JPH0676469A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To suppress the power consumption of a magnetic recording and reproducing device by stopping the reproduction function of a signal corresponding to an FM voice signal at the time of the reproduction of the FM voice signal and permitting a normal voice signal to be selected. CONSTITUTION:When the reproduction of the FM voice signal is selected and the FM voice signal with a high faithfullness degree is not recorded in a reproduction tape or the carrier level is low with noise in a demodulation voice signal, a control circuit 11 automatically selects the normal voice signal with a control signal outputted from a carrier wave detecting circuit 10 and outputs it even when the FM voice signal with the high faithfullness degree is selected by an external control signal from a terminal 51. In this state, L and R channel FM demodulating circuits 6, 7 and L and R channel NR decoders 8, 9 are not required. It is same when the normal voice signal itself is selected by the control signal. Therefore, a power source to be supplied to an unrequired circuit element is turned off with control action by the circuit 11 so that extra power consumption is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus, and more particularly to a magnetic recording / reproducing apparatus used for reproducing a plurality of audio signals.

[0002]

2. Description of the Related Art In a conventional magnetic memory reproducing apparatus, an audio signal reproducing system is constructed as shown in FIGS. FIG. 3 shows an example of an audio signal reproducing system in a VHS video cassette recorder. In this case, the rotary head unit 2 is used.
5. Head amplifier 27 corresponding to the fixed head unit 26
, L channel bandpass filter 28 and R channel bandpass filter 29, and L channel FM demodulation circuit 30 and R
Channel FM demodulation circuit 31, L channel NR decoder 32 and R channel NR decoder 33, carrier wave detection circuit 34, control circuit 35, normal sound reproduction circuit 3
6 and a matrix circuit 37,
As the audio signal output from the rotary head unit 25, two systems of audio signals are reproduced, including an FM audio signal with independent carriers for the L channel and the R channel, and a normal audio signal with bias recording output from the fixed head unit 26. , And is selected and output by the matrix circuit 37 via an external control signal input from the external control terminal 53. Normally, the normal audio signal is recorded on all the tapes, and the FM audio signal is provided with a discriminating circuit for detecting the presence / absence of the recording, and when the FM audio signal is not recorded, Even if the FM audio signal is selected by the external control signal, the presence / absence of the FM audio signal is detected, and the determination circuit automatically outputs the normal audio signal based on the detection result.

FIG. 4 shows an example of an audio signal reproducing system in an 8 mm type video tape recorder. In this case, a head amplifier 39 and a head amplifier 39 are provided corresponding to the rotary head section 38. , (L + R) channel bandpass filter 40 and (LR) channel bandpass filter 41, (L + R) channel FM demodulation circuit 42 and (LR) channel FM demodulation circuit 43, (L + R) channel NR decoder 44 and ( LR channel NR
It comprises a decoder 45 and a matrix circuit 46.

In the case of this 8 mm video tape recorder, the matrix circuit 46 is used at the time of recording an audio signal.
In, the (L + R) channel audio signal and the (LR) channel audio signal are generated and recorded as FM audio signals for independent carrier waves. Therefore,
At the time of reproduction, selection is made such that the L channel and the R channel are reproduced and output as independent stereo sound, or reproduced and outputted as the sound signal of only the L channel or the sound signal of only the R channel. However, when reproducing in a state where the audio signal of the (LR) channel is not recorded, the (LR)
Only the (L + R) channel audio signal is output from the channel audio signal reproducing circuit. PCM for these audio signals
Even if an audio signal is added, no unrecorded audio signal is output via the operation of the discrimination circuit in the same manner.

[0005]

In the conventional magnetic recording / reproducing apparatus described above, if an unrecorded audio signal is selected for reproduction output, the audio signal is naturally output by the operation of the discriminating circuit. However, at that point, the FM demodulation circuit itself is in an operating state.
Generally, in a VHS system video tape recorder, the FM demodulation circuit is provided with a noise reduction circuit or the like for applying noise reduction at the time of recording. About 100 mW is required. This power consumption value is a power value which is a problem for the magnetic recording / reproducing apparatus, and when a battery is used as a power supply source, it is fatal in consideration of the operating time of the magnetic recording / reproducing apparatus. There is a drawback that it becomes a physical defect.

[0006]

The magnetic recording / reproducing apparatus of the first invention is an L (left) channel audio signal and an R (right) channel audio signal generated by frequency-modulating independent carrier signals. In a magnetic recording / reproducing apparatus that reproduces an FM audio signal containing a sound signal and a normal audio signal that is modulated and recorded by a predetermined bias signal, an external control signal for selecting the reproduced audio signal is received from the outside, and the audio signal is not selected for reproduction. A reproduction function control means for stopping a reproduction function corresponding to an audio signal and a presence / absence of the FM audio signal are discriminated at the time of reproducing the FM audio signal. If the FM audio signal does not exist, or its level is predetermined. FM audio signal discriminating means for outputting an internal control signal for stopping the reproducing function corresponding to the FM audio signal when the level is lower than the level value. During reproduction of the FM audio signal, the reproduction function of the signal corresponding to the FM audio signal is stopped and reproduced through the control action of the reproduction function control means that operates by inputting the internal control signal. It is characterized in that the normal voice signal is selected as the voice signal.

In the magnetic recording / reproducing apparatus of the second invention, an L (left) channel audio signal and an R (left) channel audio signal, which are generated by pulse-code modulating an independent carrier signal, respectively.
(Right) In a magnetic recording / reproducing apparatus for reproducing a PCM audio signal including a channel audio signal and a normal audio signal modulated and recorded by a predetermined bias signal, an external control signal for selecting a reproduced audio signal is received from the outside. A reproduction function control means for stopping a reproduction function corresponding to an audio signal not selected for reproduction, and whether or not the PCM audio signal exists at the time of reproducing the PCM audio signal, and the PCM audio signal does not exist , Or when the level is lower than a predetermined level value, P which outputs an internal control signal for stopping the reproduction function corresponding to the PCM audio signal.
CM audio signal discriminating means, and at the time of reproducing the PCM audio signal, the P function is controlled through the control operation of the reproducing function control means which operates by inputting the internal control signal.
It is characterized in that the reproduction function of the signal corresponding to the CM audio signal is stopped and the normal audio signal is selected as the reproduced audio signal.

In the magnetic recording / reproducing apparatus of the third invention, (L + R) channel audio signals and (LR) channel audio signals which are separated by a matrix structure and are frequency-modulated with respect to independent carrier signals are generated. In a magnetic recording / reproducing apparatus for reproducing an FM audio signal including a signal, a reproducing function control means for receiving an external control signal for selecting a reproducing audio signal from the outside and stopping a reproducing function corresponding to an audio signal not selected for reproduction. When reproducing the FM audio signal, it is determined whether or not the FM audio signal of the (LR) channel exists, and if the FM audio signal does not exist,
Or, if the level is lower than a predetermined level value, an FM audio signal discriminating means for outputting an internal control signal for stopping the reproducing function of the FM audio signal of the (LR) channel is provided, and the FM audio signal is provided. At the time of reproducing a signal, the reproduction function of the signal corresponding to the FM audio signal of the (LR) channel is stopped through the control action of the reproduction function control means that operates by inputting the internal control signal. Is characterized by.

In the magnetic recording / reproducing apparatus of the fourth invention, the (L + R) channel audio signal and the (L + R) channel audio signal, which are separated by the matrix structure and are frequency-modulated and pulse code-modulated with respect to each independent carrier signal, are generated.
-R) In a magnetic recording / reproducing apparatus for reproducing a PCM audio signal including a channel audio signal, an external control signal for selecting a reproduced audio signal is received from the outside, and a reproducing function corresponding to an audio signal not selected for reproduction is stopped. The reproduction function control means and the presence or absence of the PCM audio signal of the (LR) channel are discriminated at the time of reproducing the PCM audio signal, and the P
When there is no CM audio signal or when its level is lower than a predetermined level value, a PCM audio signal determination that outputs an internal control signal for stopping the reproduction function of the PCM audio signal of the (LR) channel Means for responding to the PCM audio signal of the (LR) channel via the control action of the reproduction function control means that operates by inputting the internal control signal when the PCM audio signal is reproduced. The feature is that the signal reproducing function is stopped.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention, which is an embodiment showing a reproduction system of an audio signal when the present invention is applied to a VHS system video tape recorder. As shown in FIG. 1, this embodiment is
Corresponding to the rotary head unit 1 and the fixed head unit 2,
Head amplifier 3, L channel bandpass filter 4 and R
Channel bandpass filter 5 and L channel FM demodulation circuit 6
And an R channel FM demodulation circuit 7, an L channel NR decoder 8 and an R channel NR decoder 9, a carrier wave detection circuit 10, a control circuit 11, a normal audio reproduction circuit 12, and a matrix circuit 13. .

In FIG. 1, reproduced voice signals in this embodiment are an FM voice signal having a high fidelity obtained from the rotary head unit 1 and a normal voice signal obtained from the fixed head 2. In the case of the NTSC system, the FM audio signal has a carrier frequency of 1.3 MH in the L channel.
The z and R channels are FM-modulated with a maximum frequency deviation of 150 kHz at 1.7 MHz, and are mixed with each other to produce a rotary disc dedicated to the video track of the video tape.
It is recorded by the head. At the time of reproduction, the FM audio signal obtained from the rotary head unit 1 is amplified by the head amplifier 3 and passed through the band pass filters 4 and 5 of 1.3 MHz system and 1.7 MHz system, respectively, and the FM demodulation circuit 6 and 7 and is demodulated into an audio signal. Further, F output from the L channel bandpass filter 4
The M audio signal is also input to the carrier detection circuit 10,
Whether or not the FM audio signal exists is determined based on the presence or absence of the detection output or the detection level. The detection output from the carrier wave detection circuit 10 is used as a control signal in the switching circuit 1
1 through L channel FM demodulation circuit 6, R channel F
It is sent to the M demodulation circuit 7, the L channel NR decoder 8, the R channel NR decoder 9, the carrier wave detection circuit 12 and the matrix circuit 13. Then, these audio signals are input to the L channel NR decoders 8 and 9, respectively, and the frequency band of the audio signals band-compressed for improving the S / N ratio is returned to the original bandwidth and output. , To the matrix circuit 13. A normal audio signal obtained from the fixed head unit 2 and reproduced by the normal audio reproducing circuit 12 is also input to the matrix circuit 13, and a control signal input via the external control terminal 51 or the above-described carrier wave is input. One of the audio signals is selected and output via the control signal output from the detection circuit 10. For example, when playing back a video tape recording a Japanese television broadcast, or playing back a video tape recording a stereo broadcast, the L channel and R channel audio signals may be output as they are. When bilingual broadcasting is recorded, it is necessary to select either the L channel or the R channel. Further, when a high fidelity audio signal is not recorded on the reproduction tape, a normal audio signal is output.

As described above, the selection of the audio signal output from the matrix circuit is externally selected mainly through the external control terminal 51, but the selection control is also performed by the control signal output from the carrier detection circuit 10. To be done. That is, when the reproduction of the FM audio signal is selected and the FM audio signal of high fidelity is not recorded on the reproduction tape, or when the carrier level is low and the demodulated audio signal contains noise. Even if a high fidelity FM audio signal is selected by the control signal input from the external control terminal 51, the control circuit 11 outputs the control signal automatically via the control signal output from the carrier detection circuit 10. Normally, the normal voice signal is selected and output. And
In this state, the L channel FM demodulation circuit 6 and the R channel FM demodulation circuit 7, and the L channel NR decoder 8 and the R channel NR decoder 9 are unnecessary. This also applies when the normal audio signal itself is selected by the control signal input from the external control terminal 51. Therefore, in these states, the power supplied to the unnecessary circuit components via the control action of the control circuit 11 is cut off, whereby extra power consumption can be suppressed. Usually, the power consumption in the FM demodulation circuit is 100 to 200 m
It is about W, and the power consumption in the NR decoder is 2
It is about 0 to 300 mW, which results in 300 m
A considerable power consumption of W to 500 mW is saved.
On the contrary, when a high fidelity audio signal is selected, the power consumption can be further reduced by stopping the function of the normal audio reproduction circuit 12 for the normal audio signal.

FIG. 2 is a block diagram showing a second embodiment of the present invention, which is an embodiment showing a reproduction system of an audio signal when the present invention is applied to an 8 mm type video tape recorder. . As shown in FIG. 1, this embodiment is
A head amplifier 15 corresponding to the rotary head unit 14
, L channel bandpass filter 16 and R channel bandpass filter 17, and (L + R) channel FM demodulation circuit 18
And (R−L) channel FM demodulation circuit 19, and (L +
An R) channel NR decoder 20 and an (RL) channel NR decoder 21, a carrier wave detection circuit 22, a control circuit 23, and a matrix circuit 24 are provided.

In FIG. 2, in the 8 mm video tape recorder, originally, an audio signal of the (LR) channel is added to a monaural audio signal, that is, an audio signal of the (L + R) channel to make it stereo. At the time of recording, the matrix circuit 24 separates the audio signal into an (L + R) channel audio signal and an (LR) channel audio signal, and then performs predetermined signal processing for recording. Normally, the carrier frequency of the (L + R) channel is 1.5 MHz
And the carrier frequency of the (L + R) channel audio signal is 1.7 MHz. For this reason, there is no normal audio signal due to bias recording, as in the case of the VHS system video tape recorder. The procedure of reproducing the stereo audio signal is the same as that of the VHS system, although the processing content in the matrix circuit 24 is different.

In the case of the 8 mm system, the carrier detection circuit 22 first detects the presence / absence of the (LR) channel audio signal, and when the (LR) channel audio signal does not exist, or in that case. If the level is very low, the (LR) channel F on the (LR) channel side
Power consumption can be suppressed by stopping the functions of some circuit elements including the M demodulation circuit 19 and the (LR) channel NR decoder 21. Further, in recent years, the use of a recording / reproducing system based on the PCM system is being adopted, and even in this case, the reproducing P
When the presence or absence of the CM signal is detected and the reproduced PCM signal does not exist, or when the level thereof is very low, the function of a part of the circuit elements including the PCM demodulation circuit is stopped. Power consumption can be suppressed. Even in the case of the external control action, the power consumption is suppressed by cutting off the power supply to the component whose function is stopped at that time.

[0017]

As described above, the present invention is applied to a magnetic recording / reproducing apparatus that outputs a plurality of reproduced audio signals, and by providing a discriminating means for detecting the presence or absence of each reproduced audio signal. When there is no reproduced audio signal or the level thereof is low, the demodulation reproduction function corresponding to the reproduced audio signal is stopped, so that it is possible to suppress unnecessary power consumption.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional example.

FIG. 4 is a block diagram showing another conventional example.

[Explanation of symbols]

 1, 14, 25, 38 Rotary head unit 2, 26 Fixed head unit 3, 15, 27, 39 Head amplifier 4, 28 L channel band filter 5, 29 R channel band filter 6, 30 L channel FM demodulation circuit 7, 31 R channel FM demodulation circuit 8, 32 L channel NR decoder 9, 33 R channel NR decoder 10, 22, 34 Carrier wave detection circuit 11, 23, 35 Control circuit 12, 36 Normal audio reproduction circuit 13, 24, 37, 46 Matrix circuit 16, 40 (L + R) channel band filter 17, 41 (L-R) channel band filter 18, 42 (L + R) channel FM demodulation circuit 19, 41 (L-R) channel FM demodulation circuit 20, 44 (L-R) Channel NR decoder 21, 45 (LR) channel NP decoder

Claims (4)

[Claims] 1. An FM audio signal including an L (left) channel audio signal and an R (right) channel audio signal generated by frequency-modulating independent carrier signals and a predetermined bias signal, and modulated and recorded. In a magnetic recording / reproducing apparatus for reproducing a normal audio signal, a reproducing function control means for receiving an external control signal for selecting a reproducing audio signal from the outside and stopping a reproducing function corresponding to an audio signal not selected for reproduction. When reproducing the FM audio signal, it is determined whether or not the FM audio signal exists, and if the FM audio signal does not exist,
Or an FM audio signal discriminating means for outputting an internal control signal for stopping the reproduction function corresponding to the FM audio signal when the level is lower than a predetermined level value, at the time of reproducing the FM audio signal. In the above, the reproduction function of the signal corresponding to the FM audio signal is stopped and the normal audio signal is selected as the reproduced audio signal via the control action of the reproduction function control means that operates by inputting the internal control signal. A magnetic recording / reproducing apparatus characterized by: 2. A PCM including an L (left) channel audio signal and an R (right) channel audio signal, which are generated by pulse code modulation with respect to respective independent carrier signals.
In a magnetic recording / reproducing apparatus for reproducing an audio signal and a normal audio signal modulated and recorded by a predetermined bias signal, an external control signal for selecting a reproduced audio signal is received from an external source and an audio signal not selected for reproduction is selected. Reproduction function control means for stopping the corresponding reproduction function, and at the time of reproduction of the PCM audio signal, it is determined whether or not the PCM audio signal exists, and when the PCM audio signal does not exist, or its level is higher than a predetermined level value. And a PCM audio signal discriminating means for outputting an internal control signal for stopping the reproduction function corresponding to the PCM audio signal, the internal control signal is input during reproduction of the PCM audio signal. The reproduction function of the signal corresponding to the PCM audio signal is stopped through the control operation of the reproduction function control means that operates in the following manner. Together, magnetic recording and reproducing apparatus and selects the normal audio signal as a reproduced audio signal. 3. A magnetic field for reproducing an FM audio signal including an (L + R) channel audio signal and an (LR) channel audio signal, which are separated by a matrix structure and are frequency-modulated with respect to each independent carrier signal to be generated. In the recording / reproducing apparatus, a reproduction function control means for receiving an external control signal for selecting a reproduction audio signal from the outside and stopping a reproduction function corresponding to an audio signal not selected for reproduction, and a reproducing function control means for reproducing the FM audio signal. The presence or absence of the FM audio signal of the (LR) channel is determined, and when the FM audio signal does not exist or the level thereof is lower than a predetermined level value, the FM audio of the (LR) channel. FM audio signal discriminating means for outputting an internal control signal for stopping the signal reproduction function, and when the FM audio signal is reproduced, The magnetic recording is characterized in that the reproduction function of the signal corresponding to the FM audio signal of the (LR) channel is stopped through the control action of the reproduction function control means which operates by inputting the internal control signal. Playback device. 4. A PCM including an (L + R) channel audio signal and an (LR) channel audio signal which are separated by a matrix structure and are frequency-modulated and pulse code-modulated with respect to each independent carrier signal to be generated.
In a magnetic recording / reproducing apparatus for reproducing an audio signal, a reproducing function control means for receiving an external control signal for selecting a reproducing audio signal from the outside and stopping a reproducing function corresponding to an audio signal not selected for reproduction selection; At the time of reproducing the signal, it is determined whether or not the PCM audio signal of the (LR) channel is present, and the PCM audio signal is detected.
If there is no audio signal, or if its level is lower than a predetermined level value, the P of the (LR) channel is concerned.
PCM audio signal discriminating means for outputting an internal control signal for stopping the reproduction function of the CM audio signal, and the reproduction function control which operates by inputting the internal control signal at the time of reproducing the PCM audio signal. PC of said (LR) channel via control action by means
A magnetic recording / reproducing apparatus characterized in that a reproducing function of a signal corresponding to an M audio signal is stopped.