1918887 - After extended watchtime, skipping to next video on Youtube hangs

Status: RESOLVED WORKSFORME

(Core :: Layout, defect, P3)

Description

[hanchenlu]

Attachment: Firefox_About_Support.txt

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:130.0) Gecko/20100101 Firefox/130.0

Steps to reproduce:

I watch videos on Youtube for an extended period of time, currently with a queue of 10+ videos played. Upon reaching near the end of a video, I would click the Next Video icon on the player to skip to the next video.

Actual results:

Web page would freeze for several seconds, partially to load the video player, during which time the page would be unresponsive. Toggling fullscreen on and off is also affected and slower, with the black fade in and out taking about a full second if not more. This hanging behavior is much degraded from the normal Youtube experience from recently opening an instance of Firefox, and usually performance will improve if I restart Firefox. I have previously reported Youtube playback issues in bug 1887942 and from there I have set my gfx.direct3d11.reuse-decoder-device flag to false.

Comment 1

[hanchenlu]

Oh, forgot to include the profile capture of me reproducing. You see the big freeze right before the 3 second mark.

https://share.firefox.dev/3ZqPAiu

Comment 2

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

The Bugbug bot thinks this bug should belong to the 'Core::Audio/Video: Playback' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 3

[hanchenlu]

Captured another long one, hoping it helps
https://share.firefox.dev/47qAL1e

Comment 4

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

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

For more information, please visit BugBot documentation.

Comment 5

[az [:az]]

I notice RefreshObserver/RefreshDriverTick/requestAnimationFrameCallback hanging for ~6 seconds on this profile, though I'm not sure what the root cause is at this point.

:aosmond, would you have any ideas here?

Comment 6

[Daniel Holbert [:dholbert]]

The big hang there (in the reporter's profile from comment 1 and comment 3) seems to be attributed to style/layout doing frame-reconstruction, though really we're spending ~all of our time in mozilla::dom::FlattenedChildIterator::GetPreviousChild calling nsINode::GetPreviousSibling, to handle an element (or multiple elements?) having been inserted (so we can figure out where to build/insert its frames in the layout frame tree; or something along those lines).

I think that slow frame-reconstruction is the main issue here, and there's probably no audio/video or refresh-driver-related bugs involved.

Let's reclassify this bug as layout.

Comment 7

[Daniel Holbert [:dholbert]]

I tried to reproduce (in latest Firefox Nightly 134.0a1) but so far haven't been successful.

I clicked through a YouTube "playlist" of 10 videos (using the YouTube next-video-button), and then I built and clicked through a "queue" of 10 videos (built using the "add-to-queue" UI for one-off playlists). So far I haven't been able to reproduce any hangs in frame construction like the reporter's profiles show. (And my profiles show near-zero time in nsINode::GetPreviousSibling, and zero time in mozilla::dom::FlattenedChildIterator::GetPreviousChild.)

I tried installing the "Return YouTube Dislike" add-on that I see in the reporter's profile extensions-list, in case that mattered, but it doesn't seem to help me reproduce anything like this.

Before we dive too much further -- reporter, could you confirm whether or not this is still reproducible for you? I wonder if this was a temporary issue that ended up getting fixed already (whether in Firefox or on YouTube).

Comment 8

[Daniel Holbert [:dholbert]]

(When testing, I tried with the various UIs for YouTube -- miniplayer with/without the playlist collapsed, default view, theater view. I also didn't actually let the videos play for super-long - I just seeked forward and then clicked next.)

Reporter: if it turns out you can still reproduce, do let us know what YouTube "view" you're using to watch here (miniplayer/default/theater) in case it's relevant. Thanks!)

Also, this part from comment 0...

Toggling fullscreen on and off is also affected and slower, with the black fade in and out taking about a full second if not more.

...seems to have been filed as bug 1920229, and it looks like Markus identified the "Return YouTube Dislike" add-on as the likely-culprit over there. But on this bug here, it's not obvious to me from the profiles whether that extension is involved with the hangs.

Comment 9

[hanchenlu]

Relaying same comment from the other bug. Issue is most likely from the return dislikes extension. The issue hasn't cropped up after disabling it. I can forward the profiles to their bug tracker, as I've found an open issue that appears to match what I'm experiencing. Don't know if you guys need anything more from me regarding it if it doesn't look too be a Firefox issue

Comment 10

[Daniel Holbert [:dholbert]]

Thanks! Let's close this then.