Television – Two-way video and voice communication – User positioning
Reexamination Certificate
1999-02-03
2001-03-06
Kuntz, Curtis A. (Department: 2643)
Television
Two-way video and voice communication
User positioning
C348S014160, C375S240130
Reexamination Certificate
active
06198500
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multi-point conference system and a conference terminal device, and more particularly to a multi-point conference system in which a video conference is held using decentralized conference terminal devices and a conference terminal device used in the system.
2. Description of the Related Art
A multi-point conference system by which users who are in remote places can participate in a conference has been put to practical use. In such a multi-point conference system, conference terminal devices each of which has at least a camera device, a display device, a microphone and a loudspeaker are connected by a network such as dedicated lines, public lines or a LAN (Local Area Network). In this system, smooth image change in each of the conference terminal devices is desired.
FIGS. 1A and 1B
illustrate a conventional multi-point conference system. Referring to
FIGS. 1A and 1B
, a multi-point control unit
100
is connected with a plurality of conference terminal devices. In this case, four conference terminal devices
101
-
1
~
101
-
4
are connected to the multi-point control unit
100
.
Each of the conference terminal devices has a transmitting/receiving function for voice signals and image signals and a constitution of switching a coding operation between an interframe coding operation and an intra-frame coding operation. A conference terminal device at a transmitting side codes an initial frame of image data by the intra-frame coding operation and codes frames after the initial frame of the image data by the interframe coding operation. The interframe coding operation is then switched to the intra-frame coding operation at predetermined intervals (a predetermined number of frames). The intra-frame coded data and the interframe coded data are successively transmitted from the conference terminal device at the transmitting side. A conference terminal device at a receiving side decodes intra-frame coded data and stores the decoded frame data. When the next inter-frame coded data is received, the interframe coded data is decoded using the stored decoded frame data. A dynamic image is then displayed using the decoded frame data.
In addition, the multi-point control unit
100
has a function for distributing image data from each conference terminal device to other conference terminal devices. The various types of distribution of the image data have been proposed. For example, the following system has been known. In the system, one or more speakers who speaks now are selected. To a conference terminal device of a speaker, image data items of speakers other than the speaker are transmitted. To each of conference terminal devices of participants other than the speakers, image data items from the conference terminal devices of the speakers are transmitted.
Image information items
1
~
4
from the conference terminal devices
101
-
1
~
101
-
4
are transmitted to the multi-point control unit
100
. When a user of the conference terminal device
101
-
2
speaks, the multi-point control unit
100
transmits the image information item
2
from the conference terminal device
101
-
2
to the other conference terminal devices
101
-
1
,
101
-
3
and
101
-
4
. When a user of the conference terminal device
101
-
1
speaks after the speech of the user of the conference terminal device
101
-
2
is terminated, the image information item
1
is transmitted from the conference terminal device
101
-
1
to the multi-point control unit
100
. The multi-point control unit
100
then transmits the image information item from the conference terminal device
101
-
2
to the conference terminal device
101
-
1
and transmits the image information item
1
from the conference terminal device
101
-
1
to the other conference terminal devices
101
-
2
,
101
-
3
and
101
-
4
. This situation is shown in FIG.
1
A.
When a user of the conference terminal device
101
-
3
speaks in this state, the multi-point control unit
100
transmits the image information item from the conference terminal device
101
-
1
to the conference terminal device
101
-
3
. The multi-point control unit
100
then transmits the image information item from the conference terminal device
101
-
3
to the other conference terminal devices
101
-
1
,
101
-
2
and
101
-
4
. If the multi-point control unit
100
merely switches the transmission of the image information, there may be a case where the transmission of the image information is switched while the interframe coded data is being transmitted. In this case, a conference terminal device at the receiving side can not normally decode the coded imaged data until the intra-frame coded data is received.
Thus, the multi-point control unit
100
requests of a conference terminal device of a new speaker that the intra-frame coded data should be initially transmitted. The multi-point control unit
100
then supplies a display freeze instruction to stop displaying an image until intra-frame coded data is transmitted to the other conference terminal devices. This situation is shown in FIG.
1
B.
For example, when the state shown in
FIG. 1A
is changed to a state in which the user of the conference terminal device
101
-
3
speaks, the multi-point control unit
100
supplies the request for the intra-frame coded data and the display freeze instruction to the conference terminal device
101
-
3
. After the display freeze instruction, the image information
3
from the conference terminal device
101
-
3
is transmitted to the conference terminal device
101
-
1
. To the conference terminal devices
101
-
2
and
101
-
4
, the image information
3
substituted for the image information
1
is transmitted after the display freeze instruction.
FIG. 2
shows a coding process unit of each of the conventional conference terminal devices. Referring to
FIG. 2
, the coding process unit has a coding portion
111
, a local decoding portion
112
, a frame memory
113
, a control portion
114
, a selector (SEL)
115
, a subtractor
116
and a motion vector search portion
117
.
An image signal to be transmitted is supplied from a video camera (not shown) to the coding process unit. The image signal is then input to the motion vector searching portion
117
and the selector
115
. Speaker specifying information is input to the control portion
114
. The control portion
114
controls the selector
115
based on coding operation selecting information so that the coding operation is switched between the intra-fame predictive coding operation and the interframe predictive coding operation. When an image signal is selected by the selector
115
, the image signal is input to the coding portion
111
. The coding portion
111
codes the image signal so that the intra-frame coding operation is carried out. The difference between the input image signal and reference image information from the frame memory
113
is calculated by the subtractor
116
. The subtractor
116
outputs an interframe difference signal. When the interframe difference signal is selected by the selector
115
, the interframe difference signal is supplied to the coding portion
111
. The coding portion
111
codes the interframe difference signal so that the interframe coding operation is carried out.
Thus, when the request for the intra-frame coded data is supplied from the multi-point control unit
100
shown in
FIGS. 1A and 1B
, the control portion
114
controls the selector
115
so that image information coded by the intra-frame coding operation can be transmitted. In addition, the local decoding portion
112
decodes data coded by the coding portion
111
. The decoded data is stored as reproduced image information in the frame memory
113
. As a result, the contents in the frame memory
113
is almost the same as the contents in the frame memory of a conference terminal device at the receiving side.
The motion vector searching portion
117
searches a predetermined area of a frame which is input at a present time using a block, having a predeterm
Sakai Kiyoshi
Watanabe Hideaki
Eng George
Fujitsu Limited
Helfgott & Karas, PC.
Kuntz Curtis A.
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