This Recommendation defines the procedures for use of more than one video channel in H.320-based systems, and for labelling individual channels with a "role", which indicates
requirements for processing the channel and the role of the channel content in
ITU-T H.239-2005 history
2014ITU-T H.239-2014 Role management and additional media channels for ITU-T H.300-series terminals
2005ITU-T H.239-2005 Role management and additional media channels for H.300-series terminals Study Group 16