Telephonic communications – Echo cancellation or suppression
Reexamination Certificate
1997-11-13
2001-11-20
Kuntz, Curtis (Department: 2643)
Telephonic communications
Echo cancellation or suppression
C379S202010, C370S286000, C348S014090
Reexamination Certificate
active
06320958
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a remote conference system, and more particularly to a remote conference system which transmits voice data using multicast in a server client model.
In a conventional remote conference system, each of conference terminals and a conference controller are mutually connected. Each conference terminal transmits voice data to the conference controller. The conference controller synthesizes the voice data transmitted from each of the conference terminals, and transmits the synthesized voice data to each of the conference terminals. At the time of synthesizing the voice data, the conference controller performs echo canceling processing in order to prevent echo (e.g., howling) in each of the conference terminals.
The echo canceling processing is the one in which the voice data already transmitted from a certain conference terminal is canceled from voice data to be transmitted to that conference terminal. For example, assuming that voice data from a conference terminal A be “a”, voice data from a conference terminal B be “b”, and voice data from a conference terminal C be “c”, voice data (b+c) is transmitted to the conference terminal A, voice data (c+a) is transmitted to the conference terminal B, and voice data (a+b) is transmitted to the conference terminal C.
In the conventional remote conference system, since the different voice data are transmitted from the conference controller to the conference terminals, the conference controller must synthesize the voice data for each conference terminal one by one. In addition, the conference controller must transmit each of the voice data one by one (i.e., unicast transmission). Therefore, loads for processing in the conference controller increase and traffics on networks increase, resulting in an increase in data delay.
SUMMARY OF THE INVENTION
In view of the foregoing problem of the conventional system, an object of the present invention is to provide a remote conference system which averages the processing load over the whole of the system and suppresses the traffics on the network while possessing an echo canceling function.
In one preferable embodiment of the present invention, one conference terminal cancels its own voice data from a synthesized voice data which is obtained by synthesizing voice data produced by all of other conference terminals.
With the unique and unobvious structure of the present invention, the terminal voice data causing the echo is canceled from the synthesized voice data transmitted by a multicast transmission.
REFERENCES:
patent: 4825433 (1989-04-01), Deschaine
patent: 5379280 (1995-01-01), Cotton et al.
patent: 5436896 (1995-07-01), Anderson et al.
patent: 5940479 (1999-08-01), Guy et al.
patent: 6118763 (2000-09-01), Trumbull
Eng George
Foley & Lardner
Kuntz Curtis
NEC Corporation
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