JPH0470172A - Magnetic recording and reproducing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording/reproducing device (hereinafter referred to as 7TR) that frequency-modulates a video signal and records and reproduces it on, for example, a magnetic tape, and in particular relates to reproduction signal processing of a VTR. It is.

2. Description of the Related Art Hereinafter, reproduction signal processing of a conventional VTR will be explained with reference to the drawings.

FIG. 5 is a block diagram of a reproduction signal processing section in a conventional VTR. In FIG. 5, a signal input terminal 1 is connected to a demodulator 2, an output end of the demodulator Mr2 is connected to a low-pass filter 3, and an output end of the low-pass filter 3 is connected to a signal output terminal 4.

With the above configuration, the frequency-modulated reproduced video signal (hereinafter referred to as reproduced FM signal) of the VTR taken out from the magnetic head is supplied to the demodulator 2 and demodulated into a video signal, and then passed through the low-pass filter 3 to produce the reproduced video signal component. is taken out and output to the signal output terminal 4 for further processing.

Problems to be Solved by the Invention In the above conventional configuration, for example, when reproducing a demagnetized tape,
There was a problem in that the S/N ratio of the reproduced screen deteriorated significantly, making it very unsightly.

The present invention has been made to solve the above-mentioned conventional problems, and it is an object of the present invention to provide a VTR in which the S/N ratio of the reproduced screen does not deteriorate significantly even when a demagnetized tape is reproduced.

Means for Solving the Problems In order to solve the above problems, the VTR of the present invention includes: demodulation means for demodulating a frequency-modulated video signal; level detection means for detecting the level of the frequency-modulated video signal; and low-pass filter means whose cutoff frequency is controlled by the output signal of the level detection means, thereby controlling the passband of the output signal of the demodulation means.

Further, the VTR of the present invention includes a demodulating means for demodulating a frequency-modulated video signal, a synchronizing signal separating means for detecting a synchronizing signal period of the video signal, and an output signal of the synchronizing signal separating means and the frequency-modulated video signal. Level detection means receives a signal and detects the level of the synchronization signal period of the frequency-modulated video signal; and the cutoff frequency is controlled by the output signal of the level detection means to determine the passband of the output signal of the demodulation means. and low-pass filter means that is controlled.

Effect With the above configuration, the cut-off frequency is controlled by the low-pass filter means by the control pressure of the level detection means in accordance with the level of the frequency-modulated video signal, and the band of the demodulated video signal is determined. During magnetic tape playback, even if the level of the frequency-modulated video signal drops, by controlling the band of the demodulated video signal to a small value, the S/N ratio of the playback screen does not deteriorate significantly as in the past, and is extremely The problem of unsightliness is resolved. Further, the synchronization signal separation means detects the synchronization signal period of the video signal, and the cutoff frequency is controlled by the low-pass filter means using the control output of the level detection means according to the level of the synchronization signal period of the frequency-modulated video signal. Since the band of the video signal after demodulation is determined by Control takes place.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. Note that the same components as those in the conventional example are given the same reference numerals, and the explanation thereof will be omitted.

FIG. 1 is a block diagram of a reproduced signal processing section in a VTR showing a first embodiment of the present invention. In FIG. 1, a signal input terminal l is connected to a demodulator 2 and a level detector 11, an output terminal of the demodulator 2 is connected to a low-pass filter circuit 12, and an output terminal of the low-pass filter circuit 12 is connected to a signal output terminal 4. It is connected to the. In addition, the level detector 11
The output terminal of is connected to a low-pass filter circuit 12.

The operation of the above configuration will be explained below. First, the frequency-modulated reproduced FM signal of the VTR taken out from the magnetic head is supplied to the demodulator 2 and the level detector II, and the demodulator 2 demodulates it into a video signal, and the low-pass filter circuit 1
Output to 2. On the other hand, the level detector 11 detects the level of the frequency-modulated reproduced FM signal and outputs a signal for controlling the cutoff frequency of the low-pass filter circuit 12 according to the level of the reproduced FM signal. In the low-pass filter circuit 12, the cut-off frequency is controlled by the control signal of the level detector 11, the band of the video signal is determined, and the signal is output to the signal output terminal 4.

Here, as shown in FIG. 3, the cutoff frequency of the low-pass filter circuit 12 is A when the level of the reproduced FM signal is greater than a, and the cutoff frequency of the low-pass filter circuit 12 is A when the level of the reproduced FM signal is greater than a, and when the level of the reproduced FM signal is greater than b (<
When a), it becomes B (<A), and further level or c
When (<b), it operates so that C (<B).

In this way, even when the level of the reproduced FM signal becomes lower than a during demagnetized tape reproduction, as shown in FIG. 3, the cutoff frequency of the low-pass filter circuit 12 is controlled to be lowered, In other words, when the level of the reproduced FM signal becomes low, the cutoff frequency of the low-pass filter circuit 12 is determined to be lowered in accordance with the level of the reproduced FM signal, and the video signal band after demodulation is reduced. The S/N ratio deteriorates (5 or the screen does not become unsightly.

FIG. 2 is a block diagram of a reproduced signal processing section in a VTR showing a second embodiment of the present invention. In FIG. 2, a signal input terminal l is connected to a demodulator 2 and a level detector 13, an output terminal of the demodulator 2 is connected to a low-pass filter circuit 14, and an output terminal of the low-pass filter circuit 14 is connected to a signal output terminal. Connected to terminal 4. Further, the output end of the low-pass filter circuit 14 is connected to the synchronization signal separation circuit 15, the output end of the synchronization signal separation circuit 15 is connected to the level detector 13, and the output end of the L7 health detector 13 is connected to the low-pass filter circuit 14. It is connected.

According to the configuration described above, the frequency-modulated reproduced FM signal of the VTR taken out from the magnetic head is supplied to the demodulator 2 and the level detector 13, the operation of which will be explained below.
The demodulator 2 demodulates the video signal and outputs it to the low-pass filter circuit 14. The low-pass filter circuit 14 determines the band of the video signal and outputs the signal to the signal output terminal 4 and the synchronization signal separation circuit 15. The synchronization signal separation circuit 15 is
The synchronization signal period of the input video signal is detected and the signal is output to the level detector 13. The level detector 13 detects the level of the synchronizing signal period of the input reproduced FM signal, outputs the signal to the low-pass filter circuit 14, and controls the cutoff frequency of the low-pass filter circuit 14. As a result, the passband of the video signal from the demodulating means is controlled by the low-pass filter circuit 14.

In the case of the second embodiment as well, in the first embodiment shown in FIG.
Cutoff frequency of low-pass filter circuit 12 and reproduction F
This is the same as the relationship between the M signal level, and in the case of the second embodiment, the relationship between the cutoff frequency of the low-pass filter circuit 14 and the synchronization signal period of the reproduced FM signal is \/l.

In other words, the frequency of the low-pass filter circuit 14 becomes A when the level or b (<a
), it becomes B (<A), and then level or C (
<1) ), it operates so that C(·teB).

In this way, when the demagnetized tape is reproduced, even when the level of the synchronizing signal period of the reproduced FM signal is smaller than a, the cutoff of the low-pass filter circuit 14 is set as shown in FIG. The cutoff frequency of the low-pass filter circuit 14 is lowered according to the level of the synchronization signal period of the reproduced FM signal when the level of the reproduced FM signal becomes small, and the video signal after demodulation is reduced. Since the band is determined to be small, there is no significant deterioration of the S,.../N ratio or unsightly screen as in the conventional case. In addition, since the cutoff frequency of the low-pass filter circuit 14 is controlled by the level of the synchronization signal period of the reproduced FM signal, stable control is possible without the cutoff frequency being affected by the level t or frequency components of the video signal. I can do what I want to do.

Effects of the Invention As described above, according to the present invention, the band of the video signal after demodulation is determined according to the level of the frequency-modulated video signal or the level of the synchronization signal period. By controlling the cutoff frequency of the low-pass filter according to the level of the synchronization signal period of the frequency-modulated video signal, it is possible to prevent It is possible to perform stable control without being affected by the cutoff frequency.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a reproduced signal processing section in a VTR showing a first embodiment of the present invention, and FIG. 2 is a block diagram of a reproduced signal processing section in a VTR showing a second embodiment of the present invention. FIG. 3 is a cross-sectional characteristic diagram showing the relationship between the cutoff frequency of the low-pass filter circuit and the reproduced FM signal level in the reproduced signal processing section of the first embodiment of the present invention, and FIG. A low-pass filter characteristic diagram showing the relationship between gain and frequency in the example, FIG. 5 is a conventional VTR
FIG. 2 is a block diagram of a reproduced signal processing section in FIG. 2... Demodulator, 11.13... Level detector, 12
．． 14... Rono filter circuit, 15... Synchronous signal separation circuit.

Claims (1)

[Claims] 1. demodulation means for demodulating a frequency-modulated video signal;
Level detection means for detecting the level of the frequency-modulated video signal; and low-pass filter means whose cutoff frequency is controlled by the output signal of the level detection means to control the pass band of the output signal of the demodulation means. A magnetic recording and reproducing device. 2. demodulating means for demodulating the frequency modulated video signal;
a synchronization signal separation means for detecting a synchronization signal period of a video signal; an output signal of the synchronization signal separation means and the frequency-modulated video signal are input to detect a level of the synchronization signal period of the frequency-modulated video signal; 1. A magnetic recording and reproducing apparatus comprising: a level detecting means for detecting a signal; and a low-pass filter means whose cutoff frequency is controlled by the output signal of the level detecting means to control a passband of the output signal of the demodulating means.