JPH064995A - Reproducing device for audio signal of vtr - Google Patents

Abstract

PURPOSE:To improve S/N of audio output or to eliminate head switch noise when either of a man signal or a sub-signal is selected in a monophonic mode and a bilingual mode without increasing scale of circuits. CONSTITUTION:A FM signal reproduced by two heads 11 and 12 of which reproducing periods overlap in one part is switched by a switching circuit 15 during the overlapping period and is made the continuous. FM signal, and is supplied to main signal demodulation system 25, 27, 29, and sub-signal demodulation system 26, 28, 30. In the monaural mode, the sub-signal demodulation system 26, 28, 30 are switched to the main signal demodulation possible, sum of output of the both demodulation systems is generated by a matrix circuit 33, and outputted to a L channel terminal 34. Since the signal is made 2 times and noise is made 1.4 times of a conventional example, S/N is improved by 3 dB.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to audio signal reproduction of a VTR, and more particularly to audio signal reproduction in a monaural mode and a bilingual mode.

[0002]

2. Description of the Related Art In recent years, audio (audio) is being stereo-converted in VTRs as well. However, even in 8mm VTRs, in order to realize stereo conversion while maintaining compatibility with conventional monaural, the conventional 1. A so-called sum-difference matrix method in which a sum signal of the L channel and the R channel is recorded on a 5 MHz monaural voice frequency modulation carrier and a 1.7 MHz voice frequency modulation carrier is newly provided to record the difference signal between the L channel and the R channel. Has been adopted.

As described above, in consideration of the compatibility with the prior art, in the system in which the video signal and the audio signal are frequency-modulated so that the frequency deviation widths do not overlap with each other, and are recorded / reproduced by the same head, the monaural mode is used. At times, 1.5 Hz
Only the demodulation system of the main signal of will operate and 1.7M
The Hz sub-signal demodulation system is deactivated so as not to operate in order to attenuate the voice.

Further, in the helical scan system, in order to prevent audio discontinuity, an overlapping period in which the reproducing periods of the two rotary heads partially overlap is provided, and the heads are alternately alternated during this period. I am switching and playing.

Therefore, the signal from the rotary head has an overlapping period, and in order to perform signal processing, one signal is switched to the other signal by a switch in this period so that the reproduced signal is smoothly continuous. A switch control means is required.

In the case where the audio signal is made continuous during the overlap period as described above, the FM audio modulation signal is not always continuous at the time when the signal from the rotary head is switched by the switch, and thus the FM audio modulation signal is not always continuous. When is discontinuous, the demodulated audio signal often contains spike noise.

As a first method for removing the spike-like noise included in such a voice signal, the value of the voice signal immediately before the noise is generated is held to approximate the signal in the period in which the noise is generated. A method of (interpolation) is used, but in order to completely remove spike-like noise, the hold period must be lengthened, and the fidelity of the original sound is significantly reduced.

In order to avoid the problem caused by switching the FM audio modulation signal in this way, as a second method, the FM audio modulation signal from the facing rotary head is not switched, and the FM is dedicated to each head. A method has been proposed in which a demodulator is provided and an audio signal is switched after FM demodulation.

FIG. 6 shows a signal waveform for explaining removal of spike noise in the first method. VTR
In the reproduction mode, the rotary heads (1 channel, 2 channels) at positions opposite to each other by 180 degrees on the diameter of the rotary drum are switched alternately to obtain two systems of output. The AFM signals (a) and (b) reproduced from each head have an overlap period, but a phase difference occurs due to the difference in the traveling system during recording / reproduction (c), and such signals are overlapped. When FM switching is performed by switching with the head switching signal (d) during the period to make the continuous signal (e), spike noise as shown in (f) occurs, and so-called "head switching noise" occurs.
Therefore, the value of the audio signal at the time of head switching is held by the hold pulse (g), the audio signal is interpolated as shown by the broken line in (f), and spike noise is removed.

As a mode discrimination method, the detection is performed by detecting the envelope of the reproduced signal in each demodulation system.

[0011]

In the stereo sum-difference matrix method under the background as described above, it is necessary to increase the circuit scale when selecting either the main signal or the sub signal in the monaural mode and the bilingual mode. It is the first object of the present invention to improve the S / N of the demodulator.

In the above-mentioned stereo sum / difference matrix method, the second method has a drawback that the circuit is complicated because two rotary demodulators are required for each rotary head. Therefore, the first method is adopted. Has been done. Therefore, the fidelity of the original sound is lowered when the head is switched, or the spike noise is unavoidable.

In view of the above circumstances, it is a second object of the present invention to eliminate the head switching noise by switching the audio signal after FM demodulation without increasing the circuit scale.

[0014]

According to the present invention, in order to achieve the first object, an audio signal reproducing device of a VTR is constructed as in the following (1) and (2), and the second object is achieved. In order to achieve the above, the VTR audio signal reproducing device is configured as in the following (3), (4) and (5).

(1) In the stereo mode, an FM signal reproduced by a plurality of heads whose reproduction period is partially overlapped is switched to the overlapped period and continuous F signals are reproduced.
A VTR audio signal reproducing apparatus for generating an M signal, demodulating the continuous FM signal by a main signal demodulation system and a sub signal demodulation system, and generating an L channel audio signal and an R channel audio signal in a matrix circuit, in a monaural mode. At the same time, a VTR audio signal reproducing device provided with a switching means for switching the sub-signal demodulation system to enable demodulation of the main signal.

(2) In the stereo mode, the FM signals reproduced by a plurality of heads in which the reproducing period partially overlaps are switched to the overlapping period in the continuous F mode.
A VTR audio signal reproducing apparatus for generating an M signal, demodulating the continuous FM signal by a main signal demodulation system and a sub signal demodulation system, and generating an L channel audio signal and an R channel audio signal in a matrix circuit, in a bilingual mode. When any one of the main signal and the sub signal is selected, a switching means is provided for switching the signal that selects the signal demodulation system of the non-selected signal of the main signal demodulation system and the sub signal demodulation system so that demodulation is possible. VTR audio signal playback device.

(3) In the stereo mode, the FM signals reproduced by a plurality of heads in which the reproducing period partially overlaps are switched to the overlapping period in the continuous F mode.
A VTR audio signal reproducing apparatus for generating an M signal, demodulating the continuous FM signal by a main signal demodulation system and a sub signal demodulation system, and generating an L channel audio signal and an R channel audio signal by a matrix circuit. A VTR audio signal reproducing apparatus including a and b components.

A. In the monaural mode, the FM signal corresponding to the FM signal to be supplied to the signal demodulation system after the switching is switched to be supplied to the sub-signal demodulation system during a predetermined period before and after switching the FM signals reproduced by the plurality of heads. At the same time, a first switching means for switching the sub-signal demodulation system so that the main signal can be demodulated. b. Second switching means for switching the output of the main signal demodulation system to be interpolated by the output of the sub signal demodulation system during the overlapping period in the monaural mode to obtain a monaural audio signal without head switching noise.

(4) In the stereo mode, the FM signals reproduced by a plurality of heads whose reproduction periods are partially overlapped are switched to the overlapped periods and continuous F signals are reproduced.
A VTR audio signal reproducing apparatus for generating an M signal, demodulating the continuous FM signal by a main signal demodulation system and a sub signal demodulation system, and generating an L channel audio signal and an R channel audio signal by a matrix circuit. A VTR audio signal reproducing apparatus including a and b components.

A. The FM signal to be supplied to the signal demodulation system after the switching during a predetermined period before and after switching the FM signals reproduced by the plurality of heads when either the main signal or the sub signal is selected in the bilingual mode. A first switching means for switching to supply the corresponding FM signal to the signal demodulation system for the non-selected signal and for switching the signal demodulation system for the non-selected signal so that the selected signal can be demodulated. b. When either the main signal or the sub signal is selected in the bilingual mode, the output of the signal demodulation system for the selected signal is demodulated for the signal not selected during the overlapping period. Second switching means for obtaining the selected audio signal without head switching noise by switching so as to interpolate with the output of the system.

(5) The VTR according to the above (3) or (4), further comprising a mode discriminating means for discriminating the mode by the signal of the main signal demodulation system and the signal of the sub signal demodulation system in a period other than the predetermined period. Audio signal reproduction device.

[0022]

With the configuration (1) above, in the monaural mode,
In both the main signal demodulation system and the sub signal demodulation system, the main signal is demodulated and the sum of the outputs of both demodulation systems is obtained by the matrix circuit. With the configuration of (2) above, the main signal in the bilingual mode,
When either one of the sub-signals is selected, the main signal demodulation system,
The sub-signal demodulation system demodulates the selected signal and the matrix circuit obtains the sum of the outputs of both demodulation systems.

With the configuration (3), the monaural audio signal without head switching noise is obtained by interpolating the audio signal of the main signal demodulation system with the audio signal of the sub signal demodulation system in the overlapping period. With the configuration of (4), when either the main signal or the sub signal is selected in the bilingual mode, the voice signal is interpolated in the same manner as in the above (3) in the overlapping period, and voice without head switching noise is obtained. .

With the configuration of (5), in (3) or (4), the mode is discriminated by the signals of the main signal demodulation system and the sub signal demodulation system in the periods other than the overlapping period.

[0025]

EXAMPLES The present invention will be described in detail below with reference to examples.
Prior to the explanation of each embodiment, the VTR which is the basis of each embodiment
The audio signal reproducing device will be described. In each embodiment, V
This is a TR audio signal reproducing apparatus, and a reproduced signal is recorded in a matrix stereo mode, a monaural mode, or a bilingual (bilingual) mode.

The audio frequency modulation signal (hereinafter referred to as AFM signal) is magnetically recorded and reproduced in the form of a frequency-modulated audio signal obtained by frequency-modulating the audio signal.
The frequency spectrum of the FM signal is as shown in FIG. 5 in the 8 mm VTR.

F1-f4 shown in FIG. 5 are ATF (automati)
c is a track finding) signal, fc is a carrier frequency of the low-frequency conversion color (chroma) signal CL, fm and fs are AFM stereo carrier frequencies, and fm is an L channel and an R channel by a matrix encoder in a stereo mode. , The signal converted to the sum signal is recorded,
In the bilingual mode, a single signal that does not pass through the matrix circuit 33 such as Japanese is recorded.

Similar to fm, fs records a signal obtained by converting the L channel and the R channel into a difference signal by a matrix encoder in the stereo mode, and a single signal that does not pass through the matrix circuit 33 such as English in the bilingual mode. Is recorded. Also, fm
In the monaural mode, a monaural signal is recorded. fs is not recorded in monaural mode.

Within the FM luminance signal Y-FM band, fs is
Luminance signal sync tip frequency, and fw is peak white frequency. It is a well known fact that these frequency allocations differ depending on the recording format such as so-called high band mode and normal mode.

(Embodiment 1) FIG. 1 is a sound signal reproducing apparatus of a two-head helical scan type VTR according to a first embodiment.
It is a block diagram of. In the figure, the magnetic tape 10 has an FM
Luminance signal Y-FM, low-frequency conversion color signal CL, AFM main (main) audio and sub (sub) in stereo mode
The frequency-superimposed signal of the audio signal and the ATF pilot signal is recorded as the frequency-superimposed signal in which the AFM sub-audio signal is deleted from the above in the monaural mode.

The magnetic tape 10 includes rotary heads 11 and 12.
The frequency superimposed signal reproduced alternately by the rotary head 11 and the head amplifier 13 is input to the switch circuit 15 and the switch circuit 39, and the frequency superimposed signal reproduced by the rotary head 12 and the head amplifier 14 is switched by the switch circuit 15. It is input to the circuit 15 and the switch circuit 40.

The frequency-superimposed signal made continuous by the switch circuit 15 which is switched by the head switching pulse 16 is sent to the BPF (band pass filter) 17, HPF (high pass filter) 18, switch circuit 39, and switch circuit 40. Is entered.

The low-pass color signal CL obtained by band-passing by the BPF 17 is subjected to color signal processing by the C process circuit 19 and output from the color signal output terminal 21, and
It is input to the color signal and luminance signal mixing circuit 22. HPF
The FM luminance signal obtained by high-passing by 18 is Y
The luminance signal is processed by the process 20 and output from the luminance signal output terminal 24, and also input to the color signal and luminance signal mixing circuit 22 and output from the composite output terminal 23. The Y process 20 also performs dropout detection at the same time and outputs a dropout detection signal 44.

Rotary heads 11 and 12 and head amplifier 1
The frequency-superimposed signals reproduced by 3, 14 are switched by the switch circuit 15, which is switched by the head switching pulse 16 during the reproduction overlapping period of the rotary heads 11, 12, and become a continuous signal, and the signals are switched. BPF 25 via circuit 39
Entered in.

A obtained by bandpass from BPF25
The FM main signal (1.5 MHz) is input to the mode detection circuit 36 and the limiter circuit 27, and the limiter circuits 27, F
The audio signal is demodulated through the M demodulation circuit 29 and input to the matrix circuit 33, the switch circuit 31, and the switch circuit 32.

The switch circuit 31 includes a mode detection circuit 36.
In the stereo mode, the sound L demodulated by the matrix circuit 33 is generated by the mode detection signal output from
Output the channel signal to the L channel output terminal 34,
In the bilingual mode, the main signal demodulated into the audio signal through the FM demodulation circuit 29 is output to the L channel output terminal 34 without passing through the matrix circuit 33, whereby the stereo mode and the bilingual mode are switched. Rotating heads 11 and 12 and head amplifier 1
The frequency superposed signals reproduced by 3, 14 are switched by the switch circuit 15 which is switched by the head switching pulse 16 in the overlap period, and become a continuous frequency superposed signal, and the signal is passed through the switch circuit 40 to the BPF 26. Entered in.

The AFM sub (1.7 MHz) signal band-passed from the BPF 26 is input to the mode detection circuit 36 and the limiter circuit 28 in the stereo mode and the bilingual mode, and the limiter circuit 28 and the FM demodulation circuit 30 are input. Is demodulated to a voice signal and input to the matrix circuit 33, the switch circuit 32, and the switch circuit 31. The switch circuit 32 outputs the audio R channel signal demodulated by the matrix circuit 33 to the R channel output terminal 35 in the stereo mode in accordance with the mode detection signal output from the mode detection circuit 36, and in the bilingual mode, the FM demodulation circuit. By outputting the audio sub-signal demodulated into the audio signal to the R channel output terminal 35 without passing through the matrix circuit 33, the stereo mode and the bilingual mode can be switched as in the main signal demodulation system.

In the monaural mode, the mode detection circuit 36
The center frequency of the BPF 26 and the FM demodulation circuit 30 is set to the AFM sub (1.7M) by the mode detection signal output from
Hz) to AFM main (1.5 MHz).

As a result, in the monaural mode, the sub-signal demodulation systems 26, 28, 30 perform AFM by the above-mentioned processing.
The main signal (1.5 MHz) can be demodulated by the FM demodulation circuit 30 and output.

As described above, the function which has been conventionally fixed to the sub-signal demodulation system is changed from the central frequency so that the main signal can be demodulated, the monaural signal reproduced by the FM demodulation circuit 30 and the FM demodulation circuit 29. The reproduced monaural signal is input to the matrix circuit 33, and the matrix circuit 33 adds and subtracts the signal to output the signal. The demodulated signal of the added signal thus obtained is doubled, and the noise output generated in the FM demodulation circuits 29 and 30 is random noise. Therefore, the output thereof is a square root of 2. Therefore, the demodulation system S / N is improved by 3 dB.

The monaural demodulated signal with improved S / N is input to the switch 31 circuit and output from the L channel output terminal 34.

The mode detection circuit 36 automatically determines whether the reproduced AFM signal is recorded in the stereo mode, the monaural mode or the bilingual mode, and the obtained mode determination signal is the switch circuit 31 or the switch circuit 3.
2, switch circuit 39, switch circuit 40, display unit 38
Is input to the stereo mode and is switched to the mono mode or the bilingual mode.

As described above, in the monaural mode,
By switching the AFM sub (1.7 MHz) signal demodulation system to enable AFM main (1.5 MHz) signal demodulation and adding the outputs of both demodulation systems in the matrix circuit 33, the S / N of the demodulator is improved by 3 dB. As a result, higher quality monaural voice can be obtained.

The BPF 26 is a so-called variable g.
Needless to say, by incorporating the m-type bandpass filter in the IC, the number of components can be further reduced and switching can be easily performed.

Further, when the output of only one of the main signal and the sub signal is selected in the bilingual mode, the FM demodulation circuit and the front BPF of the unselected signal are selected in the same manner as in the monaural mode. It is possible to improve the signal output-to-noise output ratio S / N of the voice even in the bilingual mode by switching to the center frequency of the signal and adding the outputs of the demodulation circuits of both demodulation systems.

FIG. 2 is an explanatory diagram of a demodulated audio signal for explaining this embodiment. In the playback mode of the VTR, the rotary heads (1 channel, 2 channels) at positions opposite to each other by 180 degrees on the diameter of the rotary drum obtain two outputs respectively. In the monaural mode, the continuous signal (a) from the AFM signals obtained from the heads 11 and 12 is demodulated by both demodulation systems, and then the output (b),
(C) is input to the matrix circuit 33, added, and S /
N improved monaural audio signals (d) can be obtained.

(Embodiment 2) FIG. 3 shows an embodiment 2 of a "two head helical scan type VTR audio signal reproducing apparatus".
It is a block diagram of. The parts having the same functions as those in the first embodiment are designated by the same reference numerals and the description thereof is omitted here.

In the stereo mode and the bilingual mode, the rotary heads 11 and 12 and the head amplifier 1 are driven by the mode detection signal output from the mode detection circuit 36.
The frequency-superimposed signals reproduced by 3, 14 are switched by the switch circuit 15 which is switched by the head switching pulse 16 in the overlap period, and become a continuous signal, and the switch circuits 42, 4
It is input to the BPFs 25 and 26 via the A.

A obtained by band-passing from BPF25
The FM main signal (1.5 MHz) is input to the mode detection circuit 36 and the limiter circuit 27, and the limiter circuits 27, F
The M demodulation circuit 29 demodulates the audio signal and inputs the audio signal to the matrix circuit 33, the switch circuit 31, and the switch circuit 41.

The switch circuit 31 includes a mode detection circuit 36.
In the stereo mode, the sound L demodulated by the matrix circuit 33 is generated by the mode detection signal output from
Output the channel signal to the L channel output terminal 34,
In the bilingual mode, the main signal demodulated into the audio signal through the FM demodulation circuit 29 is output to the L channel output terminal 34 without passing through the matrix circuit 33, whereby the stereo mode and the bilingual mode are switched.

The AFM sub (1.7 MHz) signal that is input to the BPF 26 and obtained by bandpass is input to the mode detection circuit 36 and the limiter circuit 28, and the limiter circuit 2
The signal is demodulated into an audio signal by the FM demodulation circuit 30 via 8 and is input to the matrix circuit 33, the switch circuit 32, and the switch circuit 41. The switch circuit 32 outputs the audio R channel signal demodulated by the matrix circuit 33 to the R channel output terminal 35 in the stereo mode in accordance with the mode detection signal output from the mode detection circuit 36, and in the bilingual mode, the FM demodulation circuit. Thirty
To the matrix signal 3 which is demodulated into a voice signal and the sub-signal is demodulated.
By outputting to the R channel output terminal 35 without passing through 3, the stereo mode and the bilingual mode can be switched in the same manner as the main signal.

In the monaural mode, the gate signal 1 output from the gate pulse generating circuit 37-2 causes the switch circuit 15 to switch the switch circuit 15 for a predetermined period before and after the switch circuit 15 is switched. The switch circuit 4 supplies a signal corresponding to the frequency-superimposed signal supplied to the BPFs 42 and 43 to the BPF 26.
3 is switched. That is, the switch circuit 43 is switched from the switch circuit 15 side to the head 12 side immediately before the switch circuit 15 is switched from the head 11 side to the head 12 side. Also, during the same prescribed period, BPF2
6 and the center frequency of the FM demodulation circuit 30 are AFM sub 1.
Switching from 7 MHz to AFM main 1.5 MHz. That is, the sub-signal demodulation systems 26, 28, 30 are switched so that the main signal can be demodulated.

In this manner, the functions of the sub-signal demodulation systems 26, 28, 30 which are conventionally fixed to the sub-signal demodulation are reproduced by the FM demodulation circuit 30 by changing the center frequency so that the main signal can be demodulated. Main signal and FM demodulation circuit 29
The reproduced main signal is input to the switch 41, and the FM demodulation circuit 29 is operated by the gate signal 2 during the overlap period.
Is switched to the output of the FM demodulation circuit 30 for a short period of time, and a continuous signal from which the head switching noise generated in the FM demodulation circuit 29 is removed is input to the switch circuit 31 and the switch circuit 32. It

The continuous signals input to the switches 31 and 32 can be switched by the mode detection signal output from the mode detection circuit 36 and output to the L channel output terminal 34 or the R channel output terminal 35. It will be possible.

In the periods other than the predetermined period, the center frequency of the sub-signal demodulation signal system is returned to the center frequency of the sub-signal, so that in the periods other than the predetermined period, the mode detection circuit 36 reproduces the reproduced AFM signal in stereo. Mode, monaural mode, or bilingual mode is automatically discriminated, and the obtained mode discrimination signal is input to the switch circuit 31, the switch circuit 32, the switch circuit 41, and the display unit 38, and the stereo signal is output. mode,
It can be switched to monaural mode or bilingual mode.

The mode discriminating signal is input to the gate pulse generating circuit 37-2 to generate the gate signal 1 and the gate signal 2 according to the head switching pulse 16 and the mode.

As described above, in the monaural mode,
The AFM sub (1.7 MHz) signal is demodulated by the gate signal 1 rather than simply switching the RF signal by the head switching pulse 16 in the overlap period to obtain a continuous signal and demodulating by the main signal demodulation system. The system is switched so that the AFM main (1.5 MHz) signal can be demodulated for a predetermined period before and after the switching of the switch circuit 15, and the demodulated signal is switched by the gate signal 2 to the switch circuit 4
Switching by 1 effectively eliminates so-called head switch noise that has conventionally been generated during head switching due to discontinuity in the phase of the AFM signal, and the AFM sub-signal can be detected during periods other than the predetermined period. Therefore, the mode recorded on the tape can be discriminated.

Further, when either one of the main signal and the sub signal is selected in the bilingual mode, similarly, the signal in which the center frequency of the signal demodulation system of the unselected signal is selected by the gate signal 1 Switch to the center frequency of the switch circuit 41 by the gate signal 2
By switching the signal after demodulation, the head switching noise can be removed as in the monaural mode.

The BPF 26 is a so-called variable g.
Needless to say, by incorporating the m-type bandpass filter in the IC, the number of components can be further reduced and switching can be easily performed.

A demodulation method in the monaural mode of this embodiment will be described with reference to FIGS. In the VTR playback mode, the rotary heads (1 channel, 2 channels) are located 180 degrees opposite each other on the diameter of the rotary drum.
Respectively obtain two outputs. AF obtained from the respective heads 11 and 12 in the monaural mode
The M signal (a), (b) is switched by the switch circuit 15 by the head switching signal (d) to be continuous (e), and the signal demodulated by the main signal demodulation systems 25, 27, 29 is (f). . By switching the center frequency of the sub-signal demodulation systems 26, 28, 30 to be able to demodulate the main signal by the gate signal 1 only during a certain period (the aforementioned predetermined period) (g) before and after the switching time of the switch circuit 15, The signal demodulated by the signal demodulation system is (i). Signal (f)
The waveforms of (i) and (i) are switched by the waveform switching signal (h) of the gate signal 2, so that the signal (f) is interpolated by the signal (i) and the head switching noise is removed from the monaural audio signal (j). Can be obtained. By switching the center frequency of the sub-signal demodulation system by the gate signal 1, the sub-signal can be demodulated during the period other than the overlap period, and the mode on the magnetic tape recording can always be discriminated.

Although each of the above-described embodiments has two heads, the present invention is not limited to this, and is similarly applicable to, for example, a four-head head having a small diameter head drum.

[0062]

As described above, according to the inventions described in claims 1 to 5, the following effects can be obtained without increasing the circuit scale. According to the invention of claim 1, the S / N is improved in the monaural mode. According to the second aspect of the invention, the S / N is improved when either the main signal or the sub signal is selected in the bilingual mode.

According to the third aspect of the invention, the head switching noise can be removed in the monaural mode. In the invention of claim 4, head switching noise can be removed when either the main signal or the sub signal is selected during bilingual operation. According to the invention of claim 5, in the inventions of claims 3 and 4, the continuous mode can be discriminated.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment.

FIG. 2 is an operation explanatory diagram of the first embodiment.

FIG. 3 is a block diagram of a second embodiment.

FIG. 4 is an operation explanatory diagram of the second embodiment.

FIG. 5: Recorded spectrum diagram of 8mm VTR

FIG. 6 is an explanatory diagram of a conventional first method.

[Explanation of symbols]

 11, 12 rotary head 15 switch circuit 29, 30 FM demodulation circuit 33 matrix circuit 36 mode detection circuit

Claims (5)

[Claims] 1. An FM signal reproduced by a plurality of heads whose reproduction periods partially overlap with each other is switched to the overlapping periods in a stereo mode, and continuous FM signals are produced.
A VTR audio signal reproducing device for converting a continuous FM signal into a signal and demodulating the continuous FM signal with a main signal demodulation system and a sub signal demodulation system to generate an L channel audio signal and an R channel audio signal in a matrix circuit. An audio signal reproducing apparatus for a VTR, comprising switching means for switching the sub-signal demodulation system so that the main signal can be demodulated. 2. An FM signal reproduced by a plurality of heads whose reproduction periods partially overlap with each other, is switched to the overlapping periods in a stereo mode, and a continuous FM signal is generated.
A VTR audio signal reproducing apparatus for converting a continuous FM signal into a signal and demodulating the continuous FM signal by a main signal demodulation system and a sub signal demodulation system to generate an L channel audio signal and an R channel audio signal in a matrix circuit. When either the main signal or the sub signal is selected, there is provided a switching means for switching the signal which selects the signal demodulation system of the non-selected signal of the main signal demodulation system and the sub signal demodulation system so as to demodulate. A VTR audio signal reproducing device characterized by: 3. An FM signal reproduced by a plurality of heads whose reproducing periods partially overlap with each other is switched to the overlapping periods in a stereo mode to make a continuous FM signal.
A VTR audio signal reproducing device for converting a continuous FM signal into a signal and demodulating the continuous FM signal by a main signal demodulation system and a sub signal demodulation system to generate an L channel audio signal and an R channel audio signal in a matrix circuit. , B, a VTR audio signal reproducing apparatus characterized by including the following components. a. An FM corresponding to the FM signal supplied to the signal demodulation system after the switching during a predetermined period before and after switching the FM signals reproduced by the plurality of heads in the monaural mode
While switching to supply the signal to the sub-signal demodulation system,
First switching means for switching the sub-signal demodulation system so that the main signal can be demodulated. b. Second switching means for switching the output of the main signal demodulation system to be interpolated by the output of the sub signal demodulation system during the overlapping period in the monaural mode to obtain a monaural audio signal without head switching noise. 4. An FM signal reproduced by a plurality of heads whose reproduction periods are partially overlapped is switched to the overlapped periods in a stereo mode to continue FM
A VTR audio signal reproducing device for converting a continuous FM signal into a signal and demodulating the continuous FM signal by a main signal demodulation system and a sub signal demodulation system to generate an L channel audio signal and an R channel audio signal in a matrix circuit. , B, a VTR audio signal reproducing apparatus characterized by including the following components. a. F reproduced by the plurality of heads when either the main signal or the sub signal is selected in the bilingual mode
During a predetermined period before and after switching the M signal, the FM signal corresponding to the FM signal supplied to the signal demodulation system after the switching is switched so as to be supplied to the signal demodulation system of the unselected signal, and the unselected signal is not selected. A first switching means for switching the signal demodulation system of 1) so that the selected signal can be demodulated. b. When either the main signal or the sub signal is selected in the bilingual mode, the output of the signal demodulation system for the selected signal is demodulated for the signal not selected during the overlapping period. Second switching means for obtaining the selected audio signal without head switching noise by switching so as to interpolate with the output of the system. 5. The method according to claim 3, further comprising a mode discriminating means for discriminating a mode by a signal of the main signal demodulation system and a signal of the sub signal demodulation system in a period other than the predetermined period. VTR audio signal playback device.