The activeSourceBuffers read-only property of the MediaSource interface returns a SourceBufferList object containing a subset of the SourceBuffer objects contained within SourceBuffers — the list of objects providing the selected video track,  enabled audio tracks, and shown/hidden text tracks.
The addSourceBuffer() method of the MediaSource interface creates a new SourceBuffer of the given MIME type and adds it to the MediaSource's SourceBuffers list.
The duration property of the MediaSource interface gets and sets the duration of the current media being presented.
The endOfStream() method of the MediaSource interface signals the end of the stream.
The isTypeSupported() method of the MediaSource interface returns a Boolean value indicating if the given MIME type is supported by the current user agent — this is, if it can successfully create SourceBuffer objects for that MIME type.
The MediaSource() constructor of the MediaSource interface constructs and returns a new MediaSource object with no associated source buffers.
The readyState read-only property of the MediaSource interface returns an enum representing the state of the current MediaSource. The three possible values are:
The removeSourceBuffer() method of the MediaSource interface removes the given SourceBuffer from the SourceBuffers list associated with this MediaSource object.
The sourceBuffers read-only property of the MediaSource interface returns a SourceBufferList object containing the list of SourceBuffer objects associated with this MediaSource.