JPH0668880B2 - Reproducing apparatus and recording / reproducing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial Field B Outline of the Invention C Prior Art D Problems to be Solved by the Invention E Means for Solving Problems (FIGS. 1 and 3) F Action G Example G First Embodiments of the invention G2 Embodiments of the second invention H Effect of the invention A Industrial field of application The present invention relates to a reproducing apparatus and a sound reproducing apparatus for reproducing FM-modulated audio signals from a magnetic tape using a rotating magnetic head. The present invention relates to a recording / reproducing apparatus that FM-modulates a signal and records and reproduces it on a magnetic tape using a rotating magnetic head.

B Outline of the Invention The first invention is a reproducing apparatus for reproducing an FM-modulated audio signal from a magnetic tape by using a rotating magnetic head, and reproducing a sound signal reproduced and demodulated in the vicinity of a switching point of the rotating magnetic head, By passing through a filter circuit that has a comb-shaped characteristic that forms a trough corresponding to a frequency that is an integer multiple of the switching frequency of the rotating magnetic head, it is possible to reduce unnaturalness of the playback device and to reduce drum assembly compatibility noise. It is designed to be effectively removed.

A second invention is a recording / reproducing apparatus for FM-modulating an audio signal and recording and reproducing the same on a magnetic tape using a rotating magnetic head, wherein the reproduced and demodulated audio is reproduced near the switching point of the rotating magnetic head during reproduction. The signal is passed through a first filter circuit having a comb-shaped characteristic that forms a valley corresponding to an integer multiple of the switching frequency of the rotating magnetic head,
At the time of recording, the unnaturalness of the reproduced sound is reduced by passing the audio signal through the second filter circuit having characteristics opposite to those of the first filter circuit in the vicinity of the switching time of the rotary magnetic head and then recording. In addition, it is possible to effectively remove the noise compatible with the drum assembly.

C Conventional technology Recently, as a home VTR (video tape recorder),
A high fidelity version of the audio system has been proposed. For example, an audio signal is FM-modulated and recorded on an inclined track on a magnetic tape by a rotating magnetic head like a video signal.

In such a VTR, drum assembly compatible noise becomes a problem. Drum assembly compatibility noise is due to mechanical dimension difference of drum assembly, assembly tolerance, head tapping, cogging, drum cylindricity when reproducing magnetic tape recorded with other similar VTR set,
This noise is generated in synchronization with the switching of the rotating magnetic head due to the deviation of the linearity and the time-axis fluctuation due to tape expansion and contraction.

For example, the demodulated outputs when the unmodulated signal is reproduced by the first and second rotating magnetic heads arranged at an angular interval of about 180 ° are as shown in FIGS. 4B and 4C, respectively. Also,
A switching pulse for switching heads is shown in FIG. Therefore, the demodulation output contains periodic noise synchronized with the switching of the rotating magnetic head as shown in FIG. In FIG. 6D, the part is mainly due to the beating of the head, and the part is mainly due to the deviation of the linearity based on the cylindricity.

Such compatible noise is 50Hz depending on the rotation of the drum.
(CCIR method), 60Hz (NTSC method) has a basic cycle, and harmonic components (0 to 1kHz) are particularly annoying.

Therefore, conventionally, for example, as shown in FIG. 4E, a pulse approximately reverse to the compatibility noise as shown in FIG. 4D is added at the time of recording for correction. However, this is a so-called pre-correction, and there is a drawback that variations cannot be dealt with because a feed back loop cannot be formed. Improvements are also being made by improving mechanical precision. However, it is not enough in any case, and further measures are needed.

Therefore, the present applicant has proposed a device capable of effectively removing this drum assembly compatible noise. FIG. 5 and FIG. 10 show an example thereof.

In FIG. 5, the audio signal S _A is supplied to the terminal (1) and is supplied to the FM modulation (3A) and (3B) via the noise reduction circuit (2). Then, FM modulation is performed at carrier frequencies of ₁ and _{2, respectively} , and the modulated audio signal S is obtained.
_AFM1 and S _AFM2 are obtained. These modulated audio signals S _AFM1
And S _AFM2 are bandpass filters (4A) and (4
It is supplied to the combiners (5A) and (5B) via B).

The synthesizer (5A) and (5B), respectively the video recording circuit (not shown) from, for example, low frequency converted color signal C _D and FM-modulated luminance signal Y _FM, as shown in FIG. 6 Supplied.

The signal obtained from the combiner (5A) is supplied to the rotating magnetic head _HA through the amplifier (6A), the switching switch (7) and the rotary transformer (8). In addition, the signal obtained from the combiner (5B) is passed through the amplifier (6B), the switching switch (9) and the rotary transformer (10) to rotate the magnetic head H.
Supplied to _B.

The switching switches (7) and (9) are connected to the R side during recording and to the P side during reproduction, respectively.

The azimuth angles of the heads H _A and H _B are made different from each other. Further, the heads H _A and H _B are arranged with an angular interval of about 180 °, and are rotated once in one frame, for example.
The heads H _A and H _B are sequentially scanned on the magnetic tape every one field.

As described above, at the time of recording, the head H _A is supplied with the signal [S _AFM1 , C _D , Y _FM ] and the head H _B is supplied with the signal [S _AFM2 , C _D , Y _FM ], and the magnetic tape As shown in FIG. 7, recording tracks T _A and T _B having different recording azimuths are alternately formed on the upper surface (11).

Further, at the time of reproduction, the heads H _A and H _B are made to scan the recording tracks T _A and T _B , respectively. Therefore,
Heads H _A and H _{B respectively} record tracks T _A and T _B
The signals [S _AFM1 , C _D , Y _FM ] and [S _AFM2 , C _D , Y _FM ] are reproduced.

In FIG. 5, the signal reproduced by the head _HA is passed through an amplifier (12A) and then supplied to a bandpass filter (13A) whose center frequency is ₁ . From this bandpass filter (13A), a modulated audio signal S _AFM1 is obtained,
This is passed through the limiter circuit (14A) and FM demodulator (15A)
Is supplied to. Then, the voice signal S _A is obtained from the demodulator (15 A) and is supplied to the A side terminal of the switching switch (16).

Also, the signal reproduced by the head H _B, after being through the amplifier (12B), the center frequency is supplied to a band-pass filter (13B) is _two. A modulated audio signal S _AFM2 is obtained from the bandpass filter (13B) and is supplied to the FM demodulator (15B) via the limiter circuit (14B). An audio signal S _A is obtained from the FM demodulator (15B) and supplied to the B side terminal of the switching switch (16).

The switching of the switching switch (16) is controlled by a switching pulse obtained according to the rotational positions of the heads H _A and H _B. The one field period during which the head H _A is scanning the recording track T _A is switched to the terminal on the A side, and the one field period during which the head H _B is scanning the recording track T _B is switched to the terminal on the B side.

Therefore, the audio signal S _A is continuously obtained from the switching switch (16).

The audio signal S _A obtained from the switching switch (16) contains the drum assembly compatible noise n _DA having the periodicity as described above. For example, when recording, when the audio signal S _A supplied to the terminal (1) is as shown in FIG. 8A, the audio signal S _A obtained from the switching switch (16) is as shown in FIG. 8B. Noise n _DA is included. This noise n _DA is generated in response to the switching of the heads H _A and H _B , and has a frequency component that is an integral multiple of the switching frequency _S , and is present in the reduction of 1 kHz or less, for example. The switching frequency _S is, for example, 50 Hz in the CCIR system and 60 Hz in the NTSC system, for example.

The audio signal S _A obtained from the switching switch (16) is supplied to the filter circuit (17). This filter circuit (1
The characteristic of 7) is, as shown in FIG. 8C, a comb-shaped characteristic that becomes a valley portion in a band of 1 to 2 kHz or less, corresponding to an integer multiple of the switching frequency _S of the heads H _A and H _B. To be done.

The filter circuit (17) is composed of a processing circuit (18) and an adder (19a), and specifically, as shown in FIG.

In the figure, the reproduced audio signal S _A (n _DA ) from the switching switch (16) is supplied to the adder (19a). Also,
This audio signal S _A (n _DA ) is supplied to a low pass filter (20) having a cutoff frequency of 1 to 2 kHz via an adder (19b). This low-pass filter (20) is for determining the range in which the filter characteristics should be comb-shaped. In this case, the noise n _DA can be effectively removed, and the comb characteristic can be obtained within a range that does not impair the sound quality. The output of the low-pass filter (20) is supplied to the adder (21), and is also supplied to the adder (21) via a delay line (22) having a delay time of one field period (1V) made of CCD, for example. To be done. The addition signal from the adder (21) is supplied to the adder (19a) via the limiter circuit (23) and the inverter circuit (24).
Here, the limiter circuit (23) is for eliminating the influence when the output novel of the adder (21) becomes large and the correlation with the noise n _DA becomes large, and is not always necessary. The output of the limiter circuit (23) is the adder (19b).
Is supplied to the device to make the characteristics steep.

The filter circuit (17) exhibits a comb-like characteristic as shown by the solid line in FIG. 8C as described above, and accordingly, noise n _DA is removed from the adder (19a) as shown in FIG. The obtained audio signal S _A is obtained. In addition, in FIG.
n _O is noise other than the noise n _DA .

The audio signal S _A from the filter circuit (17) is supplied to the output terminal (26) via the noise reduction circuit (25).

Further, in the example of FIG. 5, the signals from the amplifiers (12A) and (12B) are supplied to the A side and B side terminals of the switching switch (27), respectively. This switching switch (27) is also a head _HA
The switching is controlled by a switching pulse obtained in accordance with the rotational position of H _B and H _B , and is switched in the same manner as the switching switch (16) described above. This switch (27)
Is supplied to the high-pass filter (28) and the modulated luminance signal Y _FM is taken out. Further, the signal from the switching switch (27) is supplied to the low pass filter (29) and the low frequency conversion color signal _CD is taken out. The modulated luminance signal Y _FM and the low frequency conversion color signal C _D are supplied to a reproduction video circuit (not shown) to obtain a video signal.

According to the example of FIG. 5 described above, the reproduced and demodulated audio signal S _A (n _DA ) including the noise n _DA (shown in FIG. 8B).
Can pass through the filter circuit (17) (the filter characteristics are shown in FIG. 8C), so that the output terminal (26)
As shown in FIG. 8D, the audio signal S _A from which the noise n _DA has been removed is obtained.

Next, in FIG. 10, a noise reduction circuit (2)
Filter circuit (32) between the and FM modulators (3A) and (3B)
Are to be connected. The characteristic of the filter circuit (32) is set to be the reverse characteristic of the characteristic of the filter circuit (17) shown in FIG. 8C, as shown in FIG. 8E. That is, the audio signal S _A from the noise reduction circuit (2) is added to the subtractor (3
3) and the output of this subtractor (33) is F
It is supplied to the M modulators (3A) and (3B). The output of the subtractor (33) is supplied to the subtractor (33) via the attenuator (34) and the processing circuit (35). Here, the gain of the attenuator (34) is set to "1" or less to prevent oscillation. The processing circuit (35) has the same structure as the processing circuit (18) of the filter circuit (17).

The other parts of this FIG. 10 example are configured in the same manner as the FIG. 5 example.

In the example of FIG. 10, the characteristics of the filter circuit (32) are as follows.
As shown in FIG. 8E, the terminals are not
When the audio signal S _A supplied to (1) is as shown in FIG. 8A, the FM modulator (3
The audio signal S _A supplied to A) and (3B) is shown as in FIG. At the time of reproduction, the audio signal S _A (n _DA ) obtained from the switching switch (16) is shown as in FIG.

Further, since the filter characteristic of the filter circuit (17) exhibits a comb-shaped characteristic as shown by the solid line in FIG. 7C, the audio signal from which the noise n _DA has been removed is output from this filter circuit (17) as shown in FIG. S _A is obtained. And this audio signal S
_A is supplied to the output terminal (26) through the noise reduction circuit (25).

According to the example of FIG. 10, noise n is present at the output terminal (26).
_The audio signal S _A from which the _DA has been removed is obtained, and the same effect as in the example of FIG. 5 is obtained, and the recording audio signal S _A is arranged on the reproducing side to remove the noise n _DA. Since it is recorded via the filter circuit (32) having a characteristic opposite to that of the filter circuit (17), the audio signal S _A obtained at the output terminal (26) is recorded at the valley portion of the comb-shaped characteristic by the filter circuit (17). There is no attenuation, and the sound quality is not adversely affected.

D. Problems to be Solved by the Invention In the examples shown in FIGS. 5 and 10, the low-pass filter (20) for determining the range in which the filter characteristic should be comb-shaped in order to eliminate the unnaturalness of ordinary voice, A filter circuit (1) is provided by providing a limiter circuit (23) that limits to small signal noise.
7), but it was unnatural for special sounds such as sweep signal sounds and single frequency signal sounds.

In view of the above-mentioned problems, the present invention can reduce unnaturalness of reproduced sound and effectively remove drum assembly compatible noise.

E Means for Solving the Problem (FIGS. 1 and 3) The first invention is that the audio signal reproduced and demodulated in the vicinity of the switching time point of the rotary magnetic heads H _A and H _B is transferred to the rotary magnetic head H _A. ,
The filter circuit is designed to pass through a filter circuit having a comb-shaped characteristic that forms a valley corresponding to an integer multiple of the switching frequency of H _B.

The second invention is that the rotating magnetic heads H _A and H _B are used during reproduction.
The audio signal reproduced and demodulated in the vicinity of the switching time is passed through the first filter circuit having the comb-shaped characteristic which becomes the valley portion corresponding to the frequency which is an integral multiple of the switching frequency of the rotating magnetic heads H _A and H _B. . Further, at the time of recording, the audio signal is passed through a second filter circuit having characteristics opposite to those of the first filter circuit in the vicinity of the switching time point of the rotating magnetic heads H _A and H _B , and then recorded. Is.

F action Drum assembly compatible noise, rotating magnetic head H
_A, are concentrated in the vicinity of the switching point H _B. Since the reproduced and demodulated audio signal is passed through the filter circuit having the comb characteristic in the vicinity of the switching time point of the rotary magnetic heads H _A and H _B , the drum assembly compatible noise is effectively removed. In this way, since the audio signal that can be passed through the filter circuit is limited, unnaturalness with respect to reproduced sound, particularly special sound, is reduced.

G Embodiment G1 Embodiment of First Invention First, one embodiment of the first invention will be described with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 5 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the figure, the output of the processing circuit (18) is supplied to the adder (19a) via the connection switch (36). Further, a switching pulse S _SW (shown in FIG. 2B) for head switching is supplied to the control signal generating circuit (37). From this generating circuit (37), a high level “S” is output near the head switching time. 1 "
A signal S _C (illustrated in FIG. 2C) is then generated. still,
FIG. 2A shows the demodulated output of an unmodulated signal. Then, this signal S _C is supplied to the connection switch (36) as a control signal, and the connection switch (36) is turned on when this signal S _C has a high level “1” and turned off when it has a low level “0”. It is said that

In the above configuration, the signal S
_{Since C} becomes a high level "1", the connection switch (36) is turned on, and the filter circuit (17) has a valley corresponding to an integer multiple of the head switching frequency _S , as in FIG. Partial comb characteristics (shown in FIG. 8C) will be exhibited. On the other hand, in the other period, the signal S _C becomes low level "0", the connection switch (36) is turned off, the filter circuit (17) will exhibit a flat characteristic.

According to the example of FIG. 1, since the characteristic of the filter circuit (17) becomes a comb-like characteristic in the vicinity of the head switching time when the drum assembly compatible noise n _DA is concentrated, the noise n _DA is effectively removed. It Further, according to the example of FIG. 1, since the characteristics of the filter circuit (17) are flat during the period other than the time when the head is switched, the unnaturalness of the reproduced sound, especially the special sound is reduced. A delay line (22) is used in the filter circuit (17), and the S / of this delay line (22) is
Although the poor N and the narrow dynamic range affect the sound quality, they do not have any effect in the period other than near the head switching time, and the deterioration of the sound quality can be minimized.

G2 Embodiment of Second Invention Next, an embodiment of the second invention will be described with reference to FIG. In FIG. 3, FIG. 10 and FIG.
Portions corresponding to those in the figure are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the example of FIG. 3, similarly to the example of FIG. 1, the output of the processing circuit (18) is connected to the adder (19) via the connection switch (36).
is supplied to a), the connection switch (36) is controlled by the signal S _C from the generator circuit (37).

It was but connexion, in the vicinity head switching time point, the connection since signal S _C becomes high level "1" switch (36) is turned on,
The filter circuit (17) will exhibit comb characteristics (shown in FIG. 8C) as in FIG. On the other hand, in the other period, the signal S _C becomes low level "0", the connection switch (36) is a filter circuit turned off (17) will indicate a flat characteristic.

In the example of FIG. 3, the output of the processing circuit (35) of the filter circuit (32) is supplied to the subtractor (33) via the connection switch (38). The connection switch (38) is supplied with a signal S _C from the generation circuit (37) as a control signal, and the connection switch (38) is turned on when the signal S _C is at a high level “1” and is at a low level. Turned off when "0".

It was but connexion, in the vicinity head switching time point, since the signal S _C becomes high level "1", the connection switch (38) is turned on, the filter circuit (32), as well as in FIG. 10,
A characteristic (illustrated in FIG. 8E) opposite to the comb-shaped characteristic shown by the filter circuit (17) is exhibited. On the other hand, in the other period, the signal S _C becomes low level "0", the connection switch (38) is a filter circuit turned off (32) will indicate a flat characteristic.

According to the example of FIG. 3, since the characteristic of the filter circuit (17) becomes a comb-like characteristic in the vicinity of the head switching time when the drum assembly compatible noise n _DA is concentrated, the noise n _DA is effectively removed. It And the filter circuit (32)
In the vicinity of the head switching time, the characteristic is the reverse of the comb-shaped characteristic shown in the filter circuit (17). Therefore, the audio signal S _A obtained at the output terminal (26) has a valley portion of the comb-shaped characteristic by the filter circuit (17). There is no attenuation at, and the sound quality is not adversely affected.

Further, according to the example of FIG. 3, since the characteristics of the filter circuits (17) and (32) become flat in the period other than the vicinity of the head switching time, the unnaturalness of the reproduced sound, especially the special sound is reduced. It A delay line (22) is used for the filter circuits (17) and (32), and the poor S / N and narrow dynamic range of the delay line (22) affect the sound quality.
There is no effect in a period other than near the head switching time, and the deterioration of sound quality can be minimized.

In the example of FIG. 1 described above, the connection switch (36) is provided, and the signal S _C shown in FIG. 2C is supplied to this as a control signal to control its switching. A variable gain control circuit (not shown) is provided in place of the switch (36), and the gain of this is shown in FIG. 2D or E.
You may make it variable as shown in FIG. The same applies to the connection switches (36) and (38) in FIG.

Further, in the above example, the delay line (22) of the processing circuit (18)
(See Fig. 9) has a delay time of 1V,
And when switching to _{H B} from example head _{H A,} head H
When there is a difference between when switching from _B to H _A ,
It may be configured by using a delay line having a delay time of 2V.

H Effect of the Invention As described above, in the first invention reproducing apparatus, the audio signal reproduced and demodulated in the vicinity of the switching time point of the rotating magnetic head in which the drum assembly compatible noise is concentrated has a comb-shaped characteristic. Since it can be passed through the filter circuit it has,
Drum assembly compatible noise is effectively removed. Further, since the reproduced voice signal does not pass through the filter circuit having the comb-shaped characteristic except in the period near the head switching time, the unnaturalness of the reproduced sound, especially the special sound is reduced, and the filter circuit having the comb-shaped characteristic is reduced. Sound quality deterioration due to is suppressed to a minimum.

Further, in the second invention recording / reproducing apparatus, the audio signal reproduced and demodulated in the vicinity of the switching time point of the rotating magnetic head where the drum assembly compatible noise is concentrated has the first filter circuit having the comb characteristic. As it is passed,
In the vicinity of the switching time of the rotary magnetic head, the audio signal is recorded after being passed through the second filter circuit having the characteristic opposite to that of the first filter circuit, so that the drum assembly compatible noise is effectively removed. At the same time, the influence of the first filter circuit on the reproduced audio signal is not compensated by the second filter circuit at the time of recording, so that the sound quality is not deteriorated. Also, during periods other than near the head switching time, for example, the reproduced voice signal does not pass through the filter circuit having the comb characteristic, so that the unnaturalness of the reproduced sound, particularly the special sound is reduced and the filter having the comb characteristic is reduced. Sound quality deterioration due to the circuit is minimized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the first invention, FIG. 2 is a diagram for explaining the same, FIG. 3 is a block diagram showing an embodiment of the second invention, and FIGS. FIG. 10 is a diagram for explaining the conventional example of the husband and the husband. (17) and (32) are filter circuits, (36) and (38) are connection switches, and (37) is a control signal generating circuit.

Claims (2)

[Claims] 1. A reproducing method for reproducing an audio signal by using a rotating magnetic head from a magnetic tape recorded by using an FM signal of an audio signal, wherein the rotating magnetic head is recorded in the vicinity of a switching time point of the rotating magnetic head. A reproducing apparatus, wherein the reproduced and demodulated audio signal is passed through a filter circuit having a comb-shaped characteristic that forms a valley corresponding to an integer multiple of the switching frequency of the rotating magnetic head. 2. An audio signal FM-modulated, which is recorded on a magnetic tape using a rotary magnetic head and reproduced, wherein the audio signal reproduced and demodulated in the vicinity of the switching point of the rotary magnetic head is converted into the rotary magnetic head. The voice signal is passed through a first filter circuit having a comb-shaped characteristic that forms a valley corresponding to an integer multiple of the head switching frequency, and the voice signal is changed to a characteristic of the first filter circuit in the vicinity of the switching time. A recording / reproducing apparatus characterized in that recording is performed after passing through a second filter circuit having an inverse characteristic.