I just noticed this problem too and it looks like Opera 44 is no longer using the libffmpeg.so from the chromium package. On Debian/Ubuntu the unrestricted libffmpeg.so is in the package chromium-codecs-ffmpeg-extra but Opera 44 is not using that version.
The workaround fix is to rename or delete /usr/lib/i386-linux-gnu/opera/libffmpeg.so and then move or link /usr/lib/chromium-browser/libffmpeg.so into /usr/lib/i386-linux-gnu/opera/libffmpeg.so
Directory paths above are for 32 bit system, the 64 bit systems put have a slightly different path.