JPH1117474A - Gain varying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To vary gain with excellent responsiveness by a simple method in a gain varying device for controlling an audio level by a DSP(digital signal processor). SOLUTION: The DSP 104 is provided with a coefficient updating processing part 104a and a multiplication processing part 104b and determines corresponding coefficient change amount and desired coefficient value for respective volume values. When a multiplication coefficient value and the desired coefficient value are different, the coefficient updating processing part 104a adds or subtracts the coefficient change amount to/from the multiplication coefficient value by comparing the size relation of both and updates the multiplication coefficient value. The multiplication processing part 104b multiplies the updated multiplication coefficient value to input signals and changes the gain. Thus, updating time corresponding to a volume position is almost fixed and acoustic feeling change at the time of updating is smoothed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable gain device for changing a gain in digital signal processing, and more particularly to a variable gain device used as a volume function of various audio devices.

[0002]

2. Description of the Related Art FIG. 5 shows a configuration of a main part of a conventional variable gain device. Here, an example is shown in which the volume function of the audio device is multiplied by digital signal processing. In the figure, reference numeral 501 denotes a digital signal processor (hereinafter, referred to as DSP) including a coefficient update processing unit 501a and a multiplication processing unit 501b. 502 is DSP50
A control unit such as a microcomputer for controlling the control unit 1;
02 is a volume adjustment key connected to 02. Control unit 5
Numeral 02 sets a desired coefficient value for each desired volume, and stores the desired coefficient value in the memory.

FIG. 6 shows the contents of each value set by the control unit 502. Here, respective values of a volume value, a volume gain value (-dB), a desired coefficient value (dec), and a difference (dec) between coefficient values are set, and are stored in a memory (not shown) in the control unit 502. In addition, the gain update time (m
s) is also stored. Specifically, it is a fixed-point coefficient of 16 bits, the maximum gain is 0 dB, and the coefficient value at that time is 7FFFh = 32767. Further, the volume gain value is set to change steps every 2 dB.

Next, the operation of the variable gain device shown in FIG. 5 will be described. When the volume is changed by the volume adjustment key 503, the control unit 502 selects the corresponding “desired coefficient value” from the information of the “volume value” from the information in the memory, and transfers it to the coefficient update processing unit 501a of the DSP 501. The coefficient update processing unit 501a includes a multiplication processing unit 501b
Until the multiplication coefficient value of the multiplier (not shown) becomes equal to the “desired coefficient value”, the addition or subtraction of 1 is repeatedly performed only once in one sampling period.

FIG. 7 is a flowchart showing a conventional coefficient updating process. First, it is determined whether the multiplication coefficient value matches the desired coefficient value (step 701). If they match, the coefficient update process ends. If the multiplication coefficient value does not match the desired coefficient value, the multiplication coefficient value is incremented by 1 to make it a new multiplication coefficient value (step 702), and the process ends. The time required for this update is represented by | multiplier coefficient value at start of update−desired coefficient value | × 1 sampling period (in this case, the multiplier coefficient value at the start of update is equal to the desired coefficient value at the previous update. equal). For example, if the sampling frequency is 44.1 kHz, the update time between each volume position is the “gain update time” in FIG.

[0006]

As can be seen from FIG. 6, in this variable gain device, the update time greatly differs depending on the volume position, and a smooth change in audibility cannot be obtained. This is because the gain change of the volume function is generally a logarithmic change, that is, a linear change due to a dB value, whereas the updating of the coefficient value is a linear change due to addition or subtraction.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and makes it possible to improve the responsiveness so that the update time according to the volume position is made substantially constant, and the audibility change during the update can be made smooth. It is an object to provide a variable gain device.

[0008]

According to the present invention, in controlling a gain of an input signal in a digital signal processor, a multiplication coefficient value for changing the gain does not coincide with an updated desired coefficient value. At this time, the multiplication coefficient value is updated by performing addition or subtraction of the coefficient change amount to the multiplication coefficient value once in one sampling period.

Thus, it is possible to obtain a variable gain device capable of keeping the update time corresponding to the volume position substantially constant and smoothly changing the audibility even during the update of the volume change.

[0010]

According to the first aspect of the present invention, a multiplication processing section for multiplying an input signal by a multiplier coefficient value to change a gain and updating a multiplication coefficient value accompanying the multiplication processing A digital signal processor (DSP) having a built-in coefficient update processing unit; and a control unit for controlling the digital signal processor, wherein the multiplication coefficient value matches a desired coefficient value set according to a request for changing the gain. In the variable gain device that updates the multiplication coefficient value,
When the multiplication coefficient value does not match the updated desired coefficient value, the coefficient update processing unit performs one sampling period in one sampling cycle according to the magnitude relationship between the multiplication coefficient value and the desired coefficient value.
Times, the coefficient change amount is added to or subtracted from the multiplication coefficient value to update the multiplication coefficient value, and the update time according to the volume position is updated by using a simple updating means of addition or subtraction. It has an effect that it can be made substantially constant, and a change in audibility during updating can be made smooth.

According to a second aspect of the present invention, in the digital signal processor, when the amount of change in gain that causes a smooth change in audibility is A (dB), the amount of change in coefficient after updating is a desired value before updating. Coefficient value x [{10} (A / 2
0)｝ −1] or less and the desired coefficient value before updating × [1
− {10} (− A / 20)}], and has an effect that a change in audibility can be smoothed by observing this condition.

According to a third aspect of the present invention, the coefficient update processing unit includes a coefficient change amount storage memory for storing the coefficient change amount selected by the control unit, and the desired coefficient change memory selected by the control unit. It has a desired coefficient storage memory in which coefficient values are stored, and has an effect that updating of a multiplication coefficient value can be performed easily and in a short time.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. FIG. 1 shows the configuration of a variable gain device according to the present invention. Hereinafter, an example in which the present invention is applied to a volume function of an audio device will be described.

Reference numeral 101 denotes a sound source that outputs an analog audio signal. Reference numeral 102 denotes a low-pass filter (hereinafter, referred to as LPF) that cuts the high frequency of the sound source 101, and reference numeral 103 denotes L.
A / which converts the output signal of the PF 102 into a digital signal
It is a D converter. Reference numeral 104 denotes a DSP (Digital Signal Process) for performing digital signal processing.
and a coefficient update processing unit 104a and a multiplication processing unit 104b. Reference numeral 105 denotes a D / A converter connected to the DSP 104, and converts an output of the DSP 104 into an analog signal (audio signal). 106
Is an LPF connected to the D / A converter 105,
A harmonic component in the output signal of the D / A converter 105 is removed. Reference numeral 107 denotes an amplifier connected to the LPF 106 to perform voltage amplification and power amplification of the analog audio signal, and reference numeral 108 denotes a speaker connected to the amplifier 107 to perform electro-acoustic conversion. Reference numeral 109 denotes a volume adjustment key operated by a user, and instructs a variable gain of a reproduction signal from the sound source 101. Reference numeral 110 denotes a control unit such as a microcomputer for controlling the DSP 104. In addition,
In the present embodiment, as the sampling frequency,
44.1 kHz is used.

FIG. 2 shows a coefficient update processing unit 10 of the DSP 104.
4A and a detailed configuration of the multiplication processing unit 104b. The coefficient update processing unit 104a includes a coefficient change amount storage memory 201 and a desired coefficient storage memory 202, and the multiplication processing unit 104a includes a multiplier 203 for changing a gain. Further, a memory 204 shared by the coefficient update processing unit 104a and the multiplication processing unit 104b is provided. Both the coefficient change amount storage memory 201 and the desired coefficient storage memory 202 have 16
This is a bit-length coefficient memory. The multiplier 203 is a 16-bit fixed-point coefficient, and the coefficient value when the maximum gain is 0 dB is 7FFF (hex) = 32767 (dec).
In this embodiment, the volume function has a maximum gain of 0.
In dB, each volume value is a change step every 2 dB.

A memory (not shown) in the control unit 110 includes:
As shown in FIG. 3, a first value described below corresponding to the volume value n
The coefficient change amount Sn and the desired coefficient value Dn set to satisfy the conditions (1) to (4) are stored. Further, in addition to the contents shown in FIG. 6, the coefficient difference (dec) and the gain update time (ms) when falling, the coefficient difference (dec) and the gain update time (ms) when rising are stored. In the case of the present embodiment, the coefficient update amount Sn is determined such that the gain update time is one step change of each volume value, that is, a gain change of 2 dB, and is constant within a range of 0.1 to 0.3 ms. ing.
Further, the coefficient change amount Sn is set so that the gain change per sampling cycle is 0.5 dB or less so that a smooth change in audibility can be obtained.

The gain value Vn (d at the volume position n
For each B), a coefficient change amount Sn and a desired coefficient value Dn that satisfy the first to fourth conditions are determined under the relationship of adjacent volume positions n ′ = n + 1 and n ′ = n−1. .

The first condition is that when the desired coefficient value is Dn, the adjacent volume position is n ', the desired coefficient is Dn', and the coefficient change amount is Sn ', | Dn-Dn' | = Sn'.times.m (M: natural number).

The second condition is that between the coefficient change amount Sn and the coefficient change amount Sn ′, the following condition is satisfied: Sn = Sn ′ × m (m: natural number) or Sn = Sn ′ / m (m: natural number) It is.

The third condition is that the desired coefficient value Dn is equal to the gain value V
n to be the closest approximation to achieve
In this case, the required gain update time Tn 'from the volume position n to n' is calculated by the following equation.

Tn '= | Dn-Dn' | /Sn'.times.Sampling Cycle A fourth condition is that the coefficient change amount Sn 'satisfies the following formula. Assuming that the amount of change in gain that causes a smooth change in hearing is A (dB), Sn '<Dn × [{10} (A / 20)｝ − 1] is satisfied, and Sn ′ <Dn × [1 − {10} (− A / 20)}].

Next, the operation of the variable gain device shown in FIG. 1 will be described. The coefficient update processing will be described with reference to the flowchart in FIG.

Usually, the digital audio signal is a DSP
The signal is input to the multiplication processing unit 104b in the
3 is output after the gain is varied by multiplying the multiplication coefficient value. The multiplication coefficient value is stored in the multiplication coefficient value storage memory 204 in the DSP 104.

First, when a volume operation (operation of the volume operation key 109) is performed by the user, the volume value information from the volume operation key 109 is transmitted to the control unit 110.
Transferred to The control unit 110 selects a coefficient change amount and a desired coefficient value corresponding to the volume value based on the volume value information. Next, the control unit 110 transfers the selected coefficient change amount to the coefficient change amount storage memory 201 of the DSP 104, and stores the selected desired coefficient value in the desired coefficient value storage memory 1.
04a.

Then, the coefficient update processing section 104a
As shown in (a), the contents of the respective storage memories of the multiplication coefficient value and the desired coefficient value are compared (step 401), and if they are different (multiplication coefficient value ≠ desired coefficient value), the large / small relationship is determined. (Step 402). In the case of [multiplication coefficient value <desired coefficient value], an addition process of [multiplication coefficient value + coefficient change amount] is performed, and the result is set as a multiplication coefficient value (step 403).
The coefficient update processing ends. If [multiplication coefficient value> desired coefficient value], subtraction processing of [multiplication coefficient value−coefficient change amount] is performed, and the result is set as a multiplication coefficient value (step 40).
4), the coefficient update process ends. The multiplication coefficient value is updated by adding or subtracting the coefficient change amount to or from the multiplication coefficient value, and the result is stored in the multiplication coefficient storage memory 204.

Further, in the multiplication processing section 104b, as shown in FIG. 4 (b), the input signal is multiplied by the updated multiplication coefficient value and used as an output signal (step 405).
The gain changes by this multiplication process. The processing of the coefficient update processing unit 104a and the multiplication processing unit 104b is performed only once in one sampling cycle.

For example, when the volume decreases from -6 dB to -8 dB, the volume position: n = 3 The multiplication coefficient value at the start of the gain update: Dn = D3 = 16384
(Fourth stage in FIG. 3) Coefficient change amount: Sn ′ = Sn + 1 = S4 = 256 (fifth stage in FIG. 3) Desired coefficient value: Dn ′ = D4 = 12800 (fifth stage in FIG. 3) You. In this case, the first condition: | Dn−Dn ′ | = Sn ′ × m (where m is a natural number) | 16384-12800 | = 3584 = 256 × 14

When the volume increases from -8 dB to -6 dB, the volume position: n = 4, the multiplication coefficient value at the start of the gain update: Dn = D4 = 12800
(Fifth stage in FIG. 3) Coefficient change amount: Sn ′ = S (n−1) = S3 = 512 (fourth stage in FIG. 3) Desired coefficient value: Dn ′ = D3 = 16384 (fourth stage in FIG. 3) ) Is set. In this case, the first condition: | Dn−Dn ′ | = Sn ′ × m (m is a natural number) | 12800-16384 | = 3584 = 512 × 7 is satisfied.

Therefore, under the second condition, n = 3, n '=
(N + 1) time Sn = S (n + 1) × m (m is a natural number) 512 = 256 × 2, n = 4, n ′ = (n−1) time Sn = S (n−1) / m (m Is a natural number) 256 = 512/2.

Further, D3 and D4 satisfy the first and second conditions, and are the closest approximate values for realizing -6 dB and -8 dB, and satisfy the third condition.

In this case, the time required for the volume to fall from -6 dB to -8 dB is calculated as follows: Tn '= | Dn-Dn' | /Sn'.times. T4 = | 16384-12800 | / 256/4410
0 = 0.0032 The time required for the volume to rise from -8 dB to -6 dB is n = 4 ', n' = [n-1] T3 = | 12800-16384 | / 512/4410
0 = 0.016.

Further, in order to bring about a smooth change in the sense of hearing, the amount of change in gain per sampling cycle is set to 0.5.
dB, and under the fourth condition, n = 3, n ′ = n + 1
Hour Sn ′ <Dn × [1- {10} (− A / 20)}] 256 <16384 × [1- {10} (− 0.5 / 2
0)｝] = 916 and n = 4 ′, n ′ = n−1 Sn ′ <Dn × [{10 ＾ (A / 20)｝ − 1] 512 <12800 × [{10 ＾ (0.5 / 20)｝-
1] = 758, which is satisfied.

As described above, all the values shown in FIG.
And the fourth condition is satisfied. As a result, the update time according to the volume position is kept in the range of 0.1 to 0.3 ms while using the simple update method of addition or subtraction, and the audibility during the update of the volume function is maintained. Changes can be smoothed.

As described above, since the gain change of the volume function is generally a logarithmic change, that is, a linear change in a decibel (dB) value, the amount of change in the gain differs depending on the volume position. That is, the gain change amount when updating from 0 dB to -6 dB is 1-0.5 = 0.5.
In the case of -20 dB to -26 dB, the same 6 dB
Even if the volume change amount is, the gain change amount is 0.1-
0.05 = 0.05.

According to the present invention, the coefficient updating process is performed by adding or subtracting the coefficient change amount to or from the current multiplication coefficient value only once in one sampling period to make the coefficient equal to the desired coefficient value. , The gain value V at the volume position n
The coefficient change amount Sn is determined for each n (dB), and when the gain change is large, the coefficient change amount is large, and when the gain change is small, the coefficient change amount is reduced to adjust the time required for gain update. And can be made substantially constant for any volume position. Also, the first
By satisfying the third condition, a set of coefficient change amount Sn and a desired coefficient value Dn at the volume position Vn can be coped with when the volume increases and when the volume decreases. Further, by satisfying the fourth condition, by repeating a minute change,
Since the sound is perceived as a smooth change, it is possible to prevent the generation of abnormal noise during volume operation.

As described above, while using a simple updating method such as addition or subtraction, the updating time corresponding to the volume position is kept almost constant, and a digital signal with excellent responsiveness which can bring about a smooth audibility change during updating. A variable gain device using signal processing can be provided.

[0037]

As described above, according to the present invention, the update time according to the volume position can be made substantially constant while using the simple update method of addition or subtraction, and the audibility change during the update can be made smooth. This makes it possible to form a gain variable device having excellent responsiveness.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a variable gain device according to the present invention.

FIG. 2 is a block diagram illustrating details of a coefficient update processing unit and a multiplication processing unit in FIG. 1;

FIG. 3 is an explanatory diagram showing data contents such as coefficients stored in a control unit of FIG. 1;

FIG. 4 is a flowchart showing a coefficient updating process according to the present invention.

FIG. 5 is a block diagram showing a configuration of a main part of a conventional variable gain device.

FIG. 6 is an explanatory diagram showing the contents of each value set by a control unit in FIG. 5;

FIG. 7 is a flowchart showing a conventional coefficient updating process;

[Explanation of symbols]

 Reference Signs List 101 sound source 103 A / D converter 104 digital signal processor (DSP) 104a coefficient update processing unit 104b multiplication processing unit 105 D / A converter 201 coefficient change amount storage memory 202 desired coefficient storage memory 203 multiplier 204 memory

Claims (3)

[Claims] 1. A digital signal processor (DSP) including a multiplication unit for multiplying an input signal by a multiplier coefficient value to change a gain and a coefficient update unit for updating a multiplication coefficient value accompanying the multiplication process. A control unit for controlling the digital signal processor, wherein the multiplication coefficient value is updated so that the multiplication coefficient value matches a desired coefficient value set in response to a request for changing the gain. When the multiplication coefficient value does not coincide with the updated desired coefficient value, the coefficient update processing unit sets the coefficient to the multiplication coefficient value once per sampling cycle according to a magnitude relationship between the multiplication value and the desired coefficient value. A variable gain device, wherein the multiplication coefficient value is updated by adding or subtracting a change amount. 2. The digital signal processor according to claim 1,
The amount of change in gain that produces a smooth change in hearing is represented by A (d
B), the coefficient change amount after the update is equal to or less than the desired coefficient value before the update × [{10} (A / 20)｝ − 1] and the desired coefficient value before the update × [1- ｛]. 10 ＾ (-A / 2
0)｝] The variable gain device according to claim 1, wherein the processing is performed so as to satisfy the following. 3. The coefficient update processing unit includes: a coefficient change amount storage memory in which the coefficient change amount selected by the control unit is stored; and a coefficient change amount storage memory in which the desired coefficient value selected by the control unit is stored. 2. The variable gain device according to claim 1, further comprising a coefficient storage memory.