JPH033593A - 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 applies low carrier frequency modulation to the luminance signal of the video signal, low frequency conversion to the carrier chrominance signal, and frequency modulation to the audio signal. The present invention relates to a magnetic recording/reproducing device for recording data on a computer, and particularly relates to trap control for removing an audio signal component from a demodulated luminance signal during reproduction.

The signal spectrum of the conventional NTSC system is configured as shown in Figure 6. When this signal is recorded on a magnetic tape by a magnetic recording/reproducing device, the luminance signal is converted into a low carrier frequency modulated signal using the low carrier frequency modulation recording method. Along with being converted to
The color signal is converted to a low frequency signal and recorded using a low frequency conversion direct recording method. There are two ways to record audio signals; one is direct recording using high frequency Piano, and the other is FM recording, which can be divided into two types: deep recording and frequency multiplexing. The deep recording method is a helical scan type magnetic recording/reproducing device in which an audio signal recording/reproducing head is installed at a position preceding the video signal recording/reproducing head in the rotational direction of the head/cylinder, and an audio frequency modulated signal is recorded in advance. Since the audio frequency modulated signal has a longer wavelength than the frequency modulated luminance signal, it is recorded deep in the thickness direction of the magnetic tape, and the video signal is recorded with a slight delay. Since the modulated luminance signal has a short wavelength, it is recorded on the surface layer of the magnetic tape so that the tape thickness can be used efficiently. Since the low frequency conversion color signal is recorded at a reduced recording level, it is recorded on the surface layer of the magnetic tape, so that it does not have much influence on the audio signal. Furthermore, in the frequency multiplexing method, the audio frequency modulated signal is superimposed on the video signal and recorded using the same head as the video signal. FIG. 6 shows the frequency allocation of the deep recording method, and the reason there are two carrier waves for the FM audio signal is to record in stereo.

The main blocks of the video signal circuit for reproducing these signals recorded on magnetic tape with a normal magnetic recording/reproducing device are shown in Figure 7. 1 is the magnetic tape, and a head dedicated to video recording and reproducing. The signal taken out from 2 is amplified by a preamplifier 3 and sent to a high-pass filter 4 and a reproduction carrier color code processing circuit 9. The high-pass filter 4 extracts only the luminance signal component from the signal sent to the high-pass filter 4, and the demodulator 6 demodulates the frequency-modulated luminance signal. The demodulated signal passes through a low-pass filter 7 to remove noise components in the carrier color signal band that will be added later, and sends only the luminance signal component to the adder 1°. The reproduced color signal is returned to the original carrier color signal in the reproduced carrier color signal processing circuit 9, added to the luminance signal in the adder 1o, and outputted from the output terminal 11 as a video signal.

However, as shown in Fig. 8, the demodulated luminance signal output from the demodulator e has a leakage component from the audio carrier wave in the high frequency part, and the luminance signal is changed to the carrier color while leaving this leakage component. It is added to the signal and output.

Problems to be Solved by the Invention In a magnetic recording and reproducing device that performs deep recording using a frequency modulation method for recording audio signals, the system is designed exclusively for recording and reproducing video signals so that the audio signals do not affect the video signals during playback. Although the head dedicated to audio signal recording and playback is equipped with an azimuth angle that is different from that of the head, in reality, the audio signal leaks into the video signal during playback, and the audio signal that appears during demodulation in the luminance signal playback system. The frequency fa of unnecessary components due to leakage is given by fa being the center frequency of the carrier wave frequency of the luminance signal and fb being the frequency of the FM audio carrier
Then, it is expressed as fo-4a-fb, which affects the demodulated luminance signal, causing a problem such as beat disturbance in the reproduced picture.

In view of the above problems, the present invention provides an audio signal carrier trap circuit in a reproduced luminance signal processing system by detecting the high frequency level of a reproduced luminance signal that changes over time and using it as a control signal. The present invention provides a magnetic recording and reproducing device that can reproduce good video signals by changing the characteristics of the magnetic recording device.

Means for Solving the Problems In order to solve the above problems, the magnetic recording and reproducing apparatus of the present invention performs low carrier frequency modulation on the luminance signal, low frequency conversion on the carrier color signal, and frequency modulation on the audio signal. When recorded on the same part of the magnetic tape and reproduced, the frequency-modulated luminance signal is processed by a high-pass filter, a demodulator, a first low-pass filter, and an audio signal carrier trap circuit. The carrier color signal converted to low frequency through the signal reproduction processing system is passed through a color signal reproduction processing system consisting of a second low-pass filter, a frequency converter, and a bandpass filter in this order. type magnetic recording and reproducing device, comprising means for determining the level of a high frequency of the reproduced luminance signal, and configured to control the characteristics of the audio signal carrier trap circuit based on the detection signal of the level determining means. It is.

Effect of the Invention With the above configuration, the present invention makes the characteristics of the audio signal carrier trap shallow when the high frequency level μ of the luminance signal is large in the demodulated signal of the luminance signal, and shallows the characteristic of the audio signal carrier trap when the high frequency level μ of the luminance signal is small. By deepening the characteristics of the audio signal carrier trap, unnecessary components due to the audio signal can be suppressed without damaging the high-frequency components of the luminance signal, and a good reproduced image with less beat interference can be obtained.

EXAMPLE Hereinafter, one embodiment of the present invention [IAJ's magnetic recording/reproducing apparatus will be described with reference to the drawings.

FIG. 1 is a basic block diagram on the reproducing side showing an embodiment of the magnetic recording/reproducing apparatus of the present invention, and FIG. 2 is an explanatory diagram thereof.

In FIG. 1, 1 is a magnetic tape, and 2 is a head dedicated to recording and reproducing video signals, from which a frequency-modulated luminance signal and a low frequency-converted carrier color signal are reproduced. The signal reproduced by the head 2 is amplified by a preamplifier 3 and sent to a high-pass filter 4 and a reproduced carrier color signal processing circuit 9, respectively. The signal sent to the high-pass filter 4 extracts a frequency-modulated luminance signal component, and is sent to a high-pass level discriminator 5 and a demodulator 6 in that order. The frequency-modulated luminance signal is demodulated by the demodulator 6,
The signal is passed through a trap circuit 8 that removes band noise components of carrier color signals added by a low-pass filter 7 and removes enclosed components of the audio carrier wave, and is inputted to an adder 1o.

Furthermore, the reproduction carrier color signal processing circuit 9 extracts the carrier color signal converted to a lower frequency band from the signal sent from the preamplifier 3, performs processing such as frequency conversion, and restores the carrier color signal to the original carrier color signal. It is input to adder 1Q. An adder 10 adds the luminance signal and a carrier color signal, and outputs the result from an output terminal 11 as a video signal.

On the other hand, the high-pass level discriminator 5 detects the magnitude of the high-pass level of the frequency-modulated luminance signal sent from the high-pass filter 4, and uses the output from the high-pass level discriminator 6 to control the trap circuit 8. When the high frequency level is high, the characteristic is changed to the characteristic A of the trap circuit 8 shown in Figure 2A, and when the high frequency level is low, the characteristic is changed to the characteristic B of the trap circuit 8 shown in Figure 2A. Make it. Further, when there are two audio carrier waves as shown in FIG. 2, trap circuits having the above-mentioned characteristics corresponding to the respective frequencies may be provided. In FIG. 2, C is a luminance signal and D is an unnecessary component due to an audio signal.

The high-frequency level discriminator 6 includes, for example, a well-known peaking amplifier circuit and a level comparator.

The trap circuit 8 may be switched by installing two types of trap circuits having different characteristics.

FIG. 3 is a basic block diagram thereof, and the detection signal from the high-frequency level discriminator 6 is sent to the changeover switch 12. The changeover switch 12 switches the switch so that the luminance signal demodulated by the demodulator 6 is sent to one of two trap circuits having different characteristics based on the detection signal. Here, the trap circuit A is a trap circuit with shallow characteristics, and the trap circuit opening is a trap circuit with deep characteristics, and the luminance signal that has passed through either of the traps is sent to adder 1o and reproduced. The carrier color signal sent from the carrier color signal processing circuit 9 is added by the adder 1Q, and the result is outputted from the output terminal 11 as a video signal.

The trap circuit 8 may be configured using, for example, an LCR, and may be configured to change only R according to the high frequency level of the luminance signal based on the detection signal from the high frequency level discriminator 6. FIG. 4 shows an example of this.

As described above, according to the present embodiment, by controlling the trap characteristic in the demodulated luminance signal using the high frequency level of the reproduced luminance signal, the high frequency component of the luminance signal is not impaired. A good video signal with less interference can be obtained.

Effects of the Invention As described above, the magnetic recording/reproducing apparatus of the present invention is equipped with a high-frequency level discriminating means for discriminating the high-frequency level of a reproduced luminance signal, and a demodulated signal is detected by the high-frequency level discriminating means. By controlling the characteristics of the trap circuit that removes audio signal components leaking into the luminance signal, unnecessary components from the audio signal can be removed without damaging the high-frequency components of the luminance signal, resulting in less beat interference. Good video signals can be obtained.

[Brief explanation of drawings]

FIG. 1 is a main block diagram on the reproduction side of a magnetic recording and reproducing apparatus according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of the same apparatus, and FIG. 3 is a diagram of a magnetic recording and reproducing apparatus according to another embodiment of the present invention. The main block diagram of the playback side, Figure 4 is a circuit diagram of the trap circuit used in the device, Figure 6 is a signal spectrum diagram of the NTSC system, and Figure 6 is a magnetic recording system that performs deep recording by frequency modulating the audio signal. FIG. 7 is a recording frequency allocation diagram of the reproducing apparatus, FIG. 7 is a main block diagram on the reproducing side of a conventional magnetic recording/reproducing apparatus, and FIG. 8 is an explanatory diagram of the operation of the apparatus. 1...magnetic tape, 2...head, 3
......Preamplifier, 4...High-pass filter, 5...High-frequency level discriminator, 6...
...Demodulator, 7...Low-pass filter, 8.
... Trap circuit, 9 ... Reproduction carrier color signal processing circuit, 10 ... Adder, 11 ...
・Output terminal, 12...Switching switch.

Claims (3)

[Claims] (1) The luminance signal is modulated with a low carrier wave frequency, the carrier color signal is converted into a low frequency band, the audio signal is frequency modulated and recorded on the same part of the magnetic tape, and during playback, the frequency modulated luminance signal is converted into a high frequency band. The carrier chrominance signal converted to a low frequency signal is passed through a luminance signal reproduction processing system consisting of a pass filter, a demodulator, a first low pass filter, and an audio signal carrier trap circuit in this order. A helical scan type magnetic recording/reproducing device that passes through a color signal reproduction processing system consisting of a pass filter, a frequency converter, and a band pass filter in this order, and means for determining the level of a high frequency of a reproduced volatile signal. Equipped with
A magnetic recording/reproducing apparatus characterized in that the characteristics of the audio signal carrier trap circuit are controlled by the detection signal of the level determining means. (2) The magnetic recording and reproducing apparatus according to claim 1, wherein the high-frequency level discrimination means for the luminance signal is performed using a frequency-modulated luminance signal after passing through a high-pass filter during reproduction. . (3) The characteristic control of the audio signal carrier trap circuit by the high-frequency level discrimination means of the luminance signal is such that when the high-frequency level of the luminance signal is large, the trap characteristics are deep, and when the high-frequency level of the luminance signal is small, the trap characteristics are deep. 3. The magnetic recording and reproducing apparatus according to claim 1, wherein the trap characteristics are controlled to be shallow.