JP2010157966A - Signal processing apparatus, method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate manual level adjustment in configuration for performing automatic level adjustment after the manual level adjustment. <P>SOLUTION: An audio signal input by an audio input means (28) is level-adjusted by a manual volume (36) in accordance with a manual adjustment amount. An ALC (automatic level controller) (38) performs automatic level adjustment on an output audio signal of the manual volume (36) by an adjustment amount according to its audio level. A level detector (42) detects a level of the output audio signal from the ALC (38) and supplies a detection result to a display image generating device (24). The ALC (38) supplies to the display image generating device (24) information indicative of an operating situation (whether it is during a suppression operation and an operating ratio). The display image generating device (24) displays the volume level and the information of the operating situation on a display part (26). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a signal processing apparatus, method, and program for displaying a sound level after automatic volume adjustment of input sound.

  2. Description of the Related Art Conventionally, a recording apparatus that records natural sound, such as a camcorder, is provided with automatic volume controller ALC (Automatic Level Controller) that adjusts the recording sound so as to have an appropriate level. ALC increases the recording volume level with a high signal amplification factor when the input volume is low. As a result, the playback sound can be heard without excessively increasing the volume adjustment of the playback device during playback. On the other hand, the ALC automatically reduces the signal amplification factor and suppresses the audio signal when a loud sound such as explosive sound is input. Thereby, distortion of the recording signal is reduced.

  There is a threshold for the level at which the ALC starts the suppression operation, and when the input volume of the ALC exceeds this threshold, the ALC abruptly lowers the amplification factor and minimizes the time that distortion occurs in the recording signal. This operation is called an attack operation. Further, after the attack operation, when the input signal level is reduced and there is no risk of distortion of the recording signal, the ALC gradually increases the amplification factor with a predetermined time constant and returns it to the original set value. . This avoids sudden volume changes and makes it sound more natural. This operation is called a recovery operation.

  When recording a performance of an orchestra with a large inflection, the time played at a large volume exceeding the start threshold value of the ALC suppression operation and the time played at a relatively low volume frequently change. At this time, the ALC frequently repeats the attack operation and the recovery operation, and the amplification factor of the recorded sound changes every moment. When the recorded voice is reproduced while the amplification factor frequently fluctuates in this way, the overall volume level is not stabilized and the feeling of strangeness is strong.

In order to solve such a problem, a technique has been proposed in which the level for enabling automatic volume correction is changed according to the volume adjustment operation (for example, Patent Document 1). However, it is more effective to adjust the amplification factor of the input sound volume to an appropriate level in advance by a manual volume (manual sound volume adjusting means) arranged in front of the ALC.
JP 2005-260470 A

  There is a level meter as a means for visually monitoring the recording volume level. In order to record with a good S / N, it is preferable to set a higher recording volume level. However, if the gain is increased too much with the manual volume, the ALC operating level will be exceeded at the ALC input stage. That is, it is necessary to adjust the manual volume so that the volume level increases within a range where the ALC does not reach the operating level.

  However, the level meter is usually installed so as to detect and display the level of the output sound of ALC, and does not display whether or not the suppression of ALC is functioning. Therefore, if the manual volume is adjusted by looking at the display on the level meter, the ALC functions during recording, and the recording volume may frequently fluctuate.

  It is an object of the present invention to provide a signal processing apparatus, method, and program for solving such inconvenience and appropriately notifying the user of information related to the operation state of ALC.

  In order to achieve the above object, a signal processing apparatus according to the present invention includes an audio input unit that inputs an audio signal, and a manual level adjustment that adjusts the volume of the audio signal input by the audio input unit at a manual adjustment rate. Means, an automatic level adjusting means for adjusting the level of the audio signal level adjusted by the manual level adjusting means at an adjustment rate according to the audio level, and an audio level of the output audio signal of the automatic level adjusting means. A signal processing apparatus comprising level detecting means for detecting and display means for displaying information indicating the sound level detected by the level detecting means, wherein the display means is an operating status of the automatic level adjusting means. It displays the information which shows.

  The signal processing method according to the present invention includes an audio input step for inputting an audio signal, a manual level adjustment step for adjusting the volume of the audio signal input by the audio input step at a manual adjustment rate, and the manual level adjustment. An automatic level adjustment step for adjusting the volume of the audio signal level-adjusted in steps at an adjustment rate according to the audio level, and a level detection for detecting the audio level of the audio signal level-adjusted in the automatic level adjustment step And a display step of displaying on the display means information indicating the sound level detected by the level detection step and information indicating the operating status of the automatic level adjustment step.

  A signal processing program according to the present invention includes an audio input function for inputting an audio signal to a computer, and a manual level adjustment function for causing the computer to adjust the volume of the audio signal input by the audio input function at a manual adjustment rate. An automatic level adjustment function that causes the computer to adjust the level of the audio signal level adjusted by the manual level adjustment function at an adjustment rate according to the audio level; and the computer uses the automatic level adjustment function to adjust the level. A level detection function for detecting the audio level of the adjusted audio signal, and a display means for displaying information indicating the audio level detected by the level detection function and an operating status of the automatic level adjustment means on the computer. And a display function for displaying on the screen.

  According to the present invention, since the operating status of the level adjustment means for the audio signal is displayed, it becomes a guideline for setting the adjustment amount of the manual level adjustment means, and an appropriate adjustment amount can be set.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic block diagram of a recording system of a camcorder to which an embodiment of the present invention is applied.

  The photographing lens 10 makes an optical image of a subject incident on the imaging surface of the image sensor 12. The imaging element 12 generates an electrical image signal corresponding to the optical image on the imaging surface. A CDS (Correlation Double Sampling) circuit 14 removes noise of the analog image signal from the image sensor 12 by correlated double sampling. An AGC (Automatic Gain Control) circuit 16 automatically controls the gain of the output image signal of the CDS circuit 14. The A / D converter 18 converts the output image signal of the AGC circuit 16 into a digital signal.

  The image signal processing unit 20 performs known video processing such as gamma correction and white balance correction on the digital image signal from the A / D converter 18. The image signal processing unit 20 supplies a video signal for recording to the recording unit 22 and supplies a video signal for monitor display to the display image generating unit 24. The display image generation unit 24 causes the display unit 26 to display the video signal from the image signal processing unit 20 as it is or with other information. The user can determine the composition of shooting and the start / end timing of recording by looking at the image displayed on the display unit 26.

  The voice input means 28 includes a microphone or a line input terminal that takes in sound outside the camcorder body and generates an electric voice signal. The amplifier 30 amplifies the analog audio signal from the audio input means 28 to an appropriate level. When the voice input means 28 is a microphone, the amplitude of the output voice of the microphone is small, so that the gain of the amplifier 30 needs to be increased. On the other hand, when the voice input means 28 is composed of a line input terminal, the gain of the amplifier 30 may be small. In any case, the amplifier 30 plays a role of keeping input voices having different amplitude levels within a certain level range.

  The A / D converter 32 converts the analog audio signal from the amplifier 30 into a digital audio signal. The audio signal processing unit 34 tunes the recording sound quality using filter processing or the like on the digital audio signal from the A / D converter 32.

  The manual volume 36 is a manual level adjusting unit that adjusts (amplifies or attenuates) the output audio signal of the audio signal processing unit 34 to a signal level according to a manual adjustment rate set by the user. The manual adjustment factor is an amplification factor in the case of amplification and becomes an attenuation factor in the case of attenuation, but may be expressed as an amplification factor including both.

  The ALC 38 is an automatic level adjusting unit that automatically adjusts the volume level of the output audio signal of the manual volume 36. The operation content of the ALC 38 will be described later. The ALC 38 supplies an audio signal whose volume level is automatically adjusted to the recording unit 22 and the level detector 42, and supplies information indicating the operation status of the ALC 38 to the display image generation unit 24.

  The functions of the audio signal processing unit 34, the manual volume 36, and the ALC 38 can be realized by an analog circuit. In this case, the corresponding analog circuit is arranged on the input side of the A / D converter 32.

  The recording unit 22 compresses and multiplexes the video signal from the image signal processing unit 20 and the audio signal from the ALC 38 in a predetermined format at a timing according to an instruction from the CPU 44, and records the multiplexed data on the recording medium 40. The recording medium is composed of a magnetic tape, a recordable optical disk, a magnetic disk, or a nonvolatile semiconductor memory.

  The level detector 42 detects the volume level of the output audio signal of the ALC 38 and supplies the detected value to the display image generation unit 24. The display image generation unit 24 generates a level meter 50 as shown in FIG. 2 for on-screen display (OSD) for displaying the volume level. Stepped frames indicate the volume level. The coloring of each frame is changed according to the volume level detected by the level detector 42. For example, as an example of color arrangement, the background 50a is white. According to the sound volume, the small level area 50b is expressed in yellow green, the middle level area 50c in yellow, and the maximum level area 50d in red.

  The display image generation unit 24 also generates an OSD image relating to various setting states of the camcorder. The content instructed to the CPU 44 by the user using the operation device 46 is sent from the CPU 44 to the display image generation unit 24. The display image generation unit 24 causes the display unit 26 to display setting content information according to an instruction from the CPU 44.

  The display unit 26 is a liquid crystal display panel, for example, and can display not only moving images but also still images and texts.

  FIG. 3 shows a schematic block diagram of the ALC 38. The audio signal from the manual volume 36 is supplied to the recording unit 22 and the level detector 42 via the delay circuit 60 and the amplifier 62. The delay time of the delay circuit 60 corresponds to the time required for the calculation of the ALC operation. The amplification factor of the amplifier 62 is determined and controlled by the following ALC operation. When the ALC 38 is performing a suppression operation, the amplifier 62 operates as an attenuator.

  The audio signal from the manual volume 36 is also input to the amplifier 64 for ALC calculation. The amplification factor of the amplifier 64 is linked to that of the amplifier 62. That is, when the ALC 38 is performing a suppression operation, the amplifier 64 operates as an attenuator in the same manner as the amplifier 62. The amplifier 64 supplies an audio signal having the same level as the audio signal to be recorded to the following ALC operation unit. The absolute value circuit (ABS) 66 converts the audio signal having both positive and negative polarities output from the amplifier 64 into a unipolar signal. The circuit subsequent to the ABS 66 targets only the size of the audio signal regardless of the polarity. The output signal of the ABS 66 is input to the difference unit 68 for determination of the attack operation and input to the comparator 72 for determination of the recovery operation.

  The differentiator 68 subtracts the attack level threshold value 70 from the magnitude of the absolute value signal from the ABS 66. The output of the differentiator 68 indicates how much the amplitude of the absolute value signal exceeds the attack level threshold 70. When the output of the differentiator 68 is negative, the attack level threshold value 70 is not exceeded. The calculation result of the difference unit 68 is supplied to the determination unit 82.

  When the ALC 38 is performing the suppression operation, the amplifier 64 operates as an attenuator, and the input signal to the differentiator 68 is attenuated. By comparing the difference level 68 with the attack level threshold 70, it can be determined whether further suppression is necessary.

  The comparator 72 compares the magnitude of the absolute value signal from the ABS 66 with the recovery level threshold 74 and outputs a logical value “1” when the absolute value signal is smaller than the recovery level threshold 74, otherwise. The logical value “0” is output. The integrator 76 integrates the output of the comparator 72. The integrated value of the integrator 76 is cleared every fixed period (determination period or determination period) by the output of the counter 98. The integral value of the integrator 76 holds a value that is proportional to the time during which the absolute value signal is smaller than the recovery level threshold 74 during this determination period. The counter 98 counts the determination cycle of the determiner 82. In the present embodiment, this determination period is also a reference period for calculating the ALC operating ratio.

  The comparator 78 compares the output of the integrator 76 with the recovery rate threshold value 80. The recovery ratio threshold 80 is expressed as a ratio with respect to the maximum value that the integrator 76 can output during the clear period defined by the counter 98. The comparator 78 outputs a logical value “1” when the period in which the output absolute value signal of the ABS 66 is lower than the recovery level threshold 74 exceeds the period corresponding to the recovery ratio threshold 80. This indicates that a recovery operation may be performed on the determiner 82.

  The comparator 92 compares the current amplification factor 88 of the amplifier 62 with the maximum amplification factor 90 of the amplifier 62 and supplies the difference value to the determination unit 82. That is, the comparator 92 outputs a logical value “1” when the maximum gain 90 is greater than the current gain 88. This indicates that the ALC 38 is performing a suppression operation.

  The determiner 82 determines the behavior of the ALC 38 according to the outputs of the differencer 68, the comparator 78, and the comparator 92. FIG. 4 is an operation flowchart of the determiner 82.

  First, the determiner 82 reads the output value of the differentiator 68 (S1). When the output value of the differentiator 68 is larger than “0” (S2), the attack operation is started because the attack level threshold value 70 is exceeded (S3). That is, the determiner 82 instructs the gain calculator 84 to lower the gain by an amount proportional to the magnitude of the output value of the differencer 68 (S3).

  When the output value of the differentiator 68 is “0” or less (S2), the attack operation is not performed. However, a recovery operation may be performed. For this determination, the determiner 82 reads the output of the comparator 92 (S4). When the output value of the comparator 92 is the logical value “0” (S5), since the amplification factor of the ALC 38 (amplifier 62) is maximum, the recovery operation is not performed. On the other hand, when the output value of the difference unit 68 is “1” (S5), the output of the comparator 78 is read in order to check whether or not the recovery operation execution condition is satisfied (S6). When the output value of the comparator 78 is the logical value “0” (S7), the recovery operation is not performed, and the recovery operation is not performed. When the output value of the comparator 78 is the logical value “1” (S7), since the recovery operation execution condition is satisfied, the gain calculator 84 is instructed to increase the gain to perform the recovery operation (S8). .

  Upon receiving an instruction from the determiner 82, the amplification factor calculator 84 determines the amplification factor of the ALC 38 (the amplifier 62) to be applied in the next period. That is, the amplification factor calculator 84 outputs a value obtained by subtracting the reduction amount instructed from the determiner 82 from the current amplification factor 88 when receiving an instruction to reduce the amplification factor and its magnitude from the determiner 82. However, when the subtraction result falls below a preset minimum amplification factor, the minimum amplification factor is output. In general, 1 can be considered as the minimum amplification factor, but an optimal value in accordance with the use situation may be applied. When the instruction from the determiner 82 is an increase in the amplification factor, the amplification factor calculator 84 outputs a value obtained by adding the increase amount instructed from the determiner 82 to the current amplification factor 88.

  In both cases of amplification factor reduction and amplification factor increase, the amplification factor calculator 84 outputs the calculation result to the zero-cross detector 86 and stores it as the current amplification factor 88. The zero cross detector 86 detects when the outputs of the amplifiers 62 and 64 pass the operation reference voltage, and changes the amplification factors of the amplifiers 62 and 66 at that time. Since the operation reference voltage is a zero point as the signal amplitude, the output signal level does not fluctuate even if the amplification factor is changed here. Conversely, if the amplification factor is changed at a point other than this, the output signal level at that moment fluctuates, and this fluctuation component is superimposed on the output as noise.

  As described above, the comparator 92 outputs a logical value “1” when the maximum gain 90 is larger than the current gain 88. This indicates that the ALC 38 is performing a suppression operation. The output of the comparator 92 is sent to the display image generation unit 24 as a suppression operation flag signal indicating that the suppression operation is being performed.

  The integrator 94 integrates the output of the comparator 92 during the above-described clear period, and the divider 96 divides the integrated value of the integrator 94 by the count value set in the counter 98. The integrator 94 and the divider 96 determine the ratio of the period during which the output of the comparator 92 is the logical value “1” in the period given by the counter 98. In other words, this is the operating rate of the suppression operation of the ALC 38 within the time set by the counter 98. The output of the divider 96 is supplied to the display image generation unit 24 as the operation rate information of the ALC 38.

  In accordance with the suppression operation flag signal from the ALC 38, the display image generation unit 24 can display whether or not the suppression operation is being performed and the operation rate on the screen of the display unit 26 in addition to the volume level. FIG. 5 shows an example of the display. In FIG. 5, different images are prepared as the level meter image according to the value of the suppression operation flag signal from the comparator 92. Then, information on the operation / non-operation of the suppression operation of the ALC 38 is superimposed on the level meter. In FIG. 5, for example, as the color scheme of the level meter 52, the background 52a is expressed in gray, the small level region 52b and the middle level region 52c are expressed in pink, and the maximum level region 52d is expressed in red.

  The color used is not limited to this, but a color that can express the following meaning is preferable. That is, the low level region 52b and the medium level region 52c indicate the levels suppressed by the ALC 38, and the color scheme effectively represents that the input signal to the original camcorder itself is larger. In the suppression state, it is not meaningful to provide color classifications at the small level and the medium level. The maximum level area 52d indicates the vicinity of the maximum value of the recording sound level, and has the same meaning in any of the operating / non-operating states of the ALC 38, and therefore may be red which is generally used. The background 52a is preferably supplemented with the fact that the color scheme has changed due to the operation / non-operation of the ALC 38 at the same time as enhancing the color in the meter frame.

  The display image generation unit 24 switches between the level meter described with reference to FIG. 2 and the level meter described with reference to FIG. 5 according to the operation / non-operation of the suppression operation of the ALC 38. That is, the display mode of the level meter is varied according to the operating status of the ALC 38. Thereby, the user of the camcorder can visually determine whether or not the recording volume level indicated by the level meter has been subjected to the ALC suppression operation. Further, the changing element of the level meter image is not limited to the color scheme. For example, the brightness of the entire level meter may be changed, the level meter may blink when the suppression operation is in operation, or the shape of the level meter image may be changed. Of course, these composite forms may also be used.

  The display image generation unit 24 can also display the operation rate information from the divider 96 of the ALC 38 on the display unit 26. For example, the level meter image shown in FIG. 2 or 5 is changed according to the operating rate. For example, the background 50a, 52a is a light color when the operation rate is low, and a dark color when the operation rate is high. Alternatively, the size and shape of the images 50 and 52 of the entire level meter are changed.

  Moreover, you may produce | generate the display image regarding an operation rate separately from a level meter based on operation rate information. FIG. 6 is a display example showing the operation rate. FIG. 6A displays the operation rate in a numerical format. The displayed numerical value changes according to the operating rate. At that time, if the color scheme of the background 102 is changed according to the numerical value of the operation rate, a more effective display is obtained. FIG. 6B and FIG. 6C display the operation rate in a meter format. FIG. 6B shows that the availability factor increases as the meter value 104 increases to the right. In FIG.6 (c), it shows that an operation rate is so high that the meter pointer | guide 106 swings to the right. FIG. 6D displays the transition of the operation rate for each unit time as a graph. 6 (a), (b), and (c) display only the operation rate within the unit time, whereas FIG. 6 (d) shows the operation rate time over a plurality of unit times from the past. Since the transition is displayed by the movement line 108, it is easy to grasp the time change of the operation rate.

  In this way, not only the instantaneous level of the recorded audio signal but also whether or not the ALC 38 is being suppressed can be indicated to the user as well as the operating rate of the ALC 38.

  Although the embodiment of the camcorder has been described, the present invention can be applied to an apparatus having an ALC function for automatically adjusting an input sound level and a function for displaying a volume level. For example, the present invention can also be applied to a voice recorder (IC recorder) or a personal computer that includes a microphone and captures voice.

  When implemented as a signal processing program operating on a computer, a voice input function for inputting a voice signal to the computer is provided corresponding to the voice input means 28. The function of the manual volume 36 is implemented as a manual level adjustment function, and the function of the ALC 38 is implemented as an automatic level adjustment function. The function of the level detector 42 is implemented as a level detection function, and the function of the display image generation unit 24 is implemented as a display function.

It is a schematic block diagram of one Example of this invention. It is a display example of a level meter. It is a schematic block diagram of ALC38. It is an operation | movement flowchart of the determination device 82 of FIG. It is another example of a display of a level meter. It is an example of a display which shows the operation rate of ALC38.

DESCRIPTION OF SYMBOLS 10 Shooting lens 12 Image pick-up element 14 CDS circuit 16 AGC circuit 18 A / D converter 20 Image signal processing part 22 Recording part 24 Display image generation part 26 Display part 28 Audio | voice input means 30 Amplifier 32 A / D converter 34 Audio | voice signal processing Part 36 Manual volume 38 ALC
40 Recording medium 42 Level detector 44 CPU
46 Operating device 50 Level meter 50a Background 50b Small level region 50c Middle level region 50d Maximum level region 52 Level meter 52a Background 52b Small level region 52c Middle level region 52d Maximum level region 60 Delay circuit 62 Amplifier 64 Amplifier 66 Absolute value circuit (ABS) )
68 Difference unit 70 Attack level threshold 72 Comparator 74 Recovery level threshold 76 Integrator 78 Comparator 80 Recovery ratio threshold 82 Determinator 84 Amplification factor calculator 86 Zero cross detector 88 Current gain 90 Maximum gain 92 Comparator

Claims (7)

A voice input means for inputting a voice signal;
Manual level adjustment means for adjusting the level of the sound signal input by the sound input means at a manual adjustment rate;
Automatic level adjustment means for adjusting the volume of the audio signal level-adjusted by the manual level adjustment means at an adjustment rate according to the audio level;
Level detecting means for detecting the sound level of the output sound signal of the automatic level adjusting means;
A signal processing device comprising display means for displaying information indicating the sound level detected by the level detection means,
The signal processing apparatus, wherein the display means displays information indicating an operating status of the automatic level adjustment means.   The signal processing apparatus according to claim 1, wherein the operating status is whether or not the automatic level adjusting unit is performing a suppression operation.   The signal processing apparatus according to claim 2, wherein the display unit changes a display mode of information indicating the sound level in accordance with the operation status. The automatic level adjusting means comprises means for calculating an operating rate at which the automatic level adjusting means is performing a suppression operation;
The signal processing apparatus according to claim 1, wherein the operating status is the operating ratio. The automatic level adjusting means comprises means for calculating an operating rate at which the automatic level adjusting means is performing a suppression operation;
The signal processing apparatus according to claim 1, wherein the operating status indicates the operating ratio and whether or not the automatic level adjusting unit suppresses the audio signal input by the audio input unit. . A voice input step for inputting a voice signal;
A manual level adjustment step for adjusting the volume of the audio signal input in the audio input step at a manual adjustment rate;
An automatic level adjustment step for adjusting the level of the audio signal level adjusted in the manual level adjustment step at an adjustment rate according to the audio level;
A level detection step of detecting a voice level of the voice signal level-adjusted in the automatic level adjustment step;
A signal processing method comprising: a display step of displaying information indicating the sound level detected by the level detection step and information indicating an operation status of the automatic level adjustment step on a display unit. An audio input function for inputting audio signals to the computer;
A manual level adjustment function for causing the computer to adjust the level of the volume of the audio signal input by the audio input function at a manual adjustment rate;
An automatic level adjustment function for causing the computer to adjust the volume of the audio signal level adjusted by the manual level adjustment function at an adjustment rate according to the audio level;
A level detection function for causing the computer to detect the audio level of the audio signal level-adjusted by the automatic level adjustment function;
A signal processing program comprising: a display function for causing the computer to display information indicating the sound level detected by the level detection function and information indicating an operation status of the automatic level adjustment unit on a display unit. .

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