MediaStreamIdSemanticAttributeMsIdList Property

Gets or sets the space-delimited list of msids for which a given semantic is used. An empty list of identifiers is an indication that the sender supports the indicated semantic, but has no msid groupings of the given type in the present SDP. An identifier of "*" is an indication that all "a=msid" lines in the SDP have this specific semantic. If "*" is not used, each msid-id in the SDP MUST appear in one and only one "msid-semantic" line.