JP3342718B2 - Volume control using data storage method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a volume control for adjusting a sound volume, and more particularly to an object of the present invention to prevent distortion due to compression of a dynamic range.

[0002]

2. Description of the Related Art Conventionally, as a technique in such a field, in a car audio system, a dynamic range is compressed by a volume control so as not to be drowned out by running noise and to make it easy to hear a weak sound portion. Also, BG
The dynamic range is compressed by suppressing volume of sound by volume control as M (Back Ground Music).

[0003]

However, the compression of the dynamic range of the conventional sound volume control has the following problems. FIG. 9 is a diagram showing a signal waveform obtained by compressing a dynamic range in a conventional volume control. As shown in the figure, when the sound signal level protrudes from between "H (high)" and "L (low)", for example, when the sound signal level becomes larger than "H", this is detected and the gain of the volume control is increased as indicated by the arrow. Make it smaller
Further, when it becomes smaller than "L", this is detected and the gain of the volume control is increased as shown by the arrow. Since the gain adjustment is performed in real time when the signal level exceeds a predetermined width, there is a problem that a signal waveform is distorted.

Accordingly, it is an object of the present invention to provide a volume control in which signal waveform distortion is less likely to occur during dynamic range compression.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems . First aspect of the present invention
Calculates the input level of a certain section of the acoustic signal
Control the sound signal volume based on this input level.
Input level calculation to adjust the gain of the gain section
Necessary for gain control section and input level calculation
Audio signal to delay the audio signal for a certain period of time.
Data and store the delay memory to output to the gain section.
In the volume control having the delay memo,
Lee has a first delay memory for delaying the sound signal and this second delay memory.
Second delay memo for delaying output signal from one-delay memory
Input level calculation and gain control
The control section controls the sound signal level and the output of the first delay memory.
Calculate the input level based on the force difference.

In a second aspect of the present invention, an input level of a predetermined section of a stereo sound signal is calculated, and based on the input level, a gain of a gain section for controlling a volume of the stereo sound signal is calculated. In a volume control having a gain control section and a delay memory required for calculating the input level, the input level calculation / gain control section includes an addition signal for both left and right channels of the stereo sound signal and the addition signal.
The input level is calculated based on the difference between the signal and the delay signal .

The input level calculation / gain control section is configured to reduce the gain of the gain section when the input level exceeds a certain level. Further, the input level calculation / gain control unit increases the gain of the gain unit when the input level falls below a certain level, and increases the gain of the gain unit when the input level exceeds a certain level. I try to make it smaller.

The input level calculation / gain control section has a time constant for a sudden change in gain to be set in the gain section and slowly changes the gain.

[0009]

According to the volume control using the data storage method, the input level of the sound signal is calculated, the gain of the gain section is adjusted based on the input level, and only for a certain period of time required for the calculation of the input level. The sound signal is delayed, that is, stored as sound signal data and output to the gain unit. For this reason, it is possible to prevent the occurrence of signal distortion occurring in real time. Further, according to the first aspect of the present invention, the delay memory and the input level calculation means share a delay memory, thereby simplifying the configuration. According to the second aspect of the present invention ,
The sum signal of the left and right channels of the teleo sound signal and this sum
Calculate the input level based on the difference between the signal and the delayed signal.
As compared with the case where the processing is performed for both channels,
Simplifies configuration by halving memory usage
You.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, attention has been paid to the phenomenon that signal waveform distortion has occurred since the dynamic range of an audio signal has been conventionally compressed in real time, and the audio signal data is stored in a shared memory. Consider compressing the dynamic range based on the stored signal information.
By the way, when trying to compress the dynamic range based on the amplitude of the signal, it is necessary to respond to the case where a small signal comes after a large signal or vice versa. Is not completely solved, so it is necessary to set an appropriate period and ensure hearing adaptability.

An embodiment of the present invention will be described below with reference to the drawings. This Figure 1 is a diagram showing the principle of a data storage mode volume control using the present invention. The volume control using the data storage method shown in FIG. 3 is a method of calculating a digital signal of an audio signal, calculating an input level of the digital signal, and controlling a gain described later based on the calculated input level.
A gain control unit 1; a delay memory 2 for inputting a digital signal simultaneously with the input level calculation / gain control unit 1 and delaying the input digital signal by a time required for signal processing in the input level calculation / gain control unit 1; Input level calculation / gain control unit 1
And a gain unit 3 for adjusting the amplitude of the signal from the delay memory 2 based on the input level calculated in step (1). Here, the delay memory 2 is constituted by a RAM (Random Access Memory) or the like, and the delay time is several tens ms to several hundreds ms.

FIG. 2 is a diagram showing the input level calculation / gain control unit 1 of FIG. FIG. 1A shows a first example of the input level calculation / gain control section 1, in which a square section 11 for squaring an input digital signal and a result obtained from the square section 11 are delayed for a predetermined time. The output difference between the delay memory 12, the square unit 11 and the delay memory 12 is added to form a finite integral of the digital signal within a predetermined time, and the result of converting this output into a gain is set in the gain unit 3. An adder 13 is provided. Here, the operation of the input level calculation / gain control unit 1 shown in FIG. Assuming that the digital signal input to the square unit 11 is x (nt), the output is x2
(Nt), and the delay time of the delay memory 12 is n ′
Let it be t. Here, t is a sampling time. The result of the cumulative addition of the result of the squaring unit 11 by the adding unit 13 is as follows: And the result of cumulatively adding the result of the delay memory 12 by the adder 13 is: And these differences are This equation represents the signal input level for a certain period. Note that the period of the input level to be obtained can be changed by changing n ′.

An input level calculation / gain control section 1 shown in FIG. 1B is a square section 11 for squaring input data.
An adding unit 14 for adding the output of the second unit to the other input and an adding unit 1
4 is delayed by one sampling period and output to the gain unit 3, and a predetermined coefficient (<
1) and a multiplier 16 for multiplying the result of the multiplication by 1 and outputting the result of the multiplication to the other output of the adder 14. In the case shown in FIG. 2B, the initial input level is weighted and calculated so that the influence of the past input level is reduced.
As compared with the method shown in the above, there is an advantage that the response is slightly inferior but the configuration is simple.

FIG. 3 is a diagram showing the relationship between the data input to the input level calculation / gain control unit 1 and the input level. If the amplitude of the input data is high only in part of the period n't as shown in FIG. 6A, the input level is small, and as shown in FIG. 6B, the amplitude of the input data is not particularly high. Even if the average is high, the input level becomes large.

FIG. 4 is a diagram showing the relationship between the gain set in the gain section 3 and the input level. First, the gain G (d
B) is obtained for each sampling period as follows, and is set in the gain unit 3. G = G0 + g Here, G0 is an initial setting gain (dB), and g is a variable gain (dB). Hereinafter, the setting of the variable gain will be described. As shown in FIG. 3A, the input level P0 calculated by the input level calculation / gain control unit 1 is obtained.
And an input level that is larger by a predetermined value around this as P
1, and the input level smaller by the predetermined value is P-1. For the input level P of the input level calculation / gain control unit 1, for example, if P-1≤P≤P1, the gain g of the gain unit 3 is set to 0, and if P1 <P, the gain g of the gain unit 3 is set to -6 dB. If <P-1, the gain g of the gain section 3 is set to +6 dB. When the input level changes over time as shown in FIG. 3B, a gain g is set in the gain section 3 as shown in FIG. FIG. 5 is a diagram showing the relationship between the input level and the output level when the gain is switched. As shown in FIG. 9A, the output rises with respect to the input at P-1 while the input level is falling, and P1 while the input level is rising.
Output falls with respect to input. In this case, if the ascent and descent of the input are sharp, a sense of incongruity occurs in the sense of hearing. For this reason, returning to FIG. 4D, if a time gradient is provided for the change in the gain g, as shown in FIG. 5B, the change in the output level relative to the input level is reduced at the switching point of the input level. . The time gradient of the gain g is, for example, 100 ms.
Multiply by 0 → 6dB. That is, assuming that the sampling frequency is 44.1 kHz, the gain g of the gain unit 3 is changed so that this inclination can be achieved at a period of 4410 times.
Thus, a natural effect can be obtained by slowly changing the gain g with a time constant. The case where the gain g is switched more smoothly will be described above.

FIG. 6 is a diagram showing another relationship between the input level and the output level when the gain is switched. As shown in FIG. 7A, input levels P2 and P-2 are further provided for P0 outside the input levels P1 and P-1. In this case, the input level P of the input level calculation / gain control unit 1
For example, if P-1≤P≤P1, the gain g of the gain unit 3 is set to 0, if P1 <P≤P2, the gain g of the gain unit 3 is set to -3 dB, and if P2 <P, the gain g of the gain unit 3 is set.
Is set to −6 dB, if P−2 <P ≦ P−1, the gain g of the gain unit 3 is set to 3 dB, and if P <P−2, the gain g of the gain unit 3
Is 6 dB. When the input level changes over time as shown in FIG. 6B, the gain unit 3 changes as shown in FIG.
Is set with a gain g. Also, as shown in FIG. 3D, by providing a time gradient for switching the gain, it is easy to hear at the time of switching, as described above, and it is possible to improve the sound quality in audibility. As described above, the gain switching has been performed in stages, but a modification of the gain switching will be described.

FIG. 7 is a diagram showing another example of volume control using the data storage method according to the embodiment of the present invention. In the volume control using the data storage method shown in the figure, the delay memory 2 receives digital data and has a delay memory 21 having a delay time of Xms and a delay memory 22 connected to the delay time memory 21 having a delay time of Yms. The output of the delay memory 22 is output to the gain unit 3. The gain section 3 outputs a digital signal whose volume is controlled. The input level calculation / gain control unit 1 includes a delay memory 21
A squarer 17 for squaring the input of the delay memory 21, a squarer 18 for squaring the output of the delay memory 21, and an adder 19 for cumulatively adding the difference between the squares 17 and 18 and adjusting the gain of the gain unit based on the result. . With this configuration, the delay memory 2 and the input level calculation / gain control unit 1 share the delay memory, thereby simplifying the configuration.

FIG. 8 is a diagram showing an example in which a volume control using a data storage method according to an embodiment of the present invention is used for forming a stereo signal. The volume control using the data storage method shown in FIG. 1 includes delay memories 2L and 2R for inputting digital input signals Lch and Rch, which are stereo signals, respectively.
Gain units 3L connected to L and 2R to form digital output signals Lch and Rch whose gains have been adjusted.
And 3R and a digital input signal L which is a stereo signal.
An adder 30 for adding channels and Rch, and an input level calculator / gain controller 1 for calculating the input level of the added signal and controlling the gains of the gain units 3L and 3R. According to this example, the stereo sound signal
Compared to the case where processing is performed for both the left and right channels,
And the configuration can be simplified.
The input level calculation / gain control unit 1 is shown in FIG.
Although Ru Der similar to the configuration shown in, FIG. 2 (b), the may be those shown in FIG. Thus, even for a stereo signal, the dynamic range can be compressed by adjusting the gain according to the signal input level.

[0019]

According to the present invention, in a volume control having a delay memory, the delay memory and the input level calculation means can share the delay memory to simplify the configuration. Also, according to the present invention, a stereo audio signal is provided.
Signal on both the left and right channels of the signal and the delayed signal of this added signal.
By calculating the input level based on the difference from the
Memory usage compared to processing on each channel
The amount can be halved and the configuration can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram showing a volume control using a data storage method according to an embodiment of the present invention.

FIG. 2 is a diagram showing an input level calculation / gain control unit 1 of FIG. 1;

FIG. 3 is a diagram illustrating a relationship between data input to an input level calculation / gain control unit 1 and an input level;

FIG. 4 is a diagram illustrating a relationship between a gain set in a gain unit 3 and an input level.

FIG. 5 is a diagram illustrating a relationship between an input level and an output level at the time of gain switching.

FIG. 6 is a diagram illustrating another relationship between the input level and the output level when the gain is switched.

FIG. 7 is a diagram showing another example of volume control using the data storage method according to the embodiment of the present invention.

FIG. 8 is a diagram showing an example in which a volume control using a data storage method according to an embodiment of the present invention is used for forming a stereo signal.

FIG. 9 is a diagram showing a signal waveform obtained by compressing a dynamic range in a conventional volume control.

[Explanation of symbols]

 1: Input level calculation / gain control unit 2: Delay memory 3: Gain unit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03G 3/00-3/34

Claims (4)

(57) [Claims] 1. An input level of a certain section of an acoustic signal is calculated.
Control the sound signal volume based on this input level.
Input level calculation to adjust the gain of the gain section
Necessary for gain control section and input level calculation
Audio signal to delay the audio signal for a certain period of time.
Data and store the delay memory to output to the gain section.
In the volume control, the delay memory has a first delay memo for delaying an audio signal.
Delay the output signal from the first delay memory
A second delay memory, wherein the input level calculation / gain control unit
Signal level and the output of the first delay memory,
Data storage method characterized by calculating input level
Volume control using. 2. An input level calculation / gain control unit for calculating an input level of a fixed section of a stereo sound signal and adjusting a gain of a gain unit for controlling a volume of the stereo sound signal based on the input level; In the volume control having a delay memory required for the calculation of the above, the input level calculation and gain control unit includes an addition signal of both left and right channels of the stereo sound signal and the addition.
A volume control using a data storage method, which calculates an input level based on a difference between signal delay signals . 3. The input level calculation / gain control.
When the input level falls below a certain level
The gain of the gain section and / or the input level.
When the bell exceeds a certain level, the gain
The data storage method according to claim 1 or 2, wherein the data size is reduced.
Volume control using expressions. 4. The input level calculation / gain control.
The abrupt change in gain to be set in the gain section
2. A method of slowly changing the time constant by giving a time constant to
4. A button using the data storage method described in any one of
Volume control.