Phantom sources for separation of listening and viewing positions of multipresent avatars in narrowcasting collaborative virtual environments

Our group is exploring interactive multimedia, especially for virtual and mixed reality groupware systems. The apparent paradoxes of multipresence, having avatars in multiple places or spaces simultaneously, are resolvable by an "autofocus" feature, which uses reciprocity, logical exchangability of source and sink, to project overlaid sound-scapes and simulate precedence effect to consolidate the audio display. We review an interface to control source←sink transmissions in synchronous groupware (like teleconferences, chatspaces, virtual concerts, etc.), supporting spatial audio multipresence with narrowcasting functions in a collaborative virtual environment, implemented in a Java3D application, "Multiplicity". The interface allows interactation with other clients in our groupware suite (including mobile phone, stereographic panoramic browser, and multispeaker systems). "Phantom sources" are used to control superposition of soundscapes relative to a selected viewpoint. Relative displacement from sources←sinks can be used to display phantom sources from alternate locations, exocentrically visibly and endocentrically auditorilly. A extra feature of the phantom source displacement is the accommodation of a rotatable speaker axis (including median plane arrangement).