useful information!

I don't know how to properly run mozregression to troubleshoot this bug but I found out version 69 runs bad from the beginning so probably there was a critical change between v68 and v69.

Comment 17

[Darkspirit]

comment 4: The complaining website has an article about Firefox: https://www.vsynctester.com/firefoxisbroken.html
It sounds like bug 1630389 fixed vsync for Win10, but not for previous Windows versions.

Comment 18

[cholismo]

Animation Timing Deviation is a mess too because of this bug, almost 16 ms. Test here:
https://www.testufo.com/animation-time-graph#scale=20&ppf=2&measure=animation&busywait=0

Comment 19

[cholismo]

Attachment: Animation timing deviation - Firefox 80.0.1 - Windows 7