JP5023812B2 - Digital audio processing apparatus and digital audio processing program - Google Patents

Description

  The present invention adds a variable amount corresponding to a difference value between adjacent samples of a digital audio signal to a sample on the maximum value side, and corrects the digital audio signal by subtracting from the sample on the minimum value side. The present invention relates to a processing device and a digital audio processing program.

  For example, in the CD standard, an analog audio signal is converted into a digital audio signal with a sampling frequency fs = 44.1 kHz and a quantization bit number = 16 bits, and is cut up to a band of 22.05 kHz according to the sampling theorem. In addition, in the DVD video standard and the DVD audio standard, fs = 48 kHz, 96 kHz, 192 kHz, quantization bit number = 24 bits, etc. higher than 44.1 kHz are used in order to obtain a richer presence than the CD signal. Yes. However, even if an existing CD signal is directly converted from 16 to 24 bits and converted to 48 kHz or the like by high-sampling for the purpose of obtaining a sense of reality, a band of 22.05 kHz or more is not generated. For this reason, a method has been proposed in which a high frequency band obtained by shaping the waveform of a CD signal is added to the original signal to reproduce a rich sense of reality.

  For example, as the first prior art, in Patent Document 1 below, the sampling data before and after are compared to detect the maximum value and the minimum value of the sampling data, and from the maximum value to the minimum value, from the minimum value to the maximum value. The number of samples is detected, and the difference from the previous sample is calculated for each sample excluding the maximum value and the minimum value, and this is multiplied by each coefficient according to the number of samples. Addition processing is performed on samples close to the maximum value except for, and subtraction processing is performed on samples close to the minimum value except for the minimum value. In addition, as a second conventional technique, in Patent Document 2 below, the maximum value and the minimum value are also applied, and a predetermined coefficient is used for the difference between the maximum value and the minimum value and the value one sample before. , And the multiplication result is added to the maximum value and subtracted from the minimum value. By these methods, it is possible to obtain a reproduction sound that is as sharp as an original analog signal, and has reality and clarity.

FIG. 7 shows a block diagram of a conventional digital audio processing apparatus. Here, as an example, the input audio signal is set to fs = 96 kHz and the number of quantization bits = 24 bits. The extreme value calculation means 11 compares the input audio signal with the previous sample for each sample and detects whether it is large, small, or equal, thereby detecting the maximum value and the minimum value of the waveform. To do. The sample number detection means 12 detects the number of samples (interval, that is, 1 / audio frequency) existing in a section between the obtained maximum value and minimum value. The difference value calculation means 13 obtains a difference value Δ between each sample including the maximum value and the minimum value and the value one sample before. The variable amount calculation means 14 calculates the variable amount = α × Δ by multiplying the obtained difference value Δ by each coefficient α corresponding to the number of samples included. The addition / subtraction means 15 performs a process of adding a variable amount = α × Δ for the sample on the maximum value side, and performs a process of subtracting the variable amount = α × Δ for the sample on the minimum value side.
Patent No. 3401171 (Claim 1) Japanese Patent No. 3659489 (Claim 1)

  According to the first and second conventional techniques, it is possible to convert audio information in a narrow frequency band into audio information in a wide frequency band with a small, simple and inexpensive circuit configuration, and the purpose thereof can be achieved. Each time, the difference from the previous sample is calculated, and this is multiplied by each coefficient according to the number of samples. The multiplication result is added to the sample on the local maximum side, and the sample on the local minimum side is added. Therefore, if the difference amount used for the addition process is different from the difference amount used for the subtraction process, the signal power of the original data may be changed. That is, when the total power obtained by the sum of squares of the added value and the total power obtained by the sum of the squares of the subtracted values do not coincide with each other, it is perceived that the volume level is changed.

  FIG. 8 is a diagram for explaining the waveform correction according to the prior art, and shows an example. In this figure, the interval between the local minimum value X0 and the local maximum value X3 is 3 samples (3Ts) at the sampling period (Ts [sec]), and a variable amount Δd1 is added to the sample X2 close to the local maximum value X3. A variable Δd2 is subtracted from the sample X1 close to X0. In this example, since the difference value between sample X0 and sample X1 is larger than the difference value between sample X2 and sample X3, if each coefficient α corresponding to the number of samples is constant, the obtained variable amount becomes Δd2> Δd1, and is corrected. The later signal has a power of (Δd2−Δd1) squared less than the original signal.

  Therefore, in the present invention, when a digital audio signal is corrected by adding a variable amount corresponding to a difference value between adjacent samples of the digital audio signal to the sample on the maximum value side and subtracting it from the sample on the minimum value side. Another object of the present invention is to provide a digital audio processing apparatus and a digital audio processing program capable of preventing a change in volume level while maintaining conventional quality.

In order to achieve the above object, the digital audio processing apparatus of the present invention provides
An extreme value calculating means for obtaining a maximum value and a minimum value as extreme values by comparing adjacent samples of the original digital audio information;
Sample number detection means for detecting the number of samples between adjacent extreme values;
A waveform that separates the waveform of the sample between the adjacent extreme values into a linear waveform connecting the adjacent extreme values and a differential waveform obtained by subtracting the linear waveform from the waveform of the sample between the adjacent extreme values. Separating means;
Difference value calculating means for obtaining a difference between each sample of the waveform of the straight line separated by the waveform separating means and the value one sample before;
Variable amount calculation means for multiplying each coefficient according to the obtained sample number and each difference value to obtain a variable amount for correcting the sample of the waveform of the straight line;
Adding and subtracting the variable amount to the maximum value side sample of the straight line waveform and subtracting from the minimum value side sample of the straight line waveform so as not to change the total power of the original digital audio information Means,
Waveform synthesizing means for synthesizing the linear waveform obtained by adding / subtracting the variable amount by the addition / subtraction means and the differential waveform separated by the waveform separation means,
Have.

In order to achieve the above object, the digital audio processing program of the present invention provides
An extreme value calculation step for obtaining a maximum value and a minimum value as extreme values by comparing adjacent samples of the original digital audio information; and
A sample number detection step for detecting the number of samples between adjacent extreme values;
A waveform that separates the waveform of the sample between the adjacent extreme values into a linear waveform connecting the adjacent extreme values and a differential waveform obtained by subtracting the linear waveform from the waveform of the sample between the adjacent extreme values. A separation step;
A difference value calculating step for obtaining a difference between each sample of the linear waveform separated by the waveform separating step and a value one sample before;
A variable amount calculating step for obtaining a variable amount for correcting the sample of the waveform of the straight line by multiplying each coefficient according to the obtained sample number and each difference value, respectively,
Adding and subtracting the variable amount to the maximum value side sample of the straight line waveform and subtracting from the minimum value side sample of the straight line waveform so as not to change the total power of the original digital audio information Steps,
A waveform synthesis step of synthesizing the linear waveform obtained by adding / subtracting the variable amount by the addition / subtraction step and the differential waveform separated by the waveform separation means;
Let the computer run.

In order to achieve the above object, the digital audio processing apparatus of the present invention provides
An extreme value calculation means for obtaining a maximum value and a minimum value by comparing the samples before and after the adjacent adjacent digital original audio information, and for obtaining a sample having the same value as the extreme value before and after the adjacent samples,
The number of samples between the adjacent maximum value and the minimum value, the adjacent maximum value, or the number of samples between the adjacent minimum value and the sample determined as the extreme value, and the sample determined as the extreme value are A sample number detecting means for detecting the number of samples existing in the continuing section;
A waveform of a section in which the number of samples is detected by the sample number detection means, a linear waveform connecting the start point value and end point value of the section, and a differential waveform obtained by subtracting the straight line waveform from the waveform of the section Waveform separating means for separating into
Difference value calculating means for obtaining a difference between each sample of the linear waveform separated by the waveform separating means and the value one sample before;
Variable amount calculation means for multiplying each coefficient according to the obtained sample number and each difference value to obtain a variable amount for correcting the sample of the waveform of the straight line;
Adding and subtracting the variable amount to the maximum value side sample of the straight line waveform and subtracting from the minimum value side sample of the straight line waveform so as not to change the total power of the original digital audio information Means,
Waveform synthesizing means for synthesizing the linear waveform obtained by adding / subtracting the variable amount by the addition / subtraction means and the differential waveform separated by the waveform separation means,
Have.

In order to achieve the above object, the digital audio processing program of the present invention provides
An extreme value calculation step for obtaining a maximum value and a minimum value by comparing adjacent samples of the original digital audio information, and obtaining a sample having the same value as the extreme value of adjacent samples before and after,
The number of samples between the adjacent maximum value and the minimum value, the adjacent maximum value, or the number of samples between the adjacent minimum value and the sample determined as the extreme value, and the sample determined as the extreme value are A sample number detection step for detecting the number of samples existing in the continuing section;
The waveform of the section in which the number of samples is detected by the sample number detection step, the straight waveform connecting the start point value and the end point value of the section, and the differential waveform obtained by subtracting the straight waveform from the section waveform A waveform separation step for separating into
A difference value calculation step for obtaining a difference between each sample of the linear waveform separated by the waveform separation step and a value one sample before;
A variable amount calculating step for obtaining a variable amount for correcting the sample of the waveform of the straight line by multiplying each coefficient according to the obtained sample number and each difference value, respectively,
Adding and subtracting the variable amount to the maximum value side sample of the straight line waveform and subtracting from the minimum value side sample of the straight line waveform so as not to change the total power of the original digital audio information Steps,
A waveform synthesis step of synthesizing the linear waveform obtained by adding / subtracting the variable amount by the addition / subtraction step and the differential waveform separated by the waveform separation means;
Let the computer run.

According to the digital sound processing apparatus and the digital sound processing program of the present invention, the waveform of the sample between the adjacent maximum value and the minimum value, the waveform of the straight line connecting the adjacent maximum value and the minimum value, the adjacent maximum value, and Since it is separated into a differential waveform obtained by subtracting a linear waveform from the sample waveform between the minimum values, addition or subtraction is performed only on the linear waveform sample, so the variable amount used for the addition process and the variable amount used for the subtraction process As a result, the signal power in the section between the maximum and minimum values is kept at the signal power of the original data, while maintaining the conventional quality and volume. The level change can be prevented.
In addition to the maximum value and the minimum value, a sample having the same value as the immediately preceding or immediately following sample value is determined as an extreme value, and the interval for determining the number of samples is determined by the maximum value, the minimum value, and the extreme value. Since the waveform of the straight line connecting the value of the start point and the value of the end point and the difference waveform obtained by subtracting the waveform of the straight line from the waveform of this section, addition or subtraction is performed only on the sample of the waveform of the straight line, Since the variable amount used for the addition process and the variable amount used for the subtraction process can be made the same, as a result, the signal power in the section between the maximum value and the minimum value is kept at the signal power of the original data. In other words, it is possible to prevent a change in volume level while maintaining the conventional quality.

<First Embodiment>
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram for explaining a first embodiment of a digital sound processing apparatus and a digital sound processing program according to the present invention. Here, as an example, the input audio signal is set to fs = 96 kHz and the number of quantization bits = 24 bits. The extreme value calculation means 21 compares the input audio signal with the previous sample for each sample and detects whether it is large, small, or equal, thereby determining the local maximum and minimum values of the waveform. Detect as value. The sample number detection means 22 detects the number of samples (interval, that is, 1 / audio frequency) present in the section between the obtained adjacent maximum value and minimum value.

  As shown in FIG. 2, the waveform separating means 23 separates the sample (original waveform S0) existing in the section between the obtained maximum value X3 and the minimum value X0 into a simple increase / decrease waveform S1 and a fine variation waveform S2. The simple increase / decrease waveform S1 is output to the difference value calculation means 24 and the addition / subtraction means 26, and the fine fluctuation waveform S2 is output to the waveform synthesis means 27, so that only the simple increase / decrease waveform S1 is corrected. Here, the simple increase / decrease waveform S1 is a linear waveform given by a linear expression (y = ax + b), and the fine fluctuation waveform S2 is a difference waveform obtained by subtracting the simple increase / decrease waveform S1 from the original waveform S0.

  The difference value calculation means 24 obtains a difference value Δ between each sample of the simple increase / decrease waveform S1 and the value one sample before. The variable amount calculation means 25 calculates the variable amount Δd = α × Δ by multiplying the obtained difference value Δ by each coefficient α corresponding to the number of samples included. In the addition / subtraction means 26, the variable amount Δd is added to the sample on the maximum value side and the variable amount Δd is subtracted to the sample on the minimum value side for each sample of the simple increase / decrease waveform S1. The waveform synthesis means 27 obtains the final output waveform by synthesizing the modified simple increase / decrease waveform S <b> 1 ′ and the fine variation waveform S <b> 2 that is not changed.

FIG. 2 is a diagram for explaining the waveform separating means 23 in detail, and shows an example. The original waveform S0 in the figure is the same as in FIG. 8, and the interval between the minimum value X0 and the maximum value X3 is 3 samples (3Ts) at the sampling period Ts [sec], and the sample X0 (minimum value) and immediately after that Since the difference value of the sample X1 is larger than the difference value of the sample X2 and the immediately following sample X3 (maximum value), if each coefficient α corresponding to the number of samples is constant, the waveform corrected by the conventional processing is the original waveform This is an example in which the power decreases. The waveform separation means 23 separates the original waveform S0 into a simple increase / decrease waveform S1 and a fine variation waveform S2. The simple increase / decrease waveform S1 is obtained by calculating each sample value in each sampling period after calculating a linear equation passing through two points of the minimum value X0 and the maximum value X3. Since the time interval between the minimum value X0 and the maximum value X3 is the number of samples = 3, the linear equation is obtained as the following equation 1 when the output is X′i and the index i.

X′i = (X3−X0) × (i / 3) + X0
However, i = 0, 1, 2, 3 (Formula 1)

In FIG. 2, X′0 to X′3 correspond to it. Further, X′0 = X0 for the minimum value X0 and X′3 = X3 for the maximum value X3, and the minimum value and the maximum value in the simple increase / decrease waveform S1 are respectively in the original waveform S0 before separation. It is the same as the minimum and maximum values. Further, the difference value Δ between each sample of the obtained simple increase / decrease waveform S1 and the value one sample before takes a constant value.

On the other hand, the fine fluctuation waveform S2 is obtained by subtracting the simple increase / decrease waveform S1 from the original waveform S0. When the original waveform is Xi, the simple increase / decrease waveform is X'i, and the fine fluctuation waveform is ΔXi, the following equation is established.
ΔXi = Xi-X'i
However, i = 0, 1, 2, 3 (Formula 2)
In FIG. 2, ΔX0 to ΔX3 correspond to it, and ΔX0 of the minimum value X0 and ΔX3 of the maximum value X3 are both zero.

  FIG. 3 shows a waveform correction process for the simple increase / decrease waveform S1 by the difference value calculation means 24, the variable amount calculation means 25, and the addition / subtraction means 26. In the difference value calculation means 24, a difference value Δ between each sample of the simple increase / decrease waveform S1 and the previous sample value is obtained. The variable amount calculation means 25 calculates the variable amount Δd by multiplying the obtained difference value Δ by each coefficient α corresponding to the number of samples included, but the difference value Δ is constant for any sample. Therefore, the variable amount Δd = α × Δ is also constant. The addition / subtraction means 26 adds the variable amount Δd to the sample X′2 close to the maximum value X′3 and subtracts the variable amount Δd from the sample X′1 close to the minimum value X′0. Correct the waveform. As can be seen, since the variable amount Δd used for addition and the variable amount Δd used for subtraction are the same, the waveform S0 can be corrected without changing the total power of the original waveform S0.

  FIG. 4 is a diagram for explaining the waveform synthesizing means 27 in the present invention, and shows an example. The waveform synthesizing unit 27 adds the simple increase / decrease waveform S1 'corrected by the addition / subtraction unit 26 and the fine variation waveform S2 which has not been changed after being separated by the waveform separation unit 23 to generate a final output waveform S3. The final output waveform S3 is corrected to a waveform in which the total amount of power of the original waveform S0 is maintained and the fine variation waveform S2 indicating the characteristics of the original waveform S0 is also left.

<Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to the drawings. The block diagram of the digital audio processing apparatus and digital audio processing program of the second embodiment is the same as that of FIG. 1, but the functions of some means are changed. Here, similarly to the above, the input audio signal is set to fs = 96 kHz and the number of quantization bits = 24 bits. The extreme value calculation means 21 determines whether the input audio signal is large, small, or equal by comparing the input audio signal with the previous sample for each sample, and detects the maximum value and the minimum value of the waveform. In addition, a sample whose slope of a tangent line connecting the immediately preceding or immediately following sample value is zero (that is, the same value as the immediately preceding or immediately following sample value) is also detected as an extreme value.

In the sample number detection means 22,
・ In addition to the number of samples (interval) existing in the section between the maximum and minimum values,
-The number of samples (interval) existing in the interval between samples where the local minimum and tangent slope are zero,
The number of samples (interval) existing in a section sandwiched between samples where the maximum value and the slope of the tangent are zero,
The number of samples (interval) existing in the section between the samples where the slope of the two tangents is zero,
-Number of samples (interval) existing in the interval where samples with tangent slopes of zero continue
Is detected.

  The waveform separation means 23 separates the sample (original waveform S0) existing in the section used in the sample number detection means 22 into a simple increase / decrease waveform S1 and a fine variation waveform S2. The difference value calculation means 24 obtains a difference value Δ between each sample of the simple increase / decrease waveform S1 and the value one sample before. The variable amount calculation means 25 calculates the variable amount by multiplying the obtained difference value Δ by each coefficient α corresponding to the number of samples included. The addition / subtraction means 26 performs a process for adding the variable amount Δd to each sample of the simple increase / decrease waveform S1 or a process for subtracting the variable amount Δd. The waveform synthesizing unit 27 synthesizes the corrected simple increase / decrease waveform S1 'and the fine fluctuation waveform S2 to obtain the final output waveform S3. Here, the waveform separation unit 23, the difference value calculation unit 24, the variable amount calculation unit 25, the addition / subtraction unit 26, and the waveform synthesis unit 27 are only applied in addition to the section between the maximum value and the minimum value. The first embodiment can be used as it is.

  FIG. 5 is a diagram for explaining the necessity of detecting the sample X2 in the figure in which the inclination of the tangent is zero as the extreme value in the extreme value detection means 21 of the second embodiment of the present invention. is there. In FIG. 5, the analog signal waveform x (t) and its maximum value are P, and the sample values obtained by sampling the analog signal waveform x (t) every sampling period Ts [sec] are Xi (X1 to X4). As can be seen from this figure, when the sampling period Ts and the maximum value P of the analog signal waveform x (t) do not match, the maximum value P cannot be captured by the sample value X2 and the sample value X3. That is, since the unevenness of the analog signal waveform x (t) existing between the sample values X2 and X3 cannot be captured, the tangent slope is zero (the difference value between each sample value and the previous sample value is zero). It can be said that a certain point is a singular point with the possibility that the analog signal waveform x (t) has unevenness and is flat. Therefore, such a singular point should not be included in a state where the tangential slope is increasing or decreasing, and should be newly defined as a state where the tangential slope is zero. Therefore, in the extreme value detection means 21 according to the second embodiment of the present invention, a sample having a tangent slope of zero is also detected as an extreme value.

  FIG. 6 is a diagram for explaining the extreme value detection means 21 and the sample number detection means 22 of the second embodiment of the present invention in more detail. In FIG. 6, similarly to FIG. 5, the analog signal waveform is x (t), and the sample value obtained by sampling the analog signal waveform x (t) every sampling period Ts [sec] is Xi (X1 to X10). The extreme value detection means 11 and the sample number detection means 12 according to the prior art detect only the minimum value X1 and the maximum value X10 as extreme values, and detect the number of samples (interval) between extreme values as 9 sample intervals. However, the extreme value detection means 21 according to the second embodiment of the present invention detects, as an extreme value, a sample in which the slope of the tangent is zero in addition to the minimum value X1 and the maximum value X10.

As a result, in the example of FIG. 6, the local minimum value X1, the samples X3, X4, and X7 in which the inclination of the tangent is zero, and the local maximum value X10 are detected.
A section (X1 to X3) sandwiched between the sample X3 where the minimum value X1 and the slope of the tangent are zero;
An interval (X4) in which the sample X4 in which the slope of the tangent is zero continues,
A section (X5 to X7) sandwiched between samples X4 and X7 in which the inclination of the two tangents is zero;
A section (X8 to X10) sandwiched between the sample X7 where the slope of the maximum value X10 and the tangent is zero
Can be divided into As described with reference to FIG. 5, the section X7 to X8 has a possibility that the analog signal waveform x (t) has irregularities and a flatness. Similarly, the analog signal waveform x (t) has the possibility of having irregularities and the possibility of being flat in the sections X3 to X4 and the sections X4 to X5.

The sample number detection means 22 of the second embodiment of the present invention detects the number of samples (interval) in each divided section. This
-The interval between X1 and X3 is 2 sample intervals,
・ X4 section is 1 sample interval,
・ The interval between X5 and X7 is 2 sample intervals,
-The section between X8 and X10 is detected to be two sample intervals.

  Since there is only one sample interval for the X4 section, the subsequent waveform separation means 23, difference value calculation means 24, variable amount calculation means 25, addition / subtraction means 26, and waveform synthesis means 27 for that section cannot be applied. However, even when there are a plurality of sample intervals in a section in which samples having a tangential slope of zero continue, the simple separation waveform S1 having a constant value can be obtained by the waveform separation means 23 according to the second embodiment of the present invention. It is decomposed into a fine fluctuation waveform S2 having a value of zero. That is, since it is equivalent to nothing being processed, when a section in which a sample whose tangent slope is zero continues is detected, the subsequent waveform separating means 23, difference value calculating means 24, variable amount calculating means for the section are detected. 25, the addition / subtraction means 26 and the waveform synthesis means 27 may be passed through to obtain the final output waveform S3.

  In the present invention described above, the input audio signal is set to fs = 96 kHz and the number of quantization bits = 24 bits, but may be fs = 44.1 kHz and the number of quantization bits = 16 bits according to the CD standard. Further, the audio signal is not limited to the linear PCM signal, but may be a signal resulting from encoding / decoding processing by MP3, AAC encoding method, or the like.

1 is a block diagram for explaining a first embodiment of a digital audio processing apparatus and a digital audio processing program according to the present invention. FIG. It is explanatory drawing which shows an example of a process of the waveform separation means of FIG. It is explanatory drawing which shows the waveform correction process with respect to a simple increase / decrease waveform in FIG. It is explanatory drawing which shows an example of a process of the waveform synthetic | combination means of FIG. It is explanatory drawing which shows the shift | offset | difference of the peak point by sampling. It is explanatory drawing which shows an example of the extreme value detection means and sample number detection means process in the 2nd Embodiment of this invention. It is a block diagram which shows the conventional digital audio processing apparatus. It is explanatory drawing which shows the conventional waveform correction process.

Explanation of symbols

21 Extreme value calculation means 22 Sample number detection means 23 Waveform separation means 24 Difference value calculation means 25 Variable amount calculation means 26 Addition / subtraction means 27 Waveform synthesis means

Claims (4)

An extreme value calculating means for obtaining a maximum value and a minimum value as extreme values by comparing adjacent samples of the original digital audio information;
Sample number detection means for detecting the number of samples between adjacent extreme values;
A waveform that separates the waveform of the sample between the adjacent extreme values into a linear waveform connecting the adjacent extreme values and a differential waveform obtained by subtracting the linear waveform from the waveform of the sample between the adjacent extreme values. Separating means;
Difference value calculating means for obtaining a difference between each sample of the waveform of the straight line separated by the waveform separating means and the value one sample before;
Variable amount calculation means for multiplying each coefficient according to the obtained sample number and each difference value to obtain a variable amount for correcting the sample of the waveform of the straight line;
Adding and subtracting the variable amount to the maximum value side sample of the straight line waveform and subtracting from the minimum value side sample of the straight line waveform so as not to change the total power of the original digital audio information Means,
Waveform synthesizing means for synthesizing the linear waveform obtained by adding / subtracting the variable amount by the addition / subtraction means and the differential waveform separated by the waveform separation means,
A digital audio processing apparatus. An extreme value calculation step for obtaining a maximum value and a minimum value as extreme values by comparing adjacent samples of the original digital audio information; and
A sample number detection step for detecting the number of samples between adjacent extreme values;
A waveform that separates the waveform of the sample between the adjacent extreme values into a linear waveform connecting the adjacent extreme values and a differential waveform obtained by subtracting the linear waveform from the waveform of the sample between the adjacent extreme values. A separation step;
A difference value calculating step for obtaining a difference between each sample of the linear waveform separated by the waveform separating step and a value one sample before;
A variable amount calculating step for obtaining a variable amount for correcting the sample of the waveform of the straight line by multiplying each coefficient according to the obtained sample number and each difference value, respectively,
Adding and subtracting the variable amount to the maximum value side sample of the straight line waveform and subtracting from the minimum value side sample of the straight line waveform so as not to change the total power of the original digital audio information Steps,
A waveform synthesis step of synthesizing the linear waveform obtained by adding / subtracting the variable amount by the addition / subtraction step and the differential waveform separated by the waveform separation means;
A digital audio processing apparatus program to be executed by a computer. An extreme value calculation means for obtaining a maximum value and a minimum value by comparing the samples before and after the adjacent adjacent digital original audio information, and for obtaining a sample having the same value as the extreme value before and after the adjacent samples,
The number of samples between the adjacent maximum value and the minimum value, the adjacent maximum value, or the number of samples between the adjacent minimum value and the sample determined as the extreme value, and the sample determined as the extreme value are A sample number detecting means for detecting the number of samples existing in the continuing section;
A waveform of a section in which the number of samples is detected by the sample number detection means, a linear waveform connecting the start point value and end point value of the section, and a differential waveform obtained by subtracting the straight line waveform from the waveform of the section Waveform separating means for separating into
Difference value calculating means for obtaining a difference between each sample of the linear waveform separated by the waveform separating means and the value one sample before;
Variable amount calculation means for multiplying each coefficient according to the obtained sample number and each difference value to obtain a variable amount for correcting the sample of the waveform of the straight line;
Adding and subtracting the variable amount to the maximum value side sample of the straight line waveform and subtracting from the minimum value side sample of the straight line waveform so as not to change the total power of the original digital audio information Means,
Waveform synthesizing means for synthesizing the linear waveform obtained by adding / subtracting the variable amount by the addition / subtraction means and the differential waveform separated by the waveform separation means,
A digital audio processing apparatus. An extreme value calculation step for obtaining a maximum value and a minimum value by comparing adjacent samples of the original digital audio information, and obtaining a sample having the same value as the extreme value of adjacent samples before and after,
The number of samples between the adjacent maximum value and the minimum value, the adjacent maximum value, or the number of samples between the adjacent minimum value and the sample determined as the extreme value, and the sample determined as the extreme value are A sample number detection step for detecting the number of samples existing in the continuing section;
The waveform of the section in which the number of samples is detected by the sample number detection step, the straight waveform connecting the start point value and the end point value of the section, and the differential waveform obtained by subtracting the straight waveform from the section waveform A waveform separation step for separating into
A difference value calculation step for obtaining a difference between each sample of the linear waveform separated by the waveform separation step and a value one sample before;
A variable amount calculating step for obtaining a variable amount for correcting the sample of the waveform of the straight line by multiplying each coefficient according to the obtained sample number and each difference value, respectively,
Adding and subtracting the variable amount to the maximum value side sample of the straight line waveform and subtracting from the minimum value side sample of the straight line waveform so as not to change the total power of the original digital audio information Steps,
A waveform synthesis step of synthesizing the linear waveform obtained by adding / subtracting the variable amount by the addition / subtraction step and the differential waveform separated by the waveform separation means;
A digital audio processing apparatus program to be executed by a computer.

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