摘要：This article proposes a new focus of research for multimedia
conferencing systems which allows a participant
to flexibly select another participant or a group for
media transmission. For example, in a traditional conference
system, participants voices might by default be
shared with all others, but one might want to select a
subset of the conference members to send his/her media
to or receive media from. We review the concept of
narrowcasting, a model for limiting such information
streams in a multimedia conference, and describe a design
to use existing standard protocols (SIP and SDP)
for controlling fine-grained narrowcasting sessions.
关键词：Conferencing;Device Capability;Media Direction Control;Narrowcasting;Privacy and Awareness;SDP;SIP
