Media Type Subnames

You can define multiple versions of a media profile for a single codec by using the subnames feature. You can then reference the new media profile by a combination of the media profile name and media profile subname.

Some media types are not unique per just their value in an SDP m= line, they must be uniquely identified by looking at additional SDP parameters. For example, you can define a media profile for G729, when only the parameter and value annexb=yes is present in the SDP. By creating a media profile + subname that defines both a media type and parameter, you can perform various operations on G729 only when annexb=yes is encountered.

Some applications of media type subnames are:

• maintaining different versions of the same codec with different bandwidth ceilings
• maintaining different versions of the same codec with different ptimes
• grouping codecs by using customer as a subname
• grouping codecs by using realm as a subname