1381829 - occasional judder on YouTube video with 4k 60fps VP9 hardware decoding

Status: UNCONFIRMED

(Core :: Audio/Video: Playback, defect, P2)

Description

[walmartguy]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:56.0) Gecko/20100101 Firefox/56.0
Build ID: 20170717030207

Steps to reproduce:

I open this URL (Windows 10 Redstone 2, GTX 1070) and choose 4k 60fps video:
https://youtu.be/aqz-KE-bpKQ


Actual results:

There often is judder when playing the video until I manually seeked back some seconds. This seems to "fix" it.
It's most reproducible after switching to fullscreen mode. Happens with both 55 Beta and 56 Nightly.


Expected results:

Video shouldn't show any judder since the display is running with perfect 60Hz.
It's completely judder-free in Chromium.

Comment 1

[walmartguy]

Issue still exists with FF 57.0a1 (2017-08-11).
It isually happens when I open Firefox maximized, paste in the video url and switch to fullscreen directly after playback of the 4k video has started.
It may be important that it actually instantly starts playing the video in 4k. Sometimes it's buffering up too slow and then switches down to another resolution in the beginning. In that case, choose again 4k and restart Firefox. It usually sticks to it then.

Comment 2

[Bulk Bug Changes for mreavy's org]

Mass change P1->P2 to align with new Mozilla triage process

Comment 3

[walmartguy]

Still happening with FF 58.0a1.

Comment 4

[Blake Wu [:bwu][:blakewu]]

What is the resolution of your monitor?

Comment 5

[walmartguy]

2560x1440

Comment 6

[tiffnixen]

I've been having a similar issue. Video playback will occasionally freeze for a second or so every once in a while, including on the linked video when set to 4k.

On my PC, Youtube is using VP9. The stats panel usually doesn't show any dropped frames, though on the example video it does. The issue also happens in videos that aren't playing in 4K, like in 2K. Happens regardless of whether I'm in fullscreen or not.

Firefox: 77.0.1 (64-bit)
OS: Windows 10 Pro 10.0.18362 Build 18362
Specs: Desktop PC / i5-7600k / GTX 1080 / 16GB DDR4
Monitor: 2560x1440 @ 144hz (+ gsync) primarily, with a second monitor attached.

Comment 7

[walmartguy]

Try enabling Webrender via about:config if it is disabled due to your high refresh rate display.
I think it was a bad idea to generally disable it for lots of displays >60Hz with Nvidia GPU, given how notoriously bad D3D11VA and Direct2D work with advanced layers + that GPU vendor.

Comment 8

[tiffnixen]

(In reply to walmartguy from comment #7)

Try enabling Webrender via about:config if it is disabled due to your high refresh rate display.
I think it was a bad idea to generally disable it for lots of displays >60Hz with Nvidia GPU, given how notoriously bad D3D11VA and Direct2D work with advanced layers + that GPU vendor.

Yeah, it showed as disqualified because of that. I force enabled it and now it's working fine, no stuttering.

Last time I checked, WR was enabled (several months ago, before I started experiencing stuttering). Is this disqualifier new?