JP5018860B2 - Signal processing apparatus and imaging apparatus - Google Patents

Description

  The present invention relates to a signal processing device and an imaging device that reduce a noise signal included in an audio signal.

  As a method of reducing the component (noise component) based on the noise sound from the sound signal in which the target sound and the noise sound are mixed, the noise sound is estimated from the acquired sound signal, and the estimated noise sound signal (hereinafter referred to as the noise signal) In general, the noise signal is subtracted from the audio signal (see, for example, Patent Document 1).

JP 2005-195955 A

  In such a method, when the noise sound is acquired in advance or when the noise sound is a periodic sound, the size of the noise sound and the timing including the noise sound can be easily estimated. The noise signal can be appropriately reduced. However, when the sound generated when various mechanisms in the device are driven (hereinafter referred to as operation sound) is a noise sound, the above-mentioned operation sound is generated at irregular timings, so that the noise sound included in the audio signal is not generated. It is difficult to estimate. For this reason, the audio signal after subtracting the noise signal may contain a noise component called musical noise.

  It is an object of the present invention to provide a signal processing apparatus and an imaging apparatus that can appropriately reduce operation sound included in an audio signal.

In order to solve the above-described problem, the signal processing apparatus according to the present invention provides a plurality of predetermined time intervals obtained by dividing an audio signal represented by a time function in which a target sound and an operation sound are mixed by a predetermined time width. The influence of the operation sound is reduced from signal conversion means for converting the first sound signal into a second sound signal represented by a frequency function, the second sound signal, and the sound signal indicating the operation sound. Calculating means for obtaining the third audio signal, and using as a reference signal an audio signal indicating the target sound of the plurality of second audio signals, a value of a frequency spectrum in each frequency band of the third audio signal; The frequency spectrum value in the corresponding frequency band of the reference signal multiplied by the coefficient is compared, and the value of the frequency spectrum in the third audio signal corresponds to the reference signal multiplied by the coefficient. Is different from the value of the wavenumber spectrum, the value of the third frequency spectrum in the speech signal, and correcting means for replacing said on the value of the corresponding frequency spectrum, the audio signal correction processing has been performed by the correction means, And a signal reverse conversion means for performing reverse conversion from the sound signal indicated by the frequency function to the sound signal indicated by the time function.

Further, the signal processing apparatus of the present invention is configured to obtain a plurality of first audio signals for each predetermined time obtained by dividing an audio signal represented by a time function in which a target sound and an operation sound are mixed by a predetermined time width. A third audio signal in which the influence of the operation sound is reduced from signal conversion means for converting to a second audio signal indicated by a frequency function, the second audio signal, and the audio signal indicating the operation sound. The calculation means to be obtained, and the reference obtained by multiplying the value of the frequency spectrum in each frequency band of the third audio signal by a coefficient, using the audio signal indicating the target sound of the plurality of second audio signals as a reference signal The frequency spectrum value in the corresponding frequency band of the signal is compared, and the frequency spectrum value in the third audio signal is less than the corresponding frequency spectrum value in the reference signal multiplied by the coefficient The correction means for correcting the frequency spectrum value in the third audio signal so as not to fall below the value of the corresponding frequency spectrum, and the audio signal subjected to the correction processing by the correction means, A signal reverse conversion means for performing reverse conversion from an audio signal represented by a frequency function to an audio signal represented by the time function.

Further, the signal processing apparatus of the present invention is configured to obtain a plurality of first audio signals for each predetermined time obtained by dividing an audio signal represented by a time function in which a target sound and an operation sound are mixed by a predetermined time width. A third audio signal in which the influence of the operation sound is reduced from signal conversion means for converting to a second audio signal indicated by a frequency function, the second audio signal, and the audio signal indicating the operation sound. The calculation means to be obtained, and the reference obtained by multiplying the value of the frequency spectrum in each frequency band of the third audio signal by a coefficient, using the audio signal indicating the target sound of the plurality of second audio signals as a reference signal A frequency spectrum value in the corresponding frequency band of the signal is compared, and the frequency spectrum value in the third audio signal exceeds the corresponding frequency spectrum in the reference signal multiplied by the coefficient In this case, correction means for correcting the frequency spectrum value in the third audio signal so as not to exceed the value of the corresponding frequency spectrum, and the audio signal subjected to correction processing by the correction means, And a signal reverse conversion means for performing reverse conversion from the audio signal indicated by the function to the audio signal indicated by the time function.

Further, the signal processing apparatus of the present invention is configured to obtain a plurality of first audio signals for each predetermined time obtained by dividing an audio signal represented by a time function in which a target sound and an operation sound are mixed by a predetermined time width. A third audio signal in which the influence of the operation sound is reduced from signal conversion means for converting to a second audio signal indicated by a frequency function, the second audio signal, and the audio signal indicating the operation sound. The calculation means to be obtained, and the reference obtained by multiplying the value of the frequency spectrum in each frequency band of the third audio signal by a coefficient, using the audio signal indicating the target sound of the plurality of second audio signals as a reference signal The frequency spectrum value in the corresponding frequency band of the signal is compared, and the frequency spectrum value in the third audio signal is different from the corresponding frequency spectrum value in the reference signal multiplied by the coefficient. The frequency spectrum value in the third audio signal is the value of the corresponding frequency spectrum and the frequency spectrum value in the vicinity of the frequency spectrum of the reference signal multiplied by the coefficient. A correction unit that replaces the correction value calculated by using the correction unit, and the audio signal that has been corrected by the correction unit is inversely converted from the audio signal represented by the frequency function to the audio signal represented by the time function. And a signal reverse conversion means .

Further, the signal processing apparatus of the present invention is configured to obtain a plurality of first audio signals for each predetermined time obtained by dividing an audio signal represented by a time function in which a target sound and an operation sound are mixed by a predetermined time width. A third audio signal in which the influence of the operation sound is reduced from signal conversion means for converting to a second audio signal indicated by a frequency function, the second audio signal, and the audio signal indicating the operation sound. The calculation means to be obtained, and the reference obtained by multiplying the value of the frequency spectrum in each frequency band of the third audio signal by a coefficient, using the audio signal indicating the target sound of the plurality of second audio signals as a reference signal The frequency spectrum value in the corresponding frequency band of the signal is compared, and the frequency spectrum value in the third audio signal exceeds the corresponding frequency spectrum value in the reference signal multiplied by the coefficient. When the frequency spectrum value of the third audio signal is determined, the frequency spectrum value of the reference signal multiplied by the coefficient and the value of the corresponding frequency spectrum and the frequency spectrum value of the frequency band in the vicinity thereof are used. A correction means for correcting so as not to exceed a correction value calculated by using the sound signal, and a voice signal subjected to correction processing by the correction means from a voice signal indicated by the frequency function and a voice indicated by the time function And a signal reverse conversion means for performing reverse conversion to a signal.

Further, the signal processing apparatus of the present invention is configured to obtain a plurality of first audio signals for each predetermined time obtained by dividing an audio signal represented by a time function in which a target sound and an operation sound are mixed by a predetermined time width. A third audio signal in which the influence of the operation sound is reduced from signal conversion means for converting to a second audio signal indicated by a frequency function, the second audio signal, and the audio signal indicating the operation sound. The calculation means to be obtained, and the reference obtained by multiplying the value of the frequency spectrum in each frequency band of the third audio signal by a coefficient, using the audio signal indicating the target sound of the plurality of second audio signals as a reference signal The frequency spectrum value in the corresponding frequency band of the signal is compared, and the frequency spectrum value in the third audio signal is less than the corresponding frequency spectrum value in the reference signal multiplied by the coefficient The frequency spectrum value in the third audio signal is the value of the corresponding frequency spectrum and the frequency spectrum value in the vicinity of the frequency spectrum of the reference signal multiplied by the coefficient. A correction unit that corrects the correction value so as not to fall below a correction value calculated by using the voice signal indicated by the time function from the voice signal indicated by the frequency function. And a signal reverse conversion means for performing reverse conversion to a signal.

In the case where the correction value is calculated using the corresponding frequency spectrum value and the frequency spectrum value in the frequency band in the vicinity of the frequency spectrum of the reference signal multiplied by the coefficient, the correction value corresponds to the corresponding frequency spectrum. The average of the frequency spectrum value and the frequency spectrum value of the nearby frequency band, the maximum value of the corresponding frequency spectrum value and the frequency spectrum value of the nearby frequency band, or the corresponding frequency spectrum value And the minimum value of the frequency spectrum values in the frequency band in the vicinity thereof.

The imaging device of the present invention includes an imaging unit that acquires an image signal, a sound collection unit that acquires an audio signal in synchronization with the acquisition of the image signal by the imaging unit, and any one of the signals described above The image processing apparatus includes a processing device, and a storage unit that stores an image signal acquired by the imaging unit and an audio signal subjected to signal processing by the signal processing device.

  According to the present invention, it is possible to effectively reduce the operation sound included in the audio signal.

It is a functional block diagram which shows the structure of a digital camera. It is a functional block diagram which shows the structure of a signal processing apparatus. It is a figure which shows the relationship between the audio | voice signal acquired, a window function, a frame division | segmentation, and AF operation signal. It is a figure which shows the flow of the signal processing in a signal processing apparatus. It is a figure which shows the flow of the signal processing in other embodiment.

  FIG. 1 is a functional block diagram showing the configuration of the digital camera 10. As is well known, the digital camera 10 photoelectrically converts the subject light captured by the imaging optical system 15 by the imaging device 16 and acquires image data from the electrical signal (image signal) after the photoelectric conversion.

  The imaging optical system 15 includes a plurality of lenses. The lenses constituting the imaging optical system 15 move along the optical axis L by driving the lens driving unit 18 when changing the zoom magnification or adjusting the focus. The imaging optical system 15 is provided with a diaphragm 19. This diaphragm 19 changes the amount of subject light incident on the image sensor 16 by changing the size of the aperture. The size of the aperture of the aperture 19 is changed by the aperture driver 20 so that the aperture value is set in advance.

  The shutter 21 is disposed between the imaging optical system 15 and the imaging element 16. The shutter 21 can be switched between an open state in which the imaging element 16 is irradiated with subject light captured via the imaging optical system 15 and a light shielding state in which the subject light is shielded. At the time of photographing, the shutter 21 is once held in a light shielding state and then switched to an open state. Then, when a preset time elapses after the shutter 21 is switched to the open state, the shutter 21 is switched to the light shielding state again. Note that switching between the light shielding state and the open state of the shutter 21 is performed by the shutter driving unit 22.

  The image pickup device 16 is configured by, for example, a charge coupled device (CCD), a complementary metal-oxide semiconductor (CMOS), or the like. The image sensor 16 receives subject light captured by the imaging optical system 15, converts the received light amount into signal charges (photoelectric conversion), and accumulates the converted signal charges. Thereafter, the signal charge accumulated in the image sensor 16 is output to an AFE (Analog Front End) circuit 25.

  The AFE circuit 25 includes an AGC circuit, a CDS circuit, and an A / D conversion circuit (not shown). The AFE circuit 25 performs processing such as gain control and noise removal on the input image signal. After these processes, the AFE circuit 25 converts the analog image signal into a digital image signal. The digital image signals are collected for each frame and recorded in the image memory 30. The drive timing of the image sensor 16 and the AFE circuit 25 is controlled by a timing generator (not shown).

  The image processing circuit 35 performs image processing such as white balance processing, color interpolation processing, contour compensation processing, and gamma processing on the image signal stored in the image memory 30. After these image processes, the image processing circuit 35 performs a format process for compression using a storage system such as the JPEG system. The image processing circuit 35 performs encoding processing and decoding processing on the image data. Reference numeral 37 denotes a recording I / F.

  The LCD 38 displays an image acquired by the digital camera 10, an image stored in the storage medium 36, a through image captured in a shooting standby state, and a setting image for setting or changing a shooting condition. Etc. are displayed. Examples of the image acquired by the digital camera 10 and the image stored in the storage medium 36 include moving images in addition to still images. The LCD 38 is controlled by a display control circuit 39. The speaker 40 outputs sound or the like associated with the moving image when the moving image is displayed on the LCD 38. The sound output control in the speaker 40 is executed by the sound control circuit 41.

  The sound collection unit 43 is constituted by, for example, a microphone, and acquires, for example, sound during moving image shooting or recording. The audio signal acquired by the sound collection unit 43 is recorded in the audio memory 44.

  The signal processing device 45 performs processing for reducing the noise sound included in the audio signal with respect to the audio signal acquired by the sound collection unit 43. Note that the noise sound includes an operation sound that is generated when each mechanism provided in the digital camera 10 is driven at the time of moving image recording or recording, and an operation sound that is operated when various mechanisms are driven. Can be mentioned. In addition, the signal processing device 45 compresses and encodes the acquired audio signal (including the audio signal subjected to the noise noise reduction process described above) and the audio signal subjected to the compression encoding process. The process which decodes is performed.

  The CPU 50 comprehensively controls each unit of the digital camera 10 by executing a control program (not shown) stored in the built-in memory 51. Examples of the control in the CPU 50 include control based on the operation of the release button 52 and control based on the operation of the setting operation unit 53. Examples of the control based on the operation of the release button 52 include known AE processing, AF processing, imaging processing, and the like. Control based on the operation of the setting operation unit 53 includes processing such as initial setting and setting of shooting conditions.

  In addition, the CPU 50 performs a process of writing image data acquired at the time of shooting to the storage medium 36. For example, when still image shooting is performed, the CPU 50 converts the image data that has been encoded by the image processing circuit 35 into one file (model information of the digital camera 10, shooting information at the time of shooting, and the like). (Still image files) are collectively written in the storage medium 36. Similarly, when moving image shooting is performed, each frame image data obtained by moving image shooting is subjected to encoding processing by the image processing circuit 35. Therefore, each frame image subjected to these encoding processing is processed. The data and the audio data subjected to the signal processing by the signal processing circuit 45 are collectively written in the storage medium 36 as one file (moving image file) together with the model information of the digital camera 10 and shooting information at the time of shooting. .

  Next, the configuration of the signal processing device 45 described above will be described with reference to the functional block diagram of FIG. As shown in FIG. 2, the signal processing device 45 includes a frequency conversion unit 61, a signal calculation unit 62, a storage unit 63, a signal correction unit 64, and a frequency inverse conversion unit 65.

  The frequency conversion unit 61 converts the audio signal acquired by the sound collection unit 43 from a signal (time domain signal) indicated by a time function to a signal (frequency domain signal) indicated by a frequency function. First, the frequency converter 61 determines a window width in a window function described later. After determining the window width in this window function, the frequency converting unit 61 converts the input audio signal so that the number of samples per frame is, for example, 1024 when the determined window width is one frame. To divide.

  Next, the frequency conversion unit 61 multiplies a window function such as a Hanning window while shifting by 0.5 frames, and then performs a Fourier transform process on the audio signal to which the window function is applied. As is well known, since a window function called a Hanning window is a function having both end values of 0 and a median value of 1, a signal obtained by multiplying the window functions is a signal in which the central portion is emphasized. For this reason, when a signal such as vibration that changes with time is shifted and analyzed for each frame, it is difficult to capture a characteristic part. For this reason, a characteristic portion of the signal is detected by performing an analysis that is overlapped by shifting by 0.5 frame. By performing these processes, the acquired audio signal is converted from a time domain signal to a frequency domain signal for each frame while shifting by 0.5 frame. The audio signal subjected to these processes is output to the signal calculation unit 62 and the signal correction unit 64.

  The signal calculation unit 62 performs a process of reducing noise noise included in the acquired audio signal. As described above, the audio signal acquired by the sound collection unit 43 includes a signal in which a target sound (target sound) and a noise sound (operation sound) are mixed. The signal calculation unit 62 subtracts a signal (noise signal) based on the noise sound from the sound signal output from the frequency conversion unit 61 to reduce the noise sound included in the sound signal. This noise signal consists of a frequency domain signal corresponding to the same frame width as the audio signal output from the frequency converter 61. The noise signal is stored in the storage unit 63 in advance.

  In the present embodiment, the noise signal is stored in the storage unit 63 in advance, and the noise signal stored in the storage unit 63 is subtracted from the audio signal for each frame output from the frequency conversion unit 61. The present invention is not limited to this, and the noise signal multiplied by the coefficient can be subtracted from the audio signal of each frame output from the frequency converter 61.

  In addition, the noise signal is not stored in the storage unit 63 in advance, but the noise signal is acquired using a conventional noise estimation method, or the acquired noise signal or a signal obtained by multiplying the noise signal by a coefficient is acquired. May be subtracted from the audio signal for each frame output from the frequency converter 61.

  The signal correction unit 64 performs correction on the audio signal whose noise component has been reduced by the signal calculation unit 62 (hereinafter, the audio signal that has been subjected to reduction processing). The signal correcting unit 64 receives an audio signal from the frequency domain signal of each frame, in which noise sound is not mixed, that is, only the target sound is input from the frequency converting unit 61. The signal correction unit 64 uses an audio signal of only the target sound as a reference signal, and multiplies the reference signal by a coefficient. After multiplying the reference signal by a coefficient, the signal correction unit 64 corrects the audio signal that has been subjected to reduction processing based on the reference signal multiplied by the coefficient. The corrected audio signal subjected to this correction is output to the frequency inverse transform unit 65. The frequency inverse transform unit 65 inversely transforms the corrected audio signal from a signal represented by a frequency function to a signal represented by a time function. The audio signal inversely converted into a signal represented by a time function is written in the audio memory 44.

  Next, the flow of signal processing in the signal processing device 45 will be described with reference to FIGS. 3 and 4. As shown in FIG. 3, the sound acquired by the sound collection unit 43 becomes a periodic signal in a short time of about several tens of ms. As described above, when an audio signal is input, the frequency converting unit 61 sets a window width in the window function and then performs frame division.

  As described above, the frequency conversion unit 61 multiplies a window function such as a Hanning window while shifting by 0.5 frames, and then performs a Fourier transform process on the audio signal to which the window function is applied. For this reason, when the above-described processing is performed on the audio signal input to the frequency converting unit 61, the audio signal having the area indicated by reference numeral 71 and the area indicated by reference numeral 72 as one frame, the area indicated by reference numeral 72, and An audio signal for each frame is generated in the order of an audio signal having the region indicated by reference numeral 73 as one frame, and so on, and is output to the signal calculation unit 62. When an audio signal for each frame is input, the signal calculation unit 62 reads a noise signal composed of an operation sound recorded in the recording unit 63 and subtracts the noise signal from the audio signal for each frame.

  For example, when AF (autofocus) processing is executed while sound is acquired by the sound collection unit 43, an AF operation signal is output. In response to the output of the AF operation signal, the lens driving unit 18 is driven, and the lens constituting the imaging optical system 15 moves in the optical axis L direction. When the lens driving unit 18 is driven and the lens constituting the imaging optical system 15 is moved, the operation sound is generated. For this reason, the sound signal acquired by the sound collection unit 43 is a sound signal in which the target sound and the noise sound are mixed. For example, when the timing at which the AF drive signal is output is within the area indicated by reference numeral 76, it is estimated that the noise component is superimposed on the audio signal in the subsequent areas (areas indicated by reference numerals 77 and 78). Can do.

  For example, an audio signal on which a noise component is superimposed can be expressed by the following equation (1).

x (t) = s (t) + n (t) (1)
Here, x (t) is an audio signal acquired by the sound collection unit 43, s (t) is an audio signal of a target sound, and n (t) is a noise signal such as an operation sound. These signals are shown as a time function.

  By performing the Fourier transform described above, the audio signal in which the target sound and the noise sound are mixed is converted from the signal x (t) indicated by the time function into the signal X (f) indicated by the frequency function. Note that f indicates a frequency.

  Here, if the sound signal of the target sound is Se (f), Se (f) of the sound signal of the target sound is expressed by the following equation (2).

| Se (f) | = | X (f) | -α | Ne (f) | (2)
Note that Ne (f) is a noise signal, and α is a subtraction coefficient. The value of α depends on the magnitude of the noise signal to be subtracted when obtaining the audio signal of only the target sound using the above-described equation (2). In some cases, musical noise or the like may be artificially superimposed on the audio signal after subtraction. For this reason, as a value of (alpha), it is desirable to use the value of 0.5-4.

  FIG. 4 shows the frequency spectrum of each signal (81, 82, 83, 83 ′, 84, 84 ′). In the graph of each frequency spectrum, the horizontal axis is the frequency band, and the vertical axis is the sound intensity (hereinafter referred to as the sound intensity). , Also referred to as “frequency spectrum value”).

  Hereinafter, as illustrated in FIG. 4, the acquired audio signal is denoted by reference numeral 81 and the noise signal is denoted by reference numeral 82. The signal calculation unit 62 reads out the noise signal 82 stored in the storage unit 63 and then converts the frequency spectrums 82a to 82h in the noise signal 82 from the frequency spectrum 81a to 81h in the Fourier-transformed audio signal 81 for each frequency band. Subtract to By this subtraction process, a reduced audio signal 83 with a reduced noise component is generated.

  Next, the signal correction unit 64 generates a signal (reference numeral 84 ′) obtained by multiplying the reference signal 84 by the coefficient β. After generating the signal 84 ′, the signal correction unit 64 compares the frequency spectrum of the reference signal 84 ′ multiplied by the coefficient β with the frequency spectrum of the audio signal 83 that has been subjected to the reduction process for each frequency region. That is, the sound intensity in each frequency band of the reduced audio signal 83 is compared with the sound intensity in the corresponding frequency band of the reference signal 84 ′ multiplied by the coefficient β.

  For example, when the sound intensity of a certain frequency band in the audio signal 83 that has been subjected to reduction processing is less than the value of the sound intensity of the corresponding frequency band in the reference signal 84 ′ multiplied by the coefficient β, The sound intensity value in the frequency band in the audio signal 83 is replaced with the sound intensity value in the corresponding frequency band in the reference signal 84 ′ multiplied by the coefficient β.

  Similarly, if the sound intensity in a certain frequency band in the audio signal 83 subjected to the reduction process exceeds the value of the sound intensity in the corresponding frequency band in the reference signal 84 ′ multiplied by the coefficient β, the sound signal 83 is reduced. The sound intensity value in the frequency band in the processed audio signal 83 is replaced with the sound intensity value in the corresponding frequency band in the reference signal 84 ′ multiplied by the coefficient β.

  FIG. 4 shows a case where the value (sound intensity) of the frequency spectrum 83e of the audio signal 83 subjected to the reduction process is less than the value of the frequency spectrum 84′e of the reference signal 84 ′ multiplied by the coefficient β. ing. In this case, the signal correction unit 64 replaces the value of the frequency spectrum 83e of the reduced audio signal 83 with the value of the frequency spectrum 84'e of each frequency band in the reference signal 84 'multiplied by the coefficient β.

  As a result, an audio signal (corrected audio signal) 83 ′ subjected to the correction process is generated. The corrected audio signal 83 ′ is converted from a signal represented by a frequency function into a signal represented by a time function by inverse Fourier transform or the like by the frequency inverse transform unit 65. Since the frequency domain signal of each frame is generated by the Fourier transform process while shifting by 0.5 frames, the audio signal indicated by the time function subjected to the inverse Fourier transform process by the frequency inverse transform unit 65 is , The images are joined together while shifting by 0.5 frame.

  In this way, by subtracting the component of the operation sound that occurs when the internal mechanism of the camera is driven from the sound signal, after generating the sound signal that reduces the effect of the operation sound, the effect of this operation sound is reduced. The sound signal is corrected based on the sound signal of only the target sound. For this reason, it is possible to prevent the occurrence of musical noise that occurs when an operation sound having a characteristic different from that of the original operation sound is estimated as a noise sound. Thus, in this embodiment, the noise sound contained in the acquired audio | voice signal can be reduced appropriately.

  In the present embodiment, the timing for outputting the AF drive signal is given as a requirement for the generation of the operation sound as the noise sound, but in addition to this, it is output when an operation unit such as a zoom button is operated. In the case of a digital camera equipped with a camera shake correction function, the timing at which the operation signal of the operation unit provided in the digital camera is output, the drive signal of the aperture drive unit that is driven when changing the aperture value, etc. Includes a timing at which a start signal of camera shake correction processing is output.

  In the present embodiment, in the comparison of the frequency spectrum for each frequency band, the value of the frequency spectrum (sound intensity) in a certain frequency band in the reduced audio signal 83 corresponds to the reference signal 84 ′ multiplied by the coefficient β. The frequency spectrum value of that frequency band in the reduced audio signal is changed to the frequency spectrum value of the corresponding frequency band of the reference signal multiplied by the coefficient β. Although it is substituted, it need not be limited to this.

  For example, when the value of the frequency spectrum in a certain frequency band in the reduced audio signal is less than the value of the frequency spectrum in the corresponding frequency band of the reference signal multiplied by the coefficient β, the reduced audio signal The frequency spectrum value in that frequency band may be corrected to a value that exceeds the value of the frequency spectrum in the corresponding frequency band of the reference signal multiplied by the coefficient β. In this case, the ratio of the frequency spectrum values of the adjacent frequency bands is calculated in advance for each of the reduced audio signal 83 and the reference signal 84 ′ multiplied by the coefficient β. What is necessary is just to correct | amend the value of the frequency spectrum in the audio | voice signal 83 after the reduction process so that ratio of values may correspond.

  The same applies to the case where the value of the frequency spectrum of a certain frequency band in the audio signal that has been subjected to reduction processing exceeds the value of the frequency spectrum of the corresponding frequency band of the reference signal multiplied by the coefficient β. Without replacing the value of the frequency spectrum of that frequency band in the already-processed audio signal with the value of the frequency spectrum of the corresponding frequency band of the reference signal multiplied by the coefficient β. The value of the frequency spectrum may be corrected to a value lower than the value of the frequency spectrum of the corresponding frequency band of the reference signal multiplied by the coefficient β. The correction may be performed in the same manner so that the ratios of the frequency spectrum values of the adjacent frequency bands match.

  In the present embodiment, the frequency spectrum of each frequency band of the reference signal is multiplied by the coefficient β, the frequency spectrum for each frequency band in the reference signal multiplied by the coefficient β, and the frequency band in the reduced audio signal Are compared for each frequency band, and as a result of comparison, frequency bands with different frequency spectrum values are set as the frequency band to be corrected, and the frequency spectrum of the frequency band to be corrected in the reduced audio signal is corrected. To do. Then, when correcting the frequency spectrum of the frequency band to be corrected in the reduced audio signal, based on the frequency spectrum of the corresponding frequency band (frequency band to be corrected) in the reference signal multiplied by the coefficient β, Correction is being performed. However, the method of correcting the frequency spectrum is not limited to this, and among the frequency bands in the reference signal, a plurality of frequency bands including the frequency band to be corrected (for example, frequencies adjacent to the frequency band to be corrected). Frequency) of the frequency spectrum of the band) is calculated as a simple average value, a weighted average value, a maximum value or a minimum value, and the obtained value is used as a limit value, and the frequency in the audio signal subjected to reduction processing based on the limit value Of the spectrum, it is also possible to correct the value of the frequency spectrum of the frequency band to be corrected. Hereinafter, a case where a simple average value is used will be described. It should be noted that the number of frequency spectra used when obtaining the simple average value may be set as appropriate.

  As illustrated in FIG. 5, for example, a case will be described in which the frequency band in the frequency spectrum 83e is the frequency band to be corrected among the frequency spectrums in the respective frequency bands in the audio signal 83 that has been subjected to reduction processing. The signal correction unit 64 reads out values of a plurality of frequency bands (for example, frequency spectra 86d, 86e, 86f) including a frequency band in the frequency spectrum 83e among the frequency spectrums of the respective frequency bands in the reference signal, and these frequencies. Calculate the simple average of the spectrum. Then, the signal correction unit 64 calculates the limit value by multiplying the calculated simple average value by the coefficient σ. Next, the signal correction unit 64 compares the calculated limit value with the value of the frequency spectrum of the target frequency band.

  In the comparison described above, for example, when the value of the frequency spectrum 83e is less than the calculated limit value or exceeds the calculated limit value, the signal correction unit 64 replaces the value of the frequency spectrum 83e with the limit value. To do.

  In the present embodiment, a value obtained by multiplying the frequency spectrum of each frequency band of the reference signal by a coefficient β is a limit value of each frequency band, and a correction with this limit value as the upper limit, or a correction with this limit value as the lower limit. Is going. However, after setting the value obtained by multiplying the frequency spectrum of each frequency band of the reference signal by the coefficient β as the target value instead of the limit value, the frequency to be corrected out of the frequency spectrum of the reduced audio signal It is also possible to correct the spectrum value so as to approach the target value.

  In the present embodiment, the audio signal acquired at the time of moving image shooting is described as an example. However, the present invention is not limited to this, and can be applied to the case of acquiring only an audio signal, for example. That is, the present invention can be applied to any electronic device having a recording function. In addition, although a digital camera has been described as an example of a device that performs moving image shooting, a mobile terminal such as a mobile phone or a PDA may be used. Furthermore, the program may be a program that allows a computer to execute the functions of the signal processing device shown in FIG. In this case, the program is preferably stored in a computer-readable storage medium such as a memory card, an optical disk, or a magnetic disk.

  DESCRIPTION OF SYMBOLS 10 ... Digital camera, 15 ... Imaging optical system, 16 ... Imaging device, 18 ... Lens drive part, 19 ... Aperture, 20 ... Aperture drive part, 21 ... Shutter, 22 ... Shutter drive part, 36 ... Storage medium, 43 ... Collection Sound part 44 ... Audio memory 45 ... Signal processing device 61 ... Frequency conversion part 62 ... Signal calculation part 63 ... Recording part 64 ... Signal correction part 65 ... Signal inverse conversion part

Claims (8)

A plurality of first audio signals for each predetermined time obtained by dividing an audio signal represented by a time function in which a target sound and an operation sound are mixed by a predetermined time width are second audio signals represented by a frequency function. Signal converting means for converting to
Calculating means for obtaining a third sound signal in which the influence of the operation sound is reduced from the second sound signal and the sound signal indicating the operation sound;
The frequency corresponding to the reference signal multiplied by the value of the frequency spectrum in each frequency band of the third audio signal and the coefficient , with the audio signal indicating the target sound of the plurality of second audio signals as a reference signal Comparing the value of the frequency spectrum in the band with the value of the frequency spectrum in the third audio signal different from the value of the corresponding frequency spectrum in the reference signal multiplied by the coefficient. Correction means for replacing the value of the frequency spectrum in the signal with the value of the corresponding frequency spectrum ;
Signal inverse conversion means for inversely converting the sound signal subjected to the correction processing by the correction means from the sound signal indicated by the frequency function to the sound signal indicated by the time function;
A signal processing apparatus comprising: A plurality of first audio signals for each predetermined time obtained by dividing an audio signal represented by a time function in which a target sound and an operation sound are mixed by a predetermined time width are second audio signals represented by a frequency function. Signal converting means for converting to
Calculating means for obtaining a third sound signal in which the influence of the operation sound is reduced from the second sound signal and the sound signal indicating the operation sound;
The frequency corresponding to the reference signal multiplied by the value of the frequency spectrum in each frequency band of the third audio signal and the coefficient, with the audio signal indicating the target sound of the plurality of second audio signals as a reference signal A frequency spectrum value in a band is compared, and if the frequency spectrum value in the third audio signal is less than the corresponding frequency spectrum value in the reference signal multiplied by the coefficient, Correction means for correcting the value of the frequency spectrum in the audio signal so as not to fall below the value of the corresponding frequency spectrum;
Signal inverse conversion means for inversely converting the sound signal subjected to the correction processing by the correction means from the sound signal indicated by the frequency function to the sound signal indicated by the time function;
Signal processing apparatus characterized by comprising a. A plurality of first audio signals for each predetermined time obtained by dividing an audio signal represented by a time function in which a target sound and an operation sound are mixed by a predetermined time width are second audio signals represented by a frequency function. Signal converting means for converting to
Calculating means for obtaining a third sound signal in which the influence of the operation sound is reduced from the second sound signal and the sound signal indicating the operation sound;
The frequency corresponding to the reference signal multiplied by the value of the frequency spectrum in each frequency band of the third audio signal and the coefficient, with the audio signal indicating the target sound of the plurality of second audio signals as a reference signal Comparing the value of the frequency spectrum in the band and if the value of the frequency spectrum in the third audio signal exceeds the corresponding frequency spectrum in the reference signal multiplied by the coefficient, the third audio signal Correction means for correcting the value of the frequency spectrum in so as not to exceed the value of the corresponding frequency spectrum;
Signal inverse conversion means for inversely converting the sound signal subjected to the correction processing by the correction means from the sound signal indicated by the frequency function to the sound signal indicated by the time function;
Signal processing apparatus characterized by comprising a. A plurality of first audio signals for each predetermined time obtained by dividing an audio signal represented by a time function in which a target sound and an operation sound are mixed by a predetermined time width are second audio signals represented by a frequency function. Signal converting means for converting to
Calculating means for obtaining a third sound signal in which the influence of the operation sound is reduced from the second sound signal and the sound signal indicating the operation sound;
The frequency corresponding to the reference signal multiplied by the value of the frequency spectrum in each frequency band of the third audio signal and the coefficient, with the audio signal indicating the target sound of the plurality of second audio signals as a reference signal Comparing the value of the frequency spectrum in the band with the value of the frequency spectrum in the third audio signal different from the value of the corresponding frequency spectrum in the reference signal multiplied by the coefficient. The value of the frequency spectrum in the signal is changed to a correction value calculated using the value of the corresponding frequency spectrum and the frequency spectrum of the frequency band in the vicinity of the frequency spectrum of the reference signal multiplied by the coefficient. Correction means to replace;
Signal inverse conversion means for inversely converting the sound signal subjected to the correction processing by the correction means from the sound signal indicated by the frequency function to the sound signal indicated by the time function;
Signal processing apparatus characterized by comprising a. A plurality of first audio signals for each predetermined time obtained by dividing an audio signal represented by a time function in which a target sound and an operation sound are mixed by a predetermined time width are second audio signals represented by a frequency function. Signal converting means for converting to
Calculating means for obtaining a third sound signal in which the influence of the operation sound is reduced from the second sound signal and the sound signal indicating the operation sound;
The frequency corresponding to the reference signal multiplied by the value of the frequency spectrum in each frequency band of the third audio signal and the coefficient, with the audio signal indicating the target sound of the plurality of second audio signals as a reference signal A frequency spectrum value in the band is compared, and if the frequency spectrum value in the third audio signal exceeds the corresponding frequency spectrum value in the reference signal multiplied by the coefficient, A correction value calculated from the frequency spectrum value of the audio signal using the corresponding frequency spectrum value and the frequency spectrum value of the frequency band in the vicinity of the frequency spectrum of the reference signal multiplied by the coefficient. Correction means for correcting so as not to exceed
Signal inverse conversion means for inversely converting the sound signal subjected to the correction processing by the correction means from the sound signal indicated by the frequency function to the sound signal indicated by the time function;
Signal processing apparatus characterized by comprising a. A plurality of first audio signals for each predetermined time obtained by dividing an audio signal represented by a time function in which a target sound and an operation sound are mixed by a predetermined time width are second audio signals represented by a frequency function. Signal converting means for converting to
Calculating means for obtaining a third sound signal in which the influence of the operation sound is reduced from the second sound signal and the sound signal indicating the operation sound;
The frequency corresponding to the reference signal multiplied by the value of the frequency spectrum in each frequency band of the third audio signal and the coefficient, with the audio signal indicating the target sound of the plurality of second audio signals as a reference signal A frequency spectrum value in a band is compared, and if the frequency spectrum value in the third audio signal is less than the corresponding frequency spectrum value in the reference signal multiplied by the coefficient, A correction value calculated from the frequency spectrum value of the audio signal using the corresponding frequency spectrum value and the frequency spectrum value of the frequency band in the vicinity of the frequency spectrum of the reference signal multiplied by the coefficient. Correction means for correcting so as not to fall below
Signal inverse conversion means for inversely converting the sound signal subjected to the correction processing by the correction means from the sound signal indicated by the frequency function to the sound signal indicated by the time function;
Signal processing apparatus characterized by comprising a. The signal processing device according to any one of claims 4 to 6 ,
The correction value is an average of the corresponding frequency spectrum value and the frequency spectrum value of the neighboring frequency band, the maximum value of the corresponding frequency spectrum value and the frequency spectrum value of the neighboring frequency band, Alternatively , the signal processing circuit comprises any one of the minimum value of the corresponding frequency spectrum value and the frequency spectrum value of the frequency band in the vicinity thereof . Imaging means for obtaining an image signal;
  Sound collection means for acquiring an audio signal in synchronization with acquisition of the image signal by the imaging means;
  The signal processing device according to any one of claims 1 to 7,
  Storage means for storing the image signal acquired by the imaging means and the audio signal subjected to signal processing by the signal processing device;
  An imaging apparatus comprising:

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