Television – Two-way video and voice communication – Conferencing
Reexamination Certificate
1998-11-30
2001-04-03
Kuntz, Curtis (Department: 2643)
Television
Two-way video and voice communication
Conferencing
C348S014100, C348S014100
Reexamination Certificate
active
06211902
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a video conference control apparatus, video conference control method, and video conference control system.
Conventionally in an MCU (MicroControl Unit) having a window synthesis function, image data from respective terminals are decoded, and the decoded data are reduced in accordance with the window division number. At the same time, synthesized image data obtained by window division and multiplexing is encoded again, and the encoded data is output as a synthesized window to the respective terminals.
FIG. 4
shows an example of a video conference control system having this window synthesis function. Note that
FIG. 4
shows only image synthesis, and all the functions about an audio system are not illustrated.
A video conference control system
100
is constituted by n video conference terminals
200
and a video conference control apparatus
300
connected to the video conference terminals
200
via a network. The video conference control apparatus
300
synthesizes transmitted images from the video conference terminals
200
and distributes the synthesized image to the video conference terminals
200
.
The video conference terminal
200
is a video conference terminal complying with, e.g., ITU (International Telecommunication Union)-T_H. 320. In this case, encoding/decoding complying with ITU-T_H. 261 is performed.
The video conference control apparatus
300
connected to the video conference terminals
200
via a network using n lines has a window synthesis function. An encoding circuit
350
and a decoding circuit
320
must also comply with ITU-T_H. 261. The following example is based on encoding/decoding complying with ITU-T_H. 261.
An image transmitted from each video conference terminal
200
is demultiplexed into image data, audio data, and other data by a multiplexing/demultiplexing circuit
310
of the video conference control apparatus
300
.
The terminal image data demultiplexed by the multiplexing/demultiplexing circuit
310
is decoded by the decoding circuit
320
. The decoded data is thinned to 1/N in the horizontal and vertical directions and reduced to 1/N of one frame in accordance with the window division number by a thinning circuit
330
on the basis of a thinning timing signal. The resultant data is output as divided image data to an image synthesizing circuit
340
.
The image synthesizing circuit
340
selects divided window data selected by a display window selection signal from respective divided image data, synthesizes (multiplexes) N windows on the basis of a synthesis timing signal (multiplexing timing signal), and outputs the N windows as synthesized image data to the encoding circuit
350
.
The encoding circuit
350
compresses and encodes the synthesized image data as one image frame, and distributes the synthesized window to each video conference terminal
200
via the multiplexing/demultiplexing circuit
310
. At the same time, the encoding circuit
350
outputs a compression/encoding frame timing signal to a window synthesis timing generating circuit
360
.
The window synthesis timing generating circuit
360
outputs the frame timing signal, the thinning timing signal corresponding to a set window division number N, and the synthesis timing signal.
A video conference control apparatus having almost the same arrangement as that of the video conference control apparatus
300
is disclosed in Japanese Patent Laid-Open No. 2-5690.
In the conventional video conference control apparatus
300
, the image quality may visually degrade near the boundary between divided windows.
FIG. 5
shows a display window when divided image data corresponding to the respective video conference terminals
200
are synthesized and displayed by the image synthesizing circuit
340
.
In
FIG. 5
, one effective frame area represents an image data area actually encoded by the encoding circuit
350
. This area is a unit for controlling encoding characteristics (e.g., quantization characteristics) in accordance with the information generation amount of an image in 352 pixels×288 lines in compliance with ITU-T_H. 261, and corresponds to a macroblock (16 pixels×16 lines: FCIF format) in compliance with ITU-T_H. 261. Note that
FIG. 5
exemplifies a display window for the set window division number N=16.
In this case, since divided window areas are simply set in accordance with the window division number N=16, an area where the boundary between divided window areas does not always coincide with the boundary between encoding control blocks exists.
Near such a boundary between divided windows, e.g., a divided window having a large change in motion and coarse quantization characteristics and a divided window having a small change in motion and fine quantization characteristics are processed as the same encoding control block. For this reason, the image quality of the divided window having a small change in motion and fine quantization characteristics greatly degrades.
Also in the video conference control apparatus disclosed in Japanese Patent Laid-Open No. 2-5690, the image quality may visually degrade near the boundary between divided windows.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problem, and has as its object to provide a video conference control apparatus, video conference control method, and video conference control system capable of preventing visual degradation of the image quality near the boundary between divided windows.
To achieve the above object, according to the present invention, there is provided a video conference control apparatus comprising decoding means for decoding terminal images received from a plurality of video conference terminals, thinning means for thinning the terminal images decoded by the decoding means, image synthesizing means for multiplexing the terminal images thinned by the thinning means on a predetermined image frame, thereby generating a synthesized image, encoding means for encoding the synthesized image generated by the image synthesizing means, and encoding area setting means for setting encoding areas while making a boundary between the encoding areas coincide with a boundary between corresponding divided window areas.
REFERENCES:
patent: 5953050 (1999-09-01), Kamata et al.
patent: 2-5690 (1990-01-01), None
patent: 4-156084 (1992-05-01), None
patent: 4-177993 (1992-06-01), None
patent: 6-6472 (1994-01-01), None
patent: 6-70040 (1994-03-01), None
patent: 7-30875 (1995-01-01), None
patent: 7-95553 (1995-04-01), None
Kuntz Curtis
NEC Corporation
Ostrolenk Faber Gerb & Soffen, LLP
Ramakrishnaiah Melur
LandOfFree
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