JPH10155107A - Video camera incorporating microphone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a conversation with high articulation by building in a plurality of microphones, amplifying outputs from the microphones, converting the signal into a digital signal and converting a direction of the microphone into a shake angle of a camera via a delay circuit, a gain circuit and an addition circuit thereby properly picking up a voice of an utterance party. SOLUTION: An input voice signal is picked up by microphones 11, 21, 31, amplified by microphone amplifiers 12, 22, 32 and given to A/D converters 13, 23, 33. The digital input voice signal given to variable delay units 14, 24, 34 is delayed by a delay time set by a voice input section control unit 50. The voice input section control unit 50 receives a control signal from a camera control unit 60 to set a parameter corresponding to a motion of a motor-drive panning/tilt zoom camera unit 70. The delay and the gain are decided based on the parameter to provide the directivity in a desired direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a video camera with a built-in microphone used for a video conference system or the like.

[0002]

2. Description of the Related Art Generally, a video conferencing system that is marketed can swing a directivity angle in the left, right, up and down directions in order to satisfy a request for projecting a wide area and a request for projecting a specific area in an enlarged manner. It is equipped with an electric pan-tilt zoom camera that can increase or decrease the range, in other words, continuously change the telephoto and wide-angle.
In such a system, since the participants of the conference are seated in a wide area, a plurality of microphones are usually arranged in a distributed manner for the purpose of picking up the voice of each participant evenly. In this case, the voice picked up by the microphone collects noises such as air-conditioning sounds in addition to the voices generated by the participants, so that the voice quality of the conference is impaired. In addition, it is necessary to wire a microphone connection cable from the main body of the video conference system to the table for conference participants, which has a problem in terms of safety, such as impairing the appearance and catching during walking.

[0003]

In the above-mentioned conventional example, since the sound generated by the participant and the noise obstructing the clarity of the speech are collected without being distinguished, the clarity of the conversation is impaired. was there. In addition, a microphone cable needs to be laid between the microphone and the main body in order to install the microphone on the conference table, and thus there is a problem that the appearance is impaired and the foot is hooked on the wiring on the floor. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks and realize a comfortable video conference by collecting the voice of a speaker with higher sensitivity than other noises without installing a microphone on a conference table. .

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve these problems, and has a plurality of built-in microphones, which can change a photographing display range in up, down, left, and right directions by an external control signal. In a video camera with a built-in microphone having a pan-tilt zoom function, an amplifier for amplifying an output signal from each microphone,
An analog-to-digital converter for converting a signal amplified by each amplifier into a digital signal; a delay circuit for delaying a digital signal from the analog-to-digital converter in one-to-one correspondence with the plurality of microphones; A video camera with a built-in microphone, comprising: a gain circuit for changing a gain coefficient of an output signal from the delay circuit; and an addition circuit for adding output signals from the respective gain circuits.

[0005]

Embodiments of the present invention will be described with reference to the drawings. Prior to the description of embodiments of the present invention, an outline of a beam forming technique will be described. Let the number of microphones be N and the output of the i-th microphone be ri (t).
An appropriate delay time τi is given to each of the microphones so that the output from each microphone with respect to a signal from a desired direction becomes in-phase, and the signals are added by multiplying by a weighting factor Wi to obtain an output signal. Since signals other than the signal propagating from the desired direction do not become in-phase, if added, they cancel each other out and attenuate, so that sharp directivity can be realized. Directivity characteristics are weighting factor, delay time,
It is determined by the number of microphones, and can be made to follow the position of the signal source by adaptively changing the weight coefficient and the delay amount. The output signal y (t) is represented by the following equation.

[0006]

[Table 1]

FIG. 1 shows an example in which three microphones according to an embodiment of the present invention are connected. The input audio signal is collected by microphones (11, 21, 31), amplified by microphone amplifiers (12, 22, 32) and input to analog-to-digital converters (13, 23, 33) (hereinafter A / D). In the A / D, the input audio signal is sampled, discretized, and converted into a digital input audio signal. Variable delay unit (1
The digital input audio signal input to the input units 4, 24, 34) is output after delaying the input signal by a delay time determined by the audio input unit control unit (50). The delayed digital input audio signal is supplied to the variable gain unit (1).
5, 25, 35), the voice input unit control unit (50)
Is multiplied by the gain determined by the above and added by an adder (40) to obtain a digital output audio signal. The digital output audio signal is converted to a digital-to-analog converter (41)
D / A) converts it to an analog output audio signal. However, the output format of the present apparatus may be a digital output audio signal only, and in this case, D / A is not required. A plurality of combinations from the microphone to the variable gain unit are required depending on the number of microphones. The voice input unit control unit (50) receives a control signal from the camera control unit (60). The control signal corresponds to the movement of the electric pan-tilt zoom camera unit (70).
The left and right swing angles (pan) and zoom state are shown. Based on this control signal, the audio input unit control unit (50) controls each variable delay unit (14, 24, 34) and variable gain unit (50). 15, 25, 35) are determined. Next, the voice input unit control unit (
The details of the operation 50) will be described. When the sound input to each microphone is incident from the front, the sound is collected in the same phase. However, when the light is incident from an oblique direction, as shown in FIG. 2, a time difference occurs in the input signal for each microphone. When the signals input from the microphones are added, a phase difference occurs between the signals, so that the signals are canceled and attenuated. Here, as shown in FIG. 3, if the time difference between each signal is removed from the signal collected by each microphone using a delay circuit, the signal becomes equivalent to the sound input from the front, and its direction The effect of having high directivity is obtained. The directivity can be changed by controlling the delay time of the delay circuit. Therefore, the function of the voice input unit control unit (50) is to determine the amount of delay of the variable delay unit (14, 24, 34) so as to provide directivity in a desired direction, and to make the directivity sharp. Is to determine the gain of the variable gain units (15, 25, 35) in order to change First, a delay amount determining method will be described. The microphone array shown in this embodiment is characterized in that sharp directivity is obtained. Therefore, the voice of the speaker in the direction of the camera can be efficiently collected, but the voice and noise of the speaker not in the direction of the camera are hardly collected. In general, a camera used in a video conference system can be turned in the direction of a speaker by an operator and projected, so that the directivity direction of the microphone may be changed according to the swing angle of the camera. The camera shake angle is determined by the camera control unit (
60), the direction of the camera can be known. In this system, since the input audio signal is treated as a discrete signal, the setting itself of the delay amount between the microphones becomes discrete. Therefore, the camera shake angle is quantized, the obtained index is used to search a table storing the delay amount created in advance, the delay amount of each variable delay unit is obtained, and the variable delay unit is set to a desired value. Characteristics can be obtained. When there is only one speaker, the speaker is zoomed up and projected, so there is no discomfort even if the microphone has sharp directivity, but it does not weaken the directivity when many speakers are talking at the same time Cannot be collected, and inconvenience occurs. Therefore, the camera control unit (60) has a function of controlling the sensitivity of each microphone and changing the directional characteristics. If there are many speakers or the entire participant is projected without operating the camera each time, the zoom setting of the camera is adjusted to the wide-angle side in order to widen the shooting range. Also in this case, since the camera control is performed by the camera control unit (60), the user can know the zoom setting state. In the present embodiment, the central microphone is controlled as the main unit, but the gain of the signal obtained from the central microphone is increased, and the gain of the signal obtained from the microphones at both ends is reduced. The strength of the characteristics can be controlled. As an extreme example, the widest directivity can be obtained by using only the signal obtained from the central microphone. Also in this case, it is desirable to quantize the zoom angle of the camera, search the table storing the gain amount created in advance using the obtained index, obtain the gain amount of each variable gain unit, and set the variable gain unit. Characteristic can be obtained. Thus, excellent effects can be obtained with an extremely simple configuration. FIG. 4 shows a change in the directional characteristics of the microphone according to the present embodiment when the delay amount is changed. FIG. 5 shows a change in the directional characteristics of the microphone according to the present embodiment when the gain amount is changed. Generally, as the number of microphones is increased, the directivity becomes sharper. Further, if the interval between the microphones is widened, the directional characteristics can be exhibited even at a low frequency, but in any case, the device becomes large. Also, when the A / D sampling rate is increased, the accuracy of delay amount setting is improved, and the setting accuracy of the directional direction is increased. By performing the above control, by changing the directivity direction of the microphone according to the shake angle of the camera, it is possible to efficiently collect the voice of the speaker,
When the camera zoom is set to the wide side, the voice of the entire participant is picked up by increasing the directional characteristic, and when the camera zoom is set to the tele side, the directional characteristic is sharpened,
The speaker's voice reflected on the camera can be effectively picked up.

[0008]

According to the present invention, the voice of the speaker can be efficiently collected by changing the directivity of the microphone according to the shake angle of the camera. And the effect of indoor noise and the like. In addition, when the camera zoom is set to the wide side, the voice of the entire participant can be picked up by widening the directional characteristics of the microphone. Conversely, when the camera zoom is set to the tele side, the directional characteristics should be sharpened. Can be. Accordingly, the voice of the speaker reflected on the camera can be effectively picked up. Therefore, it is possible to accurately capture the speaker and collect sound, so that conversation with less noise and high clarity can be realized, and when the entire image is projected, sound can be collected from a wide range, and the sense of presence can be secured at the same time, so it is extremely comfortable There is an effect that a simple video conference can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an embodiment according to the present invention.

FIG. 2 is an explanatory view of the principle (characteristics at oblique incidence without a delay circuit)

FIG. 3 is an explanatory diagram of the principle (in the case where a delay circuit is added to provide maximum sensitivity in an oblique incident direction).

FIG. 4 is an explanatory diagram of a change in a directivity direction according to the present embodiment.

FIG. 5 is an explanatory diagram of a change in directional characteristics according to the present embodiment.

[Explanation of symbols]

 11, 21, 31 are microphones, 12, 22, and 32 are microphone amplifiers, 13, 23, and 33 are analog-to-digital converters, 14, 24, and 34 are variable delay units, 15, 25, and 35 are variable gain units, and 40 adders , 41 digital-analog converter, 50 audio input unit control unit, 60 camera control unit, 70 electric pan-tilt zoom camera unit

Claims (3)

[Claims] 1. A video camera incorporating a plurality of microphones and having an electric pan-tilt zoom function capable of changing a shooting display range in up, down, left, and right directions by an external control signal. An amplifier for amplifying a signal; an analog-to-digital converter for converting a signal amplified by each amplifier into a digital signal;
A delay circuit for delaying a digital signal from the analog-to-digital converter corresponding to one-to-one, a gain circuit for changing a gain coefficient of an output signal from the delay circuit,
A video camera with a built-in microphone, comprising: an addition circuit for adding output signals from the respective gain circuits. 2. The delay time of the plurality of delay circuits can be arbitrarily set within a predetermined range, and a predetermined delay time is individually set according to a left-right swing angle of the video camera. 2. The video camera with a built-in microphone according to claim 1, wherein the shooting direction of the video camera and the directivity direction of the microphone are linked. 3. The gain coefficients of the plurality of gain circuits can be arbitrarily set within a predetermined range, and the gain coefficients of the video camera are individually set according to a screen display range of the video camera. 3. The video camera with a built-in microphone according to claim 2, wherein a shooting range is linked with a directional direction of the microphone.