Support standards like AC3 with 5.1 passthrough and MKV containers

[WebWeWantBot]

I want browsers to natively support AC3 (Dolby Digital) audio — including 5.1 surround sound passthrough — and the Matroska (MKV) container format.

Desktop applications like VLC, MPC-HC, and Windows Media Player have supported AC3 5.1 passthrough for over two decades. Microsoft Edge previously supported AC3 playback with 5.1 passthrough, but recent versions no longer pass through the surround channels. Chrome and Firefox do not support AC3 at all, even though AC3 patents expired years ago.

Modern browsers should be at least on par with long-established open-source and platform video players when it comes to widely-used codecs and containers. There is no longer a patent barrier for AC3, yet users who have media files with AC3 audio tracks cannot play them in the browser without transcoding.

Similarly, the Matroska container (MKV) has been a widely adopted successor to MP4 for years, supporting a broader range of codecs and features. Yet browsers that can play MP4 files refuse to play MKV files — even when the underlying codec (such as H.264 or VP9) is fully supported. Users should not need to rename or remux their files just to play them in a browser.