JP6071188B2 - Audio signal processing device - Google Patents

Description

  The present invention relates to an audio signal processing device.

  Conventionally, an imaging device is known as an audio signal processing device, and an imaging device that can generate moving image data from a captured image and simultaneously record the collected sound as an audio signal of the moving image data is known. It has been.

  In such an imaging device, when driving sound (noise, noise) generated by driving a lens or a diaphragm is collected for imaging, signal processing for reducing the driving sound is performed. Things to do are appearing. For example, in Patent Document 1, a predicted waveform signal is generated by a linear prediction method based on a voice during non-operation of the drive unit, and a voice signal during operation of the drive unit and the generated predicted waveform signal are set to a predetermined value. A technique for synthesizing at a ratio and a technique for synthesizing at a predetermined ratio are disclosed. The synthesis ratio is gradually changed from 1: 0 to 0: 1, and it can be said that synthesis is performed while performing so-called crossfading.

JP 2011-002723 A

  However, when noise reduction is performed by the method shown in Patent Document 1, there is a problem in that the calculation load increases when generating a predicted waveform signal.

  Therefore, in view of such a problem, the present invention generates a signal based on an audio signal during a period when the driving unit is not driven, and performs a process of reducing driving sound based on the generated signal. An object of the present invention is to provide an audio signal processing device capable of reducing the amount of calculation.

  In order to achieve such an object, an audio signal processing device of the present invention is an audio signal processing device having a drive unit, and includes a control unit that controls driving of the drive unit, and a periphery of the audio signal processing device. An acquisition means for acquiring an audio signal digitized at a predetermined sampling frequency, and an audio processing means for processing the audio signal acquired by the acquisition means, wherein the drive unit is not driven Sometimes a correction sound signal is generated based on a signal obtained by reducing the data amount of the sound signal acquired by the acquisition means, and the sound signal and the correction sound acquired by the acquisition means when the driving unit is driven. Using the signal synthesized with a predetermined synthesis ratio, the driving sound due to the driving of the driving unit is reduced in the audio signal acquired by the acquiring unit when the driving unit is driven. And when the drive unit is not driven based on the audio level of the audio signal acquired by the acquisition unit when the drive unit is not driven. Further, the synthesis ratio is determined so that the synthesis ratio of the corrected sound signal is increased as the voice level of the voice signal acquired by the acquisition means is smaller.

  According to the present invention, when a signal is generated based on an audio signal during a period in which the drive unit is not driven and the process of reducing the drive sound is performed based on the generated signal, the amount of calculation can be reduced. it can.

1 is a diagram illustrating a configuration of an imaging apparatus 100. FIG. It is a flowchart for demonstrating control of the operation | movement of the noise reduction process of a present Example. It is a figure which shows the functional block of the audio | voice processing part 121 of a present Example.

  Hereinafter, examples of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments.

  In this embodiment, an image pickup apparatus will be described as an example of an audio signal processing apparatus. However, any apparatus may be used as long as the apparatus has a drive unit and can perform audio signal processing, instead of the image pickup apparatus. There may be. For example, a mobile phone, a computer, a game machine, etc. may be used.

  The imaging apparatus 100 according to the present embodiment includes a driving unit such as an actuator for driving an imaging lens, a diaphragm, a shutter, and the like, and a sound collecting unit (microphone unit) for collecting surrounding sounds. . The imaging apparatus 100 according to the present embodiment has such a configuration, and the correction generated based on the audio signal during the period when the drive unit is not driven with respect to the audio signal during the period when the drive unit is driven. By synthesizing the sound signals at a predetermined ratio, it is possible to reduce the drive sound of the drive unit.

  One of the characteristic operations of the imaging apparatus 100 according to the present embodiment is processing when generating a corrected sound signal.

  The voice is acquired as an analog voice signal by, for example, a microphone unit which is a voice input unit, and is sampled at a sampling frequency of 48 kHz by, for example, an A / D conversion circuit and converted into a digital voice signal. Then, the sound processing unit performs volume adjustment processing, frequency restriction processing using a frequency filter, and the like, and stores them in the RAM.

  And when a drive part drives, a correction sound signal is produced | generated based on the audio | voice signal of the period which the drive part memorize | stored memorize | stored in RAM, the drive part memorize | stored in RAM drives It synthesize | combines with the predetermined ratio with respect to the audio | voice signal of a certain period.

  When generating the corrected sound signal, first, the sound signal stored in the RAM during the period when the driving unit is not driven is read, and, for example, an average value for every three samplings is calculated and the sampling number is set to 1. Reduce to / 3. In other words, the 48 kHz audio signal is converted to 16 kHz, and processing is performed to reduce the number of samplings.

And a correction sound signal is produced | generated based on the audio | voice signal of the period which the drive part which reduced the number of sampling is not driving. The corrected sound signal generated here is a 16 kHz audio signal, and in order to match the recorded audio signal and the sampling frequency, the sampling number is tripled and converted to a 48 kHz signal. One way to increase the number of samples is to linearly interpolate each sample of the generated 16 kHz interpolated signal. Further, after that, a rapid change in the correction sound signal may be suppressed by applying a low-pass filter.
Note that other methods may be used to increase the number of samplings.

  Further, one of the more characteristic operations of the imaging apparatus 100 according to the present embodiment is also a process for synthesizing the generated corrected sound signal with the sound signal during the period during which the drive unit is driven.

  That is, the synthesis ratio of the correction sound signal is changed according to the sound level during the period in which the drive sound of the drive unit that is the basis of the correction sound signal is not included. It should be noted that as the sound level of the drive unit that does not include the driving sound increases, the correction sound signal synthesis ratio is decreased, and the sound level of the drive unit that does not include the drive sound decreases. As a result, the synthesis rate of the corrected sound signal is increased.

  By performing such an operation, the imaging apparatus 100 according to the present embodiment can reduce the amount of calculation for generating the predicted waveform signal based on the audio signal during the period when the driving unit is not driven. Furthermore, noise that may be included in the generated corrected sound signal (noise generated when a voice having a frequency equal to or higher than the Nyquist frequency of 16 kHz causes aliasing distortion) can be made inconspicuous.

  Hereinafter, such an imaging apparatus will be described.

<Overall configuration>
FIG. 1 is a block diagram illustrating a configuration of the imaging apparatus 100 according to the present exemplary embodiment.

  The imaging apparatus 100 includes a CPU 101, a RAM 102, a flash ROM 103, and an operation unit 104. The imaging apparatus 100 includes an imaging unit 110, an image processing unit 111, an audio input unit 120, an audio processing unit 121, a display unit 130, a display control unit 131, an audio output unit 132, a recording medium 140, a recording / playback unit 141, and a communication. Part 150. In addition, the imaging apparatus 100 includes an encoding / decoding processing unit 160.

  In FIG. 1, a CPU 101 develops a control program for the image capturing apparatus 100 recorded in the Flash ROM 103 in a RAM 102 and controls each block of the image capturing apparatus 100 while using the RAM 102 as a work memory. The operation unit 104 includes switches for inputting various operations related to shooting such as a power button, a record button, a zoom adjustment button, and an autofocus button. In addition, a menu display button, a determination button, other cursor keys, a pointing device, a touch panel, and the like are provided, and an operation signal is transmitted to the CPU 101 when the user operates these keys, buttons, or touch panel.

  The imaging unit 110 converts an optical image of a subject captured by a lens into an image signal using an imaging element such as a CCD sensor or a CMOS sensor by controlling a light amount by a diaphragm, and converts the obtained analog image signal into a digital image signal. And temporarily stored in the RAM 102. The digital image signal stored in the RAM 102 is then transmitted to the image processing unit 111. The image processing unit 111 is a microcomputer equipped with a program that executes the following processing. The image processing unit 111 performs an image quality adjustment process for adjusting the white balance, color, brightness, and the like of the digital image signal based on a setting value set by the user or a setting value automatically determined from the characteristics of the image. The digital image signal that has been processed is stored in the RAM 102 again. Note that the processing of the image processing unit 111 may be executed by the CPU 101 developing a program for executing the above-described processing recorded in the flash ROM 103 on the RAM 102. The imaging unit 110 includes various driving units such as an imaging lens, a diaphragm, a shutter, and an actuator that drives these lenses. When the imaging device 100 is an interchangeable lens type imaging device, the imaging unit 110 includes a mounting unit that can replace the lens unit. The lens unit guides the optical image of the subject to the image sensor, and the mounting unit can be mounted by exchanging different types of lens units.

  The voice input unit 120 collects (collects) sounds around the imaging apparatus 100 using, for example, a built-in omnidirectional microphone, and digitizes the obtained analog voice signal by the A / D conversion unit. A digital audio signal is acquired. In the present embodiment, for example, an analog audio signal is sampled at a sampling frequency of 48 kHz and converted into a digital audio signal. The digital audio signal acquired by the audio input unit 120 is transmitted to the audio processing unit 121. The voice processing unit 121 is a microcomputer equipped with a program that executes the following processing. At the time of recording, the audio processing unit 121 performs processing such as level optimization processing, frequency limiting processing, noise reduction processing, and the like, and stores the processed digital audio signal in the RAM 102. Moreover, the process which compresses an audio | voice signal is performed as needed. As the audio compression method, a known general audio compression method such as AC3, AAC or the like is used, and the description is omitted because it is not related to the feature of the present invention. At the time of reproduction, a process of decoding compressed audio data included in an audio file or a moving image file read from the recording medium 140 by the recording / reproducing unit 141 is also performed. The processing of the audio processing unit 121 may be executed by the CPU 101 developing a program for executing the above-described processing recorded in the flash ROM 103 on the RAM 102.

  Note that the audio processing unit 121 according to the present exemplary embodiment can execute processing for reducing driving sound of a driving unit such as the imaging unit 110 as described later. For example, in the present embodiment, a corrected audio signal is generated based on an audio signal in a period during which the drive unit is driven, based on an audio signal in a period before and / or after that period. It is possible to perform a process of synthesizing with an audio signal during a period in which the driving unit is driven.

  The display control unit 131 is a microcomputer that performs display control for displaying an image on the display unit 130. The display control unit 131 reads a digital image signal temporarily stored in the memory 104 and displays the digital image signal on the display unit 130. Process. In addition, the display unit 130 also displays an image of image data included in a moving image file or a still image file read from the recording medium 140 by the recording / playback unit 141. The display unit 130 may be, for example, a liquid crystal panel or an organic EL panel mounted on the imaging device 100, or may be a display device (for example, a television, a monitor, or a projector) different from the imaging device 100. . Note that the processing of the display control unit 131 may be executed by the CPU 101 developing a program for executing the above-described processing recorded in the flash ROM 103 on the RAM 102.

  The encoding / decoding processing unit 160 is a microcomputer equipped with a program for executing the following processing. At the time of recording, the encoding / decoding processing unit 160 performs image compression processing based on the digital image signal processed by the image processing unit 111 and stored in the RAM 102 to generate compressed moving image data and still image data. Then, a process of temporarily storing in the RAM 102 is performed. Further, at the time of reproduction, a process is performed in which the compressed moving image data and still image data of the image file read from the recording medium 140 is decoded to extract a digital image signal and stored in the RAM 102. Note that a program for executing the above-described processing recorded in the flash ROM 103 by the CPU 101 may be loaded into the RAM 102 and executed.

  Next, the recording / reproducing unit 141 is a microcomputer equipped with a program for executing the following processing. In the recording / playback unit 141, when recording a moving image, various types of data such as the compressed moving image data generated by the encoding / decoding processing unit 160, the audio data generated by the audio processing unit 121, and the shooting date are stored in the RAM 102. Along with the information, it is written in the recording medium 140 as a moving image file. At the time of recording a still image, the still image data stored in the ROM 102 is recorded on the recording medium 140 as a still image file together with various information such as the shooting date. When recording a moving image file on the recording medium 140, a data stream composed of compressed moving image data and audio data is formed and sequentially recorded on the recording medium 140, and a file header or the like is added to a file such as FAT or exFAT. Record a video file on a recording medium in a form that conforms to the format. Further, at the time of reproduction, the moving image file and still image file recorded on the recording medium 140 are read according to the aforementioned file format. The read moving image file and still image file are analyzed for headers by the CPU 101, and compressed moving image data and still image data are extracted. The extracted compressed moving image data and still image data are stored in the RAM 102 and decoded by the encoding / decoding processing unit 160. Note that the processing of the recording / playback unit 141 may be executed by the CPU 101 developing a program for executing the above-described processing recorded in the flash ROM 103 in the RAM 102.

  Further, the recording medium 140 may be a recording medium built in the imaging apparatus or a removable recording medium. For example, the recording medium includes all types of recording media such as a hard disk, an optical disk, a magneto-optical disk, a CD-R, a DVD-R, a magnetic tape, a nonvolatile semiconductor memory, and a flash memory. When using removable recording media, the recording / reproducing unit 141 includes an interface for receiving the removable recording media.

  Next, the audio output unit 132 is, for example, a speaker or an audio output terminal (analog terminal / digital terminal). For example, in the case of a speaker, when an output of a predetermined digital audio signal recorded in the flash ROM 103 is instructed by the CPU 101, the digital audio signal is converted to the outside of the analog audio and output to the outside as an audio. Also, the digital audio signal indicated by the audio data stored in the moving image file is converted into an analog audio signal and output to the outside as audio. If it is an audio output terminal, the digital audio signal indicated by the audio data stored in the video file is converted into an analog audio signal and output to an external device (external speaker or the like), or the digital audio signal is directly output to the external device. Output to an audio component equipped with an optical digital connector.

  The communication unit 150 transmits and receives control signals, moving image files, still image files, various data, and the like with an external device different from the imaging device 100, and can be connected regardless of wired connection or wireless connection. It is. Note that any communication method may be used.

<Movie shooting operation>
Here, the moving image shooting operation of the imaging apparatus 100 of the present embodiment will be described.

  In the imaging apparatus 100 according to the present exemplary embodiment, the user operates the power button of the operation unit 104, and the mode switching switch of the operation unit 104 indicates which mode, for example, “movie shooting mode” or “playback mode”. This is confirmed by an instruction signal from the operation unit 104. Then, if it is determined that the video recording mode is set, the following operation is started.

  The CPU 101 causes each block of the imaging apparatus 100 to prepare for moving image shooting. Until an instruction to start shooting is input from the operation unit 104, the CPU 101 stores the digital image signal obtained by the imaging unit 110 in the RAM 102, reads the digital image signal stored in the RAM 102, and causes the display unit 130 to read the digital image signal. The display control unit 131 is controlled to display an image. The display control unit 131 may be controlled so that the digital image signal processed by the image processing unit 111 and stored in the RAM 102 is read and an image is displayed on the display unit 130.

  In the present embodiment, it is assumed that the frame rate of the digital image signal output from the imaging unit 110 is 30 frames / second. In this embodiment, the size (number of pixels) of a moving image to be recorded can be set to one size selected from a plurality of sizes.

  In this state, the CPU 101 determines whether or not an instruction to start shooting is input from the operation unit 104. When there is an instruction to start shooting, the CPU 101 stores the digital image signal obtained by the imaging unit 110 in the RAM 102 and performs image quality adjustment processing on the digital image signal stored in the RAM 102 based on the set value. The image processing unit 111 is controlled. The CPU 101 causes the image processing unit 111 to sequentially process the digital image signals output from the imaging unit 110 at 30 frames / second while moving image shooting is continued. Then, the CPU 101 sequentially stores the digital image signals processed by the image processing unit 111 in the RAM 102.

  Next, the CPU 101 controls the encoding / decoding processing unit 160 to sequentially encode the digital image signals of a plurality of frames stored in the RAM 102 to generate moving image data. At this time, the CPU 101 controls the encoding / decoding processing unit 160 so that each frame image is compression-encoded as an intra-frame prediction encoding frame and an inter-frame prediction encoding frame. Then, the CPU 101 sequentially stores each frame image encoded by the encoding / decoding processing unit 160 in the RAM 102.

  On the other hand, when there is an instruction to start shooting, the CPU 101 controls each block so as to perform processing related to sound. The CPU 101 sequentially transfers the analog audio signals output from the audio input unit 120 to the audio processing unit 121 and controls the audio processing unit 121 to perform conversion into a digital signal, sound quality adjustment processing, and the like. When the audio compression is set, the CPU 101 controls the audio processing unit 121 to compress the audio signal according to the AC3 or AAC audio compression method, for example, according to the setting. Then, the CPU 101 sequentially stores the audio data processed by the audio processing unit 121 in the RAM 102. In addition, the sound processing unit 121 of the present embodiment executes a process of reducing noise by various driving units such as an imaging lens, a diaphragm, a shutter, and an actuator for driving them at the time of shooting. This process will be described later.

  Next, the CPU 101 controls the recording / reproducing unit 141 so that the moving image data and audio data stored in the RAM 102 are sequentially recorded on the recording medium 140. At this time, for example, a set of 15 frames (0.5 seconds) of moving image data and 0.5 seconds of audio data is combined to form a data stream with various necessary information added, and recorded according to the file system The recording / reproducing unit 141 is controlled to record on the medium 140. Note that 30 frames (one second) of moving image data and one second of audio data may be combined. The CPU 101 continues these operations until there is an instruction to stop moving image shooting.

  When an instruction to stop shooting is input from the operation unit 104, the CPU 101 stops the processing of the image processing unit 111 and performs encoding / decoding processing when encoding of the digital image signal stored in the RAM 102 is completed. The encoding process of the unit 160 is stopped. Then, the CPU 101 controls the recording / reproducing unit 141 to stop the operation after recording the encoded moving image data and audio data stored in the RAM 102 to the recording medium 140 to the end. If necessary, after the end of recording, the first frame of the moving image data of the moving image file and several frames from the beginning are transmitted to the encoding / decoding processing unit 160 to be decoded, and the decoded digital image signal Thumbnail image data with the number of pixels thinned out may be generated and recorded in association with a moving image file.

  When this process ends, the CPU 101 returns each block to the moving image shooting preparation state again.

<Noise reduction processing>
Here, the noise reduction processing operation at the time of moving image shooting of the imaging apparatus 100 of the present embodiment will be described with reference to the flowchart of FIG. 2 and the functional block diagram of the audio processing unit 121 of FIG. In the following example, an example of reducing the driving noise of the diaphragm of the imaging unit 110 will be described. However, even if this is a driving sound of the imaging lens or shutter, the same noise reduction processing is performed.

  As described above, this noise reduction process is a process executed sequentially by the audio processing unit 121 during the moving image shooting process. As described above, in the noise reduction processing in the present embodiment, the audio signal in the period in which the drive unit is driven, which is the period in which noise is generated, is converted into the audio signal in the period before and / or after the drive unit is driven. This is a process of replacing with a corrected sound signal generated based on this. In the present embodiment, a period during which the audio signal that is the basis of the correction sound signal is collected, that is, a period before or after the drive unit is driven is referred to as a sampling period. This sampling period is, for example, a period of 0.2 seconds before or after the driving of the drive unit, but it may be longer or shorter than this.

  In the present embodiment, the normally recorded audio signal is sampled at 48 kHz when converted from an analog audio signal to a digital audio signal. However, when the correction sound signal is generated, the number of samplings of the digital audio signal sampled at 48 kHz in the sampling period is reduced in order to reduce the calculation amount. As a specific example, a correction sound signal is generated after an average of every three samples is obtained and converted to a 16 kHz digital audio signal having the average value. In this embodiment, the recording sound is 48 kHz, and when the number of samplings is reduced, an average value for every three samples is used. However, the recording voice is not limited to 48 kHz, and when the number of samplings is reduced, the addition average for every two samples or the average for every four samples may be used. In addition, the process of reducing the number of samplings may not use the averaging. For example, only sampling values every three samples may be used.

  Note that the flowchart of FIG. 2 shows an operation related to noise reduction processing executed under the control of the CPU 101 during the moving image shooting operation described above. Note that the noise reduction processing will be described assuming that the audio processing unit 121 performs processing for optimizing the volume of the audio signal once and uses the audio signal stored in the RAM 102.

(S210)
First, the CPU 101 analyzes, for example, the luminance of the image signal obtained by the imaging unit 110 and determines whether or not the diaphragm of the imaging unit 110 needs to be driven. The CPU 101 does not cause the audio processing unit 121 to execute noise reduction processing when driving of the diaphragm is not necessary (No in S210). On the other hand, when the diaphragm needs to be driven (Yes in S210), the CPU 101 causes the audio processing unit 121 to perform noise reduction processing.

(S220)
When it is necessary to drive the aperture (Yes in S210), the CPU 101 drives the aperture (drive unit) of the imaging unit 110 and determines the period during which the aperture (drive unit) is driven.

(S221)
When the period during which the diaphragm (driving unit) is driven is determined in S220, sampling is performed to obtain an audio signal for generating a correction sound signal for interpolating the audio signal during the period during which the diaphragm (driving unit) is driven. The period is determined. Then, the CPU 101 reads out an audio signal sampled at 48 kHz corresponding to the audio signal sampling period stored in the RAM 102 and transmits the audio signal to the audio processing unit 121. Further, the CPU 101 controls the data compression unit 310 of the audio processing unit 121 so as to reduce the number of samplings of the audio signal sampled at 48 kHz corresponding to the sampling period transmitted to the audio processing unit 121. As described above, this process is a process of converting a sound signal having a sampling frequency of 48 kHz into a sound signal having a sampling frequency of 16 kHz. As described above as a specific example, this is, for example, a process of obtaining a correction sound signal after obtaining an average of every three samples and converting it to a 16 kHz digital sound signal composed of the average value.

(S222)
Next, the CPU 101 measures the audio level of the audio signal during the sampling period with the sampling number decreased, and obtains the average value of the top N audio levels of the maximum audio level among the obtained audio levels. The level control unit 320 of the audio processing unit 121 is controlled.

(S230)
Next, the CPU 101 determines whether or not the average value of the top N audio levels of the maximum audio level stored in S222 is smaller than the threshold level in order to determine whether or not to perform noise reduction processing. . When the average value of the top N audio levels of the maximum audio level stored in S222 is smaller than the threshold level (Yes in S230), the audio processing unit 121 is controlled to execute the noise reduction process. If the average value of the top N audio levels stored in S222 is not smaller than the threshold level (No in S230), the audio processing unit 121 is controlled not to execute the noise reduction process.

  Here, the threshold level indicates an audio level that is higher than the driving sound generated by driving the driving unit, and is a level that is higher than the predetermined level in S250. According to such an operation, when the surrounding sound level before or after the generation of the driving sound is high, the driving sound is masked by the surrounding sound even if noise reduction processing is not performed in the first place. It is possible to prevent noise reduction processing. In addition, as described above, noise that may be generated when the corrected sound signal is generated (noise generated when the sound having a frequency equal to or higher than the Nyquist frequency of 16 kHz causes aliasing distortion) is included in the reduced signal. The possibility of being lost.

(S240)
When the average value of the top N audio levels of the maximum audio level stored in S222 is smaller than the threshold level (S230 Yes), the CPU 101 controls the audio processing unit 121 as follows. The CPU 101 controls the correction sound generation unit 330 of the sound processing unit 121 to generate a correction sound signal based on the sound signal of the sampling period in which the number of sampling is decreased by the data compression unit 310 in S221.

  There are several methods for generating a corrected sound signal. For example, as described in JP 2011-002723 A, a correction sound signal may be generated based on a sound signal in a sampling period using a linear prediction method. . Here, the linear prediction method is to calculate the sampling value of the (n + 1) th sample based on the sampling values from the first sample to the nth sample using, for example, an nth-order FIR filter. By sequentially executing this, sampling values of the (n + 2) th sample and the (n + 3) th sample are sequentially calculated. Note that the linear prediction method can be applied to either the forward direction or the backward direction in terms of time.

  In this embodiment, such a method is used, but the correction sound signal may be generated using a method other than this method.

  As described above, the imaging apparatus 100 according to the present embodiment generates a corrected sound signal using an audio signal whose sampling number is reduced, and thus can reduce the processing load for generating the corrected sound signal. .

(S241)
Next, the CPU 101 increases the number of samples of the 16 kHz corrected sound signal generated based on the 16 kHz sound signal in S240, and generates a 48 kHz corrected sound signal similar to the recorded sound. 121 controls the data decompression unit 340. As described above, each sample of the generated 16 kHz interpolation signal may be linearly interpolated or may be further subjected to a low-pass filter to suppress a steep change in the correction sound signal. .

(S250)
Next, the CPU 101 determines how much the 48 kHz corrected sound signal generated in S241 is to be combined with the sound signal during the period during which the diaphragm (drive unit) is driven. 121 controls the composite ratio determination unit 350. Therefore, the ratio of the average value of the top N audio levels of the maximum audio level stored in S222 to the predetermined audio level is used. As the predetermined level here, for example, an assumed sound level of the driving sound of the diaphragm (drive unit) collected by the sound input unit of the present embodiment is used. This level may be acquired, for example, by driving the diaphragm (drive unit) when the imaging apparatus 100 is activated, or may be stored in advance. That is, the predetermined sound level may indicate a different sound level for each drive unit.

  In the present embodiment, if the average value of the top N audio levels stored in S222 is P and the predetermined audio level is Q, the composite ratio X of the corrected sound signal is X = 1− ( P ÷ Q). On the other hand, the synthesis ratio Y of the audio signal during the period during which the drive unit is driven is Y = 1−X.

  That is, as the sound level of the sound signal in the sampling period increases, the ratio of the correction sound signal generated based on the sound signal in the sampling period is synthesized with the sound signal in the period during which the diaphragm (drive unit) is driven (Composition ratio) will be lowered. Thus, the CPU 101 changes the synthesis ratio of the corrected sound signal according to the sound level of the sound signal during the sampling period. Since the corrected sound signal is generated based on the audio signal during the sampling period, in other words, the composite ratio of the corrected sound signal is changed according to the sound level of the generated corrected sound signal.

  By determining the synthesis ratio in this way, noise that may be included in the generated corrected sound signal (noise generated when a voice having a frequency equal to or higher than the Nyquist frequency of 16 kHz causes aliasing distortion) is inconspicuous. can do.

(S251)
Next, the CPU 101 synthesizes the corrected sound signals generated in S241 with the synthesis ratio X determined in S250 and the audio signals during the period during which the diaphragm (driving unit) is driven with the synthesis ratio Y. The synthesis unit 360 of the audio signal processing unit 121 is controlled.

  After that, the CPU 101 stores the aperture (drive unit) stored in the RAM 102 so that the synthesized audio signal synthesized by the synthesis unit 360 is recorded as the audio signal during the drive period of the aperture (drive unit). Overwrite the audio signal during the driving period.

(S260)
Finally, the CPU 101 determines whether or not a shooting end instruction is input from the operation unit 104. If the end instruction is input, the noise reduction process ends. If not, the process proceeds to step S210. Return to, and continue control.

  As described above, the CPU 101 controls the audio processing unit 121 to execute the noise reduction process during the moving image shooting operation.

  With this configuration, the imaging apparatus 100 according to the present exemplary embodiment generates a signal based on an audio signal during a period in which the driving unit is not driven, and performs a process of reducing driving sound based on the generated signal. In this case, the amount of calculation can be reduced.

  In addition, the imaging apparatus 100 according to the present embodiment additionally includes noise that may be included in the generated corrected sound signal (noise generated when a sound having a frequency equal to or higher than the Nyquist frequency of 16 kHz causes aliasing distortion). It can be inconspicuous. This is because when the audio level of the audio signal during the sampling period is high, the drive sound of the drive unit is not noticeable, so the synthesis ratio of the correction sound signal may be lowered, or the correction sound signal is generated by lowering the synthesis ratio. This is because the aliasing distortion noise can be reduced. In addition, when the audio level of the audio signal during the sampling period is small, the aliasing distortion noise generated in the correction sound signal is reduced in the first place. Therefore, even if the synthesis ratio is increased, the aliasing distortion noise generated in the correction sound signal is large. Because it is difficult to become.

  As described above, the imaging apparatus 100 according to the present embodiment reduces the influence of the aliasing distortion noise generated in the corrected sound signal even if the corrected sound signal is generated after the data amount of the audio signal in the sampling period is thinned out, and the drive unit The driving noise can be reduced.

  In S222 of the present embodiment, the audio level of the audio signal during the sampling period in which the number of samplings is reduced in S221 is measured, and among the obtained audio levels, the highest N audio levels of the maximum audio level are measured. Average values were obtained. However, even if the audio level of the audio signal in the sampling period before the decrease in the number of samples is measured in S221 and the average value of the top N audio levels of the maximum audio level among the obtained audio levels is acquired. good.

  In S222 of the present embodiment, the audio level of the audio signal during the sampling period in which the number of samplings is reduced in S221 is measured, and among the obtained audio levels, the highest N audio levels of the maximum audio level are measured. Average values were obtained. However, in this embodiment, as a result of the data amount being reduced to 1/3 by the data compression unit 310, the 48 kHz audio signal is substantially converted to a 16 kHz audio signal. Therefore, in S222, frequency components higher than 8 kHz, which is the Nyquist frequency of 16 kHz, may be extracted by a high-pass filter, and the average value of the top N audio levels of the maximum audio level may be acquired. Then, the average value of the top N audio levels of the maximum audio level of the frequency component higher than 8 kHz is used also in the determination of whether or not the noise reduction process in S230 is executed and the calculation of the synthesis ratio in S250. That is, determination of whether or not the noise reduction process of S230 is performed using the audio level of the audio signal having a frequency higher than the Nyquist frequency of the audio signal in the sampling period after the thinning, which is the generation source of the aliasing distortion noise in the corrected sound signal And the synthesis ratio of S250 is calculated. By adopting such a configuration, the imaging apparatus 100 according to the present embodiment can increase the synthesis ratio of the correction sound signal when the influence of the aliasing distortion noise generated in the correction sound signal is low. High noise reduction processing can be performed.

  Further, the correction sound signal synthesis ratio X calculated in S250 of the present embodiment, and the audio signal synthesis ratio Y during the driving period of the drive unit are the synthesis ratios in front of the driving period of the driving unit. There may be. In this case, after the period during which the drive unit is driven, the synthesis ratio of the correction sound signal gradually approaches 0 from X, and the synthesis ratio of the audio signal during the period during which the drive unit is driven is changed from Y. You may change so that it may approach 1 gradually. Further, the composition ratio X and the composition ratio Y may always be constant values during the period during which the drive unit is driven.

  In addition, when the imaging apparatus 100 according to the present exemplary embodiment is, for example, an interchangeable lens type imaging apparatus, the CPU 101 communicates with the lens unit when the lens unit of the imaging unit 110 is mounted on the mounting unit. The identification information recorded on the recording medium is acquired. Then, based on the identification information, the type of the lens unit may be specified, the threshold level in S230 and the predetermined audio level in S250 corresponding to the type may be set, and the processing of FIG. 2 may be performed. That is, a predetermined audio level that differs for each lens unit can be set. By doing in this way, the noise reduction process corresponding to a drive sound which changes with every mounted lens unit can be performed.

  Note that the imaging apparatus 100 according to the present embodiment may be any apparatus as long as it can perform still image shooting during moving image shooting, such as a digital camera, a mobile phone, and a smartphone. Further, the present invention includes a case where a software program that implements the functions of the above-described embodiments is supplied to a system or apparatus having a computer that can execute the program and the program is executed. A computer here includes a mobile phone, a smart phone, a personal computer, etc., for example.

[Other Embodiments]
Although the present invention has been described in detail based on preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various forms within the scope of the present invention are also included in the present invention. included.

  Also, when a software program that realizes the functions of the above-described embodiments is supplied from a recording medium directly to a system or apparatus having a computer that can execute the program using wired / wireless communication, and the program is executed Are also included in the present invention. Accordingly, the program code itself supplied and installed in the computer in order to implement the functional processing of the present invention by the computer also realizes the present invention. That is, the computer program itself for realizing the functional processing of the present invention is also included in the present invention. In this case, the program may be in any form as long as it has a program function, such as an object code, a program executed by an interpreter, or script data supplied to the OS.

Claims (7)

An audio signal processing device having a drive unit,
Control means for controlling the drive of the drive unit;
Obtaining means for obtaining an audio signal digitized at a predetermined sampling frequency, which indicates the audio around the audio signal processing device;
Audio processing means for processing the audio signal acquired by the acquisition means, and correcting based on a signal obtained by reducing the data amount of the audio signal acquired by the acquisition means when the driving unit is not driven When the drive unit is driven using a signal generated by generating a sound signal and combining the audio signal acquired by the acquisition unit when the drive unit is driven and the corrected sound signal at a predetermined synthesis ratio. Audio processing means for reducing drive sound due to driving of the drive unit in the audio signal acquired by the acquisition means;
The sound processing unit is configured to acquire the sound acquired by the acquisition unit when the drive unit is not driven based on the sound level of the audio signal acquired by the acquisition unit when the drive unit is not driven. The audio signal processing apparatus, wherein the synthesis ratio is determined such that the synthesis ratio of the corrected sound signal is increased as the audio level of the signal is smaller. An audio signal processing device having a drive unit,
Control means for controlling the drive of the drive unit;
Obtaining means for obtaining an audio signal digitized at a predetermined sampling frequency, which indicates the audio around the audio signal processing device;
Audio processing means for processing the audio signal acquired by the acquisition means, and correcting based on a signal obtained by reducing the data amount of the audio signal acquired by the acquisition means when the driving unit is not driven When the drive unit is driven using a signal generated by generating a sound signal and combining the audio signal acquired by the acquisition unit when the drive unit is driven and the corrected sound signal at a predetermined synthesis ratio. Audio processing means for reducing drive sound due to driving of the drive unit in the audio signal acquired by the acquisition means;
The sound processing unit is configured to acquire the sound acquired by the acquisition unit when the drive unit is not driven based on the sound level of the audio signal acquired by the acquisition unit when the drive unit is not driven. The audio signal processing apparatus, wherein the synthesis ratio is determined such that the higher the audio level of the signal, the smaller the synthesis ratio of the corrected sound signal.   The audio processing unit determines the synthesis ratio based on the audio level of the audio signal acquired by the acquisition unit and the audio level of the driving sound of the driving unit when the driving unit is not driven. The audio signal processing apparatus according to claim 1 or 2,   When generating the corrected sound signal, the sound processing means reduces the amount of data by thinning out the number of samples of the sound signal acquired by the acquiring means when the driving unit is not driven. The audio signal processing device according to any one of claims 1 to 3. An audio signal processing device having a drive unit,
Control means for controlling the drive of the drive unit;
Obtaining means for obtaining an audio signal digitized at a predetermined sampling frequency, which indicates the audio around the audio signal processing device;
Audio processing means for processing the audio signal acquired by the acquisition means, and correcting based on a signal obtained by reducing the data amount of the audio signal acquired by the acquisition means when the driving unit is not driven When the drive unit is driven using a signal generated by generating a sound signal and combining the audio signal acquired by the acquisition unit when the drive unit is driven and the corrected sound signal at a predetermined synthesis ratio. Audio processing means for reducing drive sound due to driving of the drive unit in the audio signal acquired by the acquisition means;
The audio processing unit thins out the number of samples of the audio signal acquired by the acquisition unit when the driving unit is not driven, and obtains a signal having a sampling frequency lower than the predetermined sampling frequency. Generating the corrected sound signal based on the signal,
The sound processing means calculates the synthesis ratio based on a sound level of a sound signal having a frequency higher than the Nyquist frequency of the low sampling frequency of the sound signal acquired by the acquiring means when the driving unit is not driven. An audio signal processing apparatus characterized by determining. Imaging means for acquiring an optical image of a subject;
A mounting unit that replaceably attaches a lens unit that guides an optical image to the imaging unit;
The voice processing unit is configured to perform the synthesis based on a voice level of the voice signal acquired by the acquisition unit when the driving unit of the lens unit is not driven and a predetermined voice level that is different for each lens unit. The audio signal processing apparatus according to claim 1, wherein the ratio is determined.   The sound processing means does not perform the process of reducing the driving sound when the sound level of the sound signal acquired by the acquiring means is larger than a threshold level when the driving unit is not driven. The sound signal processing apparatus according to claim 1, wherein the sound signal processing apparatus is a sound signal processing apparatus.

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