JPS61216575A - Synchronization transmitting system - Google Patents

Abstract

PURPOSE:To simplify a circuit constitution by commonly using a sampling clock generating section of respective stations by a transmitter and a receiver in a bidirectional transmitting system by a digital signal. CONSTITUTION:In a transmitter 21 of an A station, an A/D converter 26 for converting a video signal into a digital signal and a PLO (phase lock oscillator) 25 for generating a sampling clock are contained. The transmitter 21 transmits this clock in a staff system to a B station side together with the video signal. In a receiver 22 of the B station side, a PLO 25' for receiving and reproducing the sampling clock of the A station and a D/A converter 27' are contained. As for a transmitter 24 of the B station and a receiver 23 of the A station, a similar operation is done. Therefore, the number of using the PLO can be reduced.

Description

[Detailed description of the invention] 〔table of contents〕 overview Industrial applications Conventional technology The problem that the invention aims to solve Means to solve problems action Example Effect of the invention 〔overview〕 In a bidirectional transmission system using digital signals.

The sampling clock generating section of each station is shared by the transmitter and receiver, and the Ig circuit configuration is simplified.

[Industrial application field]

This invention relates to synchronous transmission systems), particularly televisions (hereinafter referred to as T
The present invention relates to a synchronous transmission method for a two-way communication system in a telephone system (referred to as V).

In digital communication in which analog signals are sampled and transmitted, it is necessary to reproduce the sampling clock on the transmitting side on the receiving side, and to reproduce the signal in synchronization with this clock. For example, in a digital transmission TV system that converts image signals into digital signals and transmits them, it is necessary to perform sampling in synchronization with synchronization signals such as horizontal synchronization and vertical synchronization on the transmitting side, and this sampling and It is necessary to reproduce the received signal in synchronization with the clock. In a two-way communication system such as a TV telephone system, a sampling clock is required at each transmitter and receiver on the transmitting and receiving sides.

[Conventional technology]

As an example, we will explain an example of a TV system using digital communication.Figure 3 shows two stations A.

This is an example of the configuration of a conventional video telephone system in which a call is made between three parties. In the figure, 31.31' is.

The TV left camera installed at station A or station B is connected to cancer transmitters 34 and 34', respectively. Transmitter 34.
34' is provided with an A/D converter 32, 32' that converts the analog signal from the television camera into a digital signal, and a PLO (34') for generating a sampling clock in synchronization with the synchronization signal from the television camera. A phase lock oscillator) 33.33' is provided. As a result, station A.

The transmitter of station B transmits the sampled digital video signal in synchronization with the TV left camera synchronization signal.

The A station and the B station are further provided with receivers 35 and 35', which receive the digital video signals from the B station and A station mentioned above. The receivers 35 and 35' are each provided with a D/A converter 37 and 37' for converting the received digital video signal into analog, and also for converting sampling clock information in the transmitted signal as a stuff. My friend PLO36,3 generates a clock synchronized with it based on it.
6' is provided. Thereby, the received digital video signal is supplied to the TV 38, 38' as an analog video signal. Note that although audio has not been described here, it is digitized and communicated similarly to video signals.

With the above configuration), each station transmits its own signal to the other party,
This means that the signal from the other station can be received.

[Problem that the invention seeks to solve]

According to this conventional method, the sampling clock is synchronized with the synchronization signal of the video signal.

The video signal obtained in analog form from the TV left camera can be converted to a digital signal, and the received digital signal can be converted back to a video signal and sent to the TV, so both parties can watch each other's faces while looking at each other's faces. A TV phone system that allows dialogue is obtained, but there is no PL on either the transmitter/receiver of station A or B.
O is necessary and also. The problem is that sampling clock information must be transmitted in the transmitted signal.

The present invention has been made in view of these points.
It is an object of the present invention to provide a synchronous transmission method that can reduce the number of PLOs with a simple configuration.

[Means for solving problems]

A means to solve the problems mentioned above.

This will be explained using Figure 1, which is a block diagram of the principle of the present invention.

In Figure 1Cc, it is assumed that l is station A, which is one station in the communication, and is conducting bidirectional communication with the other station Bl'. Station A has a transmitter 2. Equipped with 4 receivers 9.8
The station is equipped with a transmitter 2' and a receiver 4'. Defined transmitter that converts analog signals into digital signals 4.4
' has a built-in A/D converter, and the receiver has a D
A /A converter is incorporated to convert digital signals to analog values. The A/D converter incorporated in the transmitter 2 of the A station is given a clock from the clock generator 3, and this clock is transmitted through one stack. In the receiver 4' of the B station, this transmitted clock is regenerated by the clock generator 3' and used as a clock on the receiving side. Furthermore, this clock is used as a sampling clock for the transmitter 2' of the B station. Then, the sampling clock of this transmitter 2' becomes the same as the sampling clock of station A, so by obtaining the clock from the sampling clock generator 3, the receiver 4 receives the digital signal. reproduces the signal as an analog signal.

Therefore, the clock generator for sampling.

It is sufficient to have one each on the A-station side and the B-station side.

[Effect]

As stated above, the number of clock generators can be greatly reduced since it is sufficient to have one each for the A-station side and the B-station side. Just by including the sampling clock in the transmission signal, there is no need to send it to the transmission signal to the other side.

〔Example〕

FIG. 2 shows a second embodiment of the present invention, which is an example applied to a TV telephone system. In the figure, A is.

One station in the communication is A station ts B is the other station B
It shows the station. The A station is provided with a transmitter 21 that converts the signal from the TV right camera 8 for imaging into a digital signal and sends it, and is further connected to a receiver 23 for reproducing the video signal from the B station. A TV 29 is provided. The B station, like the A station, has a transmitter 24 that converts the signal from the TV left camera 8' for imaging into a digital signal and sends it.
A receiver 22 and a TV 29' are provided. A station transmitter 2
1 includes an A/D converter 26 that converts the video signal from the TV right camera 8 into a digital signal, and generates a sampling clock synchronized with the horizontal and vertical synchronization signals of the video signal from the TV right camera 8. A PLO (facelock oscillator) 252>i is included. The transmitter 21 transmits this clock to the B station side together with the video signal using a stuffing method. The receiver a22 on the B station side includes a PLO 25' that reproduces the sampling clock of the A station transmitted using the stuffing method, and a D/A converter 27 that converts the video signal transmitted in digital form into an analog signal. ' is included. Also, the transmitter 24 of station B is equipped with a TV left camera 8'.
A/D converter 26 that converts the video signal into a digital signal.
', and the receiver 23 of station A includes a D/A converter 27 that converts the signal sent in digital form into an analog signal.

When transmitting from station A to station B, PLO25 of station A is T
Sampling with synchronized TV double signal from V right camera 8
Generates a clock. Using this clock, the A/D converter 26 samples the TV double signal and transmits it as a digital signal, and also transmits the sampling clock using a stuffing method.

Station B reproduces the signal using the sampling clock 5iPLO 25' of station A, which is transmitted using the stuffing method.

Use as receiver clock. Furthermore, the clock regenerated by the receiver of the B station is connected to the transmitter 24 of the B station and is supplied as an external clock to the TV left camera 8', and is also supplied to the A/D converter 26'. Used as sampling clock. That is.

Since the TV left camera 8' of station B is synchronized with the clock reproduced on the receiving side, sampling can be performed using that clock. Then, the transmission signal from station B is
Since it is synchronized with the clock of the PLO 25 on the station side, the receiver 23 of the A station, which reproduces the signal from the B station,
The signal can be reproduced using the sampling clock used by the transmitter of station A.

〔Effect of the invention〕

As described above, by incorporating the present invention, the number of PLOs used can be reduced with an extremely simple configuration, and as a transmission signal on one transmitting side between stations performing bidirectional communication. Since it is also possible to eliminate the need to transmit a sampling clock, it can be applied to TVg talk devices, TV conference devices, etc.

[Brief explanation of drawings]

Figure 1 is a block diagram of the principle of the present invention. FIG. 2 is a configuration diagram of an embodiment of the present invention applied to a TV telephone system. Figure 3 shows a conventional example. 1...A station 1'...B station 2.2'...
・Transmitter, 3, 3'...Clock generator 4.4'...Receiver, 21.24...Transmitter 22.23...Receiver 25.25'...
PLO26, 26'...A/D converter, 27.27'
...D/A converter 28.28'...TV right camera 2
9,29'...TV receiver patent issue Fujitsu Limited

Claims (1)

[Claims] In a bidirectional transmission system using a digital signal obtained by sampling an analog signal, a transmitter (2) of one station A is provided with a first sampling clock generator for generating a sampling clock, and the other station A is provided with a first sampling clock generator for generating a sampling clock. The receiver (4) of one station B is provided with a second sampling clock generator for regenerating the sampling clock in the transmission signal, and the receiver (4) of one station A is provided with a second sampling clock generator for regenerating the sampling clock in the transmission signal. A synchronous transmission system in a bidirectional transmission system characterized in that the transmitter (2) of the other station B is controlled by the clock from the second sampling clock generator. .