Ok i now found out about different codecs. There must be problem.

Does anyone know how to force Firefox to use avc 1.6 codec?

Link is needed so other can verify the problem your having to see what is happening.

Link of what? Video?

https://www.youtube.com/watch?v=YM1hGgyqR1c&t=410s

I tried to force that codec i posted before with some add-ons, it worked but video is still stuttering...

I tested on other computer, win 7 also, there firefox uses avc 1.6 and playback is smooth. I couldnt find way to force avc 1.6/opus 251...

i could set it to avc 1.6/ h264 something but still stuterring is going on

I would say its hardware but on edge its completely smooth playback...

Please anyone with idea of how to force that codec combination

Hi you could try this : https://addons.mozilla.org/en-US/firefox/addon/h264ify/

Firefox on youtube is using HTML5 or Flash

• https://support.google.com/youtube/topic/3014746
• https://support.mozilla.org/en-US/kb/fix-common-audio-and-video-issues
• https://support.mozilla.org/en-US/kb/html5-audio-and-video-firefox
• https://support.mozilla.org/en-US/kb/fix-video-audio-problems-firefox-windows

As to what your Video Card is trying to use or your sound no idea.

Thanks for answering but my problem is unfortunately not solved.

Yes I understand first codes is for video and second for audio. I also tryed that add on wich changed video codec but stutter is still present on 1080p YouTube video.

I shall use Edge as my full HD video playback, until Firefox solves this problem.

Anyway 720p is also good enough.

Thank you all for help!

I went to the site and loaded without problems. The problem I see going on is you go in Safe Mode and have issues which to me tells that FF was corrupted or a bad install. Anytime you have issue with software that can run in Safe Mode something is wrong with that software and needs to be uninstalled completely and deleting the Mozilla folder and reinstalling again to fix the bad install.

WestEnd said

I went to the site and loaded without problems. The problem I see going on is you go in Safe Mode and have issues which to me tells that FF was corrupted or a bad install. Anytime you have issue with software that can run in Safe Mode something is wrong with that software and needs to be uninstalled completely and deleting the Mozilla folder and reinstalling again to fix the bad install.

Hello, thanks for answer, i already reinstalled Firefox, problem is not instalation. But thanks anyway. Maybe it is something with my laptop, on PC it works without problem (although without flash player installed). I will try to uninstall flash and test.

Well, the issue at this time is with you and your install. I have no problems with any videos on any sites. You could try this : uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files , C:\Program Files(x86) & C:\ProgramData Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Reinstall with Current Release Firefox 60.0.2 with a Full Version Installer

• https://www.mozilla.org/firefox/all/

So if above does not work it maybe something you have done and is saved in your Profile. Profile : Make a new one and test ...:

• https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

If is your Profile :

• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Please let us know if this solved your issue or if need further assistance.