Video playback from HTML5 sources such as youtube, vimeo and vessel has been slow and choppy in Firefox, while they all worked well in Chrome (I'm on a slow, old box, the CPU is Core2 Duo, the video card is more recent, nVidia GTX650 with the binary drivers). Finally, I've found that Firefox 37 allowed me to play back everything at good speed and full resolution (1080p) at full screen with the following settings:
- Firefox -> Preferences -> Advanced -> General -> Use hardware acceleration when available: YES
- about:config
- media.mediasource.enabled = true
- media.mediasource.mp4.enabled = false (if set to true, youtube would not play videos with the HTML5 player at all)
- media.mediasource.webm.enabled = true
- media.mediasource.youtubeonly = true
Updated settings for Firefox 40
Quoted from http://news.softpedia.com/news/how-to-enable-1080p-youtube-support-in-f…
I also removed (reset to empty default) media.mediasource.youtubeonly
Firefox 43
According to https://bbs.archlinux.org/viewtopic.php?id=206285:
In previous version I manually edited some things in about:config regarding html5 video, so that was the cause of the problem. The new Firefox uses ffmpeg by default, instead of gstreamer. To fix it, I set `media.fragmented-mp4.gmp.enabled` to `false`.