Hi @sylarxyz, for Opera stable 37 on Linux distros based on Debian/Ubuntu, you can install the "chromium-codecs-ffmpeg-extra" package, and videos encoded in H.264 should simply work without a problem.
For any other 64-bit Linux distro (and also if you want to make it work in Opera beta and Opera developer), just follow the below steps:
Navigate to the Opera's installation folder (find the path in Opera's menu > About Opera), and create there a new folder "lib_extra",
Download the "opera-ffmpeg-codecs" package for: Opera stable, Opera beta, or Opera developer, and extract the "libffmpeg.so" file to this folder.
Alternatively, if you are using 32-bit Linux distribution, you can download the appropriate packages from here 😉
