Multiplex communications – Special services – Conferencing
Reexamination Certificate
1999-03-22
2004-08-10
Phunkulh, Bob A. (Department: 2661)
Multiplex communications
Special services
Conferencing
C348S014080, C709S204000
Reexamination Certificate
active
06775247
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention generally relates to the fields of communication systems and videoconferencing. More particularly, the invention is directed to methods and apparatus for reducing the bandwidth required to conduct a multipoint conference.
Telephone conferencing systems have been available for many years. These systems have primarily focused on providing audio conferencing. A typical conference includes a group of individuals who are telephonically connected into a discussion by an operator at a central locality. In recent years, however, the addition of video capabilities has greatly increased the bandwidth required to establish a multipoint audio-video conference.
By way of example,
FIG. 1A
illustrates a conventional network
10
for conducting an audio-video multipoint conference. The network
10
includes multiple personal conferencing systems (in this example, PCS
12
a
, PCS
12
b
, PCS
12
c
and PCS
12
d
) as well as a multimedia conference unit (MCU)
14
that is coupled to PCSs
12
a
-
12
d
. In the situation where the PCSs
12
a
-
12
d
are coupled over a local area network (LAN), the network
10
is illustrative of a conventional telephony-over-LAN (ToL) network. A PCS may be a video telephone, telephony-enabled computer, and/or portable device able to send and receive to each other directly via network
10
, which may be a LAN or a wireless network.
Generally, the MCU
14
is capable of joining PCSs
12
a
-
12
d
(ToL users in this specific example) in multipoint videoconferences. During a typical multipoint videoconference, the MCU
14
receives all video and audio signals from the participating PCSs and typically re-transmits the mixed audio signals of participating PCSs and the video signal originating from the dominant or presenting PCS to all participating PCSs, including the presenter. As seen in the example of
FIG. 1A
(which does not show audio signals but only shows video signals for simplicity), supposing PCS
12
a
is the presenter, the MCU
14
receives the audio signals and video signals from all PCSs
12
a
-
12
d
, determines PCS
12
a
to be dominant, and then re-broadcasts the mixed audio signals and video signals originally from PCS
12
a
to PCSs
12
a
-
12
d
. In this example, eight video connections (video signals
15
a
-
15
d
from PCSs
12
a
-
12
d
to MCU
14
, and video signals
16
a
-
19
a
from MCU
14
to PCSs
12
a
-
12
d
, where video signals
16
a
-
19
a
carry the video signals
15
a
sent from PCS
12
a
to MCU
14
) between the MCU
14
and the PCSs
12
a
-
12
d
via LAN hub
17
are required. This conventional system requires the MCU
14
to perform high level digital signal processing (DSP) of the multiple received and transmitted audio and video signals between all parties and MCU
14
involved in the videoconference. This high level of DSP analysis results in the MCU
14
being very expensive compared to an audio-only MCU, which is comparatively simple and inexpensive. Moreover, the use of eight video streams in addition to the audio connections normally used (not shown in
FIG. 1A
) results in heavy use of network bandwidth.
Another conventional approach to videoconferencing utilizes an MCU
14
capable of providing a multicast stream, as shown in the example of FIG.
1
B. In the example of
FIG. 1B
(which does not show audio signals but only shows video signals for simplicity), supposing PCS
12
a
is presenting, MCU
14
receives the audio signals and video signals from all PCS
12
a
-
12
d
, determines PCS
12
a
to be dominant, and then re-transmits the mixed audio signals and the video signals from PCS
12
a
to PCS
12
b
-
12
d
in a multicast stream. In this example, the required video streams are reduced to five video streams (video signals
15
a
-
15
d
from PCSs
12
a
-
12
d
to MCU
14
, and video multicast signal
20
a
from MCU
14
to PCSs
12
b
-
12
d
, where video multicast signal
20
a
carries the video signals
15
a
originally sent from PCS
12
a
to MCU
14
) between the MCU
14
and the PCSs
12
a
-
12
d
via LAN hub
17
, when the presenter PCS
12
a
views its own presentation. It should be noted that in those cases where the presenter PCS
12
a
wishes to view someone else's presentation, an additional video stream (
15
b
, shown in
FIG. 1B
as a dotted arrow from MCU
14
to LAN hub
17
, where the dotted arrow
15
b
carries the video signal of a participant, e.g. PCS
12
b
, other than the presenter) from the MCU
14
to the PCS
12
a
via LAN hub
17
is required (and video
20
a
to PCS
12
a
would replace video
15
b
to PCS
12
a
), for a total of six video streams. Although the reduction in video streams from MCU multicast capability reduces the required DSP analysis somewhat, MCU
14
must still be capable of processing at least five video streams, which is still very expensive in comparison to an audio-only MCU.
In addition to requiring expensive processing power in the MCU
14
, multiple audio and video streams for supporting the videoconference session require large network bandwidth resources, which may not be available in some circumstances when network traffic is heavy. Therefore, what is desired is an improved method and apparatus for reducing the bandwidth required to conduct a videoconference.
SUMMARY OF THE INVENTION
Broadly speaking, the invention relates to an improved method, apparatus and system for reducing the digital signal processing analysis required to support a multipoint conference call among a plurality of callers coupled via a network to a multimedia conference unit. The multimedia conference unit first determines which caller is a dominant caller, the other callers being subordinate callers. The multimedia conference unit then commands the subordinate callers to suppress a portion of their signals passed over the network. In some embodiments, the portion are video signals, and only the dominant caller transmits video signals to at least the subordinate callers either via the multimedia conference unit or directly to the subordinate callers, depending on whether point-to-point connection capability between callers exists.
In one embodiment, the callers pass audio signals and video signals over the network, and the multimedia conference unit uses the audio signals to determine which of the callers is dominant. In another embodiment, when the multimedia conference unit determines that the dominant caller has changed, the multimedia conference unit commands the previous dominant caller to stop sending video signals in the form of video packets and the new dominant caller, if not already sending video signals, to start sending video signals in the form of video packets.
These and other embodiments with advantages of the present invention will become apparent from the following detailed description and drawings.
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patent: 5684527 (1997-11-01), Terui et al.
patent: 5710491 (1998-01-01), Takagi et al.
patent: 5729532 (1998-03-01), Bales et al.
patent: 5801756 (1998-09-01), Iizawa
patent: 5818513 (1998-10-01), Sano et al.
patent: 5841763 (1998-11-01), Leondires et al.
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Beyda William J.
Shaffer Shmuel
Phunkulh Bob A.
Siemens Information and Communication Networks Inc.
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