DYNAMIC BIT ALLOCATION IN VIDEO COMBINING FOR MULTIPOINT CONFERENCING

For multipoint video conferencing over a wide-area network, a video br idge is often used to combine the coded video signals from multiple pa rticipants into a single video fdr display. The video combining can be done in the coded-domain by concatenating coded video bit-streams, or in the pixel-domain by transcoding. In this paper we compare the vide o quality using the two approaches for a multipoint video conference o ver a symmetrical wide-area network such as Integrated Service Digital Network (ISDN), We observe that in most multipoint video conferences usually only one or two persons are active at one time, while other pa rticipants are just listening with little motion. To achieve similar v ideo quality for all the conference participants, the active persons r equire higher bit rates than the inactive persons. By doing video comb ining using the transcoding approach and dynamically allocating more b its to the active persons, we show that the achieved video quality can be much better than that can be achieved using the coded-domain video combining approach.