JPS6360683A - Video signal transmission system - Google Patents

Abstract

PURPOSE:To transmit a signal having a satisfactory S/N by controlling a signal level in the high frequency component of an input video signal in accordance with a transmission range, and transmitting the video signal with the control signal. CONSTITUTION:A level control signal C is formed 6 which corresponds to room with respect to the signal level of the input video signal Sin in the transmission range of the whole system. An adder 12 outputs the video signal S in which a low frequency component signal supplied through a delay circuit 10 and a high frequency component signal supplied through a variable amplifier circuit 9 are added and synthesized and in which the signal level in the high frequency component of the input video signal is raised in accordance with the room of the transmission range. An adder 14 adds and synthesizes the level control signal C and the video signal S from respective FM demodulation circuits 10 and 13, frequency-multiplexes them, and supplies them to a video head 16. A multipling signal is recorded in a tape 17.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal transmission system for a video tape recorder or the like.

C. Summary of the Invention] The present invention provides a video signal transmission system such as a video tape recorder that performs magnetic recording and reproduction of video signals, by controlling the signal level of the high frequency component of the input video signal according to the transmission range.
By transmitting the video signal together with the level control signal, it is possible to perform signal transmission with a good S/N ratio.

[Conventional technology]

Generally, in a video tape recorder (VTR) that magnetically records and reproduces a video signal, an input video signal is directly applied with emphasis, FM modulated, and recorded on a magnetic tape.

Conventionally, in a video signal transmission system, that is, a recording/reproducing system in a VTR, if the transmission range (R) is -40 to 120 dB, for example, as shown in FIG. Since there is often a margin of several times the level, signal processing such as non-linear emphasis is applied to the video signal to effectively utilize this surplus to improve the S/N ratio.

[Problem that the invention seeks to solve]

By the way, in conventional video signal transmission systems such as VTRs, which effectively utilize the margin of the transmission range and apply signal LAFI such as non-linear emphasis to the video signal to improve the S/N, non-linear signal processing is required. Because of this, large signal distortions tend to occur (and it is difficult to faithfully transmit video signals).

Therefore, in view of the conventional problems as described above, the present invention provides a video signal transmission system with a novel configuration that can faithfully transmit a video signal with a good S/N ratio without using a nonlinear circuit. The purpose is to

[Means for solving problems]

In order to solve the above-mentioned problems, the video signal transmission system according to the present invention includes a frequency separation means for separating an input video signal into a low-frequency component and a high-frequency component, and a frequency separation means for separating each separated output from the frequency separation means. control signal forming means for performing full-wave rectification and forming a level control signal according to the margin of the transmission range based on the rectified output; and a signal level of the high frequency component signal of the input video signal separated by the frequency separating means. A variable amplification means controlled according to the level control signal adds and synthesizes the low frequency component signal of the input video signal separated by the frequency separation means and the high frequency component signal supplied via the variable amplification means. The present invention is characterized in that it comprises a signal synthesizing means, and the combined output signal obtained by the signal synthesizing means and the level control signal obtained by the control signal forming means are multiplexed and transmitted.

[Effect]

In the video signal transmission system according to the present invention, the signal level of the high frequency component of the input video signal is controlled according to the transmission range, and the signal level of the high frequency component is increased in a portion where there is margin in the transmission range, thereby increasing the S/N. By transmitting the video signal together with the level control signal of the high-frequency component, the receiving side controls the level of the high-frequency component of the video signal based on the level control signal, thereby faithfully reproducing the original video signal. can be reproduced.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In the block diagram of FIG. 1 showing an embodiment of a recording system of a video tape recorder to which the present invention is applied, an input video signal (Sin) is input from a signal input terminal 1 at a cut-off frequency (
fc ) is, for example, a 4MHz low-pass filter (LP
F) 2 and a bypass filter (HPF) 3, where it is separated into low frequency components and high frequency components. The low-frequency component signal obtained by the low-pass filter 2 is supplied to a full-wave rectification circuit (DET) 4 that detects the signal level, and is also supplied to a signal adder 12 via a delay circuit (DL) 11. ing. Further, the high-frequency component signal obtained by the bypass filter 3 is supplied to a full-wave rectification circuit (DET) 5 that detects the signal level, and is also supplied to a delay circuit (DET) 5 that detects the signal level.
L) 8 is supplied to the variable amplification circuit 9. Further, the rectified output from each of the full-wave rectifier circuits 4.5 is supplied to a control signal forming circuit 6.

Here, for example, an input video signal (S
in) is supplied to the terminal 1 for the above-mentioned signal, the control signal forming circuit 6 outputs the low-frequency component signal and the high-frequency component signal indicated by the rectified outputs of the full-wave rectifier circuits 4.5. Based on each signal level, v” in this example
A level control signal (C) as shown in FIG. 2B is formed according to the margin of the transmission range (R) of the entire reproduction system with respect to the signal level of the input video signal (Sin). The level control signal (C) formed by this control signal forming circuit 6 is supplied as a gain control signal to the variable amplification circuit 9 via a low pass filter (LPF) 7, and is also supplied via an FM modulation circuit 10. signal adder 14
is supplied to.

The variable amplification circuit 9 amplifies the high frequency component signal supplied via the delay circuit 8 according to the level control signal (C), and supplies the amplified output to the signal adder 12. . The signal adder 12 adds and synthesizes the low frequency component signal supplied via the delay circuit 10 and the high frequency component signal supplied via the variable amplification circuit 9, thereby generating the input video signal. A video signal (S) as shown in FIG. 2C in which the signal level of the high frequency component of (Sin) is increased according to the margin of the transmission range (R) is output. The video signal (S) obtained by the signal adder 11 is supplied to a signal adder 14 via an FM modulation circuit 13.

The signal adder 14 includes each of the FM modulation circuits 1
The level control signal (C) and the video signal (S), which have been FM modulated at a frequency of 0.13, are frequency-multiplexed by adding and synthesizing them, and are supplied to the video head 16 via the recording amplifier 15. The frequency multiplexed signal is transmitted to the video head 1.
6 is recorded on the magnetic tape 17.

In the embodiment configured as described above, for example, the second input video signal (Sin) supplied to the signal input terminal I is
The low-frequency component signal of the input video signal (S in) shown in Figure A is at an intermediate level, and the signal level (a) of the high-frequency component with a margin in the transmission range (R) of the recording/reproducing system is set as a signal according to the margin. The signal level (b) of the high frequency component is increased to level (a゛) as shown in Figure 2C, and the low frequency component signal is at a high level and there is no margin in the transmission range (R). The variable amplifier circuit 9
By performing the gain control, the S/N of the video signal (S) obtained from the signal adder 12 can be improved by the increase in the signal level of the high frequency component. usually,
The video signal is a video signal (S
) by reproducing the level control signal (C) recorded along with the reproduction level control signal and controlling the signal level of the high frequency component of the reproduced video signal based on this reproduction level control signal, the input video signal (Sin) is faithfully reproduced. can be played.

In the above-mentioned embodiment, the present invention is applied to a video tape recorder using an FM modulation recording method, and the video signal and the level control signal are FM-modulated and added and synthesized, thereby frequency multiplexing and recording the magnetic tape. Although the present invention is not limited to the above-described embodiment, for example, the video signal and the level control signal may be transmitted in a time-division multiplex manner.

〔Effect of the invention〕

As is clear from the description of the embodiments described above, in the video signal transmission system according to the present invention, the signal level of the high frequency component of the input video signal is controlled according to the transmission range, and the signal level of the high-frequency component of the input video signal is controlled depending on the transmission range. By increasing the signal level of the
Since the video signal is transmitted together with the level control signal of the high frequency component, signal transmission with good S/N can be performed, and on the receiving side, the video signal is adjusted based on the level control signal. By controlling the level of high-frequency components, the original video signal can be faithfully reproduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment in which the present invention is applied to a recording system of a video tape recorder, and FIG.
, FIG. 2B and FIG. 2C are waveform diagrams for explaining the operation of the above embodiment. FIG. 2A shows an input video signal, FIG. 2B shows a level control signal, and FIG. Figure C shows a video signal in which the signal level of high frequency components is controlled. FIG. 3 is a waveform diagram showing the relationship between the transmission range of the recording/reproducing system in a VTR and a general video signal. 1...Signal input terminal 2...Low pass filter 3...Bypass filter 4.5...Full wave rectifier circuit 6...Control signal forming circuit 9...Variable amplifier circuit 10.13... FM modulation circuit 12.14...Signal adder

Claims (1)

[Claims] Frequency separation means for separating an input video signal into low-frequency components and high-frequency components; full-wave rectification of each separated output by the frequency separation means; and a transmission range margin based on the rectified output. a control signal forming means for forming a level control signal according to the above; and variable amplifying means for controlling the signal level of the high frequency component signal of the input video signal separated by the frequency separating means according to the level control signal; a signal synthesizing means for adding and synthesizing the low frequency component signal of the input video signal separated by the frequency separating means and the high frequency component signal supplied via the variable amplification means, the signal obtained by the signal synthesizing means; A video signal transmission system characterized in that a composite output signal and a level control signal obtained by the control signal forming means are multiplexed and transmitted.