m.youtube.com - Video thumbnails are briefly not fully loaded when fast or slow scrolling

[claudiu64]

URL: https://m.youtube.com/watch?v=JqtgFCQu9do

Browser / Version: Firefox Mobile 126.0
Operating System: Android 11
Tested Another Browser: Yes Chrome

Problem type: Something else
Description: Incorrect scrolling
Steps to Reproduce:
When scrolling the list of youtube videos, when you scroll down you can see some kind of stuck, it should move smoothly. From what I've seen it happens very often and it happens anywhere on the site. I also specify that the "Scrool to hide toolbar" setting is activated. (It may not cause this and it may happen on other sites as well) On Chrome it scrolls in italics.

mobizen_20240427_095408_001_001_001.mp4

Browser Configuration

• gfx.webrender.software: false
• blockList: basic
• defaultUserAgent: Mozilla/5.0 (Linux; Android 11; Mobile; rv:126.0) Gecko/126.0 Firefox/126.0
• hasTouchScreen: false
• frameworks: {'fastclick': False, 'mobify': False, 'marfeel': False}
• mixed active content blocked: false
• mixed passive content blocked: false
• tracking content blocked: false

View console log messages

From webcompat.com with ❤️

[claudiu64]

I mention another situation, which seems similar, here is a test site for scrolling: https://archive.mozilla.org/pub/fenix/nightly/2024/04/
It can be seen that scrolling down the page, the screen shakes with each scrolling. In Chrome this is not the behavior.
Link to this ticket: #136396

mobizen_20240427_223012_001.mp4

[ailioaie]

We appreciate your report but I was not able to reproduce this issue. I was able to scroll in page as expected:

29.04.2024_16.23.32_REC.mp4

Tested on:
• Browser / Version: Firefox Beta 126.0b3 (2016017335-🦎126.0-20240426091720🦎)
• Operating System: Samsung A51 (Android 11) -1080 × 2400 pixels 20:9 aspect ratio (~405 ppi density)

Suggestions:
• Clear cache/data/cookies, disable Ad-blocker (if available), or create a new profile (without syncing/importing data) and check again
• If there are any changes made to the default settings of the browser (e.g. in about:config), please revert to the default settings

[qa_18/2024]

[claudiu64]

@ailioaie @ksy36 @denschub @sv-calin @softvision-raul-bucata
I've noticed that it can reproduce when we go to the link and scroll very quickly down the list, before the full site is loaded. Please test again, can you test directly from the phone? (without console, etc). I think this affects all sites, I think it might be an app issue, but it needs investigation.

[softvision-raul-bucata]

@claudiu64 Indeed, scrolling faster than usual or slower (especially when the loading icon is present - that happens on Chrome btw as well), there is a brief moment where the video thumbnail preview is not fully loaded:

20240430_163703.mp4

We appreciate your report. I was able to reproduce the issue by following the steps to reproduce

Tested with:

Browser / Version: Firefox Release 125.3.0 (2016017559-🦎125.0.3-20240425211020🦎)/ Firefox Nightly 127.0a1 (2016017991-🦎127.0a1-20240429210502🦎)/ Firefox Beta 126.0b7 (2016017911-🦎126.0-20240429091743🦎)/ Chrome Mobile Version 124.0.6367.82
Operating System: Google Pixel 3 (Android 12) -1080 x 2160 pixels, 18:9 ratio (~443 ppi density)
Operating System: Oppo Find X5 (Android 13) - 1080 x 2400 pixels, 20:9 ratio (~402 ppi density)

Notes:

1. Reproducible regardless of the status of ETP.
2. Reproducible on the latest build of Firefox Nightly and Release.
3. Works as expected using Chrome.

Moving this to NeedsDiagnosis for further investigations.

[inv_18/2024]

[claudiu64]

@softvision-raul-bucata
I note that the error is much worse at runtime than you noticed. You saw in my attached video of the error replay, the screen shakes when scrolling, this happens immediately when we hit the link and we scroll down super fast, before toolbar loads the site. Also test with a 60fps phone, not 120fps or higher, to try to reproduce the main bug as well. There seems to be more scrolling and scrolling issues.

There are also articles with this error: https://blog.veefly.com/guide/youtube-scrolling-issue-fix/

[denschub]

@claudiu64 please stop pinging everyone all the time. There is no need to. You can provide answers to questions raised without pining everyone. And if something is unclear, this issue will come up in internal discussions anyway and we'll have a look at it together. Mentioning the entire team every time won't make anything go faster - it'll just create lots of unnecessary noise.

[claudiu64]

@softvision-raul-bucata The error can be reproduced, where the video does not start and the video and audio are stuck. Also test with a 60fps phone, not 120fps or higher, to try to reproduce the main bug as well.

[softvision-raul-bucata]

@claudiu64 If you can provide a tool or setting that checks the FPS of the Android device, I will gladly do so, as I have a feeling that the devices tested on are above 60fps. The reason why the videos get stuck when scrolling is because they are not fully loaded for a brief second, and that might be observed differently, depending on the devices.

The error can be reproduced, where the video does not start and the video and audio are stuck

That seems to be an entirely different error than the one submitted here.

[inv_19/2024]