JPH0646342A - Video transmitting device - Google Patents

Abstract

PURPOSE:To make it possible to optimally hold the level of the reception signal of video transmitting devices existing dispersedly by controlling the output level of a modulated RF signal and the input level of a RF multiple signal from an external control mechanism. CONSTITUTION:A control part 14 inputs the control command from an external control mechanism and performs the output level control of a modulation channel in a modulation part with signal output level adjustment function 12 and a modulated RF signal, the input level control of a RF multiple signal to a demodulation part 13 with signal input level adjustment function, and the control of a demodulation channel. The control part 14 has a control line for modulation channel control signal transmission to the modulation part 12, a control line for a RF output level control signal transmission, a control line for RF multiple signal input level control signal transmission the demodulation part 3 and a control line for demodulation channel control signal transmission. The RF multiple signal input level to the modulation part 12 and the demodulation part 13 is provided with an AGC function in addition to the controls from the control part 14 and the signal level compensation by the AGC is performed till the control signal from the control part is inputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video transmission device.

[0002]

2. Description of the Related Art FIG. 3 is a schematic view showing an outline of a conventional video transmission device. Reference numeral 31 is a conventional video transmission device, 36 is an RF multiplex signal input terminal for inputting a known RF multiplex signal into the video transmission device 31, and 33 is an RF multiplex signal input from the RF multiplex signal input terminal 36. A demodulation unit for demodulating an RF signal of a certain channel into a baseband video / audio signal, 39 is a baseband video signal output terminal for outputting the baseband video signal from the demodulation unit 33, 310
Is a baseband audio signal output terminal for outputting the baseband audio signal from the demodulation unit 33, 37 is a baseband video signal input terminal, 38 is a baseband audio signal input terminal, 32 is the baseband video signal input terminal 37 and A modulator that modulates the baseband video / audio signal from the baseband audio signal input terminal 38 into an RF signal of a certain channel, 35 is an RF signal output terminal that outputs the RF signal from the modulator 32, and 311 is an external control mechanism. A control command input terminal for inputting a control command from the control unit 34 and a control unit 34 for controlling the modulation channel in the modulation unit 32 and the demodulation channel in the demodulation unit 33. Here, the output level of the RF signal modulated by the modulator 32 and the input level of the RF multiplex signal input to the demodulator 33 are A
It is configured to be kept constant by GC (Auto Gain Control).

[0003]

As described above, in the conventional video transmission apparatus, the RF signal output level in the modulator and the RF multiple signal input level to the demodulator are AGC.
It is structured so that it is always kept constant by the function. Further, a transmission line such as a coaxial cable has frequency characteristics such that the amount of attenuation increases as the frequency of a signal to be transmitted increases. A plurality of amplifiers, branching devices, multiplexers, etc. are connected to the transmission line, and reflected waves are generated at those connection points. Due to the frequency characteristics of the transmission line and the influence of reflected waves, the RF multiplex signal transmitted through the transmission line is distorted at each frequency and the signal level becomes different. It is difficult to compensate the signal level of the distorted RF multiplex signal only with the AGC function of the video transmission device and to transmit and receive a high quality video / audio signal, and the video transmission device exists in multiple locations. However, there was a problem that it would be more difficult to do so. The present invention solves the above problems.

[0004]

According to the present invention, a baseband video signal input terminal, a baseband audio signal input terminal, and an input baseband audio / video signal are publicly known.
Modulation means for modulating the F signal and capable of externally controlling the output level of the RF signal, and RF modulated by the modulation means
An RF signal output terminal for outputting a signal, an RF multiplex signal input terminal for inputting an RF multiplex signal, a channel having the input RF multiplex signal is demodulated into a baseband video / audio signal, and the RF multiplex signal is input. A demodulation means capable of externally controlling the level, a baseband video signal output terminal for outputting the baseband video signal demodulated by the demodulation means,
A baseband audio signal output terminal for outputting a baseband audio signal demodulated by the demodulation means, a modulation channel in the modulation means and an output level control of the modulated RF signal, and a demodulation channel in the demodulation means and an input. The control means for controlling the input level of the RF multiplex signal according to the control from the external control mechanism is provided.

[0005]

By controlling the output level of the RF signal modulated by the modulation means of the video transmission device and the input level of the RF multiplex signal input to the demodulation means by the control signal from the external control mechanism, it is possible to control at multiple points. It is possible to keep the signal levels received by the distributed video transmission devices to be optimum.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of the present invention. Reference numeral 16 is an RF multiplex signal input terminal for inputting the RF multiplex signal into the video transmission apparatus 11, and 13 is an RF multiplex signal input from the RF multiplex signal input terminal 16, and outputs an RF signal of a certain channel as a baseband image. A demodulation unit with a signal input level adjusting function capable of demodulating into an audio signal and externally controlling the input level of the RF multiplex signal, 19 is a baseband for outputting a baseband video signal from the demodulating unit with a signal input level adjusting function Video signal output terminal,
110 is a baseband audio signal output terminal for outputting the baseband audio signal from the demodulation unit with the signal input level adjusting function, 17 is a baseband video signal input terminal, 18
Is a baseband audio signal input terminal, 12 is a baseband video / audio signal from the baseband video signal input terminal 17 and the baseband audio signal input terminal 18, and modulates an RF signal of a certain channel, and outputs the RF signal. A modulation unit with a signal output level adjusting function capable of externally controlling the level, 15 is an RF signal output terminal for outputting an RF signal from the modulation unit with a signal output level adjusting function, and 111 is a control command from an external control mechanism. A control command input terminal 14 is an output level control of the modulation channel and the modulated RF signal in the modulation section 12 with the signal output level adjusting function, and an input level control of the RF multiple signal to the demodulation section with the signal input level adjusting function. And a control unit for controlling the demodulation channel, Tone channel control signal transmission control line, RF output level control signal transmission control line, and RF multiplex signal input level control signal transmission control line and demodulation channel control signal transmission control in the signal input level adjusting function demodulation unit 13 The operation of this controller is digitally controlled by an external control mechanism.

The RF signal output level of the modulation unit 12 having the signal output level adjusting function and the RF multiplex signal input level to the demodulation unit 13 having the signal input level adjusting function are controlled by the control signal from the control unit 14 as well as the AGC. It also has a function, A until the control signal from the control unit is input.
The configuration is such that signal level compensation by GC is performed.

FIG. 2 is a conceptual diagram of a system in which the present invention is applied to a bidirectional video communication transmission system to transmit / receive video / audio signals. For the sake of simplicity, this workstation uses a base station video signal input and video display, a base band audio signal input and loudspeaker function, a base band video signal output and a base band audio signal output. It has a function and a video camera with a voice input function is connected. Reference numerals 22a, 22b and 22c are workstations, 21a, 21b and 21c are video transmission devices of the present invention, 29 is a trunk line for transmitting RF multiplex signals, 212
Reference numerals a and 212b are amplifiers 210a, 210b and 210c for compensating the level of the RF multiplex signal transmitted through the main line.
Is a branching device for branching the RF multiplex signal transmitted through the main line 29, and 23a, 23b and 23c are branching devices 210a,
RF multiple signal transmission lines for drawing the RF multiple signals branched by 210b and 210c into the video transmission devices 21a, 21b and 21c, and 27a, 27b and 27c are baseband video demodulated by the video transmission devices 21a, 21b and 21c. Baseband video signal transmission lines for transmitting signals to the workstations 22a, 22b, 22c, 26a, 2
6b and 26c are baseband audio signal transmission lines for transmitting the baseband audio signals demodulated by the video transmission devices 21a, 21b and 21c to the workstations 22a, 22b and 22c, and 25a, 25b and 25c are workstations 22a and 22c. The baseband video signals from the video cameras connected to 22b and 22c are transmitted to the video transmission device 21.
a, 21b and 21c are baseband video signal transmission lines, and 214a, 214b and 214c are baseband audio signals from video cameras connected to the workstations 22a, 22b and 22c.
a, 21b, 21c are baseband audio signal transmission lines, and 28 is a workstation 22a, 22
b, 22c, the control command from the video transmission device 21a,
21b, 21c control command transmission line for transmission,
213 is a computer LAN to which a plurality of workstations are connected, and 24a, 24b and 24c are video transmission devices 21.
R for transmitting the RF signal modulated by a, 21b and 21c
F signal transmission lines 211a, 211b, and 211c are multiplexers for multiplexing the RF signal transmitted through the RF signal transmission line with the RF multiplex signal transmitted through the trunk line 29. It is assumed that the video transmission devices 21a, 21b, 21c are communicating video / audio signals through this connection. Table 1 shows examples of channels used by each video transmission device.

[0009]

[Table 1]

Here, the signal input level of the channel received by the video transmission device 21b is set to A of the video transmission device 21b.
The operation when adjusting without using the GC function will be described with reference to FIG. Here, for simplicity, the video transmission device 21
It is assumed that the input / output level control of b can be controlled in 256 steps from 0 to 255. It is determined whether the input signal level to the demodulation unit with the signal input level adjusting function of the video transmission device 21b is appropriate (FIG. 4-a). If not, the workstation 22b controlling the video transmission device 21b
It is determined whether or not the signal input level of the demodulation unit with the signal input level adjustment function can be changed (FIG. 4B). If the input level can be changed (within the range of 0 to 255), the workstation 22b sends a level control command for changing the signal input level of the demodulation unit with a signal input level adjusting function of the video transmission device 21b. (Fig. 4-c). Upon receiving the level control command from the workstation 22b, the control unit of the video transmission device 21b sends a level control signal to the demodulation unit with the signal input level adjusting function (d in FIG. 4). In Fig. 4-b, when it is not possible to change the signal input level (0 to 2
If it is outside the range of 55), the computer LAN is used to change the signal output level of the modulation unit with the signal output level adjusting function of the video transmission device 21a to the workstation 22a of the communication partner.
Make a request via 213 (Fig. 4-e). The workstation 22a determines whether or not it is possible to change the signal output level of the modulator with the signal output level adjusting function of the video transmission device 21a (FIG. 4F). Can be changed (0 to 2
If within 55 steps), the work station 22a sends a control command to the video transmission device 21a to change the signal output level of the modulator having the signal output level adjusting function (FIG. 4-g). Upon receiving the control command from the workstation 22a, the control unit of the video transmission device 21a sends an output level control signal to the modulation unit with the signal output level adjusting function (FIG. 4-h). In this way, the video transmission device 21b can input a signal having an appropriate signal level.

[0011]

As described above, according to the present invention, the RF signal output level from the modulator and the RF to the demodulator of the video transmission device are provided.
By adjusting the level of multiple signal input level digitally from an external control mechanism in addition to the AGC function,
Each of the video transmission devices distributed over the network can transmit and receive the signal of the optimum level, and at the same time, can easily adjust the signal level.

Although the RF multiplex signal and the baseband signal are used as the video / audio signals, the present invention is not limited to these types of signals.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an embodiment of a video transmission device of the present invention.

FIG. 2 is a schematic diagram of a system using the video transmission device of the present invention.

FIG. 3 is a schematic diagram of a conventional video transmission device.

FIG. 4 is a flowchart showing the operation of the video transmission device when an optimum signal input level cannot be obtained.

[Explanation of symbols]

 11 Video Transmission Device of the Present Invention 12 Modulator with Signal Output Level Adjusting Function 13 Demodulator with Signal Input Level Adjusting Function 14 Controller 15 RF Signal Output Terminal 16 RF Multiplex Signal Input Terminal 17 Baseband Video Signal Input Terminal 18 Baseband Audio Signal input terminal 19 Baseband video signal output terminal 110 Baseband audio signal output terminal 111 Control command input terminal 21a Video transmission apparatus 21b of the present invention Video transmission apparatus 21c of the present invention Video transmission apparatus 22a of the present invention 22a Control workstation 22b Control Workstation 22c control workstation 23a RF multiple signal transmission line 23b RF multiple signal transmission line 23c RF multiple signal transmission line 24a RF signal transmission line 24b RF signal transmission line 24c RF signal transmission line 25a baseband video signal transmission Line 25b Baseband video signal transmission line 25c Baseband video signal transmission line 26a Baseband audio signal transmission line 26b Baseband audio signal transmission line 26c Baseband audio signal transmission line 27a Baseband video signal transmission line 27b Baseband video signal transmission line 27c Baseband video signal transmission line 28 Control signal transmission line 29 Main line for transmitting RF multiplex signal 210a Branch device 210b Branch device 210c Branch device 211a Multiplexer 211b Multiplexer 211c Multiplexer 212a Amplifier 212b Amplifier 213 Computer LAN 214a Baseband audio signal transmission line 214b Baseband audio signal transmission line 214c Baseband audio signal transmission line 31 Conventional video transmission device 32 Modulator 33 Demodulator 34 Control unit 35 RF signal output terminal 36 RF multiplex signal Power terminal 37 baseband video signal input terminal 38 baseband audio signal input terminal 39 baseband video signal output terminal 310 baseband audio signal output terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Etsumi Kanaya 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A modulation means for modulating a baseband video signal and a baseband audio signal into an RF signal, a demodulation means for demodulating an RF multiplexed signal into a baseband video signal and a baseband audio signal, and the modulation means. And a control means for controlling the output level of the modulated RF signal and the demodulation channel of the demodulation means and the input level of the input RF multiplex signal based on an external signal.