This issue seems to keep coming up. It happens, I research how to fix it, then forget about it, then it happens again.
This time I tried re-installing chromium-ffmpeg-extra which did not work for me but then I upgraded to opera 60.0.3255.27 which did work (today)
the issue keeps coming up because every time opera upgrades it must be fixed again.
This time I found this thread: https://forums.opera.com/topic/27463/bug-html5-h-264-codec-videos-no-longer-working-on-opera-54-0-2952-41-ubuntu-18-04-lts-x86_64-xfce/7
Which recommended removing operas libffmpeg.so and creating a symlink to chrome's
These instructions may very based on where things are in your distro but for me running linux mint 18 I did this:
- find opera dir and cd into it.
- rename opera's libffmpeg.so to back it up
- create symlink to chrome's libffmpeg.so
$ which opera
$ ls -al /usr/bin | grep opera
lrwxrwxrwx 1 root root 35 Jun 4 16:33 opera -> ../lib/x86_64-linux-gnu/opera/opera
$ cd /usr/lib/x86_64-linux-gnu/opera
$ sudo mv libffmpeg.so libffmpeg.so.bak
$ sudo ln -s /usr/lib/chromium-browser/libffmpeg.so
$ ls -al | grep libffmpeg.so
lrwxrwxrwx 1 root root 38 Jun 11 06:53 libffmpeg.so -> /usr/lib/chromium-browser/libffmpeg.so
-rw-r--r-- 1 root root 1799080 Jun 4 16:33 libffmpeg.so.bak
Obviously the important line is
sudo ln -s /usr/lib/chromium-browser/libffmpeg.so But I displayed the rest so that people could figure out how to know which directory they needed to be in.
Also I have chrome browser installed. If you do not then you may have to install it for this solution to work.
I hope this is helpful.
I do not yet know if I will have to repeat these steps the next time opera upgrades ... probably.