Sometimes, updates are awful. They break things, they undo configuration options you were sure you had set at some point in the past (either resetting them to defaults or removing them entirely).
I updated my Arch install for the second time in two days in the hopes that some minor bugs would be resolved (more on that in another post), but I hadn’t noticed that Firefox was included in the update list (version 42 to 43). Sadly, not only did this break Firefox’s appearance using oxygen-gtk, but it also broke HTML5 video. Every video on Youtube refused to load following the updates unless Flash was enabled (I have it disabled), and I couldn’t figure out why. A new profile proved somewhat useful: Youtube would work–unless I copied my old profile over in bits and pieces.
After about a half hour of exploring, I found that the culprit was actually in the profile’s prefs.js. In particular, because I had found some instructions on enabling HTML5 under Linux, apparently there were some configuration options that are no longer used and conflict with Firefox 43, which enables many of these by default.
If you encounter a similar problem, the fix should be relatively easy. Simply remove:
user_pref("media.fragmented-mp4.exposed", true); user_pref("media.fragmented-mp4.gmp.enabled", true);
From your prefs.js, restart Firefox, and verify that it still works. If not, try removing all of the media.* preferences. If that still doesn’t work and you’re a user of FlashBlock, try uninstalling it and removing any residual preferences (also from prefs.js).
I used to recommend using FlashBlock in combination with NoScript to reduce the browser’s attack surface, but as fewer and fewer sites I encounter actively use Flash, I find that disabling the plugin (settings, addons, plugins) works best for me. Unfortunately, the author included a new feature to block HTML5 video by default, and I’ve found that it tends to cause breakage with some sites, most notably Youtube. Since then, I’ve had the plugin disabled, but as I no longer have a need for it, why keep it around?
Hopefully, if you’ve encountered a similar problem with HTML5 video, the suggested fixes here will work for you. If not, feel free to leave a comment or pester me on Twitter (@zancarius).
(I still haven’t gotten Firefox 43 to play nicely with oxygen-gtk3, so I may eventually consider abandoning the theme–though I find breeze-gtk still contains a variety of display bugs that make it unpleasant to use.)