1875937 - Netflix playback stutters intermittently at 24 Hz refresh rate

Status: NEW

(Core :: Graphics, defect, P3)

Description

[Michael Comella (:mcomella) [NI reported issues only: ex-Mozilla]]

I'm using macOS 13.6.1: I can't confirm if this affects other operating systems.

Steps to reproduce

1. Attach an external display that supports a 24 Hz refresh rate (I'm using a Samsung Frame TV)
2. Set the 24 Hz refresh rate on the external display (System Settings -> Displays -> Click external display -> Refresh Rate)
3. Play Netflix content (presumably content that is 24 Hz) in fullscreen (I'm using the Kingdom series which, warning, has violent content)

Expected results

Playback is smooth

Actual results

Playback is smooth for a 5-10 seconds and then stutters heavily for a few seconds. This effect is especially noticeable during the end credits when names scroll up the screen at an even pace. I'm using a high-end MacBook Pro from 2019 so I don't expect to have performance issues.

I cannot reproduce this issue in Safari. I will attach videos from my phone of the issue in Firefox and the lack of issue in Safari. I used the profiler in a new Firefox profile under several different configurations. I started the profile, waited for the stuttering to start (10-15s), and ended the profile just after the stuttering stopped. I don't see anything obvious in the profiles:

• Firefox config: https://share.firefox.dev/3vEa9Le
• Media config: https://share.firefox.dev/48JYIAf
• Graphics config: https://share.firefox.dev/3SCYOo1

fwiw, I've subjectively felt video playback on my laptop (i.e. presumably at 60 Hz) on Netflix to be less smooth in Firefox than in WebKit browsers so I wonder if a similar issue exhibits at all refresh rates but is less noticeable with more frames.

Note: my external display exhibits other strange behavior at 24 Hz. Every 5-10s, the text and UI elements get blurry but the video content does not – I wonder if it's related to the computer trying to sync its 60 Hz refresh rate with the 24 Hz display.

Comment 1

[Michael Comella (:mcomella) [NI reported issues only: ex-Mozilla]]

Attachment: Firefox: video of the issue

Sorry for the .mov but it's going to take several hours for me to download the tools to convert this locally. I can re-upload with a larger resolution video if it'd be helpful.

Comment 2

[Michael Comella (:mcomella) [NI reported issues only: ex-Mozilla]]

Attachment: Safari: video without issue

Comment 3

[Karl Tomlinson (:karlt)]

I don't see big CPU use.
ImageBridgeTransaction and ImageComposite::SetImages occur at irregular roughly 35 to 45 ms intervals, consistent with 24 fps, VsyncTimestamp at regular 16-17 ms intervals, consistent with 60 fps. |VideoFrameTimeStampJitter| <= 0.02 ms.

I guess things won't be optimal without a 24 fps vsync, so I'll move to Graphics for discussion on that.

Comment 4

[Nicolas Silva [:nical]]

I suspect that this has to do with the external monitor having a different frefresh rate from the laptop's screen.

Comment 5

[Markus Stange [:mstange]]

I agree this is worth fixing but I wouldn't consider it a performance issue, so setting impact:none.