JPH05303385A - Recording and reproducing device - Google Patents

Abstract

PURPOSE:To effectively suppress periodic noises picked up by microphone by subtracting periodic noises of a rotating body from the sound signals outputted from the microphone. CONSTITUTION:Sound signals are sampled at a sampling frequency which is an interger multiple frequency of the rotation frequency of a rotating drum and inputted to an averaging circuit 5. On the other hand, the data, which are written from a memory circuit 6 with the timing synchronized to the rotating period of the rotating drum and are written equivalent to one period prior to the rotating period of the drum, are read and inputted to the circuit 5. At the circuit 5, the averaged signals, which are the average of digital sound signals and the data read from the circuit 6, are obtained and are written into the addresses of the circuit 6. By this averaging process, the periodic noises, which are produced by mixing the sound signals picked up by a microphone 1 and the noises generated by the rotating drum, are extracted. The extracted signals are transmitted to a subtracting circuit 10 and subtracted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus for recording / reproducing an audio signal picked up by a microphone on a recording medium, such as a camera type video tape recorder.

[0002]

2. Description of the Related Art FIG. 6 shows a frequency-multiplexed recording of a sound signal picked up by, for example, a microphone and frequency-modulated (hereinafter referred to as FM modulation) on a magnetic tape together with a video signal picked up by an image pickup device and FM-modulated. , 8mm VT
FIG. 1 is a block diagram showing a configuration of a camera body type VTR according to an R system, in which 1 is a microphone, 2 is a microphone amplifier circuit, 11 is a recording audio signal processing circuit, 12 is an image pickup device, 13 is a recording video signal processing circuit, and 14 is an adding circuit. , 15 is a recording amplification circuit, 16 is a rotary transformer, 17 is a rotary head, 18 is a magnetic tape, 20 is a switch circuit, 21 is a reproduction amplification circuit, and 22 is
Playback audio signal processing circuit, 26, audio signal output terminal, 30
Is a reproduced video signal processing circuit, and 31 is a video signal output terminal.

Next, the operation will be described. At the time of recording, the audio signal picked up by the microphone 1 is
The signal is amplified to a predetermined level by the microphone amplifier circuit 2 and sent to the recorded voice signal processing circuit 11. The recording / audio processing circuit 11 performs filtering processing for suppressing signal components in unnecessary bands with fixed characteristics as shown in FIG. 5, level compression processing with a predetermined compression ratio for expanding the dynamic range, and FM modulation / demodulation. In order to suppress the triangular noise generated in the process, emphasis processing for emphasizing high frequency components is performed at the time of recording, and the FM is applied to a predetermined frequency band.
The signal is modulated and sent to the adding circuit 14. On the other hand, the video signal picked up by the image pickup device 12 is subjected to a processing such as a filtering process or an emphasis process for suppressing a signal component in an unnecessary band in the recording video signal processing circuit 13 and is FM-modulated into a predetermined frequency band. It is sent to the adder circuit 14. In the adder circuit 14, the FM-modulated audio signal and the video signal are added together to form a frequency-multiplexed recording signal. Then, the recording signal sent to the recording amplifier circuit 15 is amplified and then sent to the rotary head 17 attached to the rotary drum via the switch circuit 20 and the rotary transformer 16, and is recorded on the magnetic tape 18.

At the time of reproduction, the signal reproduced from the magnetic tape 18 by the rotary head 17 passes through the rotary transformer 16 and the switch circuit 20, is amplified by the reproduction amplifier circuit 21, and is then reproduced by the reproduction audio signal processing circuit 22. It is sent to the reproduced video signal processing circuit 30. In the reproduced audio signal processing circuit 22, the FM-modulated audio signal is separated from the frequency-multiplexed reproduced signal, subjected to FM demodulation and de-emphasis processing, and then output to the audio signal output terminal 26 as a reproduced audio signal. To be done. Similarly, in the reproduced video signal processing circuit 30, the FM-modulated video signal is separated from the frequency-multiplexed reproduced signal, FM demodulation and de-emphasis processing are performed, and the reproduced video signal is output to the video signal output terminal 31. It is output as a signal.

[0005]

The conventional recording / reproducing apparatus is configured as described above. For example, noise generated by the rotation of the rotary drum, or when the rotary head 17 contacts the magnetic tape 18 The noise generated by the vibration of the magnetic tape 18 is picked up by the microphone 1 and mixed into the audio signal picked up by the microphone 1 as noise. Although such noise is suppressed to some extent in the filtering process in the recording audio signal processing circuit 11 in the subsequent stage, for example, frequency components distributed over the middle range of several KHZ are recorded on the magnetic tape 18 with almost no suppression. Will end up. Also, for example, noise generated in the output of the microphone 1 due to the vibration generated by the rotation of the rotating drum or the vibration generated by the rotation of the capstan for running the magnetic tape 18 being transmitted to the microphone 1. ,
The same can be said. The noise due to the mixing of noise as described above can be suppressed to some extent by giving the microphone 1 directivity, but it cannot be said to be sufficient.
Further, noise caused by the transmission of vibrations to the microphone 1 can be suppressed to some extent by providing the microphone 1 with an antivibration structure, but it is difficult to provide sufficient antivibration structure due to dimensional restrictions and the like. Is.
Further, as the recording / reproducing apparatus becomes smaller, the distance between the microphone and the noise and vibration source becomes smaller, and such noise is likely to occur. Further, if such noise is once mixed and recorded, it will be reproduced as it is at the time of reproduction.

[0006] As one method for solving the above problems, for example, as proposed in Japanese Patent Application No. 226200, a microphone for noise detection is provided via a noise detection microphone provided separately from the voice pickup microphone. There has been proposed a method of obtaining a voice signal in which noise is suppressed by correcting the frequency characteristic of a noise signal generated by an adaptive filter circuit and then subtracting it from the voice signal obtained via a voice pickup microphone.

[0007] However, in the above method, while a voice signal in which noise is effectively suppressed is obtained, the voice generated from the subject or the like when performing the adaptive operation of the adaptive filter is so small that it can be almost ignored. It is necessary to make a distinction, and in some cases, the adaptive filter must be operated in a quiet place prior to the start of recording. Further, in order to converge the characteristics of the adaptive filter by using various adaptive algorithms, some convergence time is required, depending on conditions such as the adaptive algorithm used. Furthermore, it is necessary to use relatively expensive components such as a DSP (digital signal processor) in order to carry out the calculation of the adaptive filter, particularly the adaptive algorithm.

The present invention has been made in order to solve the above-mentioned problems, and the recording / reproducing apparatus has, for example,
Noise caused by rotation of a rotating body such as a rotating drum, or
It is possible to effectively suppress and record periodic noise that occurs when vibrations are mixed in a voice signal picked up by a microphone, and moreover, as in the method using the adaptive filter as described above, It is not necessary to determine that the sound generated from the sound is almost negligible, and periodic noise can be suppressed without delay time when recording is restarted while recording is stopped or power supply is stopped. In addition, when reproducing a voice signal recorded with periodic noise generated by mixing noise or vibration due to rotation of a rotating body such as a rotating drum that also performs similar rotation during reproduction, A recording / reproducing apparatus capable of effectively suppressing such noise from a reproduced audio signal can be constructed relatively easily and at low cost. The interest.

[0009]

According to a first aspect of the present invention, there is provided a recording / reproducing apparatus in which a microphone which picks up a sound and outputs it as an audio signal and a cycle caused by rotation of a rotating body of the recording / reproducing apparatus. Periodic noise extraction means for extracting the static noise from the voice signal output from the microphone,
Subtraction means for subtracting the output signal of the periodic noise extraction means from the audio signal output from the microphone.

According to the second aspect of the present invention, in the recording / reproducing apparatus, the periodic noise generated due to the rotation of the rotating body of the recording / reproducing apparatus at the time of recording is extracted from the voice signal output from the microphone and recorded / reproduced. And a subtraction unit for subtracting the output signal of the periodic noise extraction unit from the voice signal output from the microphone and recorded and reproduced.

Further, the periodic noise extracting means of the recording / reproducing apparatus according to claim 3 of the present invention synchronizes the input audio signal with the rotation frequency of the rotator and is an integer multiple of the rotation frequency of the rotator. An analog-to-digital conversion means for sampling at a sampling frequency to convert into a digital audio signal, a memory means for reading and writing in synchronization with the rotation cycle, the digital audio signal, and an output signal from the memory means. And averaging means for averaging and outputting.

Further, the recording / reproducing apparatus according to a fourth aspect of the present invention has a memory means for holding the written data even while the recording / reproducing apparatus stops recording and the power supply is stopped.

[0013]

The microphone according to claim 1 of the present invention is
Sound is picked up and a sound signal is output. The periodic noise extraction means extracts the periodic noise generated due to the rotation of the rotating body of the recording / reproducing apparatus from the audio signal output from the microphone. The subtracting means subtracts the output signal of the periodic noise extracting means from the audio signal output from the microphone.

Further, the periodic noise extracting means according to claim 2 of the present invention outputs the periodic noise generated due to the rotation of the rotating body of the recording / reproducing apparatus at the time of recording from the microphone to record / reproduce the voice signal. Extract from. The subtracting means subtracts the output signal of the periodic noise extracting means from the audio signal output from the microphone and recorded and reproduced.

In the analog-digital converting means according to claim 3 of the present invention, the input audio signal has a sampling frequency which is synchronized with the rotation frequency of the rotating body and which is approximately an integral multiple of the rotating frequency of the rotating body. Sampling and converting to digital audio signal. The memory means performs reading and writing in synchronization with the rotation cycle. The averaging means averages (outputs) the digital audio signal and the output signal from the memory means and outputs the averaged signal.

Further, the memory circuit according to the fourth aspect of the present invention holds the data even when the recording / reproducing apparatus stops recording and the power supply is stopped.

[0017]

EXAMPLES Example 1. Hereinafter, for example, 8 mmV of this invention
An example of TR will be described with reference to the drawings. In FIG. 1, 1 is a microphone, 2 is a microphone amplifier circuit, 3 is a low-pass filter, 4 is an analog / digital conversion circuit (hereinafter referred to as A / D conversion circuit), 5
Is an averaging circuit, 6 is a memory circuit, 7 is a digital / analog conversion circuit (hereinafter referred to as D / A conversion circuit), 8 is a low-pass filter, 9 is a periodic noise extraction circuit, and 10 is , A subtraction circuit, 11 a recording audio signal processing circuit, 12 an image pickup device, 13 a recording video signal processing circuit, 14
Is an adder circuit, 15 is a recording amplifier circuit, 16 is a rotary transformer, 17 is a rotary head, and 18 is a magnetic tape. However, in the present embodiment, there is a case where the periodic noise generated due to the noise accompanying the rotation of the rotary drum to which the rotary transformer 16 and the rotary head 17 are attached is mixed in the audio signal picked up by the microphone 1. explain.

Next, the operation will be described. For example,
The sound emitted from the subject is picked up by the microphone 1 to become a sound signal, amplified by the microphone amplification circuit 2 to a predetermined level, and then sent to the periodic noise extraction circuit 9. In the periodic noise extraction circuit 9, first, the input audio signal is sent to the A / D conversion circuit 4 after the unnecessary signal band component is removed by the low-pass filter 3. The input audio signal is sampled by the A / D conversion circuit 4 at a sampling frequency m · F _d (m is an integer) that is an integral multiple of the rotation frequency F _d of the rotary drum, converted into a digital audio signal, and averaged. It is input to the circuit 5. On the other hand, the timing synchronized with the rotation cycle of the rotating drum, that is, the rotation cycle of the rotating drum is T
Then, at a timing with a cycle of T / m (m is an integer), the data written one cycle before the rotation cycle of the rotary drum is read from the memory circuit 6 and input to the averaging circuit 5. It The averaging circuit 5 obtains an averaging signal of the digital audio signal converted by the A / D conversion circuit 3 and the data read from the memory circuit 6 by a simple calculation as shown in the following equation. A _n = A _n-1 + (S _n −A _n-1 ) / k where A
_n is the averaging output signal A _{n−1, which} is written one cycle before the rotation cycle of the rotary drum, and the averaging signal S _n read from the memory circuit 6 is output from the A / D conversion circuit 4. The output digital audio signal K is a constant

FIG. 2 shows how the memory circuit reads and writes at this time. Since the sampling frequency for A / D conversion is m times the rotation frequency of the rotary drum, S _n , A _n−1 , and A _n are present in m units per rotation period of the rotary drum. .. In the figure,
S _on , S _1.n, ..., S _m-1.n are the digital audio signals output from the A / D conversion circuit 4, and A _on-1 , A _{m
1.n-1, ····, A m} -1. N-1 is the averaging signal to one period before the rotation period of the rotary drum is written in the memory circuit 6, A _on, A _{1 .n} , ..., A
_m-1.n represents the averaging output signal. For example, the averaging signal A _on-1 of one rotation cycle of the rotating drum
Is read from the memory circuit 6 and the A / D conversion circuit 4
From the digital audio signal S _on output from the averaging signal A by averaging as shown in the above equation.
After obtaining _on , the data is written in the address of the memory circuit 6 in which A _on-1 was written. Such processing is repeated m times in one rotation cycle of the rotary drum.

Here, the averaging operation as described above is a method called so-called synchronous addition, and k in the above equation is used.
The signal having a periodicity synchronized with the rotation period of the rotary drum, that is, in the case of the present embodiment, was picked up by the microphone 1 by the averaging operation of several times to several tens times, though it depends on the value of The periodic noise generated by mixing the noise generated from the rotating drum with the voice is extracted. Further, if the value of k is increased to several tens of times or more, the periodic noise can be extracted with almost no influence even when the sound generated from the subject is loud.

Now, the data A _n-1 written one cycle before the rotation cycle of the rotary drum and read from the memory circuit 6, that is, the sound picked up by the microphone 1 is generated from the rotary drum. An extracted signal of noise generated by mixing noise is sent to the D / A conversion circuit 7, converted into an analog signal, and D / A is converted by the low-pass filter 8.
After removing the unnecessary band signal component generated accompanying the conversion, it is sent to the subtraction circuit 10. The cycle generated by the subtraction circuit 10 from the sound signal output from the microphone amplification circuit 2 to the output signal of the periodic noise extraction circuit 9, that is, the sound picked up by the microphone 1 mixed with the noise generated from the rotating drum. The extracted signal of the sex noise is subtracted.

As described above, the recording sound signal processing circuit 11 performs a predetermined processing on the sound signal in which the periodic noise generated by mixing the sound picked up by the microphone 1 with the noise generated from the rotating drum is suppressed. After being applied, it is recorded on the magnetic tape 11 in the same manner as in the conventional example.

Example 2. As another embodiment of the first aspect of the invention, a case where the memory circuit 6 retains written data even when recording of the recording / reproducing apparatus is stopped and power supply is stopped is described below. In FIG. 3, 6
Is a memory circuit, 40 is a power supply for recording / reproducing apparatus, 41 is
A memory circuit backup battery, 42 is a first diode, 43 is a second diode, and 44 is a power supply terminal of the memory circuit.

According to the configuration of the first embodiment, in order to obtain the periodic noise extraction signal as the output signal of the periodic noise extraction circuit 9, it is necessary to perform the averaging operation several times to several tens times. There is some delay between the start of recording and the effective suppression of periodic noise. Even during recording stop of the recording / reproducing apparatus and power supply stop, the data written in the memory circuit 6 is retained (backed up) without being lost by the memory circuit backup battery 41. This embodiment is configured to eliminate such a delay. During the recording of the recording / reproducing apparatus and the stop of the power supply, the power of the recording / reproducing apparatus is supplied to the power supply terminal 44 of the memory circuit through the first diode 42. During recording stop of the recording / reproducing apparatus and power supply stop, the battery for memory circuit backup passes through the second diode 43.
41 supplies power to the power supply terminal 44 of the memory circuit. In this way, the periodic noise before the recording is stopped, that is, the data in the memory circuit 6 is not lost when the recording is stopped and the power supply is stopped. By sending the read data to the subtraction circuit 10 and subtracting it from the audio signal output from the microphone, it is possible to immediately suppress the periodic noise.

Here, for example, when noise or vibration generated from the rotating drum or the like accompanies a change over time to some extent, when there is not such a long time before the recording is stopped or the power supply is stopped and the recording is restarted. , Stop recording, or
There is no problem even if the data written in the memory circuit 6 before the power supply is stopped, that is, the periodic noise extraction signal is regarded as that when the recording is restarted.

Example 3. Another embodiment of the first invention will be described below with reference to the drawings. Referring to FIG. The averaging signal read from the memory circuit 6 and the digital audio signal output from the A / D conversion circuit 4 are input to the subtraction circuit 10 of FIG.

Next, the operation will be described. First, in the audio signal picked up by the microphone 1, unnecessary frequency components are removed by the low-pass filter 3,
It is output as a digital audio signal by the A / D changing circuit 4. Example 1. Similarly, the averaging signal A _n read from the memory circuit 6 is sent to the subtraction circuit 10 as a digital signal. In the subtraction circuit 10, the averaged signal, that is, the extracted periodic noise is converted into an A / D signal.
After being subtracted from the digital audio signal output from the conversion circuit 4 and converted into an analog signal by the D / A conversion circuit 7, the unnecessary band signal component generated due to the D / A conversion is removed by the low-pass fighter 8. , To the recorded voice signal processing circuit 22.

As described above, the recording sound signal processing circuit 11 performs a predetermined processing on the sound signal in which the periodic noise generated by mixing the sound picked up by the microphone 1 with the noise generated from the rotating drum is suppressed. After being applied, it is recorded on the magnetic tape 11 in the same manner as in the conventional example.

Incidentally, in the above third embodiment. In the above configuration, the digital signal output from the subtraction circuit 10 is converted into an analog signal by the D / A conversion circuit 7 and then output to the recording audio signal processing circuit 11. However, the audio signal is recorded and reproduced as a digital signal. Such as a digital V
The TR is particularly characterized in that the recording process in the subsequent stage can be performed without converting the analog signal by the D / A conversion circuit.

Example 4. An embodiment of the second invention of the present invention will be described with reference to the drawings. In FIG. 5, 3 is a low-pass filter, 4 is an analog / digital conversion circuit (hereinafter referred to as A / D conversion circuit), 5 is an averaging circuit, 6 is a memory circuit, and 7 is a digital / analog. A conversion circuit (hereinafter referred to as a D / A conversion circuit), 8 is
Low-pass filter, 9 is a periodic noise extraction circuit, 10 is a subtraction circuit, 16 is a rotary transformer, 17 is a rotary head, 18 is a magnetic tape, 21 is a reproduction amplification circuit, 22 is a reproduction audio signal processing circuit, 23 Is an audio signal output terminal. However, in the present embodiment, there is a case where such periodic noise is suppressed from the recorded audio signal including the noise due to the noise caused by the rotation of the rotary drum to which the rotary transformer 16 and the rotary head 17 are attached. explain.

Next, the operation will be described. First, as in the conventional example, the frequency-multiplexed signal recorded on the magnetic tape 18 is
After being reproduced by the rotary head 17, passed through the rotary transformer 16, amplified by the reproduction amplifier circuit 21, and subjected to predetermined processing in the reproduction audio signal processing circuit 22, the periodic noise extraction circuit 9 and subtraction are performed as a reproduction audio signal. Sent to the circuit. Here, the rotation of the rotary drum at the time of recording is controlled so as to be synchronized with the vertical synchronizing signal of the recorded video signal. Therefore, a synchronizing relationship is established between the vertical synchronizing signal of the video signal and the periodic noise due to the noise accompanying the rotation of the rotating drum. During reproduction, the rotation of the rotary drum is controlled so as to synchronize with a reference signal obtained from an internal reference signal generator, unlike during recording. In this way, the reference signal differs between recording and playback,
Therefore, although the rotation speed of the rotating drum is slightly different,
The rotation of the rotary drum and the reproduced video signal are in a synchronous relationship.
Therefore, the periodic noise is synchronized with the rotation of the rotary drum even during reproduction. Therefore, similar to the first embodiment, such periodic noise included in the reproduced audio signal is
It is extracted by the periodic noise extraction circuit 9. Then, the subtraction circuit 10 subtracts the periodic noise extracted by the periodic noise extraction circuit 9 from the reproduced audio signal, and outputs the audio signal to the audio signal output terminal 23.

In this way, even when a voice signal containing periodic noise generated by mixing noise generated from the rotating drum, for example, is recorded in the voice picked up by the microphone 1, the reproduced voice signal is also recorded. It is possible to suppress and output such a periodic noise included in.

In each of the above-mentioned embodiments, the periodic noise has been described as being mainly caused by the noise generated by the rotation of the rotary drum. However, for example, it is caused by the vibration generated by the rotation of the rotary drum. Even when it does, the same effect can be obtained. Further, the rotating body serving as a noise source or a vibration source may be, for example, a capstan for running a magnetic tape. Further, the memory circuit may be a shift register or the like.

[0034]

Since the present invention is configured as described above, according to claims 1 and 3, noise or vibration caused by the rotation of a rotating body such as a rotating drum of the recording / reproducing apparatus causes a microphone. It is possible to effectively suppress and record the periodic noise generated by mixing with the audio signal picked up by the sound signal. Moreover, like the method using the adaptive filter as described above, the noise is generated from the subject. A recording / reproducing apparatus which does not need to determine that the sound is almost negligible is relatively simple and can be constructed at low cost.

According to the second aspect of the present invention, in reproducing a voice signal recorded with periodic noise generated by mixing noise or vibration caused by the rotation of a rotating body such as a rotating drum. Also, such noise can be effectively suppressed from the reproduced audio signal.

According to claim 4 of the present invention, in addition to the above effects, even when recording is restarted while recording is stopped or power supply is stopped, periodic noise is suppressed and recording is performed without delay time. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment (embodiment 1) of the first invention of the present invention.

FIG. 2 is an operation explanatory diagram of writing and reading in the memory circuit of the first invention of the present invention.

FIG. 3 is another embodiment (Embodiment 2) of the first invention of the present invention.
Block diagram showing the configuration of FIG.

FIG. 4 is another embodiment (Embodiment 3) of the first invention of the present invention.
Block diagram showing the configuration of FIG.

FIG. 5 is a block diagram showing the configuration of an embodiment (embodiment 4) of the second invention of the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional example.

FIG. 7 is a frequency characteristic diagram showing a filtering characteristic of a recorded audio signal processing circuit of a conventional example.

[Explanation of symbols]

 1 Microphone 4 Analog-to-digital conversion circuit 5 Averaging circuit 6 Memory circuit 9 Periodic noise extraction circuit 10 Subtraction circuit

Claims (4)

[Claims] 1. A recording / reproducing apparatus for recording an audio signal on a recording medium, wherein a microphone that picks up sound and outputs the audio signal and a rotating body included in the recording / reproducing apparatus from the audio signal output from the microphone. Periodic noise extraction means for extracting periodic noise caused by the rotation of
A recording / reproducing apparatus comprising: a subtracting unit that subtracts an output signal of the periodic noise extracting unit from an audio signal output from the microphone. 2. A recording / reproducing apparatus for reproducing an audio signal from a recording medium in which an audio signal picked up by a microphone and output is recorded, wherein the recording / reproducing at the time of recording from the audio signal output from the microphone and recorded / reproduced. A periodic noise extracting means for extracting the periodic noise generated due to the rotation of the rotating body of the apparatus; and a subtracting means for subtracting the output signal of the periodic noise extracting means from the digital audio signal. Characteristic recording / reproducing device. 3. The periodic noise extracting means samples the input audio signal at a sampling frequency which is synchronized with the rotation cycle of the rotating body and is approximately an integral multiple of the frequency of the rotating body to convert it into a digital audio signal. Analog-to-digital conversion means, memory means for reading and writing in synchronization with the rotation cycle, and an average for averaging and outputting the digital audio signal and the output signal from the memory means. The recording / reproducing apparatus according to claim 1 or 2, further comprising: 4. The memory means of the periodic noise extraction means retains written data even while recording of the recording / reproducing apparatus is stopped and power supply is stopped. The recording / reproducing apparatus as set forth in claim 3.