A second, but more complicated option, is to directly build libffmpeg from the chromium-browser source -- which is exactly what every packager of chromium-codecs-ffmpeg-extra does.
(the latter is what I do -- compile from source; only because I was having issues finding the extract version of chromium-codecs-ffmpeg-extra (depending on the version I might find it or not).
Like I was saying compiling libffmpeg is not easily done as it requires checking out the entire code-based for chromium browser and then checking out the specific revision -- tied to the tagged version that is needed.
Also even before checkout, there is a complicated dance needed to be done to run the depot_tools gclient (which is a custom client used to stage and build the source).
Yes, telling people just to use a different browser is an option, but for people who are largely tied to the browser that they use....that isn't really an actual option for them.
And, so since opera does not ship a proper libffmpeg.so (it is built based on chromium, the target can be changed to a chrome build). The chromium target lacks support for certain codec, but chaning the target to chrome exposes all of the extra codecs (changing the target is as simple as editing a single file and replacing a string).
in third_party/ffmpeg/ffmpeg_options.gni :
change ffmpeg_branding = _default_ffmpeg_branding
to ffmpeg_branding = "Chrome"
It means that every user who is not running Ubuntu will have to resort to some out-of-band/out-of-channel process or procedure to get proper libffmpeg support in opera (meaning taking pre-build packages and extacting the plugin, or building from source, etc -- it just the way things are.
The might even be Google trying to force people to use chrome -- since the only official build that supports the codec is a "chrome" branded build.