The HTML Media Extensions Working Group has published a Proposed Recommendation of Media Source Extensions™.

This specification allows JavaScript to dynamically construct media streams for <audio> and <video>. It defines a MediaSource object that can serve as a source of media data for an HTMLMediaElement. MediaSource objects have one or more SourceBuffer objects. Applications append data segments to the SourceBuffer objects, and can adapt the quality of appended data based on system performance and other factors. Data from the SourceBuffer objects is managed as track buffers for audio, video and text data that is decoded and played. Byte stream specifications used with these extensions are available in the byte stream format registry. Comments are welcome through 1 November 2016.

The group also published the following specifications as Working Group Notes:

• Media Source Extensions Byte Stream Format Registry
• MPEG-2 TS Byte Stream Format
• MPEG Audio Byte Stream Format
• ISO BMFF Byte Stream Format
• WebM Byte Stream Format