JPH0395703A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent sound quality from being degraded due to modulation by increasing the frequency deviation amount of a pre-emphasized sound signal, changing the amplitude or amplitude-frequency property of the signal corresponding to the amplitude of the sound signal, afterwards, executing FM modulation, recording the signal, retrieving the original property which is changed on the FM modulation, when the signal is reproduced and de-emphasized. CONSTITUTION:A magnetic recording and reproducing device is composed of a pre-emphasis circuit 2 to pre-emphasize the sound signal, compressor 3, frequency modulation circuit 5, mixing means 7, filter 11, demodulation circuit 12, expander 15 and de-emphasis circuit 17 to de-emphasize the expanded sound signal. The compression ratio of the compressor 3 is selected so as to generate frequency deviation by the frequency modulation so that the frequency difference between the instantaneous frequencies of the two reproduced signal simultaneously read from two adjacent sound recording tracks can exceed an audible frequency, and the expansion ratio of the expander 15 is selected to be equal with the compression ratio of the compressor 3. Thus, with simple circuit configuration, the sound quality can be prevented from being degraded by the over modulation.

Description

Detailed Description of the Invention (Field of Application of the Invention) The present invention prevents overmodulation of a frequency modulated audio signal in a magnetic recording/reproducing device that records a frequency modulated (FM modulated) sound/1 signal and a video signal in a superimposed manner. 6 [Background of the Invention] Conventionally, magnetic recording is performed in which a luminance signal is frequency-modulated (FM modulated) and a chromaticity signal is frequency-converted and recorded below the FM-modulated luminance signal. One of the methods for recording audio signals in a playback device (hereinafter referred to as VTR) is a method in which an FM-modulated audio signal and the above-mentioned video signal are superimposed and recorded on the same magnetic tape using a rotating head (hereinafter referred to as audio FM). By the way, there has been a remarkable improvement in recording density in recent years, and compared to VTRs of about 10 years ago,
Achieved 7 times higher density recording. With the progress of such high-density recording technology, VTRs that are more compact have begun to be developed by reducing the size of the cassette 1- and the diameter of the rotating cylinder. These small VT
In order to reduce the size and weight of the R, as well as to reduce the running speed of the magnetic tape, the conventional audio signal recording method using a fixed head has been improved in terms of wow/flutter characteristics, playback S/N, playback frequency band, etc. It is becoming difficult to obtain sufficient performance in the FM system, and there is an increasing need to adopt new audio recording and reproducing methods such as the above-mentioned audio FM superimposition method.

The characteristics of the audio FM superimposition method are as follows: (1) It is less susceptible to time axis fluctuations due to unevenness in tape running speed, so it has good flutter and flutter characteristics.

(2) The playback frequency band does not depend on the high speed of the tape layer and can be widened.

etc.

Here, the above-mentioned audio signal is converted into audio FM-! Let us consider the recording frequency spectrum of a VTR that records and plays back using the iX tatami method.

The center frequency of the audio signal carrier must be determined so as to minimize its influence on the luminance and chromaticity signals. In addition, small VTRs, especially VTs with a small rotating cylinder diameter.
In R, the relative speed between the tape and the head is low, so the recording frequency band is narrow, and the center frequency of the luminance signal W12 transmission cannot be set very high. Therefore, the center frequency of the audio signal carrier must be as low as possible below the FM modulated luminance signal.

FIGS. 1 and 2 show examples of frequency spectra when recording video signals and FM audio signals.

FIG. 1 shows an example in which an FM modulated audio signal A1 is arranged between an FM modulated luminance signal Y1 and a frequency-converted chromaticity signal Cl, and FIG.
This is an example in which 2 is arranged.

In general, VTRs use a wide head with a wider head width than the video track width, in order to obtain racking margin and to perform so-called variable-speed playback, in which the tape is played back at a tape speed different from the tape speed during recording. Use. Therefore, in the audio FM superimposition method, problems such as the above-mentioned wide head and tracking deviation occur. Resetting the signal of the adjacent video track also affects the FM audio signal of the adjacent video trunk (
Hereinafter, this is referred to as adjacent interference. ), there is a problem in that very harsh noise is generated in the reproduced audio signal.

In particular, when increasing the recording density, the rack width for the video 1 becomes narrower, so adjacent disturbances due to tracking displacement etc. are a big problem.

FIG. 3 is a plan view schematically showing the positions of the video heads H and the video racks T2 and T2, which are formed on the magnetic tape 21.

Here, when the tracking deviates as shown in FIG. 3, the noise D(t) caused by the above-mentioned adjacent interference is the video track T. which the node H is trying to trace to the video.
The level of the first FM audio signal obtained from a. The second video obtained from the adjacent video track T2
FM audio signal (signal obtained from part B in Figure 3,
Hereinafter, this will be referred to as the interfering FM audio signal. ) level is b, and the difference frequency between the desired FM audio signal and the interfering FM audio signal is Δω, then b D(t)cc−Δω(cosΔω0 ......
...(1) It is expressed as a. Here t represents time. In other words, the adjacent interference noise D(t) is output as a sine wave with a difference frequency Δω × 1 × frequency between the desired FM voice signal and the interference FM voice signal, and its amplitude is equal to the difference between the interference FM voice signal and the desired FM voice signal.
It is considered that it is proportional to the amplitude ratio b/a to the audio signal and the difference frequency Δω. Therefore, several methods have been considered to reduce the above-mentioned adjacent interference in VTRs, one of which is to form a non-recorded portion (guard band) between a video track and its adjacent video track. be. However, with the method of forming a guard band, the efficiency of using magnetic tape is extremely low.
It is impossible to measure high-density recording. Another method is to draw one video track ↓ record the video signal with a rotating head with a different bed gap inclination (azimuth angle T) for each scan, and use azimuth loss to eliminate guard bands and adjacent interference noise. Method (There is an azimuth recording power formula. Here, the azimuth loss La is expressed as follows, where the video traverse on the tape is IiiiW, the azimuth angle T, and the recording wavelength λ. Here, π represents pi. Therefore, in this azimuth recording method, the shorter the recording wavelength, the narrower the width of the video head tracing the adjacent track, and the larger the azimuth angle T, the larger the azimuth loss La becomes and the more the adjacent interference is prevented. Figure 4 shows an example of the characteristics of azimuth angle and frequency versus azimuth loss, which shows that adjacent interference is reduced by the azimuth recording method.
This is an example of characteristics when W is 58 μm, relative velocity V is 5.8 m/S, and the recording signal frequencies are 629 KHz and 3.4 MHz. By the way, as mentioned above, the center frequency of the audio carrier wave in the audio FM superimposition method cannot be set to a very high frequency, and it is difficult to increase the recording density. In order to reduce the width of the adjacent video track traced by the video head, the width of the adjacent video track traced by the video head cannot be reduced too much. Therefore, in order to reduce adjacent interference to a level that poses no problem in practice, the azimuth angle ψ must be adjusted as described above.
There is no choice but to increase the value, and in the VTR of the numerical example above,
Set the FM audio carrier frequency to 1. 3 M I-{ z, the azimuth angle needs to be 20 degrees or more. However, if the azimuth angle ψ is made too large, the relative output between the magnetic tape and the head becomes cos 'p times, which reduces the playback ability, causes problems in video head manufacturing such as yield, and tracking. This deviation causes discontinuity in the time axis of the reproduced signal at the time of head switching, so-called skew.

Here, the skew amount t is expressed as x/2tanq' L=■ (3) vh, where the tracking deviation amount Change.

In addition, particularly during so-called search playback, in which the tape is played back at a high speed, many skews occur on the screen, causing a serious problem of image quality deterioration. Therefore, there is a limit to the ability of the azimuth recording method to reduce adjacent interference in the audio FM superimposition method, and it cannot be said to be at a practically sufficient level.

Another method is to use a reproducing head having the same head width as the video track width. The problem with this method is that as the video track width becomes smaller due to high-density recording, tracking accuracy must be extremely high in order to reduce adjacent interference to a practically sufficient level, and the magnetic tape travels during recording. It is difficult to perform so-called variable speed regeneration, which is regeneration at a different traveling speed.

One possible solution to the above two problems is to introduce an auto-1-racking method in which the video head automatically and accurately traces the video track.

This auto-tracking method requires a detection head to detect where on the video track is being traced, and an electro-mechanical conversion element such as a bimorph to correct the position of the video head in the event of tracking deviation. This poses major problems, such as not only the machines and circuits becoming extremely complex, but also reliability decreasing.

The three methods explained above reduce the amplitude ratio between the interfering FM audio signal and the desired FM audio signal g, and the adjacent interfering noise D(t
), but another possible method is to increase the frequency deviation when FM modulating the audio signal, thereby increasing the reproduced audio signal level and suppressing adjacent interference noise. . In this method, even if the amount of frequency deviation is increased, the adjacent interference noise is proportional to the difference frequency between the desired wave and the interference wave, as shown in equation (L), but on the other hand, it has a component of the difference frequency. This takes advantage of the fact that the precepts within the audible frequency band hardly increase because the frequency is outside the audible frequency band. In other words, the frequency deviation B of the audio signal
If the amount is doubled, the reproduced audio output signal level will be doubled, but since the adjacent interference noise within the audible band is approximately constant, this means that the adjacent interference has actually been reduced by 6 dB.

However, in order to increase the amount of frequency deviation of the audio signal as described above, it is necessary to widen the frequency band necessary for audio signal recording by the increased amount of frequency deviation.
．． The occupied band of the FM modulated luminance signal YE or the frequency-converted chromaticity signal C1 shown in FIG. 2 must be reduced or set to a frequency higher than the center frequency of the luminance signal carrier wave.

Reducing the occupied band of the FM modulated luminance signal or the frequency-converted chromaticity signal causes image quality deterioration such as deterioration of image sharpness, deterioration of transient characteristics, and color blurring. In addition, raising the center frequency of the luminance signal carrier wave causes the recording wavelength to become shorter, and to avoid this, the diameter of the rotating cylinder must be increased, which becomes a major problem in miniaturization. there is a possibility.

Furthermore, as the audio signal occupies a wider band, it becomes more susceptible to interference from the video signal such as side willow waves of the FM modulated luminance signal and the frequency-converted chromaticity signal, and the sound quality is more likely to deteriorate due to the generation of so-called buzz sounds.

As mentioned above, each method has its own drawbacks.
With a single method, it is difficult to reduce adjacent interference to a practically sufficient level in the above-mentioned sound quality FM superimposition method, and also to achieve multi-functionality such as high recording density and variable speed playback, and miniaturization of the mechanism and circuit. It is.

Therefore, as a method to compensate for the shortcomings of the various methods mentioned above, FM
The effect of superimposing and azimuthally recording a modulated audio signal and video signal, and the recording method as a means of effectively increasing the amount of frequency deviation of the audio signal and making the difference frequency described above almost outside the audible band. Due to the synergistic effect of adding a noise removal circuit that suppresses noise by changing the amplitude and amplitude frequency characteristics depending on the amplitude of the audio signal, and returning the changed characteristics to the original values during playback. A method can be considered that can reduce adjacent interference noise to a practically sufficient level, and simultaneously realize multifunctionality such as high-density recording and variable speed playback, and miniaturization of mechanical systems and circuit systems. This method is based on the effect of reducing adjacent interference due to azimuth loss caused by the azimuth recording method, and also because increasing the amount of frequency deviation of the audio signal causes the difference frequency to go outside the audible band, and prevents components within the audible band. The property is that there is almost no increase, and the component of adjacent interference noise moves to Takagi. Adjacent interference noise is reduced by the synergistic effect of reducing auditory discomfort and the effect of suppressing adjacent interference noise, and since the azimuth recording method is adopted, high-density recording is possible. is of course possible.

Furthermore, this method also has the following features:

First, the video trunk width can be further narrowed by the amount of adjacent interference reduction, allowing high-density recording. Second, noise other than adjacent interference noise can also be reduced. Third, the amount of frequency deviation of the actual audio signal is small. This method is superior to the method of simply increasing the amount of frequency deviation because the frequency band required for recording is small, and the frequency band used when recording the FM modulated audio signal is small. , since the recording wavelength of the luminance signal can be made longer, the diameter of the rotating cylinder can be made smaller, allowing for miniaturization.
There are many advantages such as the ability to perform variable speed playback without using complicated mechanisms and circuits such as auto-tracking using electromechanical transducers (electromechanical transducers). However, the audio FM superimposition recording and reproducing system is equipped with a pre-emphasis circuit and a de-emphasis circuit in order to convert so-called triangular noise, in which the noise level peculiar to FM modulation is proportional to the noise frequency, into white noise with a constant noise level. Therefore, simply adding a means to effectively increase the amount of frequency deviation to the audio signal input terminal will not change the amplitude or amplitude frequency characteristics of the audio signal by means of effectively increasing the amount of frequency deviation. Afterwards, the high frequency part was further emphasized by the action of the Brienff 7sis circuit. There is a drawback that the input to the FM modulator becomes too large and tends to cause overmodulation, resulting in deterioration of sound quality due to overmodulation. To prevent this, it may be possible to reduce the level of the input audio signal, but this would reduce the average frequency deviation amount, and as mentioned in 1! This is a problem because the effect of reducing J3 interference noise will be weakened.

[Purpose of the invention]

An object of the present invention is to obtain a magnetic recording and reproducing device that prevents overmodulation of frequency modulated audio signals.

[Summary of the invention]

The present invention pre-emphasizes audio 13 during recording,
After effectively increasing the amount of frequency deviation of the pre-emphasized audio signal and changing the amplitude and amplitude frequency characteristics of the audio signal according to the amplitude of the audio signal, FM modulation is performed and recorded, and FM modulation is performed during playback. By restoring the changed characteristics and then de-emphasizing them, deterioration in sound quality due to overmodulation is less likely to occur.

As mentioned above, as a method for reducing adjacent interference noise in the audio FM superimposition method, FM modulation recording is performed by changing the amplitude and amplitude frequency characteristics according to the amplitude of the audio signal during recording to increase the effective frequency deviation amount. However, during playback, it is very effective to suppress noise by restoring the changed characteristics after FM demodulation, and to use the azimuth recording method in combination. Overmodulation is likely to occur due to the pre-emphasis characteristics. Therefore, in the present invention, the audio signal is first pre-emphasized during recording, and then the amplitude and amplitude frequency characteristics of the audio signal are changed to effectively increase the amount of frequency deviation to perform FM modulation, and then superimposed on the video signal. In this method, azimuthal recording is performed, and during reproduction, after FM demodulation, the changed characteristics are restored to their original state, and then de-emphasis is performed, thereby making overmodulation less likely to occur.

[Embodiments of the invention]

The present invention will be explained below with reference to embodiments shown in the drawings.

FIG. 5 is a circuit diagram showing an embodiment of an audio signal recording circuit of a rotary head type VTR which records audio signals using the magnetic recording/reproducing apparatus of the present invention. Further, FIG. 6 shows a VT for reproducing a magnetic tape recorded by the recording method of the present invention.
FIG. 2 is a circuit configuration diagram showing an example of an R audio signal reproducing circuit. In FIG. 5, the audio signal input from the input terminal 1 passes through the compression circuit 2 and then passes through the compression circuit 3 from the compression-expansion cross point according to the compression-expansion characteristics shown in FIG. The level of the large amplitude portion is changed to a small level, and the level of the small amplitude portion is changed to be higher than the noise level. Here, the gain of the 1/2 compression circuit 3 is controlled by the output signal of the detection circuit 4 which receives the pre-emphasized audio signal 2 as input, and compresses the dynamic range of the pre-emphasized audio signal to 1/2. . The output signal of the 1/2 compression circuit 3 is . FM modulation is performed by an FM modulator 5.

The output of the FM modulator 5 has unnecessary band components removed by a low-pass filter (LPF) 6, and then added to the video signal input from the input terminal 8 by an adder 7. Azimuth is recorded on the tape 10.

As mentioned above, in this recording system, the dynamic range of the pre-emphasized audio signal is compressed to 1/2, and the 1/2 compressed signal is input to the FM modulator. Compared to a method in which means for effectively increasing the shift amount is added to the input end, overmodulation is less likely to occur, and a large average frequency shift amount can be recorded.

Next, in the audio signal reproducing circuit shown in FIG.
The signal reproduced from the magnetic head 9 by the magnetic head 9 is input to the jIF pass filter (BI) 11. B1)F
il extracts the FM audio signal from the playback system.

Here, the level ratio between the desired FM audio signal and the interfering FM audio signal in the extracted FM audio signal 9 is, for example, an azimuth angle of ±17 degrees, an audio carrier frequency of 1.3 MHz, an h-rack width of 18.5 μm, and a video signal. If it is 425 μm in the head, it is about 22 dB. Further, the signal reproduced by the magnetic head 9 is also outputted from an output terminal 19 to a video signal reproduction circuit (not shown). The extracted FM audio signal is
It is demodulated into an audio signal by demodulator l2. The demodulated audio signal is processed by the LPFi3 to remove FMijl transmission leakage, etc., and then processed by the hold circuit 14 by holding the previous value of noise caused by head switching. Here, hold circuit 14
performs a previous value holding operation for a certain period of time using a control signal synchronized with the head switching signal inputted from the input terminal 20.

The output signal of the halt circuit l4 has a dynamic range of 1
Since the signal remains compressed to /2, the 2x expansion circuit 15 expands it to the original dynamic range. Here, the double expansion circuit 15 is gain-controlled by the output signal of the detection circuit 16 which receives the input signal 4 of the hold circuit 14, and doubles the dynamic range of the demodulated audio signal. . The expanded signal passes through the de-emphasis circuit 17,
It is output from the output terminal 18. The reproduced audio signal expanded by the double expansion circuit 15 undergoes the same expansion operation for its noise level and has a low noise level, so that it is output as an audio signal with suppressed adjacent interference noise.

That is, for example, in FM modulation 5, the audio input signal is OdB
When ±100KH7. The pre-emphasized audio input signal has a frequency shift of -20d.
B, if this -20 dB audio input signal is not compressed by the compression circuit 3 but is directly FM modulated by the FM modulator 5, it becomes ±lO-20 KHz (: ±100 X 10 -H K I{ Z
) frequency shift occurs. When this FM modulation signal is recorded as the adjacent video 1 racks Tl and T2 and simultaneously played back by the video header, the video track T
The difference frequency between the instantaneous frequencies of the two reproduced signals read from T2 and T2 is in the range from 0 to 20 KHz, and the adjacent interference noise on a square scale is within the audible frequency band of 20 KHz or less. However, when a -20 dB audio input signal is compressed into a -10 cif3 signal by the 172 compression circuit 3 and FM modulated, its frequency deviation becomes a frequency deviation of ±31.5 KIlz, and the frequency of the adjacent interference noise (two The difference frequency of the instantaneous frequency of the reproduced signal is distributed in the range of 0 to 63 KHz, and most of the adjacent interference noise is 20 KHz.
The frequency can be set to a frequency outside the audible frequency band.

In other words, the adjacent interference noise distributed from 0 to 20 KHz is spread in frequency to the adjacent interference noise distributed from 0 to 63 KHz, so that the noise energy within the audible frequency band is reduced. Adjacent interference noise becomes almost undetectable. If the difference frequency changes sinusoidally in each case, approximately 80% of the total period will be equal to or higher than the audible frequency. Expressing this generally, the FM modulation factor 9 has a frequency deviation of ±OKI-Iz when the input signal is OdB.
On the other hand, if the signal is compressed to the upper limit input level where all frequency deviations are within ±10 KHz (difference frequency is 20 KHz or less) and input to the FM modulator 5, the frequency is 2 x O x 10 − at the frequency 1 10 wave number. Hlog-HK
Hz).

Therefore, when the difference frequency is not compressed, the input signal level is also compressed and input to the FM modulator 5.
A frequency shift occurs in the FM modulation signal such that the difference frequency between the instantaneous frequencies of the two signals played simultaneously from adjacent video 1 to racks Tl and T2 becomes an audible frequency of 20 KHz or more, resulting in adjacent interference. is reduced.

Here, an example of the characteristics of the noise frequency spectrum of adjacent interference noise when FM audio signals are reproduced on the above-mentioned VTR is as follows.
FIG. 8 shows cases in which a noise removal circuit consisting of a 1/2 compression circuit 3 and a 2-fold expansion circuit 15 is used and cases in which it is not used. In Figure 8, ■ is when there is no noise removal circuit;
(2) shows the case where a noise removal circuit is used. As is clear from FIG. 8, it can be seen that when the noise removal circuit is used, the adjacent interference noise can be improved by about 20 dl3.

The present invention prevents sound quality deterioration due to overmodulation, and
Adjacent interference can be reduced to a practically sufficient level, and in addition,
A number of the advantages mentioned above also result. Note that the noise removal circuit described in this example does not change the amplitude-frequency characteristics, but simply compresses and expands the dynamic range. However, other methods, such as changing the amplitude-frequency characteristics, can also be used to remove noise. It may also be something that performs the following actions. Further, a device that performs a noise removal operation by changing the amplitude and amplitude frequency characteristics according to the signal level of a specific band of the audio signal during recording can also be used in the present invention. Furthermore, when changing both the amplitude and amplitude frequency characteristics of an audio signal during recording as a noise removal circuit, it is best to change the amplitude frequency characteristics first and then change the amplitude in order to prevent overmodulation. . When regenerating, all you have to do is restore the changed characteristics to their original state.

〔Effect of the invention〕

As explained above, if the present invention is used, as shown below, 1. With a simple circuit configuration, it is possible to prevent quality degradation due to overmodulation.

2. Since the number of video tracks can be further increased to five, high-density recording is possible.

3. Apparent audio signal frequency a! Since this is a method of increasing the amount of transfer, the amount of frequency in the 912 frequency range required for recording may be small.

4. Since the required frequency bandwidth is small, the diameter of the rotating cylinder can be made small.

5. Variable speed playback with good sound quality can be achieved without using complicated mechanisms or circuits.

It has many features such as these, and is highly effective in reducing the size of VTRs.

4

[Brief explanation of drawings]

1 and 2 are frequency spectrum diagrams showing examples of signal frequency spectra in the audio FM multiplexing system, FIG. 3 is a plan view of a magnetic tape for explaining +g interference, and FIG.
The figure is a characteristic diagram showing the characteristics of azimuth angle and recording wavelength versus azimuth loss, Figures 5 and 6 are circuit configuration diagrams showing one embodiment of an audio signal recording and reproducing circuit using the present invention, and Figure 7 is a characteristic diagram showing the characteristics of azimuth angle and recording wavelength versus azimuth loss. 1
FIG. 8 is an input/output characteristic diagram of the /2 compression circuit and the double expansion circuit, and a frequency characteristic diagram of adjacent interference noise amplitude showing the effect of adjacent interference noise reduction. l...Pre-emphasis circuit, 3...1/2 compression circuit. 4.16...Detection circuit, 1
5: 2x expansion circuit, l7: De-emphasis circuit. Atsushi 3 times TI T2 Circular number 1 amma 7, angle de is) Fig. 7 -10 -40 -20 0 λ angle level 2

Claims (1)

[Claims] 1. A pre-emphasis circuit that pre-emphasizes an audio signal, a compressor that compresses the pre-emphasized audio signal, a frequency modulator that frequency modulates the compressed audio signal, and an output of the frequency modulator and an image. a mixing means for mixing the signal components; a recording and reproducing means for sequentially recording the output of the mixing means on a magnetic tape as a recording locus inclined at a predetermined angle with respect to the longitudinal direction of the magnetic tape; and a recording and reproducing means for reproducing the same; A filter that extracts a frequency modulated audio signal from the read reproduction signal, a demodulator that frequency demodulates the frequency modulated audio signal from the filter, an expander that expands the demodulated signal from the demodulator, and a decompressor that expands the demodulated signal from the demodulator. It consists of a de-emphasis circuit that performs de-emphasis, and the frequency modulation generates a frequency shift such that the difference frequency between the instantaneous frequencies of two recorded signals read simultaneously from two adjacent audio recording trajectories becomes equal to or higher than the audible frequency. The compression ratio of the compressor is selected to be equal to the compression ratio of the compressor, and the expansion ratio of the expander is selected to be equal to the compression ratio of the compressor. 2. The compression ratio of the compressor and the expansion ratio of the expander are 2.
2. A magnetic recording and reproducing device according to claim 1, wherein the magnetic recording and reproducing device is selected from the following. 3. The magnetic recording and reproducing apparatus according to claim 1, wherein the amplitude frequency characteristics of the compressor and the expander are changed so that they are opposite to each other. 4. The magnetic recording and reproducing apparatus according to claim 1, wherein the recording and reproducing means comprises a rotary head having a plurality of heads having different azimuth angles. 5. A pre-emphasis circuit that pre-emphasizes an audio signal, a compressor that compresses the pre-emphasized audio signal, a frequency modulator that frequency-modulates the compressed audio signal, and an output of the frequency modulator and a video signal component. a mixing means for mixing; a recording/reproducing means for sequentially recording the output of the mixing means on a magnetic tape as a recording locus inclined at a predetermined angle with respect to the longitudinal direction of the magnetic tape; and a recording/reproducing means for reproducing the same; A filter that extracts a frequency modulated audio signal from a signal, a demodulator that frequency demodulates the frequency modulated audio signal from the filter, an expander that expands the demodulated signal from the demodulator, and a de-enhancer that de-emphasizes the expanded audio signal. 1. A magnetic recording and reproducing device comprising a phasis circuit, wherein the compression ratio of the compressor and the expansion ratio of the expander are selected to be 2. 6. A pre-emphasis circuit that pre-emphasizes an audio signal, a compressor that compresses the pre-emphasized audio signal, a frequency modulator that frequency modulates the compressed audio signal, and an output of the frequency modulator and a video signal component. and a recording means that sequentially records the output of the mixing means on a magnetic tape as recording trajectories inclined at a predetermined angle with respect to the longitudinal direction of the magnetic tape. A magnetic recording and reproducing device characterized in that the compression ratio of the compressor is selected so that the frequency modulation causes a frequency shift such that the difference frequency between the instantaneous frequencies of two frequency modulated audio signals is equal to or higher than an audible frequency. 7. The magnetic recording and reproducing apparatus according to claim 6, wherein the compression ratio of the compressor is 2. 8. The magnetic recording and reproducing apparatus according to claim 6, wherein the amplitude frequency characteristic of the compressor is changed. 9. The magnetic recording apparatus according to claim 6, wherein the recording means comprises a rotary head having a plurality of heads having different azimuth angles. 10. A pre-emphasis circuit that pre-emphasizes the audio signal, a compressor that compresses the pre-emphasized audio signal, a frequency modulator that frequency modulates the compressed audio signal, and mixes the output of the frequency modulator and the video signal component. and a recording means for sequentially recording the output of the mixing means on a magnetic tape in the longitudinal direction as a recording trajectory inclined at a predetermined angle with respect to the longitudinal direction, and the compression ratio of the compressor is 2. A magnetic recording device characterized by the following.