I am trying to get rid of Flash (using Flasblock) in my Firefox but I have a problem with YouTube.

After blocking it Firefox switched YT player to HTML5 but there is only 360p resolution available!

I searched in the internet to find a solution and I've tried changing few options in about:config to look like this:

  • media.mediasource.enabled; true
  • media.mediasource.mp4.enabled; true
  • media.mediasource.webm.enabled; true
  • media.mediasource.whitelist; true
  • media.fragmented-mp4.enabled; true
  • media.fragmented-mp4.exposed; true
  • media.fragmented-mp4.ffmpeg.enabled; false
  • media.fragmented-mp4.gmp.enabled; false
  • media.fragmented-mp4.use-blank-decoder; true

And when I go to https://www.youtube.com/html5 Everything is OK but when I try to play some video on YT I get a green screen and a beep sound.

But now I can choose the resolution.

Does anyone know how to fix this?

It works fine in Chrome

  • Could you open youtube.com/html5 in Firefox and see if everything is supported? it works fine in my Firefox. you might have an outdated version on your computer. – Nzall Aug 16 '15 at 13:41
  • I have the newest version of Firefox. This is how it looks it youtube.com/html5: imgur.com/YsMw9Qk. Afer I change these 2 entries in about:config it's all supported but I have green screen and beep sound... – Krzysztof Majewski Aug 16 '15 at 13:54
  • Try reinstalling Firefox. I have the most recent version of it as well, yet I support everything except the bottom-right option. you need to at least support H.264 video for Youtube to work. – Nzall Aug 16 '15 at 13:56
  • Also, there's no reason to use a flash blocker, just install it from your PC entirely. – Nzall Aug 16 '15 at 13:59

You have to set the option media.fragmented-mp4.use-blank-decoder to false, this is the cause of your problem.

  • Yes. I have already figured it out. But thanks anyway :) – Krzysztof Majewski Aug 17 '15 at 8:00

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