Although I’ve got a minidlna server running on the FreeBSD storage box upstairs, the disappearance of the DLNA/UPNP plugin for Gnome Videos a few versions ago left the web browser as my main way of accessing music there. Come the release of Firefox 38 and that stopped working for mp3 files. Simple fix below.
Never mind why Mozilla chose to disable mp3 playback with Firefox 38. It’s really irrelevant to me. Just one more reason to look for a replacement.
Until then, however, you can restore mp3 playback in Firefox 38 by going into about:config and setting the following two preferences:
media.gstreamer.enabled: true media.gstreamer.enable-blacklist: false
That first preference has been in Firefox’s config for awhile. Not sure about the second. When I finally got in there I found that both were set to true. Setting “media.gstreamer.enable-blacklist” to “false” restored mp3 playback for me.
Note that this preference may/will be changed on your next browser upgrade, so be vigilent!
Being a licensee of the mp3 codec implemented for gstreamer (by purchasing Fluendo’s OnePlay Codec Pack), I think I have a right to use my web browser of choice to access mp3 content. I know that isn’t the case for every Linux user, many of whom use the unlicensed implementation in gstreamer-plugins-ugly.
Cue the inspirational promotional video, legally shared on YouTube:
 That’s not a legal opinion, of course. The Rules of Professional Conduct explicitly state that retired attorney’s aren’t allowed to give legal opinions.