KR0182466B1 - Video conference system - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a videoconferencing system, wherein a video conferencing terminal connected to the same LAN network environment by adopting a coaxial cable suitably employed for transmission of a television signal is connected to the same LAN network environment. In order to enable transmission and to exchange digitally converted video / audio signals through transmission lines between different LAN network environments, video / audio signals input from audio / video input means 90a and 92 are analogized. A communication line (coaxial cable) connecting the first group of video conferencing terminals 60 (60a to 60n) and the first group of video conferencing terminals 60a to 60n to be processed and exchanged by signals in the same LAN network environment. And transmits the analog signal as a digital signal to the second group of video conferencing terminals 70a to 70n included in an external LAN environment via a dedicated line 80 via the communication line 62. In the external LAN network environment, the gateway 54 is configured to process the digital signal transmitted through the dedicated line 80 as an analog signal to be reproduced by the video conferencing terminals 60a to 60n. .

Description

Video conferencing system

1 is a diagram showing the configuration of a video conferencing system in a general LAN network.

FIG. 2 is a block diagram of a representative videoconferencing terminal applied to the videoconferencing system shown in FIG.

3 is a diagram showing the configuration of a videoconferencing system according to a preferred embodiment of the present invention.

4 is a block diagram of a representative videoconferencing terminal applied to the videoconferencing system according to the present invention shown in FIG.

5 is a block diagram of signal processing means provided for the videoconferencing system according to the present invention shown in FIG.

6 (a) to 6 (h) are waveform diagrams for explaining the operation of the videoconferencing terminal applied to the videoconferencing system according to the present invention shown in FIG.

* Explanation of symbols for main parts of the drawings

10a-10n, 20a-20n: video conferencing terminal 12, 22: LAN network

14, 24: gateway (video conferencing server) 42: video camera

44: video conferencing codec card 54: control unit

56: LAN card 58: VGA card

60a-60n, 70a-70n: video conferencing terminal 62,72: coaxial cable

64,74: Gateway 92: video camera

96: RF modulator 98, 140: RF combiner

100, 120: frequency band ejector 102,122: TV tuner

104,124: video / audio IF module 112: overlay processing unit

116: control unit 126: video encoder

128: audio encoder 136: audio decoder

138: Video Decoder

The present invention relates to a video conferencing system. More particularly, the present invention relates to an analog video conferencing signal at a television (TV) level within the same local area network (LAN) environment, and to a gateway between different LAN environments. (Gateway; video conferencing server) relates to a video conferencing system for implementing a digital video conferencing exchange system based on the data transmission speed of the leased line.

Recently, a data communication method for exchanging information while transmitting / receiving a video signal and an audio signal with a counterpart maintaining a constant distance has been proposed and applied to practical use, and such data communication provides a relatively short distance. Alternatively, a video conferencing system for exchanging video / audio signals with a counterpart located at a far distance can be realized.

According to such a video conferencing system, a video camera as a means for capturing an image and a microphone as a means for inputting audio are usually provided, and the analog video and audio signals inputted from the video camera and the microphone are converted into digital signals. The compressed video / audio data is compressed by a predetermined algorithm, and the compressed video / audio data is converted into a dedicated line (T1 / E1), an integrated service digital network (ISDN), a local area network (LAN), and a public exchange. It transmits to the other party through transmission media such as public switched telephone network (PSTN) and Asynchronous Transfer Mode (ATM), while compressing the compressed data of the video / audio signal received from the other party by a predetermined algorithm and converting it into an analog signal. The conversion is performed to the monitor as the video output device and the speaker as the volume output device.

1 is a diagram showing the configuration of a video conferencing system in a general LAN network, wherein reference numerals 10a to 10n denote video conferencing terminals of a first group, and 12 denotes video conferencing terminals 10a to 10n of the first group. 14 denotes a LAN network to be interconnected, and 14 denotes video / audio data between a first group of video conferencing terminals 10a-10n connected to a corresponding LAN network 12 with a terminal connected to an external LAN network. Represents a gateway to exchange.

Reference numerals 20a to 20n denote video conferencing terminals of the second group, 22 denotes LAN networks interconnecting the video conferencing terminals 20a to 20n of the second group, and 24 denotes corresponding LAN networks 22. Indicates a gateway for allowing the second group of videoconferencing terminals 20a-20n connected by) to exchange videoconferencing data, for example, with the videoconferencing terminals 10a-10n connected to the LAN network 12. .

30 is a LAN network to which the gateway 14 to the LAN network 12 to which the first group of videoconferencing terminals 10a to 10n are connected and the second group of video conferencing terminals 20a to 20n are connected. Dedicated as a transmission medium for transmitting videoconferencing data between videoconferencing terminals 10a-10n, 20a-20n, which are spoken between gateways 24 to 22, and connected to the LAN networks 12,22. The line T1 / E1 is shown.

FIG. 2 is a block diagram of a terminal applied to the videoconferencing system shown in FIG. 1, and FIG. 2 is a diagram showing the configuration of the videoconferencing terminal 10a connected to the LAN network 12. As shown in FIG.

In FIG. 2, 40a represents a microphone as an audio input means for inputting an audio signal during a video conference, 40b represents a speaker as an audio reproduction means for reproduction of an audio signal transmitted from the other party, and 42 is an image capture of a video signal. A video camera as image pickup means for the present invention is shown.

44 is a video conferencing codec for encoding the audio signal input from the microphone 40a and encoding (compression processing) of the video signal from the video camera 42 or decoding the video signal and the audio signal transmitted from the other party. The video conferencing codec card 44, which represents a card, encodes the audio signal input from the microphone 40a and decodes the voice signal of the counterpart to be reproduced through the speaker 40b. And an image codec 48 which decodes the image signal captured by the video camera 42 and decodes the image signal of the other party, and monitors the image signal decoded by the image codec 48 in the PC monitor 52. Overlay processing unit 50 for processing to be displayed on the screen, multiplexing for transmission of the audio signal and the video signal encoded by the audio codec 46 and the video codec 48 and the voice signal of the other party And the video signal will include the audio codec 46 and the video codec 48, the system layer MUX / DMUX (52) for demultiplexing such that the decoding processing in the.

In addition, 54 denotes a control unit which controls the exchange of video / audio signals for videoconferencing while totally controlling the videoconferencing process by the corresponding videoconferencing terminal 10a, and 56 denotes under the control of the control unit 54. FIG. Represents a LAN card in charge of a signal connection with the LAN network 12 for exchanging video conference information data with a terminal to be a video conference target, and 58 denotes video graphic data under the control of the control unit 54. A VGA card is provided to the overlay processing unit 50 so that the color image screen displayed on the PC monitor 52 can be configured.

Therefore, according to the video conferencing system in the LAN network having the above-described configuration, an audio signal is input through, for example, the microphone 40a, and an image is captured by the video camera 42 to correspond to the video conferencing codec card 44. When applied to the audio codec 46 and the video codec 48, the audio signal from the microphone 42 is encoded by a predetermined algorithm in the audio codec 46 and the image captured by the video camera 42 is The encoded video and audio signals are applied to the system layer MUX / DMUX 52 and multiplexed into a data frame structure for transmission to the other party. Under the control of the control unit 54, it is applied on the LAN network 12 via the LAN card 56 and transmitted to the video conference terminal of the other party.

Then, the video conferencing data (video / audio signal) of the other party received through the LAN network 12 is received through the LAN card 56 and the control unit 54, and the system layer MUX / DMUX 52 The video / audio data is demultiplexed and then applied to the corresponding audio codec 46 and video codec 48. Therefore, the audio signal reproduced by the audio codec 46 is reproduced through the speaker 40b, and the image signal reproduced by the image codec 48 is applied to an overlay processor 54 to control the unit. Under the control of 54, the video graphic signal applied from the VGA card 58 is overlaid and reproduced on the PC monitor 52.

On the other hand, when the video conferencing data transmitted through the LAN network 12 is to be transmitted for video conferencing with the video conferencing terminals 20a-20n connected to the LAN network 22, the video conferencing data is transferred to the gateway 14. From the dedicated line (T1 / E1) 30 and the gateway 24 provided to the LAN network 22 to the specific video conferencing terminal 20 connected to the LAN network 22, and accordingly the video conference. Exchange of data becomes possible.

However, in the video conference terminal, the maximum transmission speed of the communication line is relatively small to transmit the data of the analog video signal in real time, so the digital conversion of the video signal and the audio signal for the video conference and the data compression / restore process are inevitably involved. Will be.

That is, about 166 Mbps (720 x 480 x 30 x 16 = 165,888,000) is required to transmit 30 video signals of 720 x 480 pixels in the form of 4: 2: 2 Y Cb / Cr. Approx. 1,544 Mbps, 128 Kbps per line for ISDN, 28.8 Kbps for PSTN for VST, and 10 Mbps for LAN, while up to 5 Mbps for multiple users The following is somewhat inappropriate even for an ATM having a transmission rate of approximately 155 Mbps.

Therefore, in the case of video conferencing, in order to use the existing communication network, it reduces the aspect ratio of the digital video, reduces the spatial resolution, reduces the number of screens per second, and reduces the amount of digital video data. As a result of the data compression process, serious deterioration of image quality is caused, but it is inevitable to use the existing transmission network.

In that sense, compressed communication of data becomes indispensable in long distance communication where users of video conferencing system cannot directly install communication line. However, users need to use 10Mbps LAN network like office or small building. The video conferencing system that is constructed and uses the LAN network is quite disadvantageous for the following reasons.

In other words, the currently commercialized LAN network is 10Mbps, which is used by many people for data exchange, and many communication obstacles are involved when exchanging video conference information requiring hundreds of Kbps.

In addition, the LAN network is a packet transmission network, and since the traffic volume changes from time to time, the existing video conferencing system supporting a fixed communication speed may not be able to operate smoothly depending on the smooth amount of information communication, and the communication speed may be variable. Even if the video conferencing system is applied, a problem arises in connection with the video conferencing system having a fixed communication speed provided to another place outside the LAN network.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and adopts a coaxial cable (75?), Which is suitably used for the transmission of television (TV) signals, as a signal transmission medium. It is an object of the present invention to provide a video conferencing system for enabling transmission of video / audio signals and for digitally converted video / audio signals to be exchanged through transmission lines between different LAN environments.

In order to achieve the above object, according to a preferred embodiment of the present invention, a plurality of video conferencing terminal means for processing and exchanging the video / audio signal input from the audio / video input means into an analog signal, and the plurality of video conferencing Line means for connecting the terminal means to the LAN environment, connected to the line means to transmit the analog signal as a digital signal on a dedicated line that is speeched to the external LAN environment, and to mediate the dedicated line in the external LAN environment. And a video conferencing server means for processing a digital signal to be transmitted as an analog signal to be reproduced by the video conferencing terminal means. The line means comprises a video having a coaxial cable for transmitting analog video / audio signals. A conferencing system is provided.

Preferably, the video conferencing terminal means comprises: an RF modulator for RF modulating the video / audio signals input from the video / audio input means, respectively, so that the analog video / audio signals are transmitted through the line means; A frequency band rejector for rejecting a frequency band of the channel allocated to the video / audio signal under control, and processing the RF modulated video / audio signal into a frequency band of the rejected specific channel on the track means. A tuner means for tuning the channel of the video / audio signal received via the line means, and IF converting the video / audio signal in the channel tuned by the tuner means. Video / audio IF module, audio processing means for reproducing and applying the IF converted audio signal to the audio output means, and converting the IF converted video signal An NTSC decoder that performs coding processing (R / G / B processing), a scan converter which synchronously converts the NTSC decoded video signal into a VGA signal for display on a monitor, and converts the video signal from the scan converter into a VGA card. It also includes overlay processing means for overlay processing with support and output on the monitor.

According to the present invention, a fixed channel is allocated to the video / audio signal at the time of transmission / reception, but different channels can be allocated to the transmission / reception of the video / audio signal.

The video conferencing server means may further include: a frequency band rejector and tuner means for allocating a channel of a specific frequency band to a video / audio signal applied on the line means, and the channel selected by the tuner means. Video / audio IF module for IF conversion of audio signal, video / audio encoder for digital encoding video / audio signal IF converted by video / audio IF module, video / audio encoded by video / audio encoder A system layer MUX / DMUX which processes data into a data frame structure for reproducing video / audio data transmitted to or from the external LAN environment side, and the video / audio data of the data frame structure. In addition to including a dedicated network interface for data interfacing to transmission lines for exchange, A video / audio decoder for analog decoding the received video / audio data, an RF modulator for RF modulating the video signal and the audio signal decoded by the video / audio decoder, and the frequency of the RF modulated video / audio signal. It also includes an RF combiner that processes the frequency band of the channel rejected by the band rejector.

According to the videoconferencing system according to the present invention having the above-described configuration, a plurality of coaxial cables are employed for video / audio signals for videoconferencing, and the video / audio signals are processed at the TV level for the coaxial cables. A LAN environment is established by connecting video conferencing terminal means, and video conferencing data is exchanged at a communication speed suitable for the dedicated line through a dedicated line between LAN environments formed by coaxial cable. It is possible to exchange video / audio signals for videoconferencing with the effect of communication speed being excluded among videoconferencing terminals.

Hereinafter, with reference to the accompanying drawings, the present invention will be described in detail.

3 is a diagram showing the configuration of a videoconferencing system according to a preferred embodiment of the present invention. Reference numerals 60a through 60n denote television (TV) level analog signal processing functions for video / audio signals for videoconferencing. Represents a group of video conferencing terminals.

62 denotes a communication line for interconnecting the first group of video conferencing terminals 60a to 60n to form a LAN environment. Preferably, the communication line is composed of a coaxial cable (75Ω).

64 is a gateway (or videoconferencing server) for allowing the first group of videoconferencing terminals 60a-60n connected to the coaxial cable 62 to exchange video / audio data with a terminal connected to a communication network of an external LAN environment. ).

In addition, in Fig. 3, reference numerals 70a to 70n denote a second group video conferencing terminal having a TV-level video / audio signal processing function similar to the first group video conferencing terminals 60a to 60n. Denotes a communication line by a coaxial cable for interconnecting the second group of video conferencing terminals 70a to 70n to form a LAN environment, and 74 denotes a second group of video conference connected by the coaxial cable 72. Indicates a gateway for exchanging video conferencing data with, for example, video conferencing terminals 60a through 60n connected to the coaxial cable 62.

80 is a coaxial cable to which the gateway 64 for the coaxial cable 62 to which the first group of video conferencing terminals 60a to 60n are connected and the second group of video conferencing terminals 70a to 70n are connected. It is provided to connect the gateway 74 to the signal signal 72 and represents a dedicated line T1 / E1 as a transmission medium for transmitting videoconferencing data between LAN environments.

4 is a block diagram of a video conferencing terminal of a video conferencing system according to the present invention shown in FIG. 3, and reference numeral 90a denotes a voice input means for inputting a voice signal when video conferencing is performed. A microphone represents a microphone, and 90b represents a speaker in which an audio signal input from a video conference terminal of the other party is reproduced.

92 denotes a video camera as image pickup means for inputting a video signal when a video conference is executed.

In addition, 94 indicates that the audio signal and the video signal input from the microphone 90a and the video camera 92 are processed as a TV-level analog signal to be transmitted to the videoconferencing terminal of the other party, or the voice transmitted from the videoconferencing terminal of the other party. A video / audio signal processing means for reproducing a signal and a video signal is shown.

Preferably, according to the present invention, the video / audio signal processing means 94 includes an RF modulator 96 for RF modulating audio / video signals input from the microphone 90a and the video camera 92, and the RF modulator thereof. RF combiner (RF signal) 98 is processed in accordance with the RF-modulated audio signal (RF signal) to the channel allocated for video conferencing and applied on the coaxial cable (62) (96) Done.

In addition, the video / audio signal processing means 94 sets a frequency band of a channel allocated to video conferencing and provides a frequency band rejector for providing a transmission frequency band of the audio / video signal by the RF combiner 98 ( 100), a TV tuner 102 provided to a channel tuner for receiving analog audio / video signals of a TV level transmitted from a video conferencing terminal of the other party included in the same LAN environment, and tuned by the TV tuner 102. The video / audio IF module 104 for converting the video conference audio / video signal of the channel to the IF (intermediate frequency), and reproducing and processing only the audio signal IF processed by the video / audio IF module 104. It also includes a voice processing unit 106 to be applied to.

In addition, the video / audio signal processing means 94 decodes the video signal IF processed by the video / audio IF module 104 by NTSC scanning (NTSC scan) for TV-level video reproduction. 108, a scan converter 110 for converting the NTSC decoded video signal from the NTSC decoder 108 to enable display, and the video signal converted by the scan converter 110 on the PC monitor 114. It is also equipped with an overlay processing unit 112 for overlay processing to be displayed on.

In FIG. 4, reference numeral 116 denotes a control for executing overall control of the video conference and control of the video conference channel when the video conference terminal 60a performs the video conference with the video conference terminal of the other party. A unit 118 denotes a VGA card that supports a color screen configuration of the image signal when the overlay processing unit 112 processes the image signal and displays the image signal on the monitor 114.

FIG. 5 is a block diagram representatively showing a gateway applied to the videoconferencing system according to the present invention shown in FIG. 3, and reference numeral 120 denotes, for example, from the videoconferencing terminal 60a shown in FIG. A frequency band ejector for securing a frequency band of a channel for transmitting a video / audio signal transmitted through a coaxial cable 62 is indicated. 122 denotes a TV tuner for channel selection for transmission of a video / audio signal. Reference numeral 124 denotes a video / audio IF module for IF converting an audio / video signal corresponding to a channel tuned by the TV tuner 122.

In addition, 126 denotes a video encoder for converting the video signal IF converted by the video / audio IF module 124 into digital data and performing compression processing, and 128 denotes an IF conversion processed by the video / audio IF module 124. An audio encoder converts an audio signal into digital data and compresses the same.

In operation 130, the video / audio data compressed by the video encoder 126 and the audio encoder 128 are multiplexed into a data frame structure suitable for transmission, or a video conferencing terminal (for example, 70a) of the other party included in an external LAN environment. The system layer MUX / DMUX demultiplexes the transmitted video / audio data, and 132 denotes a dedicated line T1 / E1 for the video conference data (video / audio data) multiplexed by the system layer MUX / DMUX 130. And a dedicated network interface for transmitting to a gateway (e.g. 74) provided to an external LAN environment or for receiving video conference data transmitted from the gateway 74 side.

In FIG. 5, reference numeral 134 decodes only video data transmitted from a videoconferencing terminal (for example, 70a) connected to a coaxial cable 72 of an external LAN environment demultiplexed by the system layer MUX / DMUX 130. A video decoder to be processed is shown, and 136 denotes an audio decoder which decodes only the voice data demultiplexed and applied by the system layer MUX / DMUX 130.

138 denotes an RF modulator for RF-modulating the video / audio signal decoded by the video decoder 134 and the audio decoder 136, and 140 denotes an image / audio RF signal applied by the RF modulator 138 in the frequency band. The RF combiner is processed to fit the frequency band allocated by the rejector 120 and applied to the coaxial cable 62 to be delivered to the videoconferencing terminal 60a.

Next, the operation of the videoconferencing system according to the present invention having the above-described configuration will be described with reference to the waveform diagram shown in FIG.

First, between the videoconferencing terminal 60a (FIG. 4) included in the same LAN environment constituted by the coaxial cable 62 and the videoconferencing terminal of any one of the first group of videoconferencing terminals 60b to 60n. When the video conference is performed, first, the analog audio signal and the video signal input from the microphone 90a and the video camera 90b provided in the video conference terminal 60a are applied to the RF modulator 96. The RF modulated audio signal and the video signal are modulated under the control of the control unit 116 and coaxially processed so as to be suitable for the frequency band of the video conference channel secured by the frequency band rejector 100. The video / audio signal for video conferencing applied to the cable 62 and applied to the coaxial cable 62 is transmitted to the video conferencing terminal of the other party.

Here, FIG. 6 (a) shows the waveform of the signal accompanying one horizontal synchronization signal among the video signals of the baseband, and FIG. 6 (b) shows a part of the audio signal of the baseband, and FIG. ) Represents the frequency spectrum of the video / audio signal of the baseband, and the RF / modulator 96 RF modulates the video / audio signal of the baseband as shown in FIG. Shows the frequency spectrum shown in FIG. 6 (d), and thus the video / audio signal of the waveform shown in FIG. 6 (e) is provided to the videoconferencing terminals 60a, 60b-60n included in the same LAN environment. Will be applied.

That is, when the frequency band rejector 100 performs the reject processing of the frequency band in the frequency band of the channel '3' set as the video conference channel under the control of the control unit 116, it is shown in FIG. The obtained frequency spectrum is obtained. If the video / audio signal of the baseband shown in FIG. 6 (c) is RF modulated at the frequency of channel '3' based on the frequency spectrum, the frequency spectrum of FIG. And the video / audio signal of the frequency spectrum shown in FIG. 6 (g) is processed as the signal having the frequency spectrum of FIG. 6 (h) by the RF combiner 98. Through the coaxial cable 62 is transmitted to the video conferencing terminal (60b, ---, 60n) of the other party.

The audio / video signal (signal having a frequency spectrum of FIG. 6 (e) or 6 (h)) transmitted to the videoconferencing terminal 60a via the coaxial cable 62 is the control unit. Under the control of 116, it is detected in a channel tuned by the TV tuner 102, and the audio / video signal of the channel is subjected to IF (intermediate frequency) conversion processing in the video / audio IF module 104.

The audio signal subjected to IF conversion processing by the audio / video IF module 104 is reproduced through the speaker 90b after the reproduction processing is performed by the audio processing unit 106.

In addition, the video signal subjected to IF conversion processing by the audio / video IF module 104 is applied to the NTSC decoder 108 and decoded into an R / G / B signal for screen reproduction, and then the scan converter 110 The signal is converted based on the VGA synchronization signal to be displayed on the monitor 114 and then applied to the overlay processor 112.

The overlay processing unit 112 overlays an image signal applied from the scan converter 110 under the support of the VGA card 118 operated under the control of the control unit 116 to be reproduced on the PC monitor 114. Done.

Therefore, in the same LAN network environment formed by the coaxial cable 62 to which the videoconferencing terminals 60a (60b to 60n) shown in FIG. 4 are connected, the videoconferencing system is processed by processing video / audio signals at the TV level. Will be implemented.

Next, a process of exchanging video conference data (video / audio data) between video conference terminals (for example, 60a and 70a) included in different LAN environments implemented by the coaxial cables 62 and 72 will be described. First, the analog video / audio signal applied to the coaxial cable 62 to which the video conference terminal 60a shown in FIG. 4 is connected is subjected to the frequency band reject processing of the frequency band rejector 120 shown in FIG. A channel band detected by the channel tuner 122 is detected by the TV tuner 122, and the video / audio signal of the channel tuned by the TV tuner 122 is IF-converted by the video / audio IF module 124 to perform a video signal. Is applied to the video encoder 126 while the audio signal is applied to the audio encoder 128.

Therefore, the video / audio signal applied to the video encoder 126 and the audio encoder 128 is compressed by a predetermined algorithm after the digital conversion processing is performed, and then the digitally converted video / audio data is system layer mux. Is multiplexed into a data frame structure for transmission in the / DMUX 130 and applied on the transmission line T1 / E1 80 through a dedicated network (T1 / E1) interface 132, whereby the video conference data is externally It is transmitted to the video conferencing terminal (for example, 70a) via the gateway 74 provided in the LAN environment.

Video conferencing data transmitted from the videoconferencing terminal (for example, 70a) connected to the coaxial cable 72 via the transmission line 80 is transmitted through a dedicated network (T1 / E1) interface 132 through a system layer. The MUX / DMUX 130 demultiplexes the video / audio data into a corresponding video decoder 134 and an audio decoder 136, and accordingly decodes the video decoder 134 and the audio decoder 136. The video / audio signal is RF modulated by the RF modulator 138 and applied to the RF combiner 140.

Accordingly, the RF combiner 140 processes the video / audio RF signal applied from the RF modulator 138 to a channel of the frequency band secured by the frequency band rejector 120 to coaxial cable 62. After the video / audio signal on the coaxial cable 62 is tuned in the TV tuner 102 of the video conference terminal 60a shown in FIG. 4, post-processing is performed. Video conferencing can be performed with a video conferencing terminal in an external LAN environment.

On the other hand, in the above description, the case where the video / audio signal for video conference set by the control unit 116 is set to a specific channel (for example, '3') has been described as an example, but the channel at the time of transmission and reception of the video / audio signal Of course, it can be set separately, and if necessary, a method of allocating a unique channel for the entire video conferencing terminal is also possible.

As described above, according to the videoconferencing system according to the present invention, a plurality of videoconferencing terminals included in a LAN environment are connected by signal through a coaxial cable, so that video / audio signals of a TV level can be provided between videoconferencing terminals in the same LAN environment. Through the processing, video / audio signals can be exchanged for video conferencing, and video conferencing data can be exchanged with a video conferencing terminal in an external LAN environment in a data frame structure corresponding to a transmission line. In the transmission of the video / audio signal, the restriction on the communication speed or the occupation of the transmission line is remarkably reduced, thereby enabling smooth signal exchange.

Claims (3)

The video / audio signal input from the video / audio input means 90a, 92 is RF-modulated to exchange the video / audio signal input from the audio / video input means 90a and 92 as an analog signal. By the RF modulator 96 and the frequency band rejector 100 which rejects the frequency band of the channel allocated to the video / audio signal under the control of the control unit 116 and the frequency band rejector 100. A plurality of video conferencing terminal means (60) including an RF combiner (94) for processing the RF-modulated video / audio signal in a rejected specific channel and applying it on the line means (62) described later; 60a-60n, a line means 62 for connecting the plurality of video conference terminal means 60a-60n to a network LAN environment, and the line means 62 to communicate the analog signal with an external LAN environment. As a digital signal on the dedicated line 80 And a video conferencing server means 64 for processing the digital signal transmitted through the dedicated line 80 in an external network LAN environment as an analog signal to be reproduced by the video conferencing terminal means. And the line means (62) employs a coaxial cable for the transmission of analog video / audio signals. 2. The video conferencing terminal means (60) according to claim 1, wherein the video conferencing terminal means (60) is tuned by tuner means (102) for tuning the channel of the video / audio signal received via the line means (62). The video / audio IF module 104 for IF-converting the video / audio signal in the converted channel, the audio processing means 106 for reproducing and applying the IF-converted audio signal to the audio output means 90b, and the IF conversion. NTSC decoder 108 for decoding (R / G / B) the processed video signal, and scanning converter 110 for synchronously converting the NTSC decoded video signal to a VGA signal for display on a monitor 114. And an overlay processing unit 112 for overlaying the video signal from the scan converter 110 with the support of the VGA card 118 and outputting the image signal to the monitor 114. . 2. The frequency band rejector and tuner means (120, 122) according to claim 1, wherein the video conferencing server means (64) allocates a channel of a specific frequency band to the video / audio signal applied on the line means (62) for tuning. ), A video / audio IF module 124 for IF converting the video / audio signal of the channel selected by the tuner means 122, and a video / audio encoder for digitally encoding the IF converted video / audio signal ( 126, 128), the system layer MUX / DMUX (130) for processing the encoded video / audio data to the external LAN environment side or a data frame structure for reproduction of the video / audio data transmitted from the external LAN environment side (130, 128) And a dedicated network interface 132 for data interfacing to the transmission line 80 for the exchange of video / audio data of the data frame structure. Video / audio decoders 134 and 136 for analog decoding the received video / audio data, an RF modulator 138 for RF modulating the decoded video and audio signals, and the RF-modulated video / audio signal. And a RF combiner (140) for processing the frequency band of the channel rejected by the frequency band rejector (120).