JPH0334799A - Sound collection system - Google Patents

Abstract

PURPOSE:To collect sound without intermission by providing a switching means which uses a voice signal from a wireless microphone as an output signal when a discrimination signal inputted from a reception state discrimination means representing an excellent reception state and uses a voice signal from a wire microphone as the output signal when the signal represents a defective reception state. CONSTITUTION:A detection section 19 judges that a carrier reception state is defective when an output level of a rectifier section 18 is higher than a set level. A signal representing the discrimination result in the detection section 19 is converted into a switch changeover signal by a switching signal output section 21 and fed to a changeover switch 14. The changeover switch 14 following a switching signal from a squelch section 10 selects an input signal (c) to a recording and reproduction section 15 into a signal (a) from a wireless microphone 1 or a signal (b) from a built-in microphone. When the reception of a carrier is restored normal and the noise component level in the low frequency signal of a frequency discrimination section 9 is lower than the set level, the changeover switch 14 selects the connection of the signals (a) and (c).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sound collection system for equipment such as a video camera or an electronic still camera, which is equipped with a wireless microphone and a built-in microphone at the same time.

Conventionally, in devices equipped with two microphones like this, the operator selects and uses either the wireless microphone or the built-in microphone by switching a switch. However, if you are using a wireless microphone, for example, the distance between the wireless microphone and the receiving device (video camera body, etc.) is too far, there is an obstacle between the two, or the wireless microphone When the battery of the receiver is exhausted and the transmission output is reduced, noise is mixed into the demodulated output of the receiver, making it difficult to hear the voice. Therefore, some conventional sound collection systems include a receiving device equipped with a squelch circuit that stops audio output in such a case.

If the squelch circuit operates as described above when using a wireless microphone that is sensitive to noise, the noise will not be output as audio, but the audio you want to collect will also not be output, so when shooting with a video camera, etc. The audio is cut off in some parts.

This may make it very difficult to hear or give an unnatural feeling when playing back the recording.4 Is the present invention like this? The purpose is to solve one problem and to be able to collect sound without interruption even when using a wireless microphone.

W-Akushi-san I-Sakazuki-ni, -Mysterious=? , -FJ wormTo achieve the above objects, the present invention provides a sound collection system l that generates a single output audio signal using a wired microphone and a wired connected microphone. l/” The receiver receives the i5 radio waves transmitted from the microphone (3 signals!
j: a receiving means that generates, and based on the received signal a, generates a judgment signal representing the three means of battery tatami (3′-shaped Judgment hand kill 51-5
If the determination signal input from the reception status determination means indicates the reception status, 1. Output the audio signal from the wireless microphone as signal 2・j121. When a defect is indicated, the device is characterized in that it includes switching means for making an audio signal from the wired microphone an output signal. Furthermore, the sound collection system according to the present invention is configured to include a determination result output means for receiving the determination signal from the reception status determining means and outputting the determination result in a form that can be perceived by the operator of the sound collection system. You can.

The radio waves from the L-deck wireless microphone are received by the receiving means, and the receiving means A receives the received radio waves 1. Generates a received signal according to the received signal. For example, if the wireless microphone uses a frequency modulation (FM) method, the received signal generated may be the received FM signal itself, an intermediate frequency signal, or a low frequency signal obtained by frequency discrimination. Based on this received signal, the determining means determines whether or not the radio waves from the wire L/Smike are well received by the receiving means.6 For example, 1. In the previous example, if the received signal has been lowered to a low frequency, if the level is above a predetermined setting value, the reception status is determined to be poor. When the ratio to the level (CN ratio) becomes less than a certain value, the SN ratio of the low frequency signal becomes S! , the noise component rapidly increases) and its level increases.

The reception status determination means outputs a determination signal of good or bad according to the determination result (~, the switching means outputs the determination signal (, KOYO ζ−), and when the reception status is good, it outputs an audio signal from the 1ν earless microphone. When the output audio signal and +-1 reception status is poor, the audio from the wired microphone (, -1 is output as soon as the audio signal is output, and due to the 9 noise, the final output audio signal has radio reception (3, 51, (::, ,, noise mixed in 1
- There is no way that f:t < , - ゛, ', there is no end.

Output means 4; j, Reception status puncture (in response to No. 77, for example, displays 11' notification of poor reception or generates an alarm sound, by this spear 1, 1, this sound collection..., / stem operator The following is an example of applying the sound collection system 1 of the present invention to a video camera G. will be explained with reference to the drawings.As shown in Fig. 1, the sound collection system of this embodiment:
It consists of a microphone 12 built into the video camera body, an audio signal processing section SP, which inputs and processes signals from these microphones, a video/audio recording/reproducing section 15, and a video display section 16. The wireless microphone 1 frequency-modulates the collected audio signal and radiates it as a radio wave from the transmitting antenna 2. This radiated radio wave is received by the receiving antenna 3 of the video camera body, and thereafter, an audio signal is extracted through signal processing similar to that of a normal FM receiver.

That is, the received signal is amplified by the high frequency amplification section 4, mixed with the output of the local oscillator 6 by the frequency conversion section 5, and converted into an intermediate frequency signal.

The intermediate frequency signal is amplified by an intermediate frequency amplifying section 7, and after being suppressed from an amplitude exceeding a predetermined value by an amplitude limiting section 8, it is demodulated into a low frequency signal by a frequency discriminating section 9. The low frequency signal obtained in this way is amplified by the low frequency amplifying section 11, and recorded on a videotape (or magnetic disk in the case of an electronic still camera) by the recording/reproducing section 15 via a changeover switch 14, which will be described later. , or output to the monitor. Built-in microphone 12
The voice signal collected is amplified by the microphone amplifying section 13 and similarly sent to the recording/reproducing section 15 via the changeover switch 14.

The low frequency signal obtained by the frequency discrimination section 9 is sent to the squelch section 10.
is also entered. A squelch circuit is normally used to suppress audio output only when noise is mixed in, so as to prevent unpleasant noise from being output from speakers, etc., but in this example, this noise detection function is used to 1 to the built-in microphone 12. In an FM receiver, the squelch circuit detects the signal-to-noise ratio (SN ratio) of the low frequency signal (audio signal) when the ratio between the level of the carrier wave of the received frequency and the noise level (CN ratio) falls below a certain value.
It is assembled by taking advantage of the sudden drop in

The specific structure and operation of the squelch section 10 will be explained with reference to FIG. The noise component in the detection output (low frequency input signal) of the frequency discrimination section 9 is amplified by the noise amplification section 17 and then
Convert to DC voltage.

When the low frequency input signal contains many noise components,
Since the output level of the rectifying section 18 also becomes high, the detecting section 19 compares the level set in advance by the detection level setting section 20 and the output level of the rectifying section 18 to determine the reception status of the carrier wave. That is, when the output level of the rectifier 18 is higher than the set level, it is determined that the carrier wave reception condition is poor. The signal of the determination result in the detection section 19 is converted into a switch switching signal by the switching signal output section 21 and sent to the changeover switch 14.

According to the switching signal from the squelch unit 10, the changeover switch 14 converts the input signal (c) to the recording/reproducing unit 15 into the signal (a) from the wireless microphone 1 and the signal (a) from the built-in microphone.
b) Switch between. That is, when it is determined that the reception condition of the carrier wave is poor, the input to the recording/reproducing section 15 is switched from the low frequency amplification section 11(a) of the wireless microphone to the built-in microphone amplification section 13(b). *When the reception of transmitted waves returns to normal and the noise component level in the low frequency signal of the frequency discriminator 9 becomes lower than the set level, the changeover switch 14 switches to connection a and C. As a result, when the radio waves from the wireless microphone 1 become poorly received on the video camera body side for some reason, the sound collection is automatically switched to the built-in microphone 12.
The audio signal recorded on the videotape is never interrupted.

In this embodiment, the switching signal from the squelch unit 10 is also sent to the display unit 16 to inform the photographer looking through the viewfinder that the audio reception status from the wireless microphone 1 is poor. This allows the photographer to take measures to improve the reception condition, such as changing the position of the wireless microphone 1, or to stop collecting sound by the wireless microphone. Examples of display of wireless microphone reception status defect information on the display section 16 and examples of its circuit configuration are shown in FIGS. 3 to 6.

In the example of FIG. 3, the display unit 16 is the electronic viewfinder 2.
3 and a character display device 22. When a switching signal indicating that the reception status of radio waves from the wireless microphone 1 is poor is input from the squelch unit 10, the character display device 22 displays a predetermined alarm character signal (for example, as shown in FIG. 4). , "wireless microphone NGJ)" is output to the electronic viewfinder 23. To explain in detail,
The input pulse signals of the video vertical synchronizing signal φ■ and the horizontal synchronizing signal φH are counted, and the above-mentioned character signal is superimposed on the video signal ■S at an appropriate timing. This allows the warning text to be displayed at any position on the monitor screen 24 of the viewfinder 23.

In the examples shown in FIGS. 5 and 6, an LED 29 is lit in the outer frame of the monitor screen 28 of the optical or electronic viewfinder 27 to more simply warn the photographer. Therefore, the display section 16 is
An ED lighting circuit 26 is provided.

Furthermore, it is also possible to use an alarm or a buzzer as a means to notify that the voice reception status from the wireless microphone 1 is poor.

As explained above, according to the present invention, if the radio wave reception condition from the wireless microphone is poor, it not only blocks the audio signal from there, but also automatically blocks the audio signal from the built-in microphone. Since the system switches to sound collection, unpleasant noise does not enter the collected audio signal, and the sound can be collected without interruption. In addition, by notifying the operator of switching between this wireless microphone and the built-in microphone,
The operator will be able to take appropriate measures, such as taking measures to improve the reception situation.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a sound collection system for a video camera embodying the present invention, FIG. 2 is a block diagram showing the squelch section in detail, and FIG. 3 is a block diagram showing an example of the configuration of the display section. Fig. 4 is a diagram showing an example of the monitor screen displayed on the viewfinder by the bottom of the tank, Fig. 5 is a block diagram showing another example of the configuration of the display section, and Fig. 6 is a table in the viewfinder with the same configuration. It is a figure which shows an example. 1- Wireless microphone, 12- Built-in microphone 24,
28.--Monitor screen.

Claims (3)

[Claims] (1) In a sound collection system that generates a single output audio signal using a wireless microphone and a wired microphone, the receiving means receives radio waves transmitted from the wireless microphone and generates a received signal; reception status determination means for generating a determination signal indicating whether the radio wave reception status of the reception means is good or bad based on the signal; and a wireless microphone when the determination signal inputted from the reception status determination means indicates a good reception status. 1. A sound collection system comprising switching means that outputs an audio signal from the wired microphone as an output signal, and outputs an audio signal from the wired microphone when it indicates a defect. (2) The sound collection system according to claim 1, further comprising a determination result output means for receiving the determination signal from the reception status determining means and outputting the determination result in a form that can be perceived by an operator of the sound collection system. (3) A sound collection system that uses a wireless microphone and a wired microphone to generate a single output audio signal, comprising: a receiving means that receives radio waves transmitted from the wireless microphone and generates a received signal; reception status determination means for generating a determination signal indicating whether the radio wave reception status of the reception means is good or bad based on the signal; and receiving the determination signal input from the reception status determination means and transmitting the determination result to the sound collection system A sound collection system comprising: a determination result output means that outputs the determination result in a form that can be sensed by an operator.