live.bilibili.com - Video does not play smoothly

[webcompat-bot]

URL: https://live.bilibili.com/6

Browser / Version: Firefox 102.0
Operating System: Windows 10
Tested Another Browser: Yes Chrome

Problem type: Something else
Description: live video play on this page so much not smoothly compared with Google Chrome
Steps to Reproduce:
I try to watch live video no the page first time by Firefox. Live video play on this page so much not smoothly compared with Google Chrome.

Browser Configuration

• None

From webcompat.com with ❤️

[softvision-oana-arbuzov]

Thanks for the report, I was able to reproduce the issue. The video plays with a bit of lag and also the scrolling of the text over the video is not smooth.

I've recorded a performance profile: https://share.firefox.dev/3aEl1yy

Affected area:

<div style="position: absolute; bottom: 0px; width: 100%; z-index: 13;" class="web-player-controller-wrap" id="web-player-controller-wrap-el">
</div>

Note: The issue is not reproducible on Chrome.

Tested with:
Browser / Version: Firefox Nightly 104.0a1 (2022-07-14), Firefox Release 102.0.1
Operating System: Windows 10 Pro

Moving to Needsdiagnosis for further investigation.

[qa_28/2022]

[wisniewskit]

I see that ~24% of the time in Oana's profile is spent in Element.getBoundingClientRect, from this rough stack trace of their JS:
r.prototype.start -> e.prototype.getText -> e.prototype.textRender => e.prototype.getDivInfo

So this might be related to our current investigation of getBoundingClientRect.

Otherwise, smaller chunks of time are spent in Element.scrollHeight (~6.2%) doing reflows/style computations every frame of video (t.prototype.nextFrame), and in Element.clientWidth (~3%) while handling events, which I would guess is while moving the mouse over the text.

So let's revisit this as our investigation of getBoundingClientRect progresses.

[wisniewskit]

@softvision-raul-bucata this seems to be working fine for me now, could you confirm if you can still reproduce the performance issue on Windows 10?

[softvision-raul-bucata]

@wisniewskit I can confirm that the issue no longer reproduces.

Tested with:

Browser / Version: Firefox Nightly 114.0a1 (2023-04-24) (64-bit)
Operating System: Windows 10 PRO x64

[inv_17/2023]

[wisniewskit]

Ok, then let's close this for now. If it ever becomes reproducible again, we can reopen the bug or file a new one.