Does this happen with all videos or does the YouTube website work ?

Does the Web Console show media related messages ?

Can you post a link to a publicly accessible page (i.e. no authentication or signing on required) ?

Nightly worked for a while but recently quit. I just now restarted Nightly as it had been updated. I tried a Youtube video and it would not play. I opened Help in Nightly and took a screenshot of the error message and the version of Nightly. It is attached.

Opened Web Console and here is the error message from it

Cannot play media. No decoders for requested formats: video/webm; codecs="vp09.02.51.10.01.09.16.09", video/mp4; codecs="avc1.42001E", video/webm; codecs="vp9", audio/mp4; codecs="mp4a.40.2", audio/webm; codecs="opus", video/mp4; codecs="avc1.42001E mp4a.40.2" watch

Web page causing problem

https://www.youtube.com/watch?v=2OhndNJYnbc

Make sure you have the latest FFmpeg/libavcodec packages installed.

I have the latest versions installed. Here is the dnf info on the packages referenced. root@Vince2 vince]# dnf list ffmpeg* Last metadata expiration check: 0:01:12 ago on Wed 26 Feb 2020 12:07:11 AM EST. Installed Packages ffmpeg.x86_64 1:4.2.2-3.fc30 ffmpeg-libs.x86_64 1:4.2.2-3.fc30 Available Packages ffmpeg-devel.i686 4.1.5-1.fc30 ffmpeg-devel.x86_64 1:4.2.2-3.fc30 ffmpeg-libs.i686 4.1.5-1.fc30 ffmpegthumbnailer.i686 2.2.2-2.fc30 ffmpegthumbnailer.x86_64 2.2.2-2.fc30 ffmpegthumbnailer-devel.i686 2.2.2-2.fc30 ffmpegthumbnailer-devel.x86_64 2.2.2-2.fc30 ffmpegthumbs.x86_64 18.12.3-1.fc30 [root@Vince2 vince]# dnf list libav* Last metadata expiration check: 0:01:45 ago on Wed 26 Feb 2020 12:07:11 AM EST. Installed Packages libavc1394.i686 0.5.4-10.fc30 libavc1394.x86_64 0.5.4-10.fc30 libavdevice.x86_64 1:4.2.2-3.fc30 Available Packages libavc1394-devel.i686 0.5.4-10.fc30 libavc1394-devel.x86_64 0.5.4-10.fc30 libavdevice.i686 4.1.5-1.fc30

I'm not seeing libavcodec listed.

• https://www.ffmpeg.org/libavcodec.html
• https://www.google.com/search?sa=N&num=100&q=libavcodec

I tried to find libavcodec and it is not available as a separate package. From what I found it is included with ffmpeg

Do you check that you have current libavcodec packages/libraries installed ?

Do these videos play in other Firefox versions like release and beta ?

You can create a new profile to test if your current profile is causing the problem.

See "Creating a profile":

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

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

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

I switched to Nightly in order to watch videos because the version of FF that I had installed would not play videos. I have since updated my default FF and it now plays videos. Now tha I can watch videos in the installed version, I will stop using Nightly. To me the problem has been solved - stop using Nightly. I don't know what you intend to do with this thread but I will not be watching it any more.

Close it as unsolved if you want.

Vincent Radice