HTML5 “proprietary” audio and video includes all media types that are patented, such as MP4 (H.264/AAC). Under Linux, Vivaldi requires a suitable, third-party support file to play these. If you start Vivaldi from a “Terminal” using the command vivaldi-stable & the output will include steps to install a support file.
No suitable library forHTML5 proprietary media(MP4[H.264/AAC])was found,
therefore only open codecs will play.
Toadd support forproprietary media,issue the following command andrestart