JP2657736B2 - Video conference system using frequency multiplexing LAN - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a local area network (LAN) capable of bi-directional frequency multiplex transmission and transmission and reception of video signals between arbitrary terminal devices connected to the network. The present invention relates to a video conference system that can display a video of the other party.

[0002]

2. Description of the Related Art Conventionally, a plurality of upstream channels and a plurality of downstream channels are set in a frequency multiplexing transmission line, and the frequency of an upstream channel signal is converted into a downstream channel signal at a head end, whereby bidirectional communication is performed. There is known a LAN that enables the communication. A video (television) conference system has been proposed in which video signals are mutually communicated between terminal devices using the LAN, and a video of the other party is displayed on a receiver.

[0003]

SUMMARY OF THE INVENTION However, LAN
Has a large number of terminal devices connected to it, and there is a problem that an unintended terminal device may intercept a video signal. In order to solve this problem, it is conceivable that a channel usable in the terminal device is dedicated and fixed.
However, if the channel is fixed, video interception can be prevented for terminal devices that do not share the channel, but video signals can be intercepted by a certain terminal device among multiple terminal devices that share the channel. You may not want to let them. As described above, the method of fixedly allocating the channel to the terminal device enables the grouping of the communicable terminal devices, but selects the terminals that can freely arbitrarily communicate and the terminals that cannot intercept within the group. I can't.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a video conferencing system using a LAN, in which a receivable terminal device can be arbitrarily changed in a transmitting terminal device. And to prevent video communication leakage.

[0005]

An embodiment of the present invention for solving the above-mentioned problem is a frequency division multiplexing transmission system, in which an upstream channel signal is frequency-converted into a downstream channel signal at a head end to generate a video signal. Broadband Local Area Network (LAN) that can transmit data in both directions
In a video conference system in which video signals can be transmitted and received between any of the terminal devices connected to the LAN and mutually display the video of the other party, the terminal devices are connected to a predetermined channel. Receiving terminal device specifying means for specifying a terminal device permitted to receive the video of the terminal, and data modulation of an identification code unique to the terminal device specified by the receiving terminal device specifying device to a signal of an audio sub-channel of a baseband television signal. Modulator, scrambling means for scrambling the baseband television signal to be transmitted, and modulating the scrambled baseband television signal together with the signal output from the data modulator into a signal of a predetermined LAN channel. And a modulator for transmitting the modulated signal and a signal from a predetermined channel of the LAN. A demodulator that demodulates the signal to a sub-band television signal; a data demodulator that receives a signal of an audio sub-channel from a baseband television signal output from the demodulator and demodulates the signal to an identification code; Determining means for determining whether or not the identification code matches the identification code assigned to the own terminal device; and when it is determined that the identification code received by the determination means matches the identification code of the own device. A descrambling means for outputting a descrambled television signal of the baseband television signal, and a baseband television signal output by the descrambling means, and perform video display and audio output according to the signal. That is, an image receiver is provided.

[0006]

In the transmitting terminal device, a well-known scrambling process is performed on the baseband television signal to be transmitted, and the signal is modulated and output to a predetermined channel of the LAN. At this time, a terminal device permitted to receive the television signal is designated. Then, the identification code of the reception-permitted terminal device is data-modulated into an audio sub-channel signal in the baseband television signal band. The audio sub-channel signal is modulated and output to a predetermined LAN channel together with the baseband television signal (video signal and audio signal).

[0007] The receiving terminal device receives a signal from a predetermined channel of the LAN and demodulates the signal into a baseband television signal. Then, the audio sub-channel signal of the baseband television signal is data-demodulated and converted into an identification code. It is determined whether or not the identification code matches the identification code assigned to the own terminal device. Only when the identification code matches, the scramble of the demodulated scrambled baseband television signal is released.
The descrambled baseband television signal is input to a receiver, where the video is displayed and the audio is output.

As described above, in this system, only the terminal device designated by the transmitting terminal device can display an image, and cannot display an image on another device.

[0009]

According to the present invention, in a video conference system using a two-way LAN, a transmitting terminal device scrambles a baseband television signal, specifies a terminal device permitted to receive, and identifies the terminal device. The code is data-modulated into an audio sub-channel signal of a baseband television signal, modulated with a scrambled television signal, and transmitted to a predetermined channel of a LAN. Demodulates to a baseband television signal, demodulates the signal of the audio sub-channel to an identification code, and scrambles the baseband television signal if the identification code of the own terminal device matches the received identification code. Is released and output to the receiver.

[0010] Therefore, the terminal device can freely and variably specify the terminal device to which reception is permitted. Therefore, a video conference can be held in a secret state only between arbitrary terminal devices connected to the LAN.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to a specific embodiment. In FIG. 1, reference numeral 2 denotes a frequency multiplexing transmission line using a coaxial cable. This transmission line 2 has a bidirectional amplifier 3 for amplifying signals in the low group band and the high group band in different directions.
Is inserted. The transmission path 2 has a plurality of uplink channels assigned to a low group band and a plurality of downlink channels assigned to a high group band. Each channel is set to have a bandwidth capable of transmitting television signals (video signals and audio signals). The head end 1 has a function of a frequency translator for frequency-converting a signal transmitted on a low-group band upstream channel into a high-group band downstream channel signal.

According to this system, a signal transmitted from each terminal device to the upstream channel is transmitted to the head end 1 and frequency converted to a corresponding downstream channel signal at the head end 1. Then, by receiving this downlink channel signal in each terminal device, bidirectional communication between each terminal device becomes possible.

In the transmission line 2, terminal devices T1 to T1
Tn is provided. Each terminal device has the same configuration. In the conference room A where the terminal device T1 is installed, the voice of the speaker is picked up by the microphone 11 and converted into an audio signal. The state of the conference room A is imaged by the television camera 12, and a video signal is output. The audio signal and the video signal are converted into a scrambler (scrambler) 13 as a baseband television signal having a well-known frequency arrangement.
To enter. The scrambler 13 performs scramble processing so that the television signal cannot be easily received by the TV receiver.

The designation of a terminal device that is permitted to receive a signal transmitted by the terminal device T1 is performed as follows. The receiving terminal device setting device (receiving terminal device specifying means) 15 is a device for setting an identification code of a terminal device permitted to receive by a switch operation. The identification code set by the receiving terminal setter 15 is data-modulated by the data modulator 16 by FSK modulation. The carrier is selected so that the modulated signal is present in the band of the audio sub-channel in the baseband television signal band.

A scrambled baseband television signal (video signal and audio signal) output from the scrambler 13 and a signal data-modulated to an audio sub-channel output from the data modulator 16 are input to the modulator 14. . Then, the baseband television signal is modulated by the modulator 14 into the signal of the audio sub-channel, and is modulated into the predetermined uplink channel and transmitted to the transmission path 2.

On the other hand, when the terminal device T1 functions as a receiving terminal device, the demodulator 20 transmits a predetermined downlink channel (a downlink predetermined channel of a low group band to a high group band) by the demodulator 20 from the transmission line 2. (A predetermined channel) is received and frequency-converted into a baseband television signal. The baseband television signal is input to the data demodulator 19, and the signal of the audio sub-channel is demodulated to obtain an identification code specifying the terminal device. This identification code is stored in a digital comparator (determination means) 1
8 to one input terminal. The unique identification code assigned to the terminal device T1 is set and stored by the terminal device identification code setting device (determination means) 17. The terminal device identification code setting device 17 is composed of a dial switch and a memory for storing the switch state in "0" and "1" states. It should be noted that the terminal device identification code setting device 17 cannot be easily changed once it has been set, thus ensuring security.

When data demodulation is completed by the data demodulator 19, the digital comparator 18 is operated, and when the received identification code matches the identification code set by the terminal device identification code setting device 17, ,
A permission signal is input from the digital comparator 18 to a descrambler (scrambler) 21. When the permission signal is input, the descrambler 21 inputs the scrambled baseband television signal output from the demodulator 20 and descrambles the signal. Then, the descrambled baseband television signal is output to the TV receiver (receiver) 22, and the video is displayed and the audio is output.

As described above, in the system according to the present embodiment, the signal permitting reception of the transmission signal is transmitted using the audio sub-channel of the baseband television signal in the transmission terminal device T1. Therefore, only a channel for transmitting a television signal need be provided on the transmission path, and there is no need to provide a special channel for transmitting control data for designating a receiving terminal device. Therefore, effective use of the channel of the transmission path is achieved. In addition, since the terminal device that permits reception can be set in the transmitting terminal device, the video conference can be held in a secret state between the terminal devices that can be arbitrarily selected while the channel for transmitting the television signal is fixed.

In the above embodiment, both the video signal and the audio signal are scrambled. However, only the video signal may be scrambled.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a video conference system according to a specific embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Head end 2 ... Transmission line T1, Tn ... Terminal device 14 ... Modulator 16 ... Data modulation device 19 ... Data demodulation device 20 ... Demodulator

 ──────────────────────────────────────────────────続 き Continuing from the front page (73) Patent holder 000004226 Nippon Telegraph and Telephone Corporation 3-19-2 Nishi Shinjuku, Shinjuku-ku, Tokyo (72) Inventor Shinzo Mizuno 5-37-8 Shiba 5-chome, Minato-ku, Tokyo Hibiya Sogo Equipment Co., Ltd. (72) Inventor Togoro Abe 2--24-18 Chiyoda, Naka-ku, Nagoya City, Aichi Prefecture Inside Aichi Electronics Co., Ltd. (72) Inventor Yoshinori Kano 3--20, Marunouchi, Naka-ku, Nagoya City, Aichi Prefecture No. 6 Inside Cast Co., Ltd. (72) Inventor Kunio Suzuki 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-2-142238 (JP, A) JP-A-63 −142787 (JP, A)

Claims (1)

(57) [Claims] 1. A frequency division multiplexing transmission system comprising: a plurality of downlink channels through which signals are transmitted from a head end to a terminal; and a plurality of uplink channels through which signals are transmitted from a terminal to a head end. Using, has a broadband local area network capable of transmitting video signals in both directions, enabling transmission and reception of video signals between any terminal devices connected to the broadband local area network, In the video conference system configured to display the video of the other party, the terminal device is specified by a receiving terminal device specifying unit that specifies a terminal device that is permitted to receive the video of the predetermined channel, and is specified by the receiving terminal device specifying unit. The unique identification code of the terminal device into the audio subchannel signal of the baseband television signal. A data modulator for performing data modulation, a scrambler for scrambling a baseband television signal to be transmitted, and a baseband television signal scrambled by the scrambler together with a signal output from the data modulator together with the broadband signal. A modulator that modulates a signal of a predetermined channel of the local area network and sends out the modulated signal, a demodulator that receives a signal from the predetermined channel of the broadband local area network and demodulates the signal to a baseband television signal, A data demodulator for receiving a signal of an audio sub-channel from the baseband television signal output from the demodulator and demodulating the signal to the identification code; and the identification code demodulated by the data demodulator is allocated to the own terminal device. Identification Determining means for determining whether or not the baseband television signal matches the identification code received by the determining means; and Frequency multiplexing comprising: a descrambling means for outputting a descrambled television signal; and a receiver to which a baseband television signal output from the descrambling means is inputted and which performs video display and audio output in accordance with the signal. Video conferencing system using LAN.