WO2007114348A1

WO2007114348A1 - Reproduction sound volume adjusting device and method

Info

Publication number: WO2007114348A1
Application number: PCT/JP2007/057130
Authority: WO
Inventors: Kei Sakagami
Original assignee: Pioneer Corporation
Priority date: 2006-03-31
Filing date: 2007-03-30
Publication date: 2007-10-11

Abstract

An input audio signal is divided into signal components of a plurality of frequency bands. An envelope level of a signal component of each of the frequency bands is detected. A band signal level of each of the frequency bands is generated as frequency characteristic information. The signal component level is adjusted in accordance with the band signal level generated as the envelope level and the frequency characteristic information for each frequency band so that the signal component levels of the respective frequency bands are almost constant. The signal components which have been subjected to the level adjustment for each frequency band are added to one another to generate an output audio signal.

Description

Specification

Playback volume adjusting apparatus and method

Technical field

The present invention relates to a playback volume adjustment apparatus and method for adjusting the level of an audio signal.

Background art

As a playback volume adjustment device for adjusting the level of an audio signal, an auto gain control device that makes the level of an output signal constant without depending on the level of an audio signal of a signal source is known. (See Patent Document 1). In this conventional apparatus, an input audio signal is divided into signals having different frequency bands set in advance by a plurality of band division filter means, and each divided signal is converted to an absolute value by an absolute value conversion means. Multiplying the weighted data by the multiplication means, and adding all the values obtained by the multiplication by the addition means S is performed. Further, the value of the addition result is corrected by the gain correction means and then compared with the threshold level data, and a gain value is generated by the gain generation means according to the comparison result. The gain generation means generates a gain value smaller than a preset value of 1 if the value corrected by the gain correction means is larger than the threshold level, while it is greater than a preset gain value of 1 if it is smaller than the threshold level. Is generated. The gain value generated by the gain generating means is input to the envelope generating means and controlled so as to have an attack time and a release time having a predetermined time constant. The gain value thus controlled is multiplied by the input audio signal by the output signal multiplication means and output. Patent Document 1: JP 2004-15125 A

Disclosure of the invention

Problems to be solved by the invention

[0003] However, in such a conventional apparatus, even when the level of a part of the frequency band of the input audio signal fluctuates, the output signal level is made constant with respect to the level fluctuation. As a result, the output signal of all frequency bands fluctuates simultaneously, and there is a drawback that breathing (breathing sound) is likely to occur. [0004] The problem to be solved by the present invention includes the above-mentioned drawbacks as an example. The level of the output signal is kept constant regardless of the level of the audio signal of the signal source while preventing bleeding. It is an object of the present invention to provide an apparatus and method for adjusting the playback volume that can be used.

Means for solving the problem

[0005] The reproduction volume adjustment device of the invention according to claim 1 is a reproduction volume adjustment device that adjusts the level of an input audio signal, wherein the input audio signal is divided into signal components of a plurality of frequency bands. Level detecting means for detecting envelope levels of signal components in each of the plurality of frequency bands; and frequency characteristics for generating band signal levels in the plurality of frequency bands as frequency characteristic information of the input audio signal. By the information generation means and the envelope level detected by the level detection means for each frequency band and the frequency characteristic information generation means so that the level of the signal component of each of the plurality of frequency bands is substantially constant. Level adjusting means for adjusting the level of the signal component according to the generated band signal level, and the level adjusting means Thus it is characterized by comprising, adding means for generating an output audio signal by adding the level adjusted the signal component for each of the frequency bands.

[0006] The reproduction volume adjustment method of the invention according to claim 8 is a reproduction volume adjustment method for adjusting the level of an input audio signal, wherein the input audio signal is divided into signal components of a plurality of frequency bands. A level detecting step for detecting envelope levels of signal components in each of the plurality of frequency bands; and a frequency characteristic information generating step for generating band signal levels in each of the plurality of frequency bands as frequency characteristic information of the input audio signal; The envelope signal level detected in the level detection step for each frequency band and the band signal level generated in the frequency characteristic information generation step so that the signal component level of each of the plurality of frequency bands is substantially constant. Level adjustment stage that adjusts the level of the signal component according to the If, Les as comprising the, an adding step of generating broken, as an addition to outputting the audio signal together with the signal component level adjustment for each of the frequency bands Te in the level adjustment step, Ru. Brief Description of Drawings

[0007] FIG. 1 is a block diagram showing an embodiment of the present invention.

2 is a diagram showing a first example of level adjustment characteristics of the apparatus of FIG.

FIG. 3 is a level adjustment coefficient characteristic for obtaining the level adjustment characteristic shown in FIG.

4 is a diagram showing a second example of level adjustment characteristics of the apparatus of FIG. 1.

FIG. 5 is a level adjustment coefficient characteristic for obtaining the level adjustment characteristic shown in FIG.

FIG. 6 is a diagram showing a third example of level adjustment characteristics of the apparatus of FIG. 1.

FIG. 7 is a level adjustment coefficient characteristic for obtaining the level adjustment characteristic shown in FIG.

8 is a flowchart showing the level adjustment coefficient determination operation of each control unit in the apparatus of FIG.

FIG. 9 is a block diagram showing another embodiment of the present invention.

Explanation of symbols

[0008]:! ~ 4 level adjuster

5 Frequency characteristics analyzer

7 Preset frequency characteristics generator

11 LPF

21, 31 BPF

41 HPF

BEST MODE FOR CARRYING OUT THE INVENTION

[0009] According to the inventions according to claims 1 and 8, the input audio signal is divided into signal components of a plurality of frequency bands, and the signal for each frequency band is set so that the level of the divided signal components becomes substantially constant. The level of the component is adjusted, and the signal component of each frequency band that has been level-adjusted is calculated to generate an output audio signal.

[0010] Therefore, even if the level of any band of the input audio signal fluctuates, the level of the output signal is kept almost constant while preventing breathing that the levels of all the frequency bands of the output audio signal do not fluctuate simultaneously. can do.

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

FIG. 1 shows a playback volume adjusting apparatus according to the present invention. This playback volume adjusting device includes level adjusting units for each of the four frequency bands:! To 4, a frequency characteristic analyzing unit 5, and an adder 6.

An audio signal supplied from an audio signal source (not shown) is input to each of the level adjustment units 1 to 4. Level adjuster 1 is a low-frequency level adjuster, level adjuster 2 is a first mid-range level adjuster, level adjuster 3 is a second mid-range level adjuster, and level adjuster 4 is This is a high-frequency level adjustment unit.

[0014] The configuration of each of the level adjustment units 1 to 4 is the same except that the band dividing unit of the input stage is different from each other.

[0015] The band division unit of the low-frequency level adjustment unit 1 is an LPF (low-pass filter) 11, and the first mid-frequency level adjustment unit 2 is a BPF (band-pass filter) 21. The second mid-frequency level adjustment unit 3 is BP F31, and the high frequency level adjustment unit 4 is HPF (high pass filter) 41. LPF11 extracts the signal component of the lowest band, BPF21 extracts the signal component of the first intermediate band, BPF3 1 extracts the signal component of the second intermediate band, and HPF41 extracts the signal component of the highest band. Is extracted. The first intermediate band of BPF21 is lower than the second intermediate band of BPF31.

[0016] Note that the first and second intermediate bands may be obtained by a combination of LPF and HPF. In addition, the signal obtained through LPF without using HPF may be subtracted from the original signal.

[0017] Level adjustment unit:! To 4 each, together with a band division unit, delay units 12, 22, 32, 42, level adjusters 13, 23, 33, 43, full wave rectification units 14, 24, 34, 44 And waveform shaping sections 15, 25, 35, 45, level detection sections 16, 26, 36, 46, and control sections 17, 27, 37, 47.

[0018] Each part of the low-frequency level adjusting unit 1 will be described. The delay unit 12 is connected to the output of the LPF 11, and delays the output signal of the LPF 11. The level adjuster 13 is connected to the output of the delay unit 12 and adjusts the level of the signal delayed by the delay unit 12. The level adjustment by the level adjuster 13 is determined by the level adjustment coefficient supplied as a control signal from the control unit 17. The full-wave rectifier 14 is connected to the output of the LPF 11 and rectifies the output signal of the LPF 11 full-wave. The waveform shaping unit 15 is connected to the output of the full-wave rectification unit 14, and the full-wave rectification unit 14 Output an envelope signal indicating the envelope level of the full-wave rectified signal

. The level detection unit 16 is connected to the output of the waveform shaping unit 15 and detects the level of the envelope signal output from the waveform shaping unit 15. The controller 17 is connected to the outputs of the level detector 16 and the frequency characteristic analyzer 5. The control unit 17 determines the level adjustment coefficient of the level adjuster 13 according to the detection level obtained from the level detection unit 16 and the frequency characteristic analysis result by the frequency characteristic analysis unit 5.

[0019] The delay time of the delay unit 12 corresponds to the time required for the waveform shaping unit 15 to generate an envelope signal, and an appropriate envelope when a large level or level signal is suddenly input. In order to ensure sufficient time for the signal to be output, the time is about twice the attack time described later.

[0020] Each of the first mid-range level adjustment unit 2, the second mid-range level adjustment unit 3, and the high-frequency level adjustment unit 4 is the same as the low-frequency level adjustment unit 1. The delay unit 22 delays the output signal of the BPF 21, the delay unit 32 delays the output signal of the BPF 31, and the delay unit 42 delays the output signal of the tiPF 41. The delay times of the delay units 12, 22, 32 and 42 are the same.

[0021] The frequency characteristic analysis unit 5 analyzes the frequency characteristic of the input audio signal. The band signal level for each frequency band of the frequency characteristic analysis result by the frequency characteristic analysis unit 5 is supplied to the control units 17, 27, 37, and 47 as described above.

[0022] The adder 6 is connected to the outputs of the level adjusters 13, 23, 33, 43, and adds and outputs the output signals of the level adjusters 13, 3, 23, 33, 43.

In the playback volume adjusting apparatus having such a configuration, the input audio signal is first divided into four-band signals by LPF11, BPF21, 31 and HPF41. That is, a low frequency signal, a first mid frequency signal, a second mid frequency signal, and a high frequency signal are obtained. The low-frequency signal, the first mid-frequency signal, the second mid-frequency signal, and the high-frequency signal are delayed by delay devices 12, 22, 32, and 42 and supplied to level adjusters 13, 23, 33, and 43. .

[0024] Further, the low-frequency signal, the first mid-frequency signal, the second mid-frequency signal, and the high-frequency signal are respectively full-wave rectified by the full-wave rectifiers 14, 24, 34, and 44. The value is obtained. Next, the rectified signal is input to the waveform shapers 15, 25, 35, 45, where an envelope signal indicating the envelope of the rectified signal is generated. [0025] LPF is used to generate the envelope signal S, and the time constant (referred to as attack time) when the LPF time constant is not constant is about 1 msec. The time constant (called release time) at the time of release (when the signal becomes smaller in time series) is set to several hundred msec. The release time also changes stepwise depending on the signal level, and is set in advance so that the higher the signal level, the shorter the signal level and the longer the signal level.

Next, the generated envelope signal is supplied to the level detectors 16, 26, 36, 46. In each of the level detectors 16, 26, 36, 46, the level of the envelope signal is detected and supplied to the controllers 17, 27, 37, 47. The level of the envelope signal becomes one factor for determining the level adjustment coefficient in the control units 17, 27, 37, and 47.

The frequency characteristic analysis unit 5 analyzes the frequency characteristic of the input audio signal and supplies the band signal level for each frequency band to the control units 17, 27, 37, 47 as a result.

[0028] Each of the control units 17, 27, 37, and 47 determines a level adjustment coefficient according to the detected level of the envelope signal and the analyzed frequency characteristic.

[0029] First, a method for determining a level adjustment coefficient according to the level of the detected envelope signal will be described.

FIG. 2 shows an example of the level adjustment characteristic of the reproduction volume adjustment device. The horizontal axis of the characteristics in Fig. 2 represents the input signal level [dBFS], and the vertical axis represents the output signal level [dBFS]. Fig. 3 shows the characteristics of the level adjustment coefficient to obtain the level adjustment characteristics shown in Fig. 2. The horizontal axis of the characteristics in Fig. 3 represents the input signal level [dBFS], and the vertical axis represents the level adjustment factor. The control units 17, 27, 37, 47 calculate a level adjustment coefficient corresponding to the level of the envelope signal based on the characteristic of the level adjustment coefficient.

For example, when the input audio signal is −20 dBFS or more and OdBFS or less, the level adjustment coefficient is set so that the output signal level becomes −20 dBFS. Also, when the input audio signal is -40dBFS or less and -55dBFS or more, the level adjustment coefficient is set so that the output signal is -40dBFS.

Next, a method for determining the level adjustment coefficient according to the analyzed frequency characteristic will be described. The frequency characteristics of the input audio signal are as follows: Represented. Corresponding to this band signal level, the level adjustment characteristic when calculating the level adjustment coefficient is changed according to the level of the envelope signal.

Specifically, in addition to the level adjustment characteristics shown in FIG. 2, the level adjustment characteristics shown in FIGS. 4 and 6 are prepared, and the level adjustment characteristics shown in FIGS. 5 and 7 are used to obtain the level adjustment characteristics. Coefficient characteristics are provided. The level adjustment characteristic in Fig. 4 is a characteristic in which the level of the horizontal portion of the level adjustment characteristic in Fig. 2 is lowered, and the level adjustment characteristic in Fig. 6 is a characteristic in which the level in the horizontal part is further lowered. Here, the characteristic of the level adjustment coefficient in FIG. 3 to obtain the level adjustment characteristic in FIG. 2 is characteristic A, and the characteristic of the level adjustment coefficient in FIG. 5 to obtain the level adjustment characteristic in FIG. 4 is characteristic B. Characteristic C is the characteristic of the level adjustment coefficient in Fig. 7 to obtain the level adjustment characteristic of 6.

[0034] In order to select the characteristics of the level adjustment coefficient, each of the control units 17, 27, 37, 47 determines whether or not the band signal level is greater than the first threshold as shown in FIG. S1) If the signal level is larger than the first threshold, the level adjustment coefficient is determined according to the level of the envelope signal using the characteristic A of the level adjustment coefficient (step S2). If the band signal level is less than or equal to the first threshold, it is determined whether or not the signal level is greater than the second threshold (<first threshold) (step S3). If the band signal level is greater than the second threshold, the level adjustment coefficient is determined according to the level of the envelope signal using the characteristic B of the level adjustment coefficient (step S4). When the band signal level is less than or equal to the second threshold, the level adjustment coefficient is determined according to the level of the envelope signal using the level adjustment coefficient characteristic C (step S5). Each of the control units 17, 27, 37, 47 stores a data table of characteristics A, B, C in an internal memory (not shown), and determines a level adjustment coefficient by referring to it.

[0035] Each of the control units 17, 27, 37, 47 repeats the level adjustment coefficient determination operation at a predetermined cycle. For example, when the input audio signal is digitally processed, the predetermined period is the sampling period.

[0036] In each of the level adjustment units 13, 23, 33, and 43, the low frequency signal, the first mid frequency signal, the second mid frequency signal, and the high frequency signal delayed by the delay units 12, 22, 32, and 42, respectively. Is multiplied by the level adjustment coefficient determined by the control unit 17, 27, 37, 4 7. Delayed low-frequency signal, first midrange The signal, the second mid-range signal, and the high-frequency signal are attenuated or amplified according to the level adjustment factor for each band.

[0037] For example, in the band to which the level adjustment characteristic of Fig. 2 is applied, when the signal level of that band is -20dBFS or more and OdBFS or less, the level adjustment coefficient is set so that the output is -20dBFS. The signal level is attenuated according to the level adjustment coefficient using characteristic A. When the signal level is −40 dBFS or less and −55 dBFS or more, the signal level is amplified so that the output is −40 dBFS.

[0038] The low-frequency signal, the first mid-range signal, the second mid-range signal, and the high-frequency signal that have been level-adjusted in each of the level adjustment units 13, 23, 33, and 43 are added by the adder 6 and the result is added. Are output as a signal having a uniform reproduction volume.

Thus, according to such a playback volume adjusting device, the level adjustment coefficient is determined for each of the low frequency band, the first mid frequency band, the second mid frequency band, and the high frequency band, and the delayed low frequency signal, 1 The mid-band signal, the 2nd mid-band signal, and the high-band signal are multiplied by the corresponding level adjustment coefficients, and the resulting low-band signal, 1st mid-band signal, 2nd mid-band signal, and high-band signal are added. Output as an audio signal. Therefore, it is possible to prevent paging in which the level of all frequency bands of the output audio signal does not fluctuate simultaneously even if the level of any band of the input audio signal fluctuates. For example, when the signal source is switched, the audio signal level can be approximately equalized even if the audio signal level of the signal source before and after the switching is different, which causes sudden fluctuations in playback volume and breathing. Power to prevent the occurrence of S

In the embodiment described above, the level adjustment characteristic is changed according to the frequency characteristic of the input audio signal using the frequency characteristic analysis unit 5, but the level adjustment characteristic is changed according to predetermined frequency characteristic information. You may let them. For example, as shown in FIG. 9, a preset frequency characteristic generation unit 7 is provided, and the preset frequency characteristic generation unit 7 stores preset frequency characteristic information, and the frequency characteristic information, that is, the signal level for each band. Is supplied to the control units 17, 27, 37, 47. As a result, by changing the level adjustment characteristic according to the frequency characteristic information set in advance, regardless of the frequency characteristic of the input audio signal, the frequency characteristic is deliberately processed, and various signals with different audibility levels. The volume of the source can be made uniform. Specifically, it is possible to equalize the playback volume even if signal sources with different audibility levels are selectively connected while providing an equalizing effect such as enhancing the low range or attenuating the high range. it can. Further, a plurality of predetermined frequency characteristic information may be prepared as a plurality of different patterns so that they can be selected.

[0041] In the above embodiment, the frequency band is divided into four bands, but may be divided into a plurality of bands other than the four bands.

[0042] According to the present invention as described above, the level of the output signal can be made substantially constant without depending on the level of the audio signal of the signal source while preventing breathing.

The present invention can be applied to an apparatus having an audio reproduction system such as an amplifier, a disk player, a memory audio player, and a television receiver.

Claims

The scope of the claims

[1] A playback volume adjustment device for adjusting the level of an input audio signal,

A band dividing means for dividing the input audio signal into signal components of a plurality of frequency bands;

Level detecting means for detecting an envelope level of a signal component of each of the plurality of frequency bands;

Frequency characteristic information generating means for generating a band signal level of each of the plurality of frequency bands as frequency characteristic information of the input audio signal;

The envelope level detected by the level detecting means for each frequency band and the band signal level generated by the frequency characteristic information generating means for each frequency band so that the signal component levels of each of the plurality of frequency bands are substantially constant. Level adjusting means for adjusting the level of the signal component according to

A playback volume adjusting apparatus comprising: adding means for adding the signal components level-adjusted for each frequency band by the level adjusting means to generate an output audio signal.

2. The reproduction volume adjusting device according to claim 1, wherein the frequency characteristic information generating unit generates a band signal level of each of the plurality of frequency bands by analyzing a frequency characteristic of the input audio signal.

3. The reproduction volume adjusting device according to claim 1, wherein the frequency characteristic information generating unit stores a band signal level set in advance for each of the plurality of frequency bands and outputs the band signal level.

[4] The band dividing means includes a low-pass filter that extracts a signal component of the lowest band, a first band-pass filter that extracts a signal component of the first intermediate band, and a second higher than the first intermediate band. 2. The reproduction volume adjustment device according to claim 1, further comprising: a second band-pass filter that extracts a signal component of the intermediate band of the first and a high-pass filter that extracts a signal component of the highest band.

[5] The level detection means includes a full-wave rectifier for full-wave rectifying the signal component for each frequency band, and an envelope signal indicating an envelope of an output signal of the full-wave rectifier 2. The reproduction volume adjusting device according to claim 1, further comprising: a waveform shaping unit that generates a level detection unit; and a level detection unit that detects a level of the envelope signal.

[6] The level adjusting means includes a control unit that generates a control signal according to the envelope level and the band signal level for each frequency band, and a time corresponding to the generation time of the envelope of the signal component. 2. The reproduction volume adjustment according to claim 1, further comprising: a delay unit that delays only by a delay amount; and a level adjuster that adjusts a level of a signal component output from the delay unit in accordance with the control signal. apparatus.

[7] The control unit includes a plurality of level-level adjustment coefficient characteristics as data, selects a signal level level adjustment coefficient characteristic corresponding to the band signal level, and selects the selected signal level level adjustment coefficient characteristic. The level adjustment coefficient corresponding to the level of the envelope signal is determined as the control signal using

7. The level adjuster according to claim 6, wherein the level adjuster adjusts the level by multiplying the level of the signal component output from the delay unit by a level adjustment coefficient determined by the control unit. Playback volume adjustment device.

[8] A playback volume adjustment method for adjusting the level of an input audio signal,

A band division step for dividing the input audio signal into signal components of a plurality of frequency bands;

A level detecting step for detecting an envelope level of a signal component of each of the plurality of frequency bands;

A frequency characteristic information generating step for generating a band signal level of each of the plurality of frequency bands as frequency characteristic information of the input audio signal;

The envelope level detected in the level detection step for each frequency band and the band signal level generated in the frequency characteristic information generation step so that the level of the signal component in each of the plurality of frequency bands is substantially constant. And a level adjusting step for adjusting the level of the signal component accordingly,

A playback volume adjustment method comprising: an addition step of adding the signal components level-adjusted for each frequency band in the level adjustment step to generate an output audio signal.