JPH033592A - magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce beat disturbance and to obtain an excellent video signal by controlling a characteristic of a trap circuit eliminating a voice signal component leaked in a chrominance carrier signal reproduced by a detection signal of an audio signal detection means. CONSTITUTION:A detector 16 detects the presence of an audio signal subject to frequency modulation sent from a band pass filter 15 and the characteristic of an audio carrier trap circuit 8 is switched with an output from the detector 16. When the audio signal is detected, the characteristic of the audio signal carrier trap is utilized and when the audio signal subject to frequency modulation is not detected, the audio signal carrier trap is eliminated. Thus, beat disturbance is less and when the audio signal subject to frequency modulation is not recorded, an audio signal carrier trap circuit 8 of the color signal reproduction processing system is eliminated to obtain an excellent reproduction picture without losing the color signal band.

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 audio signal components from reproduced color signals.

Conventional technology The signal spectrum of NTS (J type) is configured as shown in Figure 5. When this signal is recorded on a magnetic tape by a magnetic recording/reproducing device, the luminance signal is converted to a low carrier frequency by a low carrier frequency modulation recording method. While being converted into a modulated signal,
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 a direct recording method using a high frequency bias, and the other is an FM recording method, which can be divided into two methods: a deep recording method and a frequency multiplexing method. 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 brightness 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 low-pass filter 7. The high-pass filter 4 extracts only the luminance signal component from the signal sent to the high-pass filter 4, and the demodulator 5 demodulates the frequency-modulated luminance signal.

The demodulated signal is sent to the adder 11 through a low-pass filter 6, which removes noise components in the carrier color signal band that will be added later, and passes only the luminance signal component. From the reproduced color signal, a low-pass filter 7 extracts only the low-pass converted color signal component, and an audio carrier trap circuit 8 removes the audio signal component leaking into the color signal band. The frequency converter 9 restores the carrier color signal to the correct carrier color signal, removes noise components in the luminance signal band to be added later, and sends it to the adder 11.

The brightness signal and the color signal are added together by an adder 11 and outputted from a video output terminal 12 as a video signal.

The audio signal is taken out from the audio recording/reproduction head 13, amplified by a preamplifier 14, and sent to a bandpass filter 15. A bandpass filter 15 extracts only the audio signal, a demodulator 17 demodulates it into an actual audio signal, a lowpass filter 18 removes high-frequency noise components, and the signal is output from an audio output terminal 19.

However, as shown in FIG. 8, regardless of the presence or absence of frequency-modulated audio signal components, the reproduced color signal output from the low-pass filter 7 is passed through the audio carrier trap-7 circuit 8.
The leakage component from the audio carrier wave is removed, and the color signal band component is also removed, and the color signal whose color signal band is narrowed is frequency-converted, added to the luminance signal, and output.

Problems to be Solved by the Invention There are high frequency bias methods and frequency modulation methods for recording audio signals, but in magnetic recording and reproducing devices that perform deep recording using the frequency modulation method, the audio signal does not affect the video signal during playback. In order to prevent this from occurring, the head dedicated to recording and reproducing audio signals has an azimuth angle that is different from that of the head dedicated to recording and reproducing video signals, but in reality, audio signals leak into video signals during playback. However, in the reproduction color signal processing system, unnecessary components due to leakage of audio signals that appear during reproduction affect the carrier color signal that is frequency-converted and restored, causing problems such as beat interference in the reproduced image. Therefore, the unnecessary components caused by the leakage of the audio signal are removed through the audio carrier trap circuit, but along with removing the unnecessary components, the color signal band is also removed, resulting in the disadvantage that the color signal components are lost in the reproduced image.

In view of the above problems, the present invention detects the reproduced audio signal that changes over time and uses it as a control signal, thereby changing the characteristics of the audio signal carrier trap circuit in the reproduced color signal processing system. The present invention provides a magnetic recording and reproducing device that is capable of reproducing video signals.

Means for Solving the Problems In order to solve the above problems, the magnetic recording and reproducing device 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. The frequency-modulated luminance signal recorded on the same part of the magnetic tape and during reproduction is passed through a luminance signal reproduction processing system consisting of a high-pass filter, a demodulator, and a first low-pass filter in this order. The carrier chrominance signal converted to a low frequency band is passed through a chrominance signal reproduction processing system consisting of a second low-pass filter, an audio signal carrier trap circuit, a frequency converter, and a first band-pass filter. The audio signal is passed through an audio signal reproduction processing system consisting of a second band-pass filter, a demodulator, and a third low-pass filter in this order. The apparatus is equipped with a signal detecting means, and is configured to control the characteristics of the audio signal carrier trap circuit based on the detection signal of the audio signal detecting means.

According to the above-described configuration, the present invention makes use of the characteristics of the audio signal carrier trap when a frequency-modulated audio signal is detected in the reproduction signal of the color signal, and when the frequency-modulated audio signal is not detected, the audio signal is By excluding the carrier wave trap, when a frequency modulated audio signal is recorded, beat interference is reduced by suppressing unnecessary components from the audio signal leaking into the reproduced color signal, and the frequency modulated audio signal is recorded. If not, the audio signal carrier trap circuit of the color signal reproduction processing system can be excluded to obtain a good reproduced image without impairing the color signal band.

EMBODIMENT A magnetic recording/reproducing apparatus according to an embodiment of the present invention will be described below 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 low-pass filter 7, respectively. The signal sent to the high-pass filter 4 extracts the frequency-modulated luminance signal component, and the demodulator 6 demodulates the frequency-modulated luminance signal, and the low-pass filter 6 extracts the luminance signal component. Noise components in the band of the carrier color signals to be added are removed and inputted to the adder 11. Furthermore, the low-pass filter 7 extracts the carrier color signal converted to a lower frequency band from the signal sent from the preamplifier 3, and
The color signal that passes through the audio carrier trap circuit 8 and is low-frequency converted by the frequency converter 9 is restored to the original color signal and is added after removing the noise component in the luminance signal band that will be added later by the band-pass filter 1o. The signal is input to the device 11. Adder 11
The luminance signal and the chrominance signal are added together and output as a video signal from the video output terminal 11. The audio signal is taken out from the audio recording/reproduction head 13, amplified by the preamplifier 14, and only the audio signal is taken out by the bandpass filter 16.

The signal passes through the detector 16, is demodulated into the correct audio signal by the demodulator 17, removes high-frequency noise components by the low-pass filter 18, and outputs the audio signal from the audio output terminal 19.

On the other hand, the detector 16 is configured to detect the presence or absence of a frequency-modulated audio signal sent from the band-pass filter 15, and to switch the characteristics of the audio carrier trap circuit 8 based on the output from the detector 16. When a signal is detected, the trap characteristics shown in FIG. 2a are applied, and when no audio signal is detected, the trap characteristics are excluded as shown in FIG. Furthermore, when there are two audio carrier waves as shown in FIG. 2, it is effective to provide a trap circuit for the audio carrier component close to the carrier color signal. In FIG. 2, C is a color signal and D is an unnecessary component due to an audio signal.

The detector 16 is composed of, for example, a well-known peaking amplifier circuit and a level comparator.

The audio carrier trap circuit 8 may be switched by installing a changeover switch. FIG. 3 is a basic block diagram thereof, and the detection signal from the detector 16 is sent to the changeover switch 2o. The changeover switch 20 switches the color signal sent from the low-pass filter 7 according to the detection signal so that it is sent to either the audio carrier trap circuit 8 or the frequency converter 9.

The audio carrier trap circuit 8 may be configured using, for example, an LCR, and may be configured to be added to or excluded from the circuit depending on the detection signal from the detector 16. FIG. 4 shows an example of this.

As described above, according to this embodiment, by controlling the trap characteristics in the reproduced carrier color signal depending on the presence or absence of a frequency-modulated audio signal, the color signal band is controlled when there is no frequency-modulated audio signal. You can get a better video signal than before without any loss.

Effects of the Invention As described above, the magnetic recording and reproducing apparatus of the present invention is equipped with a detection means for detecting a reproduced audio signal, and the detection signal of the audio signal detection means leaks into the reproduced carrier color signal. By configuring the trap circuit to control the characteristics of the trap circuit that removes the audio signal components that are present in the signal, and by suppressing unnecessary components caused by the audio signal that leak into the color signal band when frequency-modulated audio signals are recorded. Beat interference can be reduced, and when a frequency modulated audio signal is not recorded, a good video signal can be obtained without damaging the color signal band.

[Brief explanation of drawings]

FIG. 1 is a main block diagram on the reproduction side of a magnetic recording and reproducing device in one embodiment of the present invention, FIG. 2 is an explanatory diagram of its operation, and FIG. 3 is a reproduction side of a magnetic recording and reproducing device in another embodiment of the present invention. Figure 4 is a specific circuit diagram of the trap circuit used in the device, Figure 5 is a signal spectrum diagram of the NTSC system, and Figure 6 is a magnetic recording system that performs deep recording by frequency modulating audio signals. A recording frequency allocation diagram of the reproducing apparatus, FIG. 7 is a main block diagram of the reproducing side of the conventional magnetic recording/reproducing apparatus, and FIG. 8 is an explanatory diagram of its operation. 1... Magnetic tape, 2... Video recording/playback head, 3... Preamplifier, 4...
...High-pass filter, 5...Demodulator, 6.
...Low pass filter, 7...Low pass filter, 8...Audio carrier trap circuit, 9...Frequency converter, 1o... ... Bandpass filter, 11... Adder, 12...
...Video output terminal, 13...Audio recording/playback head, 14...Preamplifier, 15...
...Bandpass filter, 16...Detector, 1
7...Demodulator, 18...Low pass filter, 19...Audio output terminal, 2o...
...Selector 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 low frequency is passed through a luminance signal reproduction processing system consisting of a pass filter, a demodulator, and a first low pass filter in that order, and then the carrier color signal is passed through a second low pass filter and an audio signal. The audio signal passes through a color signal reproduction processing system consisting of a carrier trap circuit, a frequency converter, and a first band-pass filter, and then passes through a second band-pass filter, a demodulator, and a third low-pass filter. A helical scan type magnetic recording and reproducing apparatus that passes through an audio signal reproduction processing system consisting of a filter in order, and is equipped with a means for detecting a reproduced audio signal, and a detection signal of the audio signal detecting means is used to detect the audio signal. A magnetic recording/reproducing device characterized by being configured to control the characteristics of a carrier wave trap circuit. (2) The magnetic recording and reproducing apparatus according to claim 1, wherein the audio signal detection means is performed using a frequency-modulated audio signal that has passed through a band-pass filter during reproduction. (3) The characteristics of the audio signal carrier trap circuit are controlled by the audio signal detection means so that when an audio signal is detected, the characteristics of the trap circuit are utilized, and when no audio signal is detected, the characteristics of the trap are excluded. A magnetic recording and reproducing device according to claim 1 or 2, characterized in that: