JPH0564130A - Video signal recording and reproducing device - Google Patents

Abstract

PURPOSE:To provide the video signal recording and reproducing device able to intermittently record an audio signal by applying integration detection to the audio signal, applying logarithmic compression to the signal and inserting the result to a synchronizing signal area of a video signal as a DC potential. CONSTITUTION:A synchronizing signal is separated at a synchronizing separator circuit 2 from a video signal subject to clamping at a clamp circuit 1, the synchronizing signal separated from the video signal is led to a timing circuit 3 and used for a control signal for a changeover circuit 4. On the other hand, an audio signal is given to an integration detection circuit 5, in which the signal is converted into a DC potential proportional to the amplitude of the audio signal and the result is inputted to a logarithmic compression circuit 6, in which the potential is converted into a DC potential proportional to the logarithm of the amplitude of the audio signal. The DC potential is selected in place of the video signal at the circuit 4 by using a control signal outputted from the circuit 3 and inserted to a synchronizing signal area being a desired area of the video signal as the DC potential. Through the constitution above, the amplitude of the audio signal is recorded as a luminance change in the video signal and then the device recording the audio signal is realized without remarkable revision of conventional circuit configuration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal recording / reproducing apparatus capable of intermittently recording a video signal.

[0002]

2. Description of the Related Art In recent years, a device capable of intermittent recording by applying a home video tape recorder (hereinafter abbreviated as VTR) has been put on the market. There is.

A video signal recording / reproducing apparatus capable of intermittently recording a video signal is generally called a time-lapse VTR and can record for a long time because of the characteristic of intermittent recording. For this reason, it is used for surveillance and academic purposes. Here, the intermittent recording does not mean that the recording medium travels constantly to record the video signal as in a general apparatus, and therefore the audio signal cannot be recorded. However, for surveillance and academic purposes, there was a growing demand for recording audio signals in addition to video signals. As a technology that enables this,
Although a device to which digital technology is applied has been put into practical use, the reality is that the cost has increased significantly and it has not been generalized.

A conventional video signal recording / reproducing apparatus capable of intermittent recording will be described below with reference to the drawings.

As shown in FIG. 2, the input video signal is clamped by the clamp circuit 1 to the horizontal synchronizing signal, and then part of the video signal is added to the sync separating circuit 2 while the other part is added to the FM modulating circuit 7. After being added, the recording signal amplifier circuit 8
Amplified by and output. The video signal input here is the one that is intermittently taken out and is FM-modulated by the FM modulation circuit 7 in order to record it on the time-lapse VTR device. Conventionally, a process for recording an audio signal is performed. Was never done.

[0006]

However, the above-mentioned conventional structure has a problem in that the video signal can be recorded intermittently, but the audio signal cannot be recorded at all.

The present invention solves the above-mentioned conventional problems, and provides an apparatus capable of recording an audio signal at a low cost in an intermittent recording video signal recording / reproducing apparatus without significantly changing the conventional circuit configuration. The purpose is that.

[0008]

To achieve the above object, a video signal recording / reproducing apparatus of the present invention comprises a clamp circuit for clamping an input video signal and a sync separation circuit for separating a sync signal from the video signal. , A timing circuit for obtaining a desired timing from the separated sync signal, an integral detection circuit for integrating and detecting the input audio signal, and a logarithmic compression circuit for logarithmically compressing the integrated and detected audio signal. The video signal and the logarithmically compressed audio signal are switched using the output signal from the timing circuit as a control signal, and an FM modulator that FM-modulates the output from the switching circuit.

[0009]

According to the present invention, with the above construction, an audio signal is integrated-detected and logarithmically compressed and inserted into the sync signal area of the video signal. Therefore, the size of the audio signal can be recorded as a change in the brightness of the video signal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the input video signal is input to the switching circuit 4 after the clamp circuit 1, while the input audio signal passes through the integrating circuit 5 and the logarithmic compression circuit 6 and then the switching circuit 4. To enter. Further, a part of the output from the clamp circuit 1 obtains the switching control signal of the switching circuit 4 by the output signals from the sync separation circuit 2 and the timing circuit 3. The output from the switching circuit 4 is FM
The signal is output through the modulation circuit 7 and the recording signal amplification circuit 8.

The operation of the video signal recording / reproducing apparatus configured as described above will be described with reference to FIG. First, the input video signal is clamped by the clamp circuit 1. Here, the clamp has a function of fixing the DC potential of the video signal, and is for removing the DC fluctuation component that the video signal receives in the transmission system. The next process is FM
It is also necessary to determine the frequency shift when modulating.

A sync separation circuit 2 separates the clamped video signal from the sync signal. The separated synchronizing signal is introduced into the timing circuit 3 and serves as a control signal for the switching circuit 4. Here, the sync signal includes a horizontal sync signal and a vertical sync signal, and generally, the horizontal sync signal is counted and determined based on the vertical sync signal, and 12 to 14H, which has a small influence on the video signal, is selected. This signal is input to the switching circuit 4 as a control signal.

The separately input voice signal is converted into a DC potential in the integral detection circuit 5 which is proportional to the size of the voice signal. This DC potential is input to the logarithmic compression circuit 6 and converted into a DC potential proportional to the logarithm of the size of the audio signal. The time constant of the integral detection circuit 5 is selected to be about 30 msec or more. This is because it is restricted by the vertical synchronizing signal of the video signal. The maximum and minimum values of the DC potential proportional to the size of the audio signal are set to the white level and black level of the video signal.

The DC potential is switched to the video signal by the switching circuit 4 by the control signal output from the timing circuit 3. By this switching operation, the audio signal is inserted as a DC potential in the synchronization signal area which is a desired area of the video signal. Therefore, the size of the audio signal is recorded as a change in the brightness of the video signal.
In the surveillance / academic field, there are cases where the audio signal itself is required and cases where it is sufficient to be able to identify the audio signal size.
The present invention realizes the latter. The video signal including the size of the switched audio signal is input to the FM modulation circuit, becomes an FM signal, is amplified by the recording signal amplification circuit 8, and is recorded on the recording medium.

[0016]

As is apparent from the above description of the embodiment, the present invention does not significantly change the configuration of the conventional device, and the integration detection circuit and the logarithmic compression circuit of the audio signal are also the input VU of the audio signal. It can be shared in many cases when it is included in the meter circuit.

It is obvious that the apparatus of the present invention can be implemented without restriction such as a magnetic tape as a recording medium or an optical disk. Therefore, the device of the present invention can be realized at a relatively low cost, so that it can be expected to make a great contribution to industry, and an excellent video signal recording / reproducing device which is industrially valuable can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of a video signal recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram of a main part of a conventional video signal recording / reproducing apparatus.

[Explanation of symbols]

 1 Clamp Circuit 2 Sync Separation Circuit 3 Timing Circuit 4 Switching Circuit 5 Integral Detection Circuit 6 Logarithmic Compression Circuit 7 FM Modulation Circuit

Claims (1)

[Claims] 1. A clamp circuit for clamping a video signal, and a sync separation circuit for separating a sync signal from the video signal,
Timing circuit for obtaining desired timing from separated sync signal, integral detection circuit for integrating and detecting audio signal, logarithmic compression circuit for logarithmically compressing integrated detected audio signal, clamped video signal and logarithmic compression A video signal recording / reproducing apparatus having a switching circuit that switches the generated audio signal using the output signal from the timing circuit as a control signal, and an FM modulator that FM-modulates the output from the switching circuit.