JPH07311903A - Magnetic recording apparatus with built-in microphone - Google Patents

Abstract

PURPOSE:To remove tapping sounds of a tape by a pre-holding audio signals of a built-in microphone for a period when the tapping sounds are presumed to be generated. CONSTITUTION:An output of an ALC circuit 9 is input to an FM modulator 15 through a noise-reducing circuit 12 and a switch 14. After the output is FM modulated at the modulator 15, the output is, through a recording circuit 30 of a VTR part, recorded together with a video signal to a magnetic tape by magnetic heads A and B. Meanwhile, when it comes a time point delayed a fixed time from an edge of an RF switching pulse, namely, when tapping sounds of a tape are to be brought about, an output of a monomultiplier 21 becomes an H level because of a quasi-stable period, and therefore a pre-hold circuit 6 holds the immediately preceding level during the period. Since the quasi-stable period is set to agree with a time period while the tapping sounds continue, the pre-holding is kept while the tapping sounds are generated. The tapping sounds are thus completely removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a microphone (hereinafter referred to as
The present invention relates to a sound pickup device of a camera-integrated VTR in which a camera unit having a built-in microphone) and a VTR unit for recording video and audio signals formed by the camera unit on a magnetic tape are integrated.

[0002]

2. Description of the Related Art In a camera-integrated VTR such as an 8 mm camcorder, noise generated by rotation of a cylinder around which a tape is wound, that is, a so-called tape tapping noise is picked up by a microphone, which is desired as annoying noise. Will be recorded on the tape together with the sound signal of.

Conventionally, in order to remove this noise, the frequency characteristic of the built-in microphone is lowered, or the sound signal component of the frequency at which the tape tapping sound is distributed is dropped by a trap filter to reduce the tape tapping sound. .

[0004]

Usually, the frequency spectrum of the tapping sound itself is 2.8 k in the audio signal.
Since this band is in the vicinity of Hz, this band exists in the audible band of the original audio signal desired to be recorded, and it is necessary to reduce the band component of this tapping sound with a filter in a part of the band of the desired audio signal. Will also be reduced, and the sound quality of the audio signal will be impaired.

[0005]

According to the present invention, a built-in microphone, a cylinder around which a magnetic tape is wound, at least two magnetic heads mounted on the cylinder, and one of the magnetic heads is a signal to the magnetic tape. RF for controlling the timing for sequentially selecting recording heads
RF switching pulse creating means for creating a switching pulse, pre-holding means for inputting a voice signal generated by a microphone, directly outputting the voice signal when not operating, and pre-holding the voice signal when operating. Only between the recording means for recording the output of the pre-holding means on the magnetic tape, the timing signal generating means for generating the timing signal for a certain period H after the predetermined time T from the edge of the RF switching pulse, and the period during which the timing signal is generated. A feature is that the pre-holding means is kept in an operating state, and particularly when the external microphone is attached to the external mic attachment part, the audio signal input to the pre-holding circuit is replaced by the recording circuit instead of the output of the pre-holding circuit. It is characterized by comprising a switching means for supplying to the.

As another means, a trap means for removing a predetermined frequency component from the voice signal generated by the built-in microphone, a voice signal generated by the microphone and a selection for selectively selecting the output of the trap means. Means, recording means for recording the output of the selecting means on the magnetic tape, and a predetermined period H after a predetermined time T from the edge of the RF switching pulse.
A timing signal generating means for generating a timing signal is provided over a range, and the output of the trap means is selected by the selecting means only while the timing signal is being generated. , A switching means for supplying a sound signal from a microphone to the recording circuit instead of the output of the selecting means.

Furthermore, the audio signal generated by the built-in microphone, which is selected as the output of the trap means by the selecting means, is delayed by the delay means by the time required for signal processing by the trap means. Characterize.

[0008]

Since the present invention is configured as described above, only the frequency band component in which the audio signal of the built-in microphone is pre-held or the tape tapping sound is present in the period when the tape tapping sound is expected to be generated. . Furthermore, passing the audio signal through the pre-holding means or the trapping means is limited when the built-in microphone is used.
When using an external microphone, the unnecessary tapping sound removal operation can be prohibited.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit block diagram of the first embodiment device. In the figure, 1 is a built-in microphone that is integrally mounted in advance in a VTR body with a built-in camera, 2 is an external microphone jack into which an external microphone can be inserted separately from the built-in microphone 1, and 3 is an external audio source, such as a tape player. Is a line input terminal capable of inputting an audio signal from the microphone 1. The audio signal picked up by the microphone 1 is supplied to the fixed terminal 4a of the switch 4, and the audio signal input from the external microphone jack 2 is input by the switch 4. It is supplied to the fixed terminal 4b. Here, the output line of the external microphone jack 2 is connected to the voltage line Vcc via a resistor. If the external microphone is not connected to the external microphone jack 2, the output line is grounded, and if the external microphone is connected. The output line is blocked from being grounded, and the audio signal from the external microphone is biased with the voltage Vcc and output.

Reference numeral 5 is a microphone amplifier for amplifying the audio signal of either the microphone 1 selected by the switch 4 in the preceding stage or the external microphone. The output of this amplifier is from the front hold circuit 6 and the switch 7 in the succeeding stage. It is output to the fixed contact 7b.

The front hold circuit 6 is a mono-multi 2 which will be described later.
The preceding audio signal level is held in the one-output metastable period, and the output of the pre-hold circuit 6 is output to the fixed contact 7a of the switch 7. Fixed contacts 7a, 7
The output of the switch 7 that selects the audio signal applied to b is output to the fixed terminal 8 a of the switch 8. here,
The switching control of the switches 4 and 7 is executed by the output of the external microphone jack 2, and when the output line of the external microphone jack 2 is grounded and the output level is zero level (L level), both switches are on the fixed contacts 4a, 7a side. Switch to
If the voltage Vcc is at a biased level (H level), it switches to the fixed contacts 4b, 7b side.

A voice signal input from the line input terminal 3 is applied to the fixed contact 8b of the switch 8, and the switch 8 is switched by a manual operation of a switching operation button for selecting camera input or external line input. If the selection signal is at the H level, the camera side is selected and the fixed terminal 8a is switched to select the switch 7 output. If the selection signal is at the L level, The audio signal from the line input terminal is selected by switching to the fixed contact 8b.

The output of this switch 8 is the ALC circuit 9 in the subsequent stage.
Through the fixed contact 10a of the switch 10 and the switch 11
Is output to the fixed contact 11a. Here, the ALC circuit 9 performs level control so that the input audio signal has a constant level.

Both the switches 10 and 11 are switched to the fixed contacts 10a and 11a side in the recording mode. In this recording mode, the output of the ALC circuit 9 is supplied to the noise reduction circuit 12 via the switch 10 and the switch 11 is also supplied.
Then, it is amplified by the line amplifier 13 and supplied to the speaker as a monitor output.

The noise reduction circuit 12 is a well-known type which reduces noise in the entire audible band in the audio signal, and the output of the noise reduction circuit 12 is output to the fixed contact 14a of the switch 14.

Similarly to the switches 10 and 11, the switch 14 also switches to the fixed contact 14a side in the recording mode,
In the recording mode, the output of the noise reduction circuit 12 that has passed through the switch 14 is FM-modulated by the FM modulator 15 to be VTR.
It is supplied to the recording circuit 30 of the other part, mixed with a video signal obtained by an image pickup circuit (not shown), and output to the switch 31.

The switch 31 is selectively switched to one of the fixed terminals 31a and 31b in response to an RF switching pulse, which will be described later, so that the video and audio signals are transferred to the magnetic head A,
It is alternately output to B every one field (= 1/60 sec).

Reference numeral 16 denotes a bandpass filter (BPF) which receives a reproduction RF signal reproduced from the magnetic tape in the reproduction circuit 32 of the VTR section in the reproduction mode and extracts only the FM audio signal in the RF signal. FM
The audio signal is FM demodulated by the FM demodulator 17 and output to the fixed contact 10b of the switch 10.

In the reproduction mode, the switches 10, 11, 14 are switched to the fixed contacts 10b, 11b, 14b, and the reproduced voice signal is input to the noise reduction circuit 12 to reduce noise, and then the switches 14, 11, line amplifier. It is supplied to the speaker via 13 and the reproduction audio signal can be monitored.

Magnetic tape 3 in recording circuit 30 of VTR section
At the time of recording a signal on the disk 3, at least two magnetic heads A and B having different azimuths are arranged to face the cylinder 34 as shown in FIG. The magnetic heads A and B are adapted to exchange signals with the tape by rotating the cylinder while being pulled out and wound around the cylinder 34. Which of the magnetic heads A and B is selected is
The R switching pulse is determined by the RF switching pulse as shown in FIG. 2B, and the RF switching pulse is RF switched based on the PG pulse from the well-known PG detector 22 that magnetically detects the rotation state of the cylinder 34. Created by the pulse creation circuit 23, this head switching sequentially switches a pair of heads every half rotation of the cylinder, and one of the heads is always in contact with the magnetic tape wound around the cylinder to enable signal exchange. become. Incidentally, FIG.
When the RF switching pulse in (b) is at H level,
The switch 31 is switched to the fixed contact 31a side and signal recording is performed by the magnetic head A. When the switch 31 is at the L level, it is switched to the fixed contact 31b side and signal recording is performed by the magnetic head 31b.

Cylinder 34 around which magnetic tape 33 is wound
The tape tapping sound generated by rotating the cylinder is a noise generated when the magnetic head mounted on the cylinder separates from the magnetic tape wound on the cylinder, and is an ideal state where the magnetic tape is wound 180 degrees around the cylinder. Then, the separation of each head from the magnetic tape occurs in synchronization with the switching timing of the head, that is, in synchronization with the edge of the RF switching pulse. In reality, however, the magnetic tape is (180 + α) with respect to the cylinder.
The heads are switched every 180 degrees in a state in which the heads are wound only once, that is, in the state of being additionally wound by α degrees. Therefore, the position where the tape tapping sound is generated is delayed from the edge of the RF switching pulse by the time required for the head to rotate by this α degree (time T described later).

In other words, the tape tapping sound is generated at a time point when the head abutting against the magnetic tape and the magnetic tape have a constant relative positional relationship, and from the switching time of the head, that is, the rising edge or the falling edge of the RF switching pulse. It is generally known that it occurs at a time point that is delayed by a fixed time T (about 0.5 msec), and that this generation period is about time K (about 1.8 msec).

Therefore, in this embodiment, the RF switching pulse used for head switching in the VTR section is delayed by the delay circuit 20.
To enter. Here, as shown in (c) of FIG. 2, the delay time of the delay circuit 20 is set to the constant time T, and the output of the delay circuit 20 is input to the monomulti 21,
As shown in FIG. 2D, the time H during which the tapping sound is considered to last the metastable time of the mono-multi 21 is considered to be H.
Is set to. As described above, the pre-hold circuit 6 holds the immediately preceding level during the metastable time of the output of the monomulti 21.

Next, the operation of the circuit block diagram of FIG. 1 will be described. When the external microphone is not connected to the external microphone jack 2, the output of the external microphone jack 2 is always at L level, and the switches 4 and 7 are switched to the fixed contacts 4a and 7a side, respectively. Further, when the switch 8 is switched to the fixed contact 8a side by the operation of the selection operation button and the camera portion of the VTR with camera is in the photographing state and the VTR portion is in the recording state, the switches 10, 11, 14 are switched. Switch to the fixed contacts 10a, 11a, 14a, respectively, and in this state, the audio signal picked up by the built-in microphone 1 is amplified by the microphone amplifier 5 via the switch 4 and input to the pre-hold circuit 6. To be done.

In this state, when the output of the mono-multi 21 is at the L level, the pre-hold circuit 6 does not execute the pre-hold operation, and the output of the microphone amplifier 5 remains as it is.
Is input to the fixed terminal 11a of the switch 11 via the switches 7 and 8 and the ALC circuit 9, and is output to the speaker as a monitor output via the line amplifier 13.
Further, the output of the ALC circuit 9 is inputted to the FM modulator 15 through the noise reduction circuit 12 and the switch 14 and is FM-modulated. Recorded on tape.

On the other hand, when the time point delayed by a certain time T from the edge of the RF switching pulse, that is, the time point when the tapping sound is generated, the output of the mono-multi 21 becomes a metastable period and becomes H level. Then, as shown in FIG. 2 (e), the pre-hold circuit 6 holds the previous level, and the metastable period is set so as to coincide with the period during which the tapping sound continues. Therefore, the front hold is continued while the tapping sound is generated, and the tapping sound is completely removed.

Also, with the external microphone attached to the external microphone jack 2, the camera section is in a photographing state, and the VTR
When the section is set to the recording state, the output of the external microphone jack 2 maintains the H level, both the switches 4 and 7 are switched to the fixed contacts 4b and 7b side, and the audio signal from the built-in microphone 1 is switched by the switch 4. The sound signal of the external microphone is cut off, input to the microphone amplifier 6 via the switch 4, and this output is input as it is to the ALC circuit 9 via the switches 7 and 8, and is monitored and recorded on the magnetic tape. . At this time, the mono-multi 21 outputs the same output as described above, and the pre-hold circuit 6 also executes the same operation, but since the output of the pre-hold circuit 6 is cut off by the switch 7, It does not affect the circuits described below. That is,
When the external microphone is used, it is used at a place far from the VTR section as compared with the built-in microphone 1. Therefore, the tapping sound produced in the VTR section is not picked up by the external microphone. The tape tapping sound removing operation by the front hold circuit 6 is not necessary.

Further, when a voice signal is input from the outside through the line input terminal 3, the switch 8 is activated by a selection signal.
Is switched to the fixed contact 8b side, the external audio signal is input to the ALC circuit 9 instead of the audio signal from the built-in microphone 1 or the external microphone, and the circuit operation of the latter stage is the same. Also in this case, since the tapping sound is not picked up by the microphone 1, the removal of the tapping sound by the front hold circuit 6 is substantially unnecessary.

In the first embodiment, the front hold circuit 6 is used.
The tape tapping sound is removed by the following method. However, paying attention to the fact that the main component of the tape tapping sound is around 2.8 kHz in NTSC, and it can be expected that the tape tapping sound is generated during the period. That is, in the metastable period of the output of the monomulti 21, it is possible to remove the audio signal component around 2.8 kHz by the trap circuit.

FIG. 4 is a diagram for explaining a second embodiment apparatus which adopts the tape tapping sound removing method using the trap circuit 50. 4 is different from FIG. 1 in that instead of the previous value hold circuit 6, a trap circuit 50 and a switch 51 are inserted in series between the microphone amplifier 5 and the switch 7, and one fixed terminal 51a of the switch 51 is a trap. The fixed terminal 51b, which is connected to the output end of the circuit 50, is directly coupled to the microphone amplifier 5 without passing through the trap circuit 50, and the switching control of the switch 51 is executed by the output of the monomulti 21. Here, the trap circuit 50 has frequency characteristics set so as to remove a frequency component in the vicinity of 2.8 kHz that may include a tape tapping sound in the input audio signal.

Next, the operation of the circuit block diagram of FIG. 4 will be described. No external microphone is attached to the external microphone jack 2,
When the recording mode is selected with the selection signal selecting the camera side, the audio signal from the microphone 1 is output from the microphone amplifier 5 via the switch 4. Here, when the output of the monomulti 21 is not in the metastable period, that is, in the period in which the tapping sound is not generated, the switch 51 is set to the fixed contact 51.
The audio signal from the microphone amplifier 5 is switched to the b side,
It is directly output to the fixed contact 7a side of the switch 7 without passing through the trap circuit 50, and is output to the monitor through the switch 8, the ALC circuit 9, the switch 11, and the line amplifier 13 without being processed by the trap circuit. At the same time, switch 10, noise reduction circuit 12, switch 1
4, through the FM modulator 15 and the recording circuit 30, the data is recorded on the magnetic tape.

On the other hand, while the output of the monomulti 21 is in the metastable period, that is, in the period in which the tape tapping sound is generated, the switch 51 is switched to the fixed contact 51a side and the trap circuit 50 outputs 2 of the audio signals. The component near 0.8 kHz is removed, and as a result, the tapping sound is removed. In this way, the audio signal that has passed through the trap circuit 50 becomes a monitor output and is recorded on the magnetic tape as in the case described above.

In any of the above-mentioned embodiments, if the level immediately before is expected to be held or the component around 2.8 kHz is removed during the period when it is expected that the tape tapping sound is generated, this period is reached. Some normal audio signal, or
Although the audio signal near 2.8 kHz is also removed, and the sound quality of the audio signal from the built-in microphone 1 is impaired, the quasi-stable period H (≈1.8 mse of mono-multi) occurs.
c) is the period of RF switching pulse 1/60 SEC
It is much smaller than (≈16 msec), and there is no particular problem in the case of a voice signal.

In any of the above-mentioned embodiments, the reproducing operation in the reproducing circuit 32 is executed by using the magnetic heads A and B used at the time of recording, and, for example, the magnetic head A.
A head having the same azimuth angle as the magnetic head B and a head having the same azimuth angle as the magnetic head A near the magnetic head B to make four heads, and reproducing is performed by sequentially switching each head. It goes without saying that it is also possible to do so.

Further, as in the second embodiment shown in FIG. 4, when an audio signal is passed through the trap circuit 50, the trap circuit 5
A voice signal that does not pass through 0 is delayed by the time required for processing by the trap circuit 50, and when the switch 51 switches to a signal that does not pass the trap circuit 50, Distortion occurs due to delay.

Therefore, in order to prevent the occurrence of this distortion, it is effective to replace the circuit configuration from the microphone amplifier 5 to the switch 7 in FIG. 4 with the circuit configuration as shown in FIG. 5 or 6. Here, in the third embodiment shown in FIG. 5, the output end of the microphone amplifier 5 and the fixed contact 51b of the switch 51.
The CCD 70 is inserted between them. The CCD 70 functions as a shift register, and when the time required for signal transfer from the input stage to the output stage of the CCD 70 is matched with the time required for processing in the trap circuit 50 in advance, the CCD 70 is substantially output to the switch 51b. Signal is CCD
70 is delayed as a delay circuit, and there is no time difference due to the delay between any of the signals output to the fixed contacts 51a and 51b of the switch 51. Therefore, when the switch 51 is switched, the distortion due to the delay is removed. Become.

Further, although the audio signal is delayed in an analog manner by the CCD 70 in FIG. 5, it may be replaced by a digital delay as in the fourth embodiment shown in FIG. In FIG. 6, an A / D converter 75 for converting a voice signal into a digital value is connected to the output stage of the microphone amplifier 5, and the fixed contact 5 of the A / D converter 75 and the switch 51 is connected.
A digital trap circuit 76 is inserted between 1a and A / D
The digital delay circuit 7 is provided between the converter 75 and the fixed contact 51b.
7 is further inserted, and a D / A converter 78 for converting a digital audio signal into an analog signal again is inserted between the switch 51 and the fixed contact 7a of the switch 7.

The audio signal converted into a digital value by the D / A converter 75 is simultaneously supplied to the digital trap circuit 76 and the digital delay circuit 77. The digital trap circuit 76 digitally realizes the trap operation with the same characteristics as the trap circuit 50 of FIG. 4, and the component corresponding to the tape tapping sound in the vicinity of 2.8 kHz in the audio signal is removed.

On the other hand, the digital delay circuit 77 has a time T required for the trap processing in the digital trap circuit 76.
The input signal is delayed by 0. For example, an even number of inverters are connected in series, or sequentially written in the memory, and the time T
This can be configured by executing the reading with a delay of 0.

In this way, the output of the digital trap circuit 76 and the digital delay circuit 7 both delayed by the time T0.
No distortion is generated in the 7th output, and the digital audio signal selected by the switch 51 is returned to the analog audio signal by the D / A converter 78.

In particular, unlike the analog method, in the case of the digital trap circuit 76, the output signal always has a delay of a constant time regardless of the frequency of the input signal, so the delay in the digital delay circuit 77 is distortion-removed. Especially effective for.

[0042]

As described above, according to the present invention, by pre-holding the audio signal of the built-in microphone during the period when the tape-tapping sound is expected to be generated, the tape-tapping sound is maintained without changing the frequency characteristic of the built-in microphone. Can be removed. Further, by passing the audio signal of the built-in microphone to the trap means only during the period when the tapping sound is expected to be generated, it is possible to minimize the frequency characteristic of the built-in microphone and remove the tape tapping sound. . Further, since the passage of the audio signal through the pre-holding means or the trap means is limited to the use of the built-in microphone, the unnecessary tape tapping sound removing operation can be prohibited when the external microphone is used. Furthermore, by delaying the audio signal that does not pass through the trap means by the processing time in the trap means, it is possible to prevent distortion of the audio signal when switching to the trap means.

[Brief description of drawings]

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

FIG. 2 is a timing chart of the first embodiment of the present invention.

FIG. 3 is a diagram illustrating head switching according to the first embodiment of this invention.

FIG. 4 is a circuit block diagram of a second embodiment of the present invention.

FIG. 5 is a circuit block diagram of a third embodiment of the present invention.

FIG. 6 is a circuit block diagram of a fourth embodiment of the present invention.

[Explanation of symbols]

 1 Built-in Microphone 33 Magnetic Tape 34 Cylinder A Magnetic Head B Magnetic Head 23 RF Switching Pulse Creating Circuit 6 Pre-holding Circuit 30 Recording Circuit 31 Mono Multi 2 External Microphone Jack 4 Switch 7 Switch 50 Trap Circuit 51 Switch 70 CCD 77 Digital Delay Circuit

Claims (5)

[Claims] 1. A built-in microphone, a cylinder around which a magnetic tape is wound, at least two magnetic heads mounted on the cylinder, and one of the magnetic heads is sequentially selected as a signal recording head for the magnetic tape. RF switching pulse creating means for creating an RF switching pulse for controlling the timing for operating the audio signal and an audio signal generated by the built-in microphone are input, the audio signal is directly output when not operating, and the audio signal is output when operating. Pre-holding means for pre-holding, recording means for recording the output of the pre-holding means on a magnetic tape, and timing signal generating means for generating a timing signal for a fixed time K after a predetermined time T from the edge of the RF switching pulse. And only when the timing signal is generated. Microphone built-in magnetic recording apparatus characterized by holding the shield means in operation. 2. A switching means for supplying to the recording circuit an audio signal input to the pre-hold circuit instead of the output of the pre-hold circuit while the external microphone is attached to the external mic attachment section. The magnetic recording device with a built-in microphone according to claim 1. 3. A built-in microphone, a cylinder around which a magnetic tape is wound, at least two magnetic heads mounted on the cylinder, and one of the magnetic heads is sequentially selected as a signal recording head for the magnetic tape. RF switching pulse creating means for creating an RF switching pulse for controlling the timing for controlling, a trap means for removing a predetermined frequency component in a sound signal generated by the built-in microphone, and a sound generated by the built-in microphone. A selection means for selectively selecting a signal and the output of the trap means, a recording means for recording the output of the selection means on a magnetic tape, and a timing signal for a predetermined time K after a predetermined time T from the edge of the RF switching pulse. Timing signal generating means for Flip and microphone built-in magnetic recording apparatus and selects the trap unit output by said selection means only during that. 4. The built-in microphone according to claim 3, further comprising switching means for supplying an audio signal from the built-in microphone to the recording circuit instead of the output of the selecting means while the external microphone is being mounted on the external microphone mounting portion. Type magnetic recording device. 5. An audio signal generated by the built-in microphone, which is selected as the output of the trap means by the selecting means, is delayed by the delay means by a time required for signal processing by the trap means. The magnetic recording device with a built-in microphone according to claim 3, wherein