JPS61234112A - Processing circuit for sound signal - Google Patents

Abstract

PURPOSE:To reduce aurally unpleasant feeling at the transient point (when muting is released, when recording is made consecutively, etc.) of recording or reproducing sound signals, by installing a variable-gain circuit to a recording or reproducing system and gradually changing the gain at the transient point of the sound signals. CONSTITUTION:A record muting signal SMR as shown in Fig. B is supplied to a soft muting control circuit 47 at the time of recording. A control signal SC as shown in Fig. C produced from the signal SMR is supplied to a VCA 40 after it is added to a signal from a control circuit 44 at an adder 48. In the case of, for example, recording, when the muting is released by turning on a switching circuit 42 and a recording sound signal SA as shown is Fig. A is supplied to an input terminal 36, the gain of the VCA 40 constituting a negative feedback circuit is large at the releasing time and gradually becomes smaller because of the control signal SC. As a result, the recording sound signal SA whose level gradually becomes higher from the releasing time as shown in Fig. D is obtained at an output terminal 45 and aurally unpleasant feeling can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an audio signal processing circuit for recording and reproducing audio signals.

[Summary of the invention]

The present invention is an audio signal processing circuit for recording and reproducing an audio signal, by controlling the level at the transition point of the audio signal, thereby reducing the auditory discomfort at the transition point. .

[Conventional technology]

In a VTR (video tape recorder), an audio signal can be FM-modulated in a band between an FM-modulated luminance signal and a low-frequency converted chroma signal, frequency-multiplexed with a video signal, and recorded on a tilted track. Proposed.

FIGS. 5 and 6 show an example of a recording system and a reproducing system of such a VTR.

First, the recording system shown in FIG. 5 will be explained.

In the figure, a video signal Sv is supplied to a terminal (11). This video signal SV is supplied to a low-pass filter (2), and a luminance signal Y is taken out. This luminance signal Y is sent to a pre-emphasis circuit (3). and is supplied to the FM modulation circuit (5) via the clamp circuit (4).
For example, the sync chip is 4.2M from the M modulation circuit (5).
Hz, F so that the white beak is 5.4MHz
A modulated luminance signal YFM subjected to M modulation is obtained and supplied to an adder circuit (7) via a bypass filter +61.

In addition, the video signal SV from the terminal (11) is supplied to a bandpass filter (8) to take out the chroma signal C, which is passed through the frequency converter (1 (IIc supply) via the ACC circuit (9). Then, from this frequency converter σα, the carrier frequency is set to 743kHz, for example.
A low-pass converted chroma signal CD of z is obtained and supplied to an adder circuit (7) via a low-pass filter αV.

The audio signal S is supplied to the terminal α2.

This audio signal S is filtered by a low-pass filter α for band limiting.
3, and is supplied to the I'M modulation circuit α9 via a noise reduction circuit α4 including a pre-emphasis circuit and a compression circuit. Then, from this FM modulation circuit σ, the carrier frequency is, for example, 1.5 MHz, and the frequency deviation is ±150 KH.
A modulated audio signal AFM that is FM modulated with z is obtained, and a bandpass filter (L.

The signal is supplied to the adder circuit (7) via the adder circuit (7).

Therefore, from the adder circuit (7), the modulated luminance signal YFM
, a low frequency converted chroma signal cD and a modulated audio signal AFM are obtained, and this sum signal Sp is sent to a rotating magnetic head (18A) via a recording amplifier (l'n).

(18B). And these addition signals SP
is recorded as an inclined track on a magnetic tape aS which is wound obliquely around a tape guide drum (not shown).

Next, the reproduction system shown in FIG. 6 will be explained.

In the figure, a head (18A) is attached to the magnetic tape α9.

At (18B), the above-mentioned addition signal Sp is reproduced. This addition signal Sp is supplied to a bypass filter C211 via a reproducing amplifier (2), and a modulated luminance signal YFM is extracted. This modulated luminance signal YFM is passed through the limiter to FM
The luminance signal Y is supplied to the demodulation circuit (c), demodulated, and supplied to the addition circuit (c) via the de-emphasis circuit 041.

Further, the addition signal Sp from the reproducing amplifier is supplied to a low-pass filter □□□ to extract a low-pass converted chroma signal cD, and this chroma signal CD is supplied to a frequency converter. Then, from this frequency converter, a chroma signal C with a carrier frequency of, for example, 3.58 MHz is obtained, which is passed through a bandpass filter (to) to an adder circuit (c).
supplied to Therefore, the addition circuit (c) outputs an addition signal of the luminance signal Y and the chroma signal C, that is, the video signal SV.
is obtained and supplied to terminal □□□.

In addition, the addition signal Sp from the reproduction amplifier is supplied to a bandpass filter ■ whose center frequency is 1.5MHz.
The modulated audio signal AFM is taken out and supplied to six FM demodulation circuits via a limiter 6υ. Then, the audio signal SA is demodulated in this FM demodulation circuit c3, and this audio signal SA is supplied to the terminal (g) via a noise reduction circuit (b) including a low-pass filter (c), a de-emphasis circuit, and an expansion circuit. be done.

Further, the noise reduction circuits α and (2) in FIGS. 5 and 6 are configured as conventionally known, for example, as shown in FIG. 7.

In the figure, ``■'' is an input terminal to which a recorded audio signal Sm is supplied during recording and a reproduced audio signal Sm is supplied during playback.

This input terminal (to) is connected to the non-inverting input terminal of the operational amplifier C371. The output terminal of this operational amplifier OD is connected to its inverting input terminal via a resistor. Also, the output signal of this operational amplifier OD.

The number is the Lohas filter C3 that constitutes the En7 assist circuit.
1. VCA (Voltage Control Amplifier) (4G, low pass filter (4υ) that constitutes the emphasis circuit and switch circuit (43) is supplied to the inverting input terminal of the operational amplifier C371 through a series circuit. This switch circuit (43 is The output signal of the operational amplifier 0η is turned on and turned off during playback.The output signal of the operational amplifier 0η is passed through a bypass filter (43) that constitutes a weighting circuit (operation compensation circuit) to a control circuit (2) that includes a wave detector, a smoothing circuit, etc. supplied,
This control circuit (4J) uses a control signal to control the VCA (4J).
A gain of 0 is controlled. In this case, the smaller the level of the eight input audio signals, the smaller the gain of VCAC4 (i).

Further, output terminals (4) of the audio signal Sm during recording are derived from the output terminal of the operational amplifier 071, and output terminals (461) of the audio signal Sm during playback are derived from the output side of the low-pass filter (41). Ru.

In such a configuration, the switch circuit (4
2 is turned on and the low-pass filter shines, VCA (41),
The path of the low-pass filter (41) constitutes a negative feedback path,
At the output terminal (c), an audio signal Sm whose high frequency range is emphasized and whose level is compressed is obtained. On the other hand, during playback, the switch circuit (c) is turned off and the operation is reverse to that during recording, so that the restored audio signal Sm is obtained at the output terminal (c). Therefore, a good noise reduction effect can be obtained.

Note that a noise reduction circuit similar to the example shown in FIG.
(see figure).

[Problem that the invention seeks to solve]

By the way, for example, in the above-mentioned VTR, when the recording muting is canceled and the audio signal Sm to be recorded suddenly appears as shown in No. 81rA, the audio signal Sm to be reproduced also appears as shown in FIG. The sound appears suddenly, causing discomfort to the auditory sense. For example, in splicing recording, when the audio signals SA are not consecutive as shown in FIG. 9A, the reproduced audio signal s
A is also discontinuous as shown in B of the figure, which gives an unpleasant feeling to the auditory sense. The same applies when muting is applied during playback due to poor playback conditions.

In view of the above points, the present invention is intended to alleviate such auditory discomfort.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a variable gain circuit in the recording system or the reproduction system. As this variable gain circuit, for example, a noise reduction circuit I (Incorporated) is also used.

The gain of the variable gain circuit is gradually changed at transition points of the audio signal S (when muting is released, when recording is repeated, etc.).

[Effect]

At the transition point of the audio signal Sm, the level of the audio signal S^ is gradually changed, for example from low to high when muting is released, so that the sound does not suddenly come out when muting is released, for example. (, auditory discomfort is reduced.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIG. In FIG. 1, parts corresponding to those in FIG. 7 are given the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 1, (47) is a soft muting control circuit, and during recording, a recording muting signal SMB is supplied to this control circuit (47) as shown in FIG. 2B. This control circuit (A?) generates a control signal SC as shown in C in the figure, and this control signal SC is added to the control signal from the control circuit (441) by an adder (C). After VCA (supplied in 4Q).

In the above configuration, when recording (switch circuit (6) is on), muting is canceled and the terminal is tapped as shown in Figure 2A.
When a recorded audio signal SA as shown in FIG.
Therefore, the output terminal (C) K is high at the time of release and gradually becomes low after that, and the output terminal (C) K outputs the recorded audio signal S, whose level is gradually increased from the time of release, as shown in Fig. 2 DK. can get.

In this way, according to this example, the audio signal sA to be recorded when muting is released does not appear suddenly, and therefore the audio signal S to be reproduced also does not appear suddenly, thereby reducing the auditory sense. Pleasure is prevented.

Further, according to this example, since a noise reduction circuit is used as the variable gain circuit, it can be constructed at low cost.

Although the above embodiment is an example in which recording muting is canceled, when recording muting is not performed and audio signals are recorded discontinuously, the following procedure is performed.

That is, in FIG. 1, the control circuit (4η) is supplied with a recording start signal S8 as shown in FIG. 3B during recording (switch circuit (6) is on). The control circuit 0η generates a control signal SC as shown in FIG.

In this case, when the terminal (to) is supplied with a discontinuous recording audio signal Sm as shown in FIG.
It is once increased at the recording start point of the audio signal, and then gradually decreased, and a recorded audio signal S as shown in FIG. 3 DVc is obtained at the output terminal (45).

Therefore, in this case as well, auditory discomfort is prevented.

Furthermore, when the reproduction condition is poor during reproduction and muting is performed, the following procedure is performed.

That is, in FIG. 1, the control circuit Uη is supplied with a muting control signal SMP as shown in FIG. 4B during reproduction (switch circuit (c) is off).

The control circuit 0η generates a control signal SC as shown in FIG.

In this case, when the reproduced audio signal S as shown in FIG.
Thereafter, the level is gradually increased, and the audio signal S, whose level is gradually increased from when it is released, is obtained at the output terminal decoy, as shown in the fourth diagram.

Therefore, in this case as well, auditory discomfort can be prevented.

In addition to the above-mentioned cases, fade-in and fade-out can be similarly performed during recording and reproduction.

Further, although the above-mentioned embodiment utilizes a noise reduction circuit, a variable gain circuit may be provided separately in the recording system or the reproduction system.

〔Effect of the invention〕

According to the present invention described above, at the transition point of the recorded or reproduced audio signal, the level is gradually changed.
Auditory discomfort at this transition point can be reduced.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, fs2 diagram is a diagram for explaining the same, FIG. 3 and WXA diagram are diagrams for explaining other embodiments of the present invention, respectively, and FIG. - FIG. 9 are diagrams for explaining conventional examples. I and (2) are noise reduction circuits, 07) is a voltage control amplifier, and 07) is a soft muting control circuit. Figure 1: Illustration of Article 4 Audio signal Figure 3: Illustration of reproduced audio signal Figure 4 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] In a circuit for recording or reproducing an audio signal, a variable gain circuit is provided in the recording system or the reproducing system, and at a transition point of the audio signal, a variable gain circuit is generated based on a signal indicating the transition point. An audio signal processing circuit characterized in that the gain of the variable gain circuit is gradually changed by a control signal.