The about:config options media.windows-media-foundation.enabled does not exist for me.
I cannot play instagram videos at all, or twitter videos, tumblr videos or vines on tumblr (vines on the vine site do work). Various other random players which I don't know the name of (such as the first video on this page http://www.rugbydump.com/2016/05/5073/ben-botica-inexplicably-kicks-the-ball-away-as-harlequins-attempt-late-comeback-in-final) don't work either. As the title states, the option media.windows-media-foundation.enabled in about:config doesn't exist, and neither does media.fragmented-mp4.enabled. Changing media.mediasource.mp4.enabled or media.wmf.enabled to false does not fix the problem. I have started Firefox in safe mode, reset it and reinstalled it. I've also downloaded the feature pack for Windows 10. My graphics card drivers, plugins and add-ons are all up to date. Other data given below. This is becoming incredibly frustrating.
Modified by 4ltman
الحل المُختار
thanks, so firefox depends on the decoders for h264 that your system provides (have to be separately downloaded in windows n versions). i think this one is the newest version that should apply to a fully updated version: https://www.microsoft.com/en-us/download/details.aspx?id=49919 an older download for systems before the november upgrade would be here: https://www.microsoft.com/en-us/download/details.aspx?id=48231
maybe its installation didn't work the first time?
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is the issue still reproducible while you run firefox in safemode? (that wasn't clear from your description)
Yes, the issue prevails while in safe mode.
do you get any error message instead of the video playback?
& does it make a difference when you reset all the custom entries in about:config that begin with "gfx.crash-guard.status." and restart afterwards? (supportsHardwareH264: No; Failed to create H264 decoder in your system details would suggest there may be some issues there)
For twitter videos it gives the error message "This browser does not support video playback." No other video types give an error message. When I click on an instagram video the play button icon disappears but it won't play. For vines on tumblr it will loop but just shows a black image, no audio. For tumblr videos it gives no response at all.
Resetting those entries make no difference.
what status/supported features do you get at this page? https://www.youtube.com/html5
"H.264" and "MSE & H.264" are not enabled (red ! icon). All others are fine.
ok, this looks like the root of the issue in a likelihood. are you on a N version of windows 10 & does it say the same in a new profile? Profile Manager - Create, remove or switch Firefox profiles
It is Windows 10 N. I've created a new profile but I don't know how to check whether it says the same as the firefox profile, I only know how to check for Windows 10 N by going to System>About in settings.
الحل المُختار
thanks, so firefox depends on the decoders for h264 that your system provides (have to be separately downloaded in windows n versions). i think this one is the newest version that should apply to a fully updated version: https://www.microsoft.com/en-us/download/details.aspx?id=49919 an older download for systems before the november upgrade would be here: https://www.microsoft.com/en-us/download/details.aspx?id=48231
maybe its installation didn't work the first time?
Wow, thanks that's fixed it. Yeah I'm not sure what happened originally, I tried downloading that earlier one just a little while ago and it did nothing, but the most recent one has done the job.
So Windows 10 has just updated, and as a result the problem has now reoccurred. To anyone else with the issue, wait for the Firefox update then download this https://www.microsoft.com/en-us/download/details.aspx?id=53356
Modified by 4ltman
yes, unfortunately the download changes after each major microsoft update. also see our article on the subject for current download links: Fix video and audio problems on Firefox for Windows N editions
4ltman said
So Windows 10 has just updated, and as a result the problem has now reoccurred. To anyone else with the issue, wait for the Firefox update then download this
Not a issue for those who do not have a N or KN version of Windows.