Why would Firefox stop playing HTML 5 videos on youtube?
My firefox browser recently stopped playing some youtube videos that it played many times previously for several years. Now I get the ominous black screen that says "Your browser does not recognize any of the video formats available." If I "Click here to visit our frequently asked questions about HTML 5 video" the youtube help page says the browser does not support H.264.
Background information: "OpenH264 Video Codec ..." is installed as a plug-in and activated. Flash is installed, but the current version is outdated and has been disabled for a long time. I have very few other add-ons or plug-ins, and disabling them or starting Firefox in safe mode does not help.
Here are all entries in about:config that mention h264 (none of which I ever manually changed): media.gmp-gmpopenh264.abi;x86_64-msvc-x64 media.gmp-gmpopenh264.enabled;true media.gmp-gmpopenh264.lastUpdate;1510594527 media.gmp-gmpopenh264.version;1.7.1 media.gmp.decoder.h264;0 media.navigator.video.h264.level;31 media.navigator.video.h264.max_br;0 media.navigator.video.h264.max_mbps;0
I was always unable to play Vine videos when they existed, and often can't play embedded video on other sites, but youtube always worked before, always, for several years. Either youtube has migrated a lot of their videos to a new format, or something changed on my system that I am not aware of. The question is how to identify or troubleshoot the problem.
All Replies (3)
Hi argnotagain, the Cisco plugin is used for WebRTC applications like Google Voice. For MP4/H.264 video, Firefox uses Media Foundation, a component supplied by Microsoft. Some versions of Windows do not come with Media Founation pre-bundled and it needs to be installed separately. See: Fix video and audio problems on Firefox for Windows N editions.
Assuming you have Media Foundation installed, could you check these settings:
(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk.
(2) In the search box above the list, type or paste webm and pause while the list is filtered
(3) If the media.webm.enabled preference is bolded and "modified" or "user set" to false, double-click it to restore the default value of true
(4) In the search box above the list, type or paste wmf and pause while the list is filtered
(5) If the media.wmf.enabled preference is bolded and "modified" or "user set" to false, double-click it to restore the default value of true
(6) In the search box above the list, type or paste mp4 and pause while the list is filtered
(7) If the media.mediasource.mp4.enabled preference is bolded and "modified" or "user set" to false, double-click it to restore the default value of true
(8) If the media.mp4.enabled preference is bolded and "modified" or "user set" to false, double-click it to restore the default value of true
(9) In the search box above the list, type or paste mediaso and pause while the list is filtered
(10) If the media.mediasource.enabled preference is bolded and "modified" or "user set" to false, double-click it to restore the default value of true
Then check the following page again:
Does YouTube report that all formats, except perhaps the last one, are available?
By the way, two Flash-related things:
(1) If you have any Flash extensions for YouTube, remove (or at least disable) those to avoid HTML5 video being blocked. You can do that on the Add-ons page. Either:
- Ctrl+Shift+a (Mac: Command+Shift+a)
- "3-bar" menu button (or Tools menu) > Add-ons
- type or paste about:addons in the address bar and press Enter/Return
In the left column of the Add-ons page, click Extensions.
Then cast a critical eye over the list on the right side. Any extensions Firefox installs for built-in features are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Anything referring to Flash on YouTube is obsolete and may cause problems with HTML5 video. If in doubt, disable (or remove).
(2) Your Firefox reported your Flash as version 24, which is very outdated. See: Flash Plugin - Keep it up to date and troubleshoot problems.
My system has Windows Media Foundation installed, but it's a very old version. I can't install the latest version because I don't have the latest service pack, and can't install the latest service pack because of one of those mysterious Windows errors that not even god can diagnose. So maybe I am out of luck. Perhaps the problem is that youtube has been migrating its content to a different format, and nothing changed on my system, and I could never play h.264 media.