JPH0385074A - Magnetic tape recording and reproducing device - Google Patents

Abstract

PURPOSE:To record a QDPSK signal with a prescribed spectrum shape at all times by detecting a spectrum shape of a reproduced QDPSK signal, discriminating the propriety of the spectrum shape of the signal and controlling the recording equalizing characteristic of the signal to a proper value. CONSTITUTION:A PCM audio signal reproduced by a PCM monitor head 60 is amplified by a monitor signal reproduction amplifier 61 and inputted to a REC EQ control section 62. Then a frequency component symmetrical to a carrier frequency of a QDPSK signal 34 is separated from the PCM signal subject to reproduction amplification by BPF 63, 64 and a reproduction signal level is detected by DETs 65, 66. Based on the result of detection, a coefficient control circuit 67 discriminates the propriety of the spectrum shape of the signal 34, the proper recording equalizing characteristic is selected to the PCM audio signal and the recording equalizing characteristic of the PCM audio signal is set always to a proper value.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic tape recording and reproducing device for recording and reproducing video signals, FM audio signals, and PCM audio signals, and particularly relates to a magnetic tape recording and reproducing device for recording and reproducing video signals, FM audio signals, and PCM audio signals, and particularly to a magnetic tape recording and reproducing device for recording and reproducing video signals, FM audio signals, and PCM audio signals. It's about control.

[Conventional technology]

FIG. 6 is a block diagram showing the configuration of a conventional magnetic tape recording/reproducing apparatus disclosed in, for example, Japanese Unexamined Patent Publication No. 63-288402, in which a video signal and an FM audio signal are
-VH3 type magnetic tape recording/reproducing main unit (hereinafter referred to as 5-VH
Recorded and played back using the same method as the S-method VTR),
For example, a PCM signal of about 2.6 Mbps is recorded and reproduced by performing offset type four-phase differential phase shift 1 (hereinafter referred to as four-phase phase modulation).

6 In FIG. 6, 1 is a video signal recording processing circuit, 2 is a video signal recording amplifier, 3 is a rotating drum, 4 is a composite video signal magnetic head (hereinafter referred to as composite video head), 5 is a magnetic tape, 6 7 is a video signal reproducing amplifier, and 7 is a video signal reproducing processing circuit. 8 is an FM audio signal recording processing circuit; 9
Addition circuit for FM audio signals of both R channels, 1
0 is an FM audio signal recording amplifier, 11 is a magnetic head for FM audio signals (hereinafter referred to as FMA head), 12 is an FM audio signal reproducing amplifier, and 13a is a band pass filter for separating the L-channel component of the FM audio signal ( Below, BPF-
13b is a band pass filter (hereinafter referred to as BPF-R) for separating the R-channel component of the FM audio signal, and 14 is an FM audio signal reproduction processing circuit.

In addition, 15 is an analog-digital converter (hereinafter referred to as AD
C), 16 is a digital audio recording processing circuit, 17
18 is an offset type 4-phase differential phase modulation circuit (hereinafter referred to as 4-phase phase modulation circuit); 18 is a PCM audio signal recording amplifier;
19 is a PCM audio signal magnetic head (hereinafter referred to as PCM head), 20 is a PCM audio signal regeneration amplifier, and 21 is an offset type 4-phase differential phase modulation signal demodulation circuit (hereinafter referred to as 4
22 is a digital audio reproduction processing circuit, 23 is a digital-to-analog converter C and below, D
(referred to as AC).

FIG. 7 is a diagram showing the spectra of the video signal, FM audio signal, and PCM audio signal of the conventional magnetic tape recording/reproducing apparatus having the above configuration. , Y-FM signal)
32, 33, and 34 are spectra of low-pass converted color signals (hereinafter referred to as C(L) signals), and 32, 33, and 34 are FM-modulated L-channel audio signals (hereinafter referred to as FMA-L signals), respectively.
FM-modulated R-channel audio signal (hereinafter referred to as FMA-R signal), and quadrature phase modulated PCM audio signal (hereinafter referred to as QDPSK signal).

Next, the operation of the above configuration will be explained.

In FIG. 6, a baseband video signal is input to the video signal recording processing circuit 1, and the luminance signal component of the baseband video signal is processed such that the synchronization tip level is 5.4MHz and the white peak level is 7.0MHz. The color signal component is FM-modulated and converted into a Y-FM signal 30, and the color signal component is low-frequency converted so that the carrier frequency is approximately 629 KHz, and the color signal component is
After being converted into the L5 signal 31, the Y-FM signal 30 and the C(L) signal 31 are added together and sent to the video signal recording amplifier 2 as an RF video signal having the spectrum shown in FIG. 7(a).
A rotary transformer (not shown) built in the one-rotation drum 3 and a composite video are recorded on the magnetic tape 5 via the RAD 4.

Further, the RF video signal reproduced by the composite video radar 4 is amplified by a video signal reproduction amplifier 6, restored to a baseband video signal by a video signal reproduction processing circuit 7, and output.

The FM audio signal is input to the FM audio signal recording processing circuit 8, and after noise reduction processing is performed, the L channel is 1.3
The MHz and R channels are frequency modulated with a 1.7 MHz carrier wave and are FM with the spectrum shown in Figure 7 (C).
The signals are converted into an A-L signal 32 and an FMA-R signal 33, which are added in an adder circuit 9, and then sent as an FMA signal to an FM audio signal recording amplifier 10, a rotary transformer (not shown) built in the rotating drum 3, and an FMA head. 11 and is recorded on the magnetic tape 5.

Further, the FMA signal reproduced by the FMA head 11 is amplified by the FM audio signal reproduction amplifier 12, and then
FMA- by BPF-L13a and BPF-R13b
The signal is separated into an L signal 32 and an FMA-R signal 33, subjected to frequency demodulation and noise reduction processing by the FM audio signal reproduction processing circuit 14, and then restored to an audio signal.

On the other hand, the PCM audio signal is converted into a digital signal by the ADC 15, and then sent to the digital audio recording processing circuit 16.
The signal is pulse code modulated with an error correction code added thereto, converted into a PCM signal of about 2.6 Mbps, and then subjected to offset type four-phase differential phase modulation in the four-phase phase modulation circuit 17, as shown in FIGS. QDPSK signal 34 with a bandwidth of ±0°65 MHz centered on the carrier wave.
is converted to The carrier frequency of this QDPSK signal 34 is 2.8 MH, considering interference with the RF video signal.
Z or higher is desirable.

Here, the QD PSK signal 34 and the RF
Let's consider the optimal carrier frequency for the video signal. Assuming that the QDPSK signal 34 is recorded deeper than the RF video signal, the carrier frequency of the QDPSK signal 34 is low because the RF video signal tends to partially erase high-frequency signals. Since the carrier frequency of the QDPSK signal 34 is set to 2.5 MHz, the carrier frequency of the QDPSK signal 34 is set to 2.5 MHz.

This QDPSK signal 34 is then recorded on the magnetic tape 5 via the PCM audio signal recording amplifier 1B, a rotary transformer (not shown) built in the rotating drum 3, and the PCM head 19.

In addition, the QDPS reproduced by the PCM head 19
The K signal 34 is amplified by the PCM audio signal regeneration amplifier 20, then restored to a PCM signal by the 4-phase phase demodulation circuit 21, further subjected to processing such as error correction by the digital audio reproduction processing circuit 22, and then processed by the DAC 23. It is restored to an audio signal and output.

Next, the recording traces of the RF video signal, FM audio signal, and PCM audio signal on the magnetic tape 5 will be described. As mentioned above, in the multilayer recording method in which multiple signals are recorded overlappingly on almost the same recording track, each signal becomes a noise component due to crosstalk and interferes with each other, so the azimuth angle of each magnetic head is changed. Interference is being reduced.

Note that since the FM audio signal, PCM audio signal, and video signal are sequentially recorded on the magnetic tape 5, there are three recording layers, so such a recording method will be referred to as a three-layer recording method.

Fig. 8(a), (bl shows an example of the specifications and arrangement of each magnetic head in a conventional magnetic tape recording/reproducing device using the three-layer recording method. Also, as shown in Fig. 9, the composite video head 4a is a standard VSP-R head 41a of R azimuth head for mode (SP mode) and triple recording time mode (
vEP-L head 4 of L azimuth head for EP mode)
2a is attached at a distance of approximately 7401 Im (corresponding to approximately 1.41 Im), and the composite video head 4b is VSP-L.
The head 41b and the VEP-R head 42b are similarly attached, and the composite audio head 40a is equipped with an L-azimuth FMA-L head lla and a PCM-L head 19a.
are attached at a distance of approximately 740 μm, and similarly FMA-R heads llb and P
It is assumed that the CM-R head 19b is attached. Note that the specifications and mounting angles of each magnetic head constituting the composite video head 4 and the composite audio head 40 are determined by the angle.

The installation height and other details are shown in Figure 8 (b), and the composite video head 4. The FMA head 11 is based on a 5-vH3 type VTR.

FIG. 10 is a diagram for explaining the relationship between the mounting angle and mounting height of each magnetic head and the recording traces recorded on the magnetic tape 5. For example, in FIG. 10(a), O
The mark is ■5P-R head 41a, the mark is FMA i, to 7
Dolla and P CM -L H/Do 19a is installed at the height, and the square mark is at the angle O.

FMA-L head lla, PCM-L when converted to
The head height of the head 19a is shown, and therefore the relative position of the recording trace is shown. Similarly, the ○ mark in Figure 10 (b) is V.
EP-L head 42a, mark and mark are FMA-L head l
1a and the mounting of the PCM-L head 19a indicate the height and the relative position of the recording trace. Note that the vSP-R head 41
a, VEP-L head 42a, FMA-L head lla
and PCM-L head 19a have a corner angle of 1.4 mm.
Although the difference is 1.4°, the difference of 1.4° is omitted to simplify the explanation.

FIG. 11 shows the magnetic tape 5 in the perpendicular direction to the recording trace.
2 is a cross-sectional view of the magnetic layer 36 formed on the base film 35 of the magnetic tape 5, in which an FM audio signal, a PCM audio signal, and a video signal are recorded in this order, and the FM audio signal recording layer 37. PCM audio signal recording layer 38. A video signal recording layer 39 is formed.

Next, demodulation of the QDPSK signal 34 will be explained.

Ru.

FIG. 12 shows in detail the configuration of the four-phase phase demodulation circuit 21 shown in FIG. Carrier regeneration circuit 52. The operation of 0 or more that is restored as a PCM signal by the clock regeneration circuit 53 and the data regeneration circuit 54 is described, for example, in the document "National Technical Report J (National Tec
hnical report V.

1, 30. No, 1. p1 of the paper "PCM audio demodulator for direct satellite broadcasting" published in Feb. 1984)
P and Q data regeneration using the synchronous detection method shown in Fig. 6 of Section 5, and carrier signal regeneration using the inverse modulation method, and clock signal regeneration of the digital phase comparison type shown in Fig. 15 of p. 19 of the same paper are performed. , Q data is subjected to signal processing such as differential decoding and serial/parallel conversion in the data reproducing circuit 54, and is restored to the original PCM signal.

Next, reproduction equalization of the QDPSK signal 34 will be explained.

The above-mentioned QDPSK signal 34 can be obtained from, for example, Figure 4 on page 64 of "Fundamentals of Digital Modulation and Demodulation Circuits" (Ohmsha 1984).
．． 7, i.e. about 2.6M
If a bps PCM signal is subjected to four-phase phase modulation with respect to a 2.5 MH2 carrier signal, a signal with a spread of approximately ±0.65 MHz as shown by "record" in FIG. 13 will be obtained. By recording the QDPSK signal 34 on the magnetic tape 5 in three layers together with the video signal and the FM audio signal, it is partially erased by the video signal recorded on the upper layer, and the erasure is more for the high frequency side signal. Therefore, the PCM head 19.
QD regenerated by PCM audio signal regeneration amplifier 20
The PSK signal 34 has a spectrum shape with low frequency emphasis and high frequency suppression as shown in FIG. 13 GI "Reproduction". A reproduction equalizer 50 is used to restore the spectrum of the reproduced signal to the spectrum at the time of recording and to perform the four-phase phase demodulation operation correctly, and a COS equalizer with flat group delay characteristics is generally used. The reproduction equalizer 50 has equalization characteristics as shown in FIG. 14, for example.
The above-mentioned equalization characteristic restores the spectrum of the reproduced signal to the spectrum at the time of recording.

However, the 5-VH3 system VTR has standard mode (SP mode) and triple mode (EP mode) as recording modes, and the spectrum of the QDPSK signal 34 reproduced due to differences in recording conditions such as recording current and recording track width. The shapes are different.

Furthermore, the spectral shape of the reproduced QDPSK signal 34 tends to change due to variations in the characteristics of the magnetic head and the characteristics of the magnetic tape 5, and accordingly, the reproduction equalizer 50 having only one type of equalization characteristic cannot perform appropriate equalization.

[Problem to be solved by the invention]

Conventional magnetic tape recording and reproducing devices are configured as described above, and due to differences in recording modes, variations in characteristics of magnetic heads, characteristics of magnetic tape, etc., playback QDPSK
The spectrum of the signal tends to change, so a reproduction equalizer with only one type of equalization characteristic cannot perform appropriate equalization, and preparing as many reproduction equalizers as necessary poses problems such as an increase in the number of parts and cost. was there.

This invention was made to solve the above-mentioned problems, and is not affected by differences in recording modes, variations in magnetic head characteristics, magnetic tape characteristics, etc.
It is an object of the present invention to provide a magnetic tape recording/reproducing device that can always obtain a reproduced QDPSK signal having a constant spectral shape.

[Means to solve the problem]

The magnetic tape recording and reproducing device according to the present invention includes video signals,
At the same time as each signal of the FM audio signal and the PCM audio signal is recorded, the PCM audio signal is reproduced by a PCM audio signal monitor head, and the suitability of the spectral shape of the QDPSK signal is determined by means for detecting the spectral shape of the reproduced QDPSK signal, A control means is provided for controlling the recording equalization characteristic of the QDPSK signal to an appropriate value based on the determination result.

[Effect]

According to this invention, a video signal, an FM audio signal and a PCM
At the same time as each signal of the audio signal is recorded, the PCM audio signal is played back by the PCM audio signal monitor head, and the playback Q is
Q by detecting the spectral shape of the DPSK signal
A control means is provided to determine the appropriateness of the spectral shape of the DPSK signal, and to control the recording equalization characteristics of the QD PSK signal to an appropriate value based on the determination result. scattering.

It is possible to record a QDPSK signal that always has a constant spectral shape without being affected by the characteristics of the magnetic tape.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a video signal according to an embodiment of the present invention.

At the same time as recording FM audio signals and PCM audio signals,
Component countries of a magnetic tape recording and reproducing apparatus for monitoring and reproducing PCM audio signals. FIG. 2 shows a video signal of a magnetic tape recording and reproducing apparatus according to an embodiment of the present invention.

A diagram showing the specifications and arrangement of a magnetic head for recording and reproducing PCM audio signals and FM audio signals and a PCM audio signal monitor head,
FIGS. 3 and 4 show video signals according to an embodiment of the present invention,
A diagram showing the recording traces of the PCM audio signal and FM audio signal and the locus of the PCM audio signal monitor head. Figure 5 shows the QDPSK signal 3 reproduced by the PCM audio signal monitor head.
FIG. 4 is a diagram for explaining how the spectral shape of No. 4 is detected.

In FIG. 1, 1 is a video signal recording processing circuit, 2 is a video signal recording amplifier, 3 is a rotating drum, 4 is a composite video head, 5 is a magnetic tape, 8 is an FM audio signal recording processing circuit,
9 is an adder circuit, 10 is an FM audio signal recording amplifier, 11 is an FMA head, 15 is an ADC 116 is a digital audio recording processing circuit, 17 is a four-phase phase modulation circuit, 18 is a PCM audio signal recording amplifier, 19 is a PCM head, 60 is PCM
An audio signal monitor head (hereinafter referred to as PCM monitor head), 61 is a PCM audio monitor signal regeneration amplifier (hereinafter referred to as
62 is a recording equalization characteristic control section (hereinafter referred to as RECEQ, control section);
．． 64 is a band-limiting filter (hereinafter referred to as the 1st and 28th PF) for separating frequency components that are approximately symmetrical in height with respect to the carrier frequency of the QDPSK signal, and 65.66 is a signal level detector (hereinafter referred to as the 1st PF). .20th ET),
67 is a coefficient control circuit, and 68 is a frequency-gain characteristic variable recording equalizer (hereinafter referred to as RECEQ).

Next, the operation will be explained.

The operations 1 to 5.8 to 11.15 to 19 in FIG. 1 are the same as those in FIG. 6, so their explanation will be omitted.

The video signal, FM audio signal and PCM audio signal are recorded in three layers on the magnetic tape 5 via respective recording signal paths,
At the same time, the PCM monitor head 60 reproduces the PCM audio signal.

FIGS. 2(a) and 2(b) show the specifications of each magnetic head according to the present invention.

Mounting angle and mounting height are shown, PCM-
PCM monitor R with the same azimuth as R head 19b
The head 60a is mounted 70 degrees ahead of the composite video head 4a, and similarly, the PCM monitor L head 60b, which has the same azimuth as the PCM-L head 19a, is mounted 70 degrees ahead of the composite video head 4b. It shall be installed in position.

Also video signals in SP mode and EP mode.

The recording traces of the PCM audio signal and FM audio signal and the locus of the PCM monitor head 60 are shown in FIGS. 3 and 4, and the recording traces 37 to 3 of the video signal, PCM audio signal, and FM audio signal
9 is the same as the conventional example shown in FIG. Third
In the SP mode shown in the figure, the PCM monitor R head 40a is mounted at an angle of 70°, and the head height is -
Since it is attached at a position of 11.8 .mu.m, when converted to an angle of 0.degree., the head height corresponds to -34.4 .mu.m as shown by the square mark. Therefore, the position indicated by 46a is the locus of the PCM monitor R head 40a. The above PC
The M monitor R head trajectory 46a is the composite audio head 40b.
overlaps with the PCM audio signal recording trace 38b formed one field ago by the PCM-R head 19b at the bottom of the tank,
Moreover, since the azimuth angles also match, playback is possible even while recording is in progress. Similarly, in the EP mode shown in FIG. 4, the PCM monitor R head 40a is mounted at an angle of O0.
When converted to , this corresponds to a head height of -19.3 μm, so the PCM monitor R head trajectory 46a overlaps with the PCM recording trace 38b formed three fields ago by the PCM-R head 19b, so playback is not possible even though recording is in progress. It is possible.

As described above, since the PCM monitor head 60 is added, it is now possible to know the recording status of the PCM audio signal even during recording.

After the PCM audio signal reproduced by the PCM monitor head 60 is amplified by the monitor signal reproduction amplifier 61,
RECEQ is input to the control unit 62.

The regenerated and amplified PCM signal is transmitted to the first BPF 63 and the second BPF 63.
The 8PF 64 separates frequency components that are symmetrical in height, for example, at ±0.5 MHz with respect to the carrier frequency of the QDPSK signal 34 as shown by "L" and "H" in FIG. 66 detects the reproduction signal level.

The coefficient control circuit 67 calculates the QDPS based on the above detection result.
It is determined whether the spectrum shape of the K signal 34 is appropriate, and if it is inappropriate, an appropriate recording equalization characteristic is selected for the above-mentioned PCM audio signal, for example, a frequency-gain characteristic variable CO
By controlling the coefficients of RECBQ and 6B bottomed out by the S equalizer for each channel by the audio head switching signal (A-H3W), the recording equalization characteristic of the PCM audio signal is always set to an appropriate value.

As described above, it is possible to record PCM audio signals with appropriate recording equalization characteristics according to differences in recording modes, variations in magnetic head/end characteristics, characteristics of Tl11 tape, etc., and play back QDPSK signals that always have a constant spectral shape. I get a signal.

In the above embodiment, the video signal, the PCM audio signal, and the F
Figure 2 shows an example of the specifications, mounting angle and mounting height of the magnetic head for recording and reproducing M audio signals and the PCM monitor head. may be the angle and the height.

Further, in the above embodiment, a video signal, a PCM audio signal, and an F
Although the magnetic head for recording and reproducing M audio signals is constructed using a composite video head and a composite audio head, each may be constructed using a single head.

Furthermore, in the above embodiment, the spectrum shape of the reproduced QDPSK signal was detected using frequency components that are symmetrical in height and located at ±0.5 MHz with respect to the carrier frequency, but it may be performed using other frequency components.

Further, in the above embodiment, the RECEQ 68 is a frequency-gain characteristic variable COS equalizer, but other types of equalizers may be used.

Furthermore, although the above embodiment has been described using the 5-VH3 system as an example, video systems of other standards such as the VH3 system, the β system, the 8-video system, and the High Eight system may be used.

〔Effect of the invention〕

As described above, according to the magnetic tape recording and reproducing apparatus according to the present invention, each signal of a video signal, FM audio signal, and PCM audio signal is recorded, and at the same time, the PCM audio signal is reproduced by the PCM monitor head, and the reproduced QDPSK signal is to detect the spectral shape of the QDPSK signal.
Equipped with a control means to control the recording equalization characteristics of the PSK signal to an appropriate value, it is possible to always maintain a constant spectral shape without being affected by differences in recording modes, variations in the characteristics of the M1 head, characteristics of the magnetic tape, etc. QDPS with
This makes it possible to record the K signal, and has the effect of realizing a high-quality three-layer recording type magnetic tape recording/reproducing device.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a block diagram showing the configuration of a magnetic tape recording and reproducing device according to an embodiment of the present invention, and Fig. 2 is a block diagram showing the configuration of a magnetic tape recording and reproducing device according to an embodiment of the present invention. Figures 3 and 4 show the specifications of the magnetic head and PCM monitor head, the mounting angle and the mounting height, and FIGS. FIG. 5 is a diagram showing the recording trace and the locus of the PCM audio signal monitor head. FIG. 5 is a diagram for explaining the detection of the spectrum shape of the reproduced QDPSK signal. FIG. 6 is a block diagram showing the configuration of a conventional magnetic tape recording and reproducing device. , FIG. 7 is a diagram showing the spectrum of a video signal, FM audio signal, and PCM audio signal by a conventional magnetic tape recording and reproducing device, and FIG. 8 is a diagram showing a conventional magnetic head for recording and reproducing video signals, PCM audio signals, and FM audio signals. Figure 9 shows an example of a composite video head and a composite audio head. Figures 10 and 11 show conventional video signals and PCM audio. The mounting of the magnetic head for recording and reproducing signals and FM audio signals is at a corner, and the mounting is a diagram for explaining the three-layer recording trace depending on the height. Fig. 12 is a configuration diagram of a conventional four-phase phase demodulation circuit. Fig. 13 The figure shows an example of a spectrum during recording and reproduction of a QDPSK signal, and FIG. 14 is a diagram showing an example of equalization characteristics of a reproduction equalizer. DESCRIPTION OF SYMBOLS 1... Video signal recording processing circuit, 2... Video signal recording amplifier, 3... Rotating drum, 4... Video head,
5... Magnetic tape, 8... FM audio signal recording processing circuit, 9... Adding circuit, 10... FM audio signal recording amplifier, 11...-FMA head, 15...-ADC, 16
...Digital audio signal recording processing circuit, 17...4
Phase modulation circuit, 18... PCM audio signal recording amplifier, 19... PCM head, 60... PCM monitor head, 61... Monitor signal reproducing amplifier, 62... R
ECEQ. Control unit, 63...1st BPF, 64...28th P
F. 65...1st DET, 66...2nd DET, 67.
...Coefficient control circuit, 68...RECEQ,. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) An FM audio signal obtained by frequency modulating an audio signal, a PCM audio signal obtained by converting the above audio signal or another audio signal into digital data and phase modulating it, a frequency-converted luminance signal, and a low-frequency-converted chrominance signal. In a magnetic tape recording and reproducing apparatus that sequentially records and reproduces a composite video signal from the lower layer of a magnetic tape using a dedicated magnetic head, each signal of the FM audio signal, the PCM audio signal, and the video signal A PCM that simultaneously reproduces the PCM audio signal from the magnetic tape when recording the PCM audio signal.
an audio signal monitor head; and a reproduced P obtained by the PCM audio signal monitor head.
at least two or more bandpass filters for detecting the spectral shape of the CM audio signal; a signal level detection means for detecting the output level of each of the bandpass filters; and based on the detection result by the signal level detection means. A recording equalization characteristic control means for determining the appropriateness of the spectrum shape of a reproduced PCM audio signal and setting an appropriate recording equalization characteristic for the PCM audio signal; and a recording equalization characteristic control means for controlling the recording equalization characteristic for the PCM audio signal to an appropriate value What is claimed is: 1. A magnetic tape recording and reproducing apparatus comprising: a variable frequency-gain characteristic recording equalizer for controlling the frequency-gain characteristic;