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 seekable read-only property of the HTMLMediaElement returns a TimeRanges object that contains the time ranges that the user is able to seek to, if any.
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 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 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.