JP2011205184A - Equalizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an equalizer for restraining deterioration in an S/N ratio by reducing an attenuation factor when attenuating a digital sound signal in a prestage of equalizing processing.SOLUTION: The equalizer 50 sets the order of equalizing for each frequency band so that equalizer parts 30a to 30x of attenuation setting attenuate the digital sound signal before the equalizer parts 30a to 30x of amplification setting amplify the digital sound signal, and prevents saturation so long as an attenuation factor of an attenuate processing part 20 is an attenuation factor according to overall characteristics of the equalizer parts 30a to 30x. Therefore, the attenuation rate of the attenuate processing part 20 is reduced, and hence deterioration in an S/N ratio is minimized.

Description

  The present invention relates to an equalizer device capable of suppressing a decrease in S / N ratio.

  Conventionally, many audio / video devices equipped with an equalizer device that amplifies or attenuates an audio signal in a specific frequency band and outputs the sound quality according to the user's preference or the sound quality suitable for the viewing environment have been commercialized. Yes. With the digitalization of audio / video equipment, it has become common for equalization processing by an equalizer device to be performed at the stage of digital audio signals. However, the digital audio signal cannot be amplified beyond the full bit, that is, the maximum volume. In this case, saturation occurs, the waveform is clipped, and waveform distortion occurs. As a general technique for preventing saturation, there is a method in which the digital audio signal is attenuated as a whole in advance by the equalizing process in advance of performing the equalizing process. However, since the S / N ratio decreases as the attenuation rate with respect to the digital audio signal before the equalizing process is increased, it is not preferable to attenuate the digital audio signal more than necessary.

  Here, the following [Patent Document 1] describes an invention relating to a volume control device that switches between volume control at the digital signal stage and volume control at the analog signal stage in accordance with the level of the output volume and suppresses a decrease in the S / N ratio. Is disclosed.

JP 2000-174574 A

  The invention disclosed in [Patent Document 1] can suppress a decrease in the S / N ratio accompanying an increase or decrease in the output volume level. However, the reduction in the S / N ratio in the equalizing process has not yet been solved, and further improvement is desired in this respect.

  The present invention has been made in view of the above circumstances, and can reduce the attenuation rate when the digital audio signal is attenuated in the stage before performing the equalizing process, and as a result, suppress the decrease in the S / N ratio. It is an object of the present invention to provide an equalizer device capable of performing the above.

The present invention
(1) an attenuation processing unit that attenuates and outputs an input first digital audio signal;
It is set to amplify a predetermined frequency band of the second digital audio signal output by the attenuation processing unit with an amplification gain, or to attenuate a predetermined frequency band of the second digital audio signal with an attenuation gain. An equalizer processing unit configured to equalize the second digital audio signal by sequentially amplifying or attenuating the second digital audio signal for each predetermined frequency band by the plurality of equalizer units;
When changing the gain of at least one equalizer unit among the plurality of equalizer units, the equalizer unit set to the amplification gain after the gain change has a gain before the second digital audio signal is amplified. An equalizer control unit that changes the order of equalization for each frequency band by the equalizer processing unit so that the equalizer unit set to the attenuation gain after the change of attenuates the second digital audio signal;
A level at which the setting of the attenuation processing unit is changed so as to obtain an attenuation factor corresponding to the maximum amplification factor of the input / output frequency characteristics of the equalizer processing unit when the equalizer control unit changes the gain of at least one equalizer unit. The above-described problem is solved by providing an equalizer device 50 including a control unit.
(2) a digital / analog converter that converts the digital audio signal equalized by the equalizer processor into an analog audio signal;
An analog signal amplifier that amplifies the analog audio signal converted by the digital / analog converter;
The level control unit is configured to change the setting of the analog signal amplifying unit so that an amplification factor corresponding to the maximum amplification factor is obtained when the equalizer control unit changes a gain of at least one of the equalizer units. The above problem is solved by providing the equalizer device 50 according to the above (1).
(3) The level control unit changes the settings of the attenuation processing unit and the analog signal amplification unit substantially simultaneously with the equalizer control unit changing the order of equalization for each frequency band by the equalizer processing unit. The above-described problem is solved by providing the equalizer device 50 described in (2) above.

  The equalizer device according to the present invention can reduce the attenuation rate when the digital audio signal is attenuated in the stage before performing the equalizing process. Thereby, the fall of S / N ratio can be suppressed.

It is a block diagram which shows the equalizer apparatus which concerns on this invention. It is a figure explaining rearrangement of a signal input order. It is a figure which shows an example of the setting change screen of the equalizer apparatus which concerns on this invention. It is a flowchart which shows operation | movement of the equalizer apparatus which concerns on this invention. It is a 2nd flowchart which shows operation | movement of the equalizer apparatus which concerns on this invention. It is a figure explaining the change pattern in the setting change process of this invention.

  An embodiment of an equalizer device according to the present invention will be described with reference to the drawings. In the following description, the gain and the attenuation rate are collectively referred to as a gain. The equalizer device 50 according to the present embodiment shown in FIG. 1 includes an attenuation processing unit 20 that attenuates a digital audio signal input to the input terminal 10 at a stage before performing equalizing processing. The equalizer device 50 according to the present embodiment shown in FIG. 1 further includes a plurality of equalizer units 30a to 30x that sequentially amplify or attenuate a digital audio signal in a predetermined frequency band according to a set gain. An equalizer processing unit 32 for equalizing the digital audio signal attenuated by the attenuation processing unit 20 by the equalizer units 30a to 30x; a digital / analog conversion unit 22 for converting the digital audio signal equalized by the equalizer processing unit 32 into an analog audio signal; The analog signal amplification unit 24 that amplifies the converted analog audio signal and outputs the amplified analog audio signal to the output terminal 12, the operation unit 26 that inputs the gain setting for each of the equalizer units 30a to 30x, and the equalizer control that controls the equalizer processing unit 32 Unit 34 and the equalizer processing unit 32. It has a level controller 36 for setting a reference amplification factor of the attenuation factor and the analog signal amplifier 24 of the attenuating section 20 according to the maximum gain of the bar-ol characteristics, a. The maximum amplification factor is an amplification factor at a frequency at which the gain in the frequency characteristic is maximized.

  Next, rearrangement of the signal input order (the order in which the equalizer units 30a to 30x amplify or attenuate the digital audio signal) to the equalizer units 30a to 30x, which is a feature of the equalizer device 50 according to the present invention, will be described. Here, description will be made using an example in which the equalizer processing unit 32 includes an equalizer unit 30a that amplifies or attenuates a low frequency side frequency band and an equalizer unit 30b that amplifies or attenuates a high frequency side frequency band. . The frequency band on the high frequency side here is a frequency higher than the center frequency of the frequency band on the low frequency side that is amplified or attenuated by the equalizer section 30a that amplifies or attenuates the frequency band on the low frequency side. The frequency band.

  First, the equalizer unit 30a and the equalizer unit 30b are both input, taking as an example the case where the gain of the equalizer unit 30a on the low frequency side and the gain of the equalizer unit 30a on the high frequency side are both +10 dB (amplification of 10 dB). An operation of the equalizer device 50 when a digital audio signal is amplified will be described.

  The frequency characteristic of the equalizer unit 30a at this time is, for example, the frequency characteristic A1 shown in FIG. 2A, and the frequency characteristic of the equalizer unit 30b is, for example, the frequency characteristic B1 shown in FIG. The overall characteristic that is the overall frequency characteristic of the equalizer processing unit 32 is an overall characteristic C1 in which the frequency characteristic A2 and the frequency characteristic B2 are combined as shown in FIG. As described above, the digital audio signal before being input to the equalizer processing unit 32 is input, and the equalizer processing unit 32 after the plurality of equalizer units included in the equalizer processing unit 32 amplifies or attenuates the digital audio signal is output. An input / output frequency characteristic when a digital audio signal is output is referred to as an overall characteristic.

  The overall characteristic C1 is a combination of the frequency characteristic A1 by the equalizer unit 30a and the frequency characteristic B1 by the equalizer unit 30b, and its maximum amplification factor is 13.85 dB. At this time, the maximum amplification factor of the equalizer processing unit 32 as a whole is 13.85 dB which is equal to the maximum amplification factor of the overall characteristic C1. In this case, if the attenuation processing unit 20 performs attenuation of 13.85 dB or more and sufficient headroom is not secured, saturation occurs when a full-bit digital audio signal is input to the equalizer processing unit 32, and the waveform is distorted. . Therefore, in the case of the example of FIG. 2A, the attenuation processing unit 20 attenuates the digital audio signal with an attenuation rate corresponding to the maximum amplification factor of the equalizer processing unit 32, that is, 13.85 dB which is the maximum amplification factor of the overall characteristic C1. I do.

  Next, in the case where the gain of the equalizer unit 30a is set to -10 dB (10 dB attenuation) and the gain of the equalizer unit 30b is set to +10 dB (amplification of 10 dB), the digital audio signal input to the equalizer unit 30a is amplified. The operation of the equalizer device 50 when the equalizer unit 30b attenuates the input digital audio signal will be described. Note that the order in which amplification or attenuation is performed in the initial setting is referred to as equalizer section 30a → equalizer section 30b.

  The frequency characteristic of the equalizer unit 30a at this time is the frequency characteristic A2 shown in FIG. 2B, and the frequency characteristic of the equalizer unit 30b is the frequency characteristic B2. The overall characteristic of the equalizer processing unit 32 is an overall characteristic C2 in which the frequency characteristic A2 and the frequency characteristic B2 are combined. At this time, the maximum amplification factor of the overall characteristic C2 is 8.65 dB, which is smaller than the amplification factor (+10 dB) of the equalizer unit 30b. As described above, since the order of amplification or attenuation of the equalizer unit 30a and the equalizer unit 30b in the initial setting is the order of the equalizer unit 30a → the equalizer unit 30b, the digital audio signal input to the equalizer processing unit 32 is first the equalizer unit. The signal is attenuated by 10 dB at 30a, and then amplified by 10 dB at the equalizer unit 30b. That is, the digital audio signal input to the amplification setting equalizer unit 30b is attenuated by the attenuation processing unit 20 and the equalizer unit 30a in the preceding stage. Therefore, the maximum amplification factor of the equalizer processing unit 32 as a whole is 8.65 dB, which is equal to the maximum amplification factor of the overall characteristic C2, not the amplification factor (+10 dB) of the equalizer unit 30b. Therefore, if the attenuation processing unit 20 performs attenuation with an attenuation rate corresponding to 8.65 dB, which is the maximum amplification factor of the overall characteristic C2, sufficient headroom for the equalizer processing unit 32 can be ensured. In other words, since the equalizer unit 30a attenuates the digital audio signal before the equalizer unit 30b amplifies the digital audio signal, the equalizer unit 30b attenuates at an attenuation rate corresponding to 8.65 dB which is the maximum amplification factor of the overall characteristic C2. For example, the occurrence of saturation can be prevented.

  Next, in the case where the gain of the equalizer unit 30a is +10 dB (amplification of 10 dB) and the gain of the equalizer unit 30b is −10 dB (attenuation of 10 dB), the digital audio signal input by the equalizer unit 30a is amplified, An operation of the equalizer device 50 when the digital audio signal input to the equalizer unit 30b is attenuated will be described. At this time, the frequency characteristic of the equalizer unit 30a is the frequency characteristic A3 shown in FIG. 2C, and the frequency characteristic of the equalizer unit 30b is the frequency characteristic B3. The overall characteristic of the equalizer processing unit 32 is an overall characteristic C3 in which the frequency characteristic A3 and the frequency characteristic B3 are combined. At this time, the maximum amplification factor of the overall characteristic C3 is 8.65 dB. Here, when the digital audio signal is amplified and attenuated in the order of the equalizer unit 30a → equalizer unit 30b, which is the order in which the amplification or attenuation of the initial setting is performed, the digital audio signal input to the equalizer processing unit 32 is first the equalizer unit. It is amplified by 10 dB at 30a. Therefore, even if the maximum amplification factor of the overall characteristic C3 is 8.65 dB, it is amplified by 10 dB during the process of the equalizer processing unit 32. Therefore, in this case, it is necessary to set the attenuation rate of the attenuation processing unit 20 in accordance with the maximum amplification rate during the processing in the equalizer processing unit 32, that is, 10 dB that is the amplification rate of the equalizer unit 30a. That is, the attenuation processing unit 20 needs to perform attenuation with an attenuation rate corresponding to 10 dB which is the maximum amplification rate of the frequency characteristic A3 of the equalizer unit 30a.

  However, if the digital audio signal is input first from the equalizer unit 30b whose gain is set to attenuation, the attenuation processing unit 20 and the equalizer unit 30b are amplified before the digital audio signal is amplified by the amplification unit equalizer 30a. And can be attenuated. That is, if the digital audio signal is input first from the equalizer unit 30b whose gain is set to attenuation, the attenuation processing unit 20 attenuates at an attenuation rate corresponding to 8.65 dB which is the maximum amplification factor of the overall characteristic C3. By doing so, sufficient headroom for the processing of the equalizer processing unit 32 can be ensured, and the occurrence of saturation can be prevented. That is, when the signal input order is not rearranged, the attenuation rate of the attenuation processing unit 20 is 10 dB, whereas when the signal input order is rearranged, the attenuation rate of the attenuation processing unit 20 is 8. It can be reduced to .65 dB. And the fall of S / N ratio can be suppressed by the reduction | decrease. The above is the principle of suppressing a decrease in the S / N ratio due to rearrangement of the signal input order.

  Next, the operation of the equalizer device 50 will be described in more detail with reference to FIG. Here, for the sake of convenience, the attenuation processing unit 20 is set in advance to have an attenuation factor that attenuates the digital audio signal by the amount amplified by the maximum amplification factor of the overall characteristic of the equalizer processing unit 32, and the analog signal amplification Description will be made assuming that the unit 24 is set to an amplification factor equal to the maximum amplification factor of the overall characteristic of the equalizer processing unit 32. That is, if the maximum amplification factor of the overall characteristic of the equalizer processing unit 32 is 8.65 dB, the attenuation rate of the attenuation processing unit 20 is 8.65 dB (−8.65 dB), and the reference amplification rate of the analog signal amplification unit 24 is also It becomes 8.65 dB (+8.65 dB). However, the gain obtained by multiplying the maximum amplification factor of the overall characteristic of the equalizer processing unit 32 by a predetermined coefficient may be used as the attenuation rate of the attenuation processing unit 20 and the reference amplification rate of the analog signal amplification unit 24.

  First, in a state where the equalizer device 50 is activated, the user operates the operation unit 26 to perform an operation input for instructing a gain change to the equalizer units 30a to 30x (step S102). This operation input is an operation input for instructing a change in gain of the equalizer units 30a to 30x in which the frequency bands to be amplified or attenuated are set, and the gain is set for each frequency band set in the equalizer units 30a to 30x. Operation input to be specified.

  Examples of the operation unit 26 include a touch panel on which an equalizer setting change image is displayed, and a volume and switch corresponding to the equalizer units 30a to 30x. As an example of the operation unit 26, FIG. 3 shows a touch panel on which an equalizer setting change image is displayed. FIG. 3 shows an example in which the equalizer processing unit 32 is composed of five equalizer units 30a to 30e. In addition, it is good also as a structure which starts an equalizer setting change process automatically irrespective of a user's operation input. For example, a gain calculation unit that detects the acoustic characteristics of the viewing space around the acoustic device using the equalizer device of the present embodiment and calculates a gain according to the acoustic characteristics is provided, and the equalizer control unit 32 has the gain calculation unit You may make it change the gain of the equalizer parts 30a-30x so that it may become the calculated gain.

  As an example, it is assumed that in step S102, the user operates the operation unit 26 to input an operation input for changing the gains of the equalizer units 30a to 30x, for example, as illustrated in FIG. In other words, it is assumed that an operation input is input to instruct the gains of the equalizer units 30a to 30e to become the gains corresponding to the gains indicated by hatching in FIG. This instructs to change the gain of the equalizer section 30a to -5 dB, the gain of the equalizer section 30b to +10 dB, the gain of the equalizer section 30c to 0 dB, the gain of the equalizer section 30d to -10 dB, and the gain of the equalizer section 30e to +5 dB. Operation input. Further, as an example, it is assumed that the gains of the respective equalizer units 30a to 30e before the gain change at the time when the operation input is performed are 0 dB. The above is an example of the operation for instructing the user to change the gain to the equalizer units 30a to 30x.

  The equalizer setting change process starts when a signal instructing the gain change of the equalizer units 30a to 30x is input. Here, an example is shown in which the user proceeds to the next step after changing the settings for all the equalizer units 30a to 30x, but an operation input for instructing to change the gain is input to one equalizer unit 30a to 30x. It is preferable to perform a series of equalizer setting change processing whenever necessary.

  When an operation input that instructs the equalizer units 30a to 30x to change the gain is input, the equalizer control unit 34 changes the gain set to the equalizer units 30a to 30x after the gain is changed in response to the operation input. Compare (step S103).

  Next, the equalizer control unit 34 performs a signal input order rearrangement process for the equalizer units 30a to 30x in accordance with a rearrangement process described later in accordance with the gain comparison result in step S103 (step S104). When rearrangement processing of a plurality of equalizer units occurs in this way, it is preferable to perform rearrangement processing of the plurality of equalizer units within a time corresponding to the sampling frequency of the digital audio signal. By doing so, the continuity of the digital audio signal is maintained.

  As the signal input order rearrangement processing, for example, the following processing can be considered. The first rearrangement process is a process of rearranging the gains after changing the gains of the equalizer units 30a to 30x in ascending order. This first rearrangement process is the simplest and is particularly effective when the number of equalizer units 30a to 30x is small.

  Further, in the second rearrangement process, the gains before and after the change of the equalizer units 30a to 30x in which the setting is changed are confirmed, and if the change is to the attenuation setting, the signal input order is changed to the amplification setting first. If so, the signal input order is rearranged so as to be last. According to the second rearrangement process, the time required for the rearrangement process can be relatively shortened particularly when the number of equalizer units 30a to 30x is large.

  Further, the third rearrangement process confirms the gains of the equalizer units 30a to 30x in which the setting change is performed, and if the gains after the change in the equalizer units 30a to 30x in which the setting change is performed are attenuation settings, This is a process in which the input order is first, and if the changed gain is amplification setting, the signal input order is last. According to the third rearrangement process, since there is no comparison of the gain before and after the change, the rearrangement process can be determined based on the gain after the change, and the determination process is simplified more than the second rearrangement process. be able to.

  Further, in the fourth rearrangement process, the gains before and after the change of the equalizer units 30a to 30x in which the setting is changed are confirmed, and the setting change of the equalizer units 30a to 30x in which the setting change is performed is changed to the attenuation setting. If so, the signal input order of the equalizer unit 30x is replaced with the first equalizer unit 30a to 30x among the equalizer units 30a to 30x of the amplification setting at that time, and if the change is made to the amplification setting, the equalizer unit This is a process of replacing the signal input order of 30x with the equalizer sections 30a to 30x having the last input order among the equalizer sections 30a to 30x having attenuation settings at that time. According to the fourth rearrangement process, since the equalizer unit 30x that changes the gain is replaced with the equalizer units 30a to 30x at the boundary between the attenuation setting and the amplification setting, the rearrangement of the equalizer units 30a to 30x can be minimized. it can.

  In each of the above rearrangement processes, the signal input order is rearranged so that the equalizer unit that is set to attenuation after the gain change is input before the equalizer unit that is set to amplification after the gain change. That is, when changing the gain for the plurality of equalizer units 30a to 30x, the equalizer control unit 34 amplifies the digital audio signal after the gain change, before the equalizer units 30a to 30x amplify the digital audio signal. The equalizer processing unit 32 is set so that the equalizer units 30a to 30x that attenuate the digital audio signal after the gain change attenuate the digital audio signal. In other words, since the frequency band to be amplified or attenuated is set in each of the equalizer units 30a to 30x, the equalizer control unit 34 determines the order of equalization for each frequency band set in each of the equalizer processing units 30a to 30x. change.

  The rearrangement process is appropriately optimized depending on the number of equalizer units 30a to 30x, the ability of the equalizer control unit 34, the circuit configuration of the equalizer device 50 and the mounted electrical device, and the like. Further, when all the equalizer units 30a to 30x are set to attenuation or amplification (including the case where the gains of all the equalizer units 30a to 30x are 0 dB), it is not necessary to perform the rearrangement process. A process for skipping the rearrangement process may be added. Here, it is assumed that the equalizer control unit 34 performs the first rearrangement process described above. Therefore, in the case of the example in FIG. 3, the equalizer control unit 34 changes the signal input order from the equalizer unit 30d (gain -10 dB) to the equalizer unit 30a (gain -5 dB) to the equalizer unit 30c (gain 0 dB) to the equalizer unit 30e ( The order is changed in the order of gain + 5 dB) → equalizer unit 30b (gain + 10 dB). At the time of step S104, only the signal input order is rearranged, and the gain change of the equalizer units 30a to 30x is performed in step S136 described later.

  Next, the equalizer control unit 34 calculates the overall characteristics of the equalizer units 30a to 30x after changing the signal input order and gain, that is, the overall characteristics of the equalizer processing unit 32 after changing the signal input order and gain. Then, a signal indicating the maximum amplification factor is output to the level control unit 36 (step S106). However, since the gain changes of the equalizer units 30a to 30x are not actually performed at the present time, the equalizer control unit 34 calculates the overall characteristic by calculation. To calculate the overall characteristics, a sweep response that changes the frequency of the sine wave, frequency analysis using DFT or FFT, or a table of preset equalizer settings can be tabulated, and the assumed overall characteristics can be stored in memory. May be. Here, it is assumed that the maximum amplification factor of the overall characteristic of the equalizer processing unit 32 after changing the signal input order and gain is 8.65 dB.

  When the signal indicating the maximum amplification factor of the overall characteristic is input from the equalizer control unit 34, the level control unit 36 changes the attenuation factor setting of the attenuation processing unit 20 so that the attenuation factor according to the maximum amplification factor of the overall characteristic is obtained. Is performed (step S132). That is, the level control unit 36 performs an attenuation rate setting change process of the attenuation processing unit 20 in advance so that the attenuation rate attenuates the digital audio signal in advance by the amount amplified by the maximum amplification factor of the overall characteristic of the equalizer processing unit 32. Will be done.

  Further, the level control unit 36 performs setting change processing of the reference amplification factor of the analog signal amplification unit 24 so that the reference amplification factor corresponds to the attenuation factor of the attenuation processing unit 20 (step S134). That is, the level control unit 36 performs the setting change process of the reference amplification factor of the analog signal amplification unit 24 so that the amplification factor is equal to the maximum amplification factor of the overall characteristic of the equalizer processing unit 32. Further, the equalizer control unit 34 performs setting change processing (gain change processing) for each of the equalizer units 30a to 30x of the equalizer processing unit 32 so as to be a value input by the user (step S136).

  Here, since the maximum amplification factor of the overall characteristic is 8.65 dB, the level control unit 36 changes the attenuation rate of the attenuation processing unit 20 to 8.65 dB (−8.65 dB), and the analog signal amplification unit. The reference amplification factor of 24 is changed to 8.65 dB (+8.65 dB). Further, the equalizer control unit 34 sets the gain of the equalizer unit 30a to −5 dB, the gain of the equalizer unit 30b to +10 dB, the gain of the equalizer unit 30c to 0 dB, the gain of the equalizer unit 30d to −10 dB, and the equalizer unit 30e. Change the gain to +5 dB. This completes the setting change process for each unit (step S200).

  Note that the attenuation rate of the attenuation processing unit 20 and the reference amplification rate of the analog signal amplification unit 24 may be set to gains that can be set according to the performance and specifications of the IC. For example, in the current attenuation processing unit 20 with an attenuation factor of 8.65 dB (−8.65 dB) and a reference amplification factor of 8.65 dB (+8.65 dB) with the analog signal amplification unit 24, the settable step of the IC is 1 dB step. In this case, the attenuation factor 9 dB (−9 dB) of the attenuation processing unit 20 and the reference amplification factor 9 dB (+9 dB) of the analog signal amplification unit 24 may be used. In order to prevent saturation, it is preferable to make the absolute value larger than the original gain.

  Further, the following procedure shown in the flowchart of FIG.

  In the procedure shown in the flowchart of FIG. 5, as will be described later, the overall gain maximum gain of the equalizer processing unit 32 is compared with the maximum gain before gain change. Note that the maximum amplification factor before gain change refers to the equalizer unit 30a when each equalizer unit 30a to 30x sequentially amplifies or attenuates the digital audio signal when only the signal input order is changed without changing the gain. It is assumed that it is the largest amplification factor among the maximum amplification factors of the frequency characteristics at each stage of amplification or attenuation processing by ˜30x.

  For example, when the equalizer processing unit 32 is configured by three equalizer units 30a to 30c, and the signal input order of the equalizer units 30a to 30c is the equalizer unit 30c → the equalizer unit 30a → the equalizer unit 30b, only the equalizer unit 30c is a digital audio signal. Of the frequency characteristics when the equalizer section 30c and the equalizer section 30a amplify or attenuate the digital audio signal, and all the equalizer sections 30a to 30c are digital. Among the maximum amplification factors of the frequency characteristics when the audio signal is amplified or attenuated, the one with the largest amplification factor is the maximum amplification factor before the gain change. That is, the maximum amplification factor of the frequency characteristic of only the equalizer unit 30c, the maximum amplification factor of the frequency characteristic obtained by combining the frequency characteristic of the equalizer unit 30c and the frequency characteristic of the equalizer unit 30a, and the frequency characteristics of all the equalizer units 30a to 30c. Among the maximum gains of the frequency characteristics combined with the above, the one with the highest gain is the maximum gain before gain change.

  The maximum gain before the gain change is calculated by calculating the frequency characteristics of all the equalizer characteristics 30a to 30x of the equalizer settings 30a to 30x, and the maximum gain of the frequency characteristics before the gain change. The maximum amplification factor may be used. The maximum gain before gain change is a table of preset equalizer setting patterns, and the assumed maximum gain before gain change is stored in memory so that the signal input order and each gain of the equalizer units 30a to 30x are stored. It may be selected and acquired according to the above.

  Next, the operation of the equalizer device 50 shown in the flowchart of FIG. 5 will be described. First, similar to FIG. 4, after the input operation instructing the user to change the gain (step S <b> 102) and the gain comparison process by the equalizer controller 34 (step S <b> 103), the equalizer controller 34 performs the above-described gain change. The maximum amplification factor is calculated, and the maximum amplification factor before gain change is compared with the maximum amplification factor of the overall characteristic of the equalizer processing unit 32 before the signal input order and gain change, that is, at the present time (step S302). If the current maximum amplification factor of the overall characteristic is larger than the maximum gain before the gain change, the equalizer setting change process is performed according to the flow after step S104 similar to FIG. If the maximum gain before gain change is greater than the current maximum gain of the overall characteristic, the equalizer controller 34 outputs a signal indicating the maximum gain before gain to the level controller 36 (step S306). .

  When the signal indicating the maximum gain before gain change is input from the equalizer control unit 34, the level control unit 36 performs an attenuation rate setting change process of the attenuation processing unit 20 so as to obtain an attenuation rate corresponding to the maximum gain before gain change. This is performed (step S332). Further, the level control unit 36 performs a setting change process for the reference amplification factor of the analog signal amplification unit 24 so as to obtain a reference amplification factor corresponding to the attenuation factor of the attenuation processing unit 20 (step S334). Next, the process proceeds to step S104, and equalizer setting change processing is performed according to the same flow as in FIG.

  When the equalizer units 30a to 30x change the gain after rearranging the signal input order, the signal input to the equalizer units 30a to 30x for amplification setting is performed from the rearrangement process of the signal input order to the gain change process. There is a case where the order comes before the equalizer units 30a to 30x of the attenuation setting. In such a case, if the gain change process has a long time, there is a possibility that saturation will occur due to insufficient headroom.

  However, in the procedure shown in FIG. 5, when gains for the equalizer units 30a to 30x are input, the maximum overall amplification factor and the maximum amplification factor before gain change of the equalizer unit 32 at present, that is, the gain after the signal input sequence change. When the maximum gain before change is larger than the maximum gain before change, the attenuation factor of the attenuation processing unit 20 is quickly changed to a setting that does not cause saturation based on the maximum gain before change. To do. Therefore, even if the signal input order of the equalizer section for amplification setting precedes the equalizer sections 30a to 30x for attenuation setting until the gain change is completed, saturation does not occur. The above is an operation example of the equalizer device 50 when changing the setting of each unit.

  Next, the operation of the equalizer device 50 will be described focusing on the processing for the input digital audio signal.

  Even during the operation shown in FIG. 4 or 5, a digital audio signal is output from a sound source such as a CD player, a DVD player, a hard disk, or a tuner, and the attenuation processing unit of the equalizer device 50 is input via the input terminal 10. 20 is entered.

  The attenuation processing unit 20 attenuates the input digital audio signal (first digital audio signal) with the attenuation rate set by the level control unit 36 and outputs the attenuated signal to the equalizer processing unit 32. For example, when the equalizer units 30a to 30e are set as shown in FIG. 3 and the equalizer setting change processing is completed, the attenuation rate of the attenuation processing unit 20 is 8.65 dB.

  The equalizer processing unit 32 equalizes the digital audio signal (second digital audio signal) attenuated by the attenuation processing unit 20 with the equalizer units 30 a to 30 x and outputs the equalized signal to the digital / analog conversion unit 22. The signal input order to the equalizer units 30a to 30x at this time is preceded by the equalizer units 30a to 30x for attenuation setting by the rearrangement process of the equalizer control unit 34. That is, frequency bands that are amplified or attenuated are respectively set in the equalizer units 30a to 30x, and the equalizer processing unit 32 uses the plurality of equalizer units 30a to 30x to output the digital audio signal attenuated by the attenuation processing unit 20 to a predetermined frequency. Equalizing is performed by sequentially amplifying or attenuating each band.

  The digital / analog converter 22 converts the digital audio signal equalized by the equalizer processor 32 into an analog audio signal and outputs the analog audio signal to the analog signal amplifier 24.

  The analog signal amplification unit 24 amplifies the converted analog audio signal with the reference amplification factor set by the level control unit 36 and outputs the amplified signal to the output terminal 12. When the equalizer units 30a to 30e are set as shown in FIG. 3 and the equalizer setting changing process is completed, the reference amplification factor of the analog signal amplifying unit 24 is 8.65 dB.

  The analog audio signal output from the output terminal 12 is amplified by, for example, an amplifier and then input to audio output means such as a speaker and reproduced as an audio output. When the user operates the volume control or the like, the amplification factor of the analog signal amplification unit 24 increases or decreases from the reference amplification factor, and the sound output volume increases or decreases accordingly. The above is the processing performed by the equalizer device 50 for the input digital audio signal.

  Note that the setting change process (step S132) of the attenuation processing unit 20 and the setting change process (step S134) of the analog signal amplification unit 24 are preferably performed substantially simultaneously. In this way, only the equalizing setting change is reflected in the audio output without changing the total volume.

  However, in general, the attenuation processing unit 20 is provided in a DSP (Digital Signal Processor), and the analog signal amplification unit 24 is often provided in a circuit or control element different from the DSP. For this reason, it may be difficult to simultaneously perform the setting change process (step S132) of the attenuation processing unit 20 and the setting change process (step S134) of the analog signal amplification unit 24.

  Next, it is effective when the setting change process (step S132) of the attenuation processing unit 20 and the setting change process (step S134) of the analog signal amplifying unit 24 are difficult to be performed at the same time. An example of how to change the gain will be described with reference to FIG. In FIG. 6, the plus characteristic indicates the amplification factor of the analog signal amplifier 24, and the minus characteristic indicates the attenuation factor of the attenuation processing unit 20.

  For example, as shown in FIG. 6A, at time t, the level control unit 36 changes the attenuation rate of the attenuation processing unit 20 from -3 dB to -10 dB (step S132), and analog signal amplification. When the setting change process (step S134) for changing the reference amplification factor of the unit 24 from +3 dB to +10 dB is performed substantially simultaneously, a time difference may occur at the time when the two setting change processes are performed. For example, even if the setting change process of the attenuation processing unit 20 is performed at the time t, the setting change process of the analog signal amplification unit 24 may be performed at a time t ′ that is later than the time t. During the period from time t to time t ′, the attenuation rate of the attenuation processing unit 20 and the reference amplification rate of the analog signal amplifying unit 24 are remarkably unbalanced, and depending on the setting, the volume during this period may increase or decrease excessively. There is. This excessive increase / decrease in volume is not preferable because it causes the user to feel uncomfortable or uncomfortable.

  Therefore, as shown in FIG. 6B, the gain change changes gradually with time by performing the setting change process of the attenuation processing unit 20 and the setting change process of the equalizer processing unit 32 gradually and linearly. As shown in FIG. 6C, the gain is changed exponentially, so that the gain change gradually changes with time and the gain change gradually changes with time. If the level control unit 36 performs setting change processing of the attenuation processing unit 20 and the analog signal amplification unit 24 substantially simultaneously, the setting change processing of the attenuation processing unit 20 and the setting change processing of the analog signal amplification unit 24 are completely completed. Even if not performed simultaneously, the attenuation rate of the attenuation processing unit 20 and the analog signal amplification unit 2 in the time from the time t to the time t ′ The difference between the reference gain of the can be suppressed relatively small. Therefore, the volume does not increase or decrease excessively, and the user does not feel uncomfortable or uncomfortable. Note that the pattern setting at this time may be any as long as audio output is performed substantially simultaneously within a range in which the user does not feel uncomfortable. These can also be applied to the setting change processing in the above-described steps S332 and S334.

  In FIG. 6A, among the control signals input from the level control unit 36 to the attenuation processing unit 20 and the analog signal amplification unit 24 in order to change the settings of the attenuation processing unit 20 and the analog signal amplification unit 24, A configuration may be adopted in which the attenuation processing unit 20 and the analog signal amplifying unit 24 can be set simultaneously at time t ′ by delaying and outputting the control signal to be output first from time t to time t ′.

  Further, it is preferable that the setting change process (step S136) of the equalizer processing unit 32 is changed in stages from the viewpoint of maintaining the continuity of the audio output. For example, when the equalizer control unit 34 changes the gain of the equalizer processing unit 32 from 5 dB to 10 dB, it does not change from 5 dB to 10 dB all at once, but at every sampling time, 5 dB → 6 dB → 7 dB → 8 dB → 9 dB → 10 dB It is preferable that the signal is not changed suddenly by changing it stepwise. Thus, in addition to performing the setting change process of the attenuation processing unit 20 and the setting change process of the analog signal amplifying unit 24 with the above-described gain change pattern, the setting change process of the equalizer processing unit 32 is also changed stepwise. It is most preferable that these three setting change processes are started almost at the same time within a range where there is no sense of incongruity in the user's sense of hearing and are completed almost simultaneously.

  As described above, the equalizer device 50 according to the present invention rearranges the signal input order so that signals are input from the equalizer units 30a to 30x with the gain set to attenuation among the equalizer units 30a to 30x. Accordingly, the amplification factor during the equalization of the equalizer processing unit 32 is the maximum overall characteristic even during the equalization because the equalizer units 30a to 30x that are always set for attenuation always attenuate first regardless of the number of the equalizer units 30a to 30x. The amplification factor is never exceeded. Therefore, the attenuation processing unit 20 can prevent the occurrence of saturation by attenuating the digital audio signal with an attenuation factor corresponding to the maximum amplification factor of the overall characteristic. Therefore, the attenuation rate of the attenuation processing unit 20 can always be minimized, and thereby the decrease in the S / N ratio can be minimized.

  That is, the equalizer device 50 according to the present invention can always ensure sufficient headroom, and even if a full-bit digital audio signal is input to the equalizer processing unit 32, saturation does not occur.

  Furthermore, the above-described three setting change processes are performed by causing the setting change process of the attenuation processing unit 20, the setting change process of the equalizer processing unit 32, and the setting change process of the analog signal amplifying unit 24 to be performed substantially simultaneously in the predetermined pattern described above. Can be started substantially simultaneously and completed almost simultaneously. Thereby, it is possible to maintain the continuity of the audio output, and it is possible to perform the equalizer setting changing process with less discomfort to the user.

  As described above, the equalizer control unit 34 according to the present invention includes the equalizer units 30a to 30x that attenuate the digital audio signal before the equalizer units 30a to 30x that amplify the digital audio signal amplify the digital audio signal. The equalizer processor 32 is set so as to attenuate the digital audio signal. For this reason, the attenuation processing unit 20 may attenuate the digital audio signal with an attenuation rate corresponding to the maximum amplification factor of the overall characteristic of the equalizer processing unit 32, and the attenuation rate when the attenuation processing unit 20 attenuates the digital audio signal. Since it can be made as small as necessary, it is possible to prevent the occurrence of saturation and to suppress a decrease in the S / N ratio.

  In addition, since said equalizer apparatus 50 is an example, the structure of each part, an operation | movement flow, the pattern at the time of a setting change process, etc. can be changed and implemented in the range which does not deviate from the summary of this invention. Further, the method of instructing the change of the gain in the present embodiment is an example, and is not limited to this. In the present embodiment, the example in which the user changes the gain of each of the equalizer units 30a to 30x has been described. However, it is not necessary to individually change the gains of the equalizer units 30a to 30x, and the gains of the plurality of equalizer units 30a to 30x A configuration may be adopted in which a storage unit that stores a setting table is provided, and the gain of the plurality of equalizer units 30a to 30x can be changed by a single operation by the user performing an operation input for designating one table. In addition, a gain changing unit that automatically changes the gain of the equalizer units 30a to 30x according to the acoustic characteristics of the viewing space around the audio device that uses the equalizer device of the present embodiment is provided, and the equalizer units 30a to 30x are automatically configured. The gain may be changed. Further, the level control unit 36 sets the gain of the attenuation processing unit 20 and the analog signal amplification unit 24 as an example. However, the level control unit 36 sets only the gain of the attenuation processing unit 20 and the analog signal amplification unit 24. Other means for setting the gain may be provided. Further, the example in which the gain of the equalizer units 30a to 30x is changed after changing the signal input order to the equalizer units 30a to 30x has been described, but the signal input order may be changed after the gain is changed. .

  Moreover, although the example which rearranges the signal input order to equalizer part 30a-30x was demonstrated, not only this but the equalizer control part 34 is an equalizer part which amplifies a digital audio | voice signal after a gain is changed. The equalizer processing unit may be set so that the equalizer unit that attenuates the digital audio signal after the gain is changed attenuates the digital audio signal before the signal is amplified. For example, the equalizer control unit 34 may change the center frequency or the width of the frequency band that the equalizer units 30a to 30x amplify or attenuate without rearranging the signal input order, or may combine them. . That is, the operation of the equalizer control unit 34 is not limited to rearranging the signal input order to the equalizer units 30a to 30x, and the equalizer control unit 34 can change the order of equalization for each frequency band by the equalizer processing unit 34. That's fine.

20 Attenuation processing section
22 Digital / analog converter
24 Analog signal amplifier
30a-30x equalizer section
32 Equalizer processing section
34 Equalizer control section
36 Level control unit
50 Equalizer device

Claims (3)

An attenuation processing unit for attenuating and outputting the input first digital audio signal;
It is set to amplify a predetermined frequency band of the second digital audio signal output by the attenuation processing unit with an amplification gain, or to attenuate a predetermined frequency band of the second digital audio signal with an attenuation gain. An equalizer processing unit configured to equalize the second digital audio signal by sequentially amplifying or attenuating the second digital audio signal for each predetermined frequency band by the plurality of equalizer units;
When changing the gain of at least one equalizer unit among the plurality of equalizer units, the equalizer unit set to the amplification gain after the gain change has a gain before the second digital audio signal is amplified. An equalizer control unit that changes the order of equalization for each frequency band by the equalizer processing unit so that the equalizer unit set to the attenuation gain after the change of attenuates the second digital audio signal;
A level at which the setting of the attenuation processing unit is changed so as to obtain an attenuation factor corresponding to the maximum amplification factor of the input / output frequency characteristics of the equalizer processing unit when the equalizer control unit changes the gain of at least one equalizer unit. And an equalizer device. A digital / analog converter that converts the digital audio signal equalized by the equalizer processor into an analog audio signal;
An analog signal amplifier that amplifies the analog audio signal converted by the digital / analog converter;
The level control unit is configured to change the setting of the analog signal amplifying unit so that an amplification factor corresponding to the maximum amplification factor is obtained when the equalizer control unit changes a gain of at least one of the equalizer units. The equalizer device according to claim 1. The level control unit changes the settings of the attenuation processing unit and the analog signal amplification unit substantially simultaneously with the equalizer control unit changing the order of equalization for each frequency band by the equalizer processing unit. The equalizer device according to claim 2.

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