JPH07109696B2 - Playback device - Google Patents

Description

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

A Industrial field of use B Outline of invention C Conventional technology (Figs. 5 and 6) D Problems to be solved by the invention E Means for solving problems F Action G Example G ₁ Recording system Explanation of Fig. 1 Explanation of G ₂ regeneration system (Figs. 1, 2, 3) G ₃ Explanation of other examples (Fig. 4) H Effect of the invention A Industrial field of application This invention Relates to a reproducing apparatus for a multi-channel information signal recorded as a track for each channel, such as a 2-channel audio signal in a VTR, and particularly for a circuit for determining whether or not noise reduction is applied to the reproduced signal. Involved in improvement.

B. Summary of the Invention The present invention is a pilot signal indicating whether or not noise reduction is applied at the time of recording, and a signal synchronized with a reference signal recorded as a separate track on a recording medium is recorded on an information signal track. The reproduction reference signal is synchronously detected to determine whether or not the reproduction signal is passed through the noise reduction circuit, and the configuration is devised so that the determination circuit can be one common to the information signals of the plurality of channels. The configuration can be simplified.

C Conventional technology In the VTR, the audio signal is considered in consideration of 2 channel stereo of TV sound multiplex broadcasting, 2 language broadcasting, etc.
At the end of the tape in the width direction, it is possible to record as a two-channel track along the longitudinal direction of the tape.

In this case, in order to improve the S / N and obtain a high quality audio signal, noise reduction is applied to the audio signal. That is, for example, the high frequency band of the audio signal is raised at the time of recording and the recording is performed, and the reverse operation is performed at the time of reproduction to particularly reduce the tape hiss noise.

Therefore, the audio signal passed through the recording noise reduction circuit at the time of recording needs to pass through the reproduction noise reduction circuit at the time of reproduction.

Therefore, during playback, it is automatically determined whether or not noise reduction has been applied to the recorded audio signal,
It is desired that the reproduced audio signal be passed through a reproduction noise reduction circuit.

In the VTR, the applicant has previously proposed the following as an automatic discrimination method of noise reduction during reproduction.

In other words, this system synchronizes with the 30 Hz control signal recorded on the longitudinal track at the end of the tape in the width direction.
Presence / absence of pilot signal by superimposing and recording the Hz signal as a pilot signal on the audio track and providing a circuit to extract the pilot signal component from the reproduced audio signal during playback and synchronously detecting the extracted signal with the playback control signal The noise reduction circuit at the time of reproduction controls the insertion of the reproduced audio signal (see Japanese Patent Laid-Open No. 61-34703).

FIG. 5 shows an example of a reproducing apparatus adopting the previously proposed automatic discrimination method.

In the figure, HA ₁ and HA ₂ are audio magnetic heads for the first and second channels, and these heads HA
Playback signals from ₁ and HA ₂ are playback amplifiers (1 ₁ ) and (1 ₂ )
Is supplied to one of the input ends of the switch circuits (3 ₁ ) and (3 ₂ ) via the respective amplifiers (1 ₁ ) and (1 ₂ ) and the signal for reproduction is a noise reduction circuit (2 ₁ ). And switch circuit (3 ₁ ) via (2 ₂ ) respectively
And (3 ₂ ) are supplied to the other input terminals. The switching circuits (3 ₁ ) and (3 ₂ ) are switching-controlled by the discrimination outputs from the noise discrimination automatic discrimination circuits (10 ₁ ) and (10 ₂ ) of each channel as described later.

The signal from the switching circuit (3 ₁₎ and (3 ₂₎ is derived in the audio amplifier (4 ₁₎ and (4 ₂₎ via the output terminal of each channel (5 ₁₎ and (5 ₂₎ .

Since the automatic discriminating circuits (10 ₁ ) and (10 ₂ ) have exactly the same configuration in the first channel and the second channel,
Suffix 1 is assigned to the same number for each constituent circuit of the automatic discrimination circuit (10 ₁ ) and (10 ₂ ) of the channel and the second channel.
And 2 are added to automatically determine the first channel (1
0 ₁ ) will be described.

That is, the reproduction signal from the amplifier (1 ₁ ) is supplied to the low-pass filter (11 ₁ ) to extract the pilot signal SP (15 Hz), and the pilot signal SP is extracted from the balanced modulation circuit (1
It is supplied to the 2 ₁₎ and (13 _1).

On the other hand, a 30 Hz reproduction control signal PC (FIG. 6A) from the control signal head HC is supplied to the servo circuit (22) via the amplifier (21) to perform phase servo of the rotary head drive.

The reproduction control signal PC via the amplifier (21) is divided by 1/2 in the frequency dividing circuit (23) to be a 15 Hz signal, which is used as a reference signal REF (FIG. 6B) through the low pass filter (24). The reference signal REF is taken out and supplied to the balanced modulation circuit (12 ₁ ).
The inverted reference signal ▲ ▼ (FIG. 6D) whose polarity has been inverted by 5) is supplied to the balanced modulation circuit (13 ₁ ). In these balanced modulation circuits (12 ₁ ) and (13 ₁ ), the reference signal REF and ▲
By ▼, the output signal of the low-pass filter (11 ₁ ) is synchronously detected.

Therefore, when the reproduction pilot signal SP is obtained from the low pass filter (11 ₁ ), these balanced modulation circuits (12
Positive detection output SDa (Fig. 6E) is obtained on _one of ( ₁ ) and (13 ₁ ), and negative detection output SDb (Fig. 6F) is obtained on the other. Then, these detection outputs SDa and SDb are supplied to the difference detection circuit (16 ₁ ) through the low-pass filters (14 ₁ ) and (15 ₁ ), and the output of the difference between the direct current components of both detection outputs SDa and SDb is Obtained from the comparison circuit (1
7 ₁ ) and is compared with the reference voltage E. As a result, a high level output SW ₁ is obtained from this comparison circuit (17 ₁ ).
This controls the switch circuit (3 ₁ ) and this output
When SW ₁ is at high level, the reproduced audio signal is output through the noise reduction circuit for reproduction (2 ₁ ) as shown in the figure.

When the reproduction pilot SP cannot be obtained from the low pass filter (11 ₁ ), the output of the balanced modulation circuit (12 ₁ ) (13 ₁ ) becomes a minute level and the output of the difference detection circuit (16 ₁ ) becomes the reference voltage E. Compare circuit (17 ₁ ) as it will never be larger
Output becomes low level, the switch circuit (3 ₁ ) is switched to the state opposite to that shown in the figure, and the noise reduction circuit (2 ₁ ) is bypassed.

Automatic noise reduction circuit for the second channel (10
₂ ) also operates in exactly the same way, the switching circuit (3 ₂ ) is switching-controlled by the output SW ₂ of the comparison circuit (17 ₂ ), and the on / off of the playback noise signal (2 ₂ ) for the playback audio signal is controlled. To be done.

It should be noted that in the example of FIG. 5, two synchronous (phase) detection circuits are provided for the automatic noise reduction discrimination circuits (10 ₁ ) and (10 ₂ ) for each channel. Since the frequency dividing circuit (23) for forming the signal REF is not generally initialized, the phase relationship between the reference signal REF and the reproduction pilot signal SP cannot be uniquely determined, and the determination is surely performed. This is because.

D Problems to be Solved by the Invention As described above, conventionally, the noise reduction automatic discrimination circuit (1) is separately provided for each of the first channel and the second channel.
Since 0 ₁ ) and (10 ₂ ) are provided, the circuit configuration becomes complicated.

By the way, when the left and right two-channel audio signals are considered as the information signals of the first and second channels, noise reduction is not applied independently to the left and right, but it is normally applied to both channels simultaneously. Further, even in the case of multilingual broadcasting of audio, it is a general usage to apply noise reduction commonly to the main and sub audio.

In consideration of such circumstances, the present invention devises the configuration of the automatic noise reduction determination circuit to simplify the circuit configuration.

E Means for Solving Problems In the present invention, the automatic simplification circuit for noise reduction for each channel is integrated to simplify the configuration. A pilot signal is reproduced from a reproduction information signal for each channel. When a plurality of pilot signal extracting means for extracting, a means for reproducing a reference signal, and outputs of a plurality of pine lot signal extracting means are supplied, and the pilot signal exists even in one of the plurality of outputs, the pilot signal is extracted. An analog OR circuit for outputting, a circuit for synchronously detecting the output of the analog OR circuit by a reference signal, and a means for controlling ON / OFF of the noise reduction circuit for the information signal based on the output of the detection circuit.

F. When a reproduction pilot signal is obtained by one of the pilot signal extracting means for a plurality of channels, the reproduction pilot signal is obtained at the output of the analog OR circuit, and this reproduction pilot signal is detected in the detection circuit common to the plurality of channels. Synchronous detection is performed by the reference signal, and the detection output controls ON / OFF of insertion of the noise reduction circuit of the information signal system of each channel with respect to the reproduction signal.

G. Embodiment FIG. 1 shows an example in which the present invention is applied to a VTR audio signal system capable of recording and reproducing audio signals for two channels, and the recording system will also be described.

That is, (31), (32), (33) and (34) are recording / reproducing changeover switches, which are connected to the contact R during recording and to the contact P during reproduction.
Connected respectively.

Description of G ₁ recording system Then, at the time of recording, the audio signals of the first channel and the second channel are amplified through the amplifiers (42 ₁ ) and (42 ₂ ), respectively, and then the switch circuit (4 ₁ )
And (44 ₂ ) are supplied to one input terminal of the recording noise reduction circuits (43 ₁ ) and (43 ₂ ) which serve to raise the high frequency of the signal through the amplifiers (42 ₁ ) and (42 ₂ ). ) Through switch circuits (44 ₁ ) and (44
It is supplied to the other input terminal of ₂ ).

The switch circuits (44 ₁ ) and (44 ₂ ) are selectively switched between one input terminal and the other input terminal by a control signal through terminals (47 ₁ ) and (47 ₂ ) obtained according to a user's selection operation. . Then, the switch circuits (44 ₁ ) and (4
4 ₂ ) output signals are added to the adder circuits (45 ₁ ) and (4 4) respectively.
5 ₂ ), recording amplifiers (46 ₁ ) and (46 ₂ ), and switches (31) and (32) for audio signal magnetic heads.
It is supplied to HA ₁ and HA ₂ and recorded as independent tracks along the longitudinal direction of the tape at the widthwise end of the magnetic tape.

Further, the vertical synchronizing signal VD extracted from the video signal is supplied to the frequency dividing circuit (52) through the input terminal (51) and is frequency-divided into 30 Hz signals, which are the amplifier (53) and the switch ( It is supplied to the control signal magnetic head HC via 33) and is recorded as a track separate from the audio track along the longitudinal direction of the tape at the widthwise end of the magnetic tape.

In addition, the 30 Hz signal from the frequency dividing circuit (52) is further supplied to the frequency dividing circuit (54) via the switch (34) and is halved.
It is divided into a 15Hz signal, and this signal is passed through the low pass filter (55) and amplifier (56), and the attenuator (5
It is supplied to 7) and adjusted to an appropriate level. The output signal of the attenuator (57) serves as a pilot signal indicating whether or not the audio signal is recorded by passing through the recording noise reduction circuits (43 ₁ ) and (43 ₂ ).

That is, the pilot signal from the attenuator (57) is supplied to the adder circuits (45 ₁ ) and (45 ₂ ) via the switch circuits (58 ₁ ) and (58 ₂ ), respectively. The switch circuits (58 ₁ ) and (58 ₂ ) are turned on in synchronization with the switching of the switch circuits (44 ₁ ) and (44 ₂ ) by a control signal from the terminals (47 ₁ ) and (47 ₂ ). Controlled off. That is, switch circuit (44 ₁ ) (4
4 ₂ ) is switched and the recording noise reduction circuits (43 ₁ ) and (43 ₂ ) are on, the switch circuit (58
₁ ) and (58 ₂ ) are turned on, the pilot signal is recorded by being superimposed on the audio signal, and the recording noise reduction circuits (43 ₁ ) and (43 ₂ ) are bypassed and turned off, the switch is turned on. Circuits (58 ₁ ) and (58 ₂ ) are also turned off and no pilot signal is recorded.

G ₂ Playback system description Next, at the time of playback, the playback outputs of the heads HA ₁ and HA ₂ are output via the switches (31) and (32) to the playback amplifier (61 ₁ ).
And (61 ₂ ) and the outputs of the reproduction amplifiers (61 ₁ ) and (61 ₂ ) are switched by switching circuits (63 ₁ ) and (6 6) by the output of the noise reduction automatic discrimination circuit (70) described later.
3 ₂ ) is switched, so that when an audio signal with noise reduction applied is played back, the high frequency range of the playback signal is restored to its original level through the playback noise reduction circuits (62 ₁ ) and (62 ₂ ) and the amplifier (64 ₁ ) and (64 ₂ ) to the output terminals (65 ₁ ) and (65 ₂ ), and when playing back an audio signal that has not been subjected to noise reduction, the playback signal is the playback noise reduction circuit (62 ₁ )
And (62 ₂ ) are bypassed and output terminals (65 ₁ ) and (65 2
₂ ).

In this reproduction system, the automatic noise reduction discrimination circuit (70) is one system common to the first channel and the second channel. The reproduction amplifiers (61 ₁ ) and (61 ₂ )
The reproduced signal from the low pass filter (71 ₁ ) and (71 ₂ )
When noise reduction is applied to the
The 15 Hz pilot signal is extracted. The output signals of the low pass filters (71 ₁ ) and (71 ₂ ) are supplied to the analog OR circuit (72).

This analog OR circuit (2), as shown as a conceptual diagram in the block diagram, outputs a logical OR of two input signals,
It is like taking a logical OR output with one of the two input signals.

The analog OR circuit (2) is provided for the following reason.

That is, considering the presence or absence of a pilot signal of each channel and the phase with respect to the reference signal, "0" when there is no pilot signal, "1" when there is a pilot signal synchronized with the reference signal, and "1" when there is a pilot signal of opposite phase. When "-1", the first channel CH _1, the combination of the pilot signals which can be taken by the second channel CH ₂ is as follows.

Thus, a combination of two channels Pine lot signal is nine, moreover CH ₁ is "1", CH ₂ is "-
1 ”, the phase of the pilot signal is the first channel CH
_In some cases, ₁ and the second channel CH ₂ may be reversed. Therefore, if the channels CH ₁ and CH ₂ are simply added (logically summed), the output will have a pilot signal,
It becomes "0" and cannot be detected.

Further, considering the case of "-1", the digital logic circuit configuration as shown in the conceptual diagram cannot be adopted, and as an embodiment of this analog OR circuit (72), the configuration as shown in FIG. 2 or FIG. It is said that

In the circuits of FIGS. 2 and 3, (721) and (722)
Are input terminals to which the output signals of the low-pass filters (71 ₁ ) and (72 ₂ ) are respectively supplied, and (723) is an output terminal.

The resistance values are R ₁ = R ₂ , R ₃ = R ₄ , R ₁ ′ = R ₂ ′, R ₃ ′
= R ₄ ′. Note that R ₅ and R ₆ are bias resistors.

Thus, as long as the pilot signal is obtained from either the low-pass filter (71 ₁ ) or (71 ₂ ) from the analog OR circuit (72), the pilot signal output is obtained. This pilot signal output is supplied to the balanced modulation circuits (73) and (74).

On the other hand, the reproduction control signal from the magnetic head HC for control signal is supplied to the servo circuit (82) through the amplifier (81) through the switch (33) and to the frequency dividing circuit (54) through the switch (34). It is supplied and divided by 1/2 to be a 15Hz signal, which is obtained as a reference signal REF through the low-pass filter (55) and amplifier (56), and is supplied to the modulation circuit (73) and the inverter (59). The polarity is inverted to form an inverted reference signal ▲ ▼, which is supplied to the balanced modulation circuit (74) to synchronously detect the pilot signal.

The detection outputs from the balanced modulation circuits (73) and (74) are supplied to the difference detection circuit (77) through the low pass filters (75) and (76), respectively, and the difference output is supplied to the reference voltage E in the comparison circuit (78). Then, in the same manner as described above, the high level signal SW is obtained when the pilot signal is detected and the low level signal SW is obtained when the pilot signal is not detected. The switch circuits (63 ₁ ) and (63 ₂ ) are commonly controlled by this signal SW.

In this example, the switch circuits (63 ₁ ) and (63 ₂ ) are considered to be manually controllable. That is, the comparison circuit (78) and switching circuit (63 ₁₎ of the AND gate (66 ₁₎ between the comparison circuit (78) and switching circuit (63 ₂₎ and between the AND gate (66 ₂₎ Are provided, the output SW of the comparator circuit (78) is supplied as one input of the AND gates (66 ₁ ) and (66 ₂ ), and the switches (67 ₁ ) and (67 ₂ ) Output is supplied. With this arrangement, when the switches (67 ₁ ) and (67 ₂ ) are switched to the contact A side as shown in the figure, the AND gates (66 ₁ ) and (6 6
6 ₂ ) is always closed and the signal SW is directly supplied to the switch circuits (63 ₁ ) and (63 ₂ ), but the switches (67 ₁ ) (67 ₂ ) are connected to the other contact B side. When switched, the switch circuit (63
₁ ) (63 ₂ ) can be switched to a switching state that bypasses the noise reduction circuits (62 ₁ ) (62 ₂ ).

G ₃ Description of other examples Note that the noise reduction automatic discrimination circuit (70) does not use two balanced modulation circuits as in the example in the figure, but instead of using an analog OR circuit (72) as shown in the fourth head. Is supplied to one balanced modulation circuit (91) and is synchronously detected by the reference signal REF, and the detected output is supplied to a pair of level comparators (93) and (94) via a low pass filter (92). The comparison output may be supplied to the comparison circuit (78) via the OR gate (95).

In this case, a positive comparison output is obtained when the positive detection output corresponding to FIG. 6E is input to the comparator (93), and the negative comparison output corresponding to FIG. 6F is obtained in the comparator (94). A positive comparison output is obtained when a sex detection output is input to it.
That is, the comparison output is always obtained and the pilot signal can be detected regardless of the in-phase or the opposite phase.

Of course, the present invention can be applied to the case of recording / reproducing information signals of two or more channels.

H Effect of the Invention According to the present invention, the pilot signal of each channel is supplied to the analog logical sum circuit, so that the automatic noise reduction discrimination circuit can be completed with only one system common to a plurality of channels. The circuit configuration can be greatly simplified.

[Brief description of drawings]

FIG. 1 is a block diagram of a recording / reproducing apparatus including an embodiment of the present invention, FIGS. 2 and 3 are circuit diagrams of specific examples of essential circuits, and FIG. 4 is another structural example of essential parts. FIG. 5, FIG. 5 is a block diagram of a conventional device, and FIG. 6 is a diagram for explaining it. HA ₁ and HA ₂ are audio signal heads, HC is a control signal head, (62 ₁ ) and (62 ₂ ) are noise reduction circuits for reproduction, (63 ₁ ) and (63 ₂ ) are switch circuits,
(71 ₁ ) and (71 ₂ ) are low-pass filters for extracting pilot signals, (72) are analog OR circuits, and (73) and (74) are balanced modulation circuits for synchronous detection.

Claims (1)

[Claims] 1. An information signal of a plurality of channels is recorded as a track independent of each channel, and a pilot signal for identifying ON / OFF of an in-noise reduction circuit synchronized with a reference signal for each channel is the information signal. A device for reproducing a recording medium which is recorded on an information signal track of each of the channels while being superposed on the recording medium and the reference signal is recorded on a track different from the information signal track, and b) for each channel. A plurality of pilot signal extracting means for extracting the pilot signal from the reproduction information signal; c) means for reproducing the reference signal; and d) outputs of the plurality of pilot signal extracting means, one of the plurality of outputs being supplied. And an analog OR circuit that outputs the pilot signal when the pilot signal is present, e) This analog theory A reproducing apparatus comprising: a detection circuit for synchronously detecting the output of the summing circuit by the reference signal; and f) means for controlling ON / OFF of the noise reduction circuit for the information signal based on the output of the detection circuit.