JPS59138181A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent deterioration by recording a sound signal with frequency modulation after sampling it in a frequency of mfH at recording and sampling the frequency-modulated sound signal reproduced at reproduction by a signal in the mfH after demodulation and obtaining the sound signal. CONSTITUTION:A signal AL is demodulated from FM demodulators 431, 432 and applied to a switch circuit 45L through LPF441, 442. A signal AL' obtained from the switch circuit 45L is applied to a sampling value holding circuit 80L. A signal SH' in a frequency of 3fH is impressed to the holding circuit 80L from a PLL circuit 81 as a sampling signal. If a time axis error shown in solid lines is produced in the signal AL' obtained at the switch circuit 45L at the switching time point of heads 190 and 19 by the skew, and when the period of the sample part of the signal AL' is changed into tau'(not equal to tau) at the switching point of time from the normal value tau, since a signal SH' applied to a sampling value holding circuit 80L is unchanged, a signal AL'' is obtained at the output side of the sampling circuit 80L and the same signal as the normal value is obtained. Thus, the 1st sound signal AL unchanged normally from an LPF47L is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a rotary head type VTR (video tape recorder) that records and reproduces, for example, an audio signal by frequency modulation (FM modulation) and frequency multiplexing with a video signal. The present invention relates to a magnetic recording and reproducing device suitable for application to.

Background Art and Its Problems In a rotating head type VTR, a luminance signal YFM that is FM modulated on the high frequency side and a chroma signal CD that is converted on the low frequency side are synthesized (Fig. 1A shows an example of the frequency spectrum). ), two rotating magnetic heads having different azimuth angles are used to record on an inclined track on a magnetic tape without placing a guard band.

In such a VTR, audio signals are usually recorded using a fixed head on tracks that are continuous in the running direction of the tape in a manner similar to that of a so-called audio tape recorder.

However, in the case of the above-mentioned VTR, when the recording density is increased, the tape running speed becomes extremely slow.As a result, when recording audio signals, the relative speed between the fixed head and the tape decreases, making it difficult to obtain a good audio signal. The disadvantage is that it is difficult to record.

Therefore, conventionally, as shown in FIG. 1B, the audio signal is
It has been proposed to perform FM modulation in a band between the modulated luminance signal YFM and the low frequency converted chroma signal CD, frequency multiplex it with a video signal, and record it on a tilted track. In FIG. 1B, AFM is an FM modulated audio signal.

That is, in FIG. 2, (1) is a tuner, and the video signal from this tuner (1) is sent to an AGC amplifier (
2), the signal is supplied to the PM modulator (5) through the emphasis circuit (3) and the clamp circuit (4).
A modulated luminance signal YFM that is FM-modulated so as to have a frequency of Hz is generated.

In addition, the video signal from the tuner (1) is supplied to the low frequency filter (9) through the band pass filter (6), ACC circuit (power, and frequency converter (8)), and is converted to a low frequency converter with a subcarrier frequency of 688 kHz. A signal cD is formed.

Furthermore, the first audio signal (left signal for stereo, main signal for dual audio) AL and second audio signal (right signal for stereo, subsignal for dual audio) AR from the tuner (1) are respectively AGC amplifiers. (IOL), (1oR),
Noise canceller (IIL), (tIRL pre-emphasis circuit (12L), (12R,)
'M modulator (1'4t).

(1,42) and (14a), (144), each with a carrier frequency of 1.325 MHz, for example.
, 1.475 MHz.

FM modulation is performed at 1.625 MHz and 1.775 MHz so that the frequency deviation width is a constant 150 kHz, and the respective mechanisms are as shown in Figure 3, ALFI < AI, F2 < ARFa < ARF.
Modulated audio signal AFM CAL adjusted to be 4
FI.

ALF2, ARFa, 'ARF4] are formed. Of these, the modulated audio signals ALFI-ARFa are supplied to the mixing amplifier (16o) through band/pass filters (151) and (153), respectively, and the modulated audio signals ALF2 and ARF4 are supplied to the mixing amplifier (16o) through bandpass filters (152) and (153), respectively. 154) through the mixing amplifier (
16e). This mixing amplifier (16o),
The signals from (16e) are sent to the adder circuit (17o).
, (17e). This addition circuit (17o)
.

(1, 7e) are commonly supplied with an upper value modulated luminance signal YFM and a lower frequency converted chroma signal cD. These added signals are then sent to recording amplifiers (18o) and (18e), respectively.
Rotating magnetic heads (1
9o).

(19e).

Also, first and second audio signals AL from the tuner (1).

The AR connects the conventional fixed magnetic heads (21L) and (2
1R) is also supplied.

In this device, the head (19o) ultimately receives the modulated audio signals ALF2, a signal from which ARF4 has been removed, and the head (19o).
19e), the modulated audio signal ALFt, ARFa
A signal from which the signal is removed is provided.

As shown in FIG. 4, these heads (19o), , (19e) alternately form inclined tracks to and te with different recording anomalous values on the tape T, each recording a signal (YFM + CD + ALF).
I +ARF3) or signal CYFM +CD 10A
LF2 + ARF4] is recorded. Incidentally, the inclined tracks to and te are each longer than one field, and are formed so that signal overlap is provided between the respective tracks. Also, continuous tracks tL in the tape running direction.

The first and second audio signals AL and AR are recorded on tR by the heads (21L) and (21R) in the same way as in the conventional case. Furthermore, the continuous track tc has a serve system (not shown).
A control signal CTL from is recorded.

In this way, video signals and audio signals are recorded.

To reproduce the signal recorded as above, for example, the following steps are performed.

That is, in FIG. 5, the rotating head (19o).

The playback signal of (19e) is transmitted to the amplifier (40o),
(40e). This Anne f (40
The signal from o) is passed through band filters (411
) and (413), and also an f (40e)
A signal from 1.475 MHz and 1
．． 775 MHz bandpass filter (412),
(414). The signals from these 9-pass filters (4h) to (414) are sent to the FM demodulator (4h) through limiter circuits (421) to (424), respectively.
431) to (434), respectively, and the audio signal A
L and AR are demodulated. These audio signals AL.

AR cut each Ronox filter (441) ~ (44
4). This Rho Panu filter (441)
, (442) are supplied to the switch circuit (45L), and the signals from the loaf 4 filters (44a), (4
44) is supplied to the switch circuit (45R). These switch circuits (45L)' and (45R) are controlled by a head switching signal supplied to a terminal (4) from a gas generator provided in connection with the rotating drum, for example.This switch circuit (45L)' , (451
The signals from '() are each low-pass filtered (47L
), (47R), noise canceller (48L),
(48R), de-emphasis circuit (49L).

(49R), switch circuit (51L), (5tR)
It is supplied to the audio output terminals (52L) and (52R,) through. Also fixed head (21L), (21R
) are transmitted to the reproducing circuits (22L) and (2
2R) through the switch circuit (stL).

(51FL).

Further, signals from the antennas f (40o) and (40e) are supplied to the switch circuit (60), and this switch circuit fi1 is controlled by the signal from the terminal j469.

The signal from this switch circuit (60) is supplied to a Hynox filter (61) to extract a modulated luminance signal YFM, and this signal is sent to a limiter circuit (63, FMJ adjustment section,
The luminance signal Y is supplied to the de-emphasis circuit f64).
is in the key of O.

In addition, the signal from the switch circuit is supplied to the low-pass filter (to) and a low-pass converted chroma signal CD is taken out. The chroma signal C is extracted. The luminance signal Y and the chroma signal C are mixed in a mixing circuit to form a video signal control, which is supplied to the video output terminal.

In this way, the video signal and the audio signal are reproduced.

In this case, since the audio signal is FM modulated and recorded and reproduced together with the video signal by the rotary head, the audio signal will not deteriorate even if the tape running speed is reduced.

In addition, in the recorded modulated audio signal, crosstalk from adjacent tracks is reduced due to A-zomas loss, and the carrier frequency is different between adjacent tracks by 150 kHz, so the frequency of the beat signal is outside the audible band. , it is possible to perform good reproduction without interference.

However, in this circuit, the first and second audio signals AL obtained alternately from -, rad (19o) and (19e)
, AR are sequentially output several times to form a continuous signal, so for example, the first and second audio signals Ar reproduced at the time of switching the heads (19o) and (19e),
, There was a longing for AR to cause time axis errors due to skew and degrade sound quality.

In order to correct such time axis errors, there is a method of simultaneously recording an unmodulated mother plot signal sp I LOT in addition to the modulated audio signal AFM, as shown in FIG. 1C.

According to this, for example, if there is a skew, the demodulated signal of this 9-pilot signal 5PILOT becomes as shown in FIG. 6B, and the skew is detected. Figure A shows a head switching signal, and Figure C shows a demodulated signal when there is no skew. Therefore, by providing, for example, a time pace corrector (TBC) on the output side of the first and second audio signals AL and AR and controlling it with the above-mentioned demodulation signal, the time axis error can be removed.

However, in the device that performs correction in this way, in addition to the audio signal AFM, the mother pilot signal 5PILOT is also used.
Therefore, as shown in FIG. 1C, it is necessary to limit the band of the video signal (modulated luminance signal YFM), resulting in a deterioration in image quality.

OBJECTS OF THE INVENTION In view of the above, it is an object of the present invention to make it possible to eliminate time axis errors in audio signals due to skew, etc., which may cause deterioration in image quality.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a magnetic recording and reproducing apparatus that frequency-modulates an audio signal, frequency-multiplexes it with a video signal, and records and reproduces the audio signal.
After sampling at a frequency of H (m is an integer, fH is a horizontal frequency), the frequency is modulated, and at the time of playback, the frequency-modulated audio signal to be reproduced is demodulated and then sampled with a signal of mfH to obtain the above audio signal. It is characterized by this.

The present invention is configured as described above, and even if there is a time axis error due to skew or the like in the demodulated signal during playback, it is sampled with the mfH signal to obtain the audio signal. Time axis errors are removed.

Therefore, according to the present invention, since there is no need to limit the band of the video signal in any way, it is possible to eliminate time axis errors in the audio signal due to skew, etc., without causing deterioration in image quality.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 7 shows the recording system circuit of this example. In FIG. 7, parts corresponding to those in FIG. 2 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 7, the first audio signal AL obtained by the pre-emphasis circuit (12L) is transmitted by the sampling circuit (70L).
) K is supplied and sampled. This sampling circuit (70L) is supplied with a signal s of a frequency of mfH (m is an integer, fH is a horizontal frequency), in this example, a frequency of 3fH, from the PLL circuit (Phaselot Clouzot circuit) συ.
H is supplied as a sampling signal. Also, PLL
A horizontal synchronization signal H5ync separated from the video signal by a synchronization separation circuit q is supplied to the circuit συ. in this case,
When the first audio signal AL changes as shown in FIG. 8A, an AM modulated signal AL', for example, as shown in FIG. 8B is obtained from this sampling circuit (70L). Figure B
, the sampling period 'is a penalty signal AL' from this sampling circuit (70L) is F
F'M is supplied to the M modulators (141) and (142)
Modulated.

Further, the second audio signal AR obtained from the pre-emphasis circuit (12B,) is supplied to the sampling circuit (70R) and sampled. This sampling circuit (7
The sampling circuit (70L) is also configured in the same manner as the sampling circuit (70L) described above, and the signal sH is supplied to the PLL circuit (71) as a sampling signal to perform sampling/pulling of the second audio signal AR. The signal AR' from this sampling circuit (70R) is sent to the FM modulator (14s) and (144).
and is FM modulated.

The rest of the structure is the same as the example shown in FIG.

Further, FIG. 9 shows a reproduction system circuit of this example. In FIG. 9, parts corresponding to those in FIG. 5 are given the same reference numerals.
A detailed explanation thereof will be omitted.

In FIG. 9, FMO regulators (431) and (432)
The signal AL' is demodulated from , and is supplied to the switch circuit (45LE) through low-pass filters (441) and (442), respectively.
45L) is supplied to a sample and hold circuit (80L). This Sansol hold circuit (80L) is supplied with a signal SH' having a frequency of mfH, in this example, a frequency of 3fH, as a sampling signal from υ of the PLL circuit. A horizontal synchronization signal T4sync separated from the video signal by a synchronization separation circuit C8 is supplied to the PLL circuit (81) as a reference signal. As described above, the signal AL' is obtained by sampling the first audio signal AL with the signal sH having a frequency of 3fH. Therefore, in this sample hold time i@(!OL),
The sampled portion of signal AL' is further sampled with signal SH' and held. Therefore,
The amount of information remains unchanged, and the first audio signal AL can be obtained by passing it through a loaf 4 filter.

The signal ALtl sampled and held by this sample hold circuit (80L) is passed through the low gas filter (40L).
7L), and this ronos filter (47L)
A first audio signal AL is then obtained. And this number;
1 audio signal AL is supplied to a noise canceller (48L).

In addition, in FIG. 9, FM cradle (43a) and
4), the signal AR' is demodulated and obtained, and the low and
It is supplied to the switch circuit (45R) through chair filters (44a) and (444). The signal AR' obtained from this switch circuit (45B) is supplied to a sample and hold circuit (80B). This sample hold circuit (80R) is configured similarly to the above-mentioned Sansol hold circuit (80L), and the PLL circuit analysis signal S
H' is supplied as a sampling signal. Therefore, in this sample hold circuit (80R), the signal A
The sampled portion of R' will be further sampled with signal SH' and held. Therefore, the amount of information does not change, and the second audio signal AR can be obtained by passing this through the low-29 filter. The signal AR/' sampled and held in this sample and hold circuit (80R) is passed through a low path filter (47R).
A second audio signal AR is obtained from this loaf 9 filter (47R). This second audio signal AR is then supplied to the noise canceller (48R).

The rest of the structure is the same as the example shown in FIG.

This example is configured as described above, and the normal reproduction system switch circuit (45L) outputs a signal A as shown by the broken line in FIG. 10B.
L' is obtained. What is shown in FIG. 2A is a head switching signal. The sample and hold circuit (80L) is supplied with a signal SH' having a frequency of 3 fH' shown in C in the figure as a sampling signal. Therefore, a signal AL'' as shown in the figure is obtained from the output side of this sample and hold circuit (80L).This signal AL,'' is then supplied to the low pass filter (47I), and this low pass filter (47L) Thus, the first audio signal AL as shown in E of the figure is obtained.

Here, due to skew, for example, when the heads (19o) and (19e) are switched, the switch circuit (45'
Let us consider the case where a time axis error occurs in the signal AL' obtained in the signal L) as shown by the solid line in FIG. 10B. That is, while the period of the sample portion of signal AL' is normally τ,
Consider the case where τ' (+τ) occurs at the time of switching.

In this case as well, the sample hold circuit (80L)
Since the signal SH' (shown in FIG. 10 CK) supplied to the circuit does not change, a signal AL' as shown in FIG. You get the same thing. Therefore, the same first audio signal AL (shown in FIG. 10E) as in normal times can be obtained from the rono and the filter (47L).

The same applies to the system of the second audio signal AR.

According to this example, during playback, it is possible to obtain good first and second audio signals AL and AR without time axis errors due to skew etc. from the LONO filters (47L) and (47R). can. Moreover, in this example, since the band of the video signal is not limited in any way, there is no reason to degrade the image quality.

In the above embodiment, the time axis error due to skew has been described as an example, but time axis errors due to other causes can be similarly removed. In addition, according to the above embodiment, the signal SR(S)(') is given as an example of a frequency of 3 fH, but as described above, m fH (m is an integer,
fH may be a horizontal frequency). The audio signal band is 1
If it is up to about 5kHz, 2fH is also possible.

Effects of the Invention According to the present invention described above, when recording audio signals, mf
After sampling at the H frequency, frequency modulation is performed and recorded, and at the same time, the frequency modulated audio signal that is reproduced during playback is demodulated and then sampled with the mfH signal to obtain the audio signal. Even if there is a time axis error in the signal due to skew or the like, the time axis error is removed during the sampling process. Therefore, according to the present invention, since there is no need to limit the band of the video signal in any way, it is possible to eliminate time axis errors in the audio signal due to skew, etc., without causing deterioration in image quality.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the frequency spectrum of a recording signal, Figs. 2 and 5 are circuit diagrams of a conventional recording system and a reproducing system, respectively, and Figs. 7 and 9 are circuit diagrams of the recording system and reproduction system in an embodiment of the present invention, respectively, and FIG. 8 and FIG. FIG. 9 is a diagram for explaining the example in FIG. 7 and the example in FIG. 9; (70L) and (70R,) are sampling circuits, respectively;
(80L) and U (sob) are each Sansol hold circuits.

Claims (1)

[Claims] In a magnetic recording and reproducing device that frequency-modulates an audio signal, frequency-multiplexes it with a video signal, and records and reproduces the same, the audio signal is converted to mfH (m is an integer, fH is a horizontal frequency) during recording.
After sampling at the frequency of , frequency modulation is performed, and
1. A magnetic recording and reproducing apparatus characterized in that during reproduction, the frequency modulated audio signal to be reproduced is sampled with an mfH signal after being sampled to obtain the audio signal.