JPH0683360A - Device and method for loop waveform generation - Google Patents

Abstract

PURPOSE:To generate a loop Waveform whose loop start point and end point meet zero-cross positions of a waveform from digital waveform data according to simple specification. CONSTITUTION:The number M of sampling points in each basic cycle of a waveform having a reference pitch is calculated when the waveform signal is sampled in sampling cycles T. Then when the waveform section of one basic cycle for loop regeneration is specified, the loop section from the start zero-cross position LST of the waveform section to the end zero-cross position LET of the loop section is extracted to calculate the loop section length (LET-LST). This loop section length is divided by M to calculate a sampling cycle T'. Then the signal is resampled in sampling cycles T' so that the LST and LET are included as sampling points LSP and LEP, thereby generating loop waveform data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loop waveform generating device and a loop waveform generating method for generating a loop waveform from digital waveform data.

[0002]

2. Description of the Related Art An analog musical tone signal obtained by collecting a performance sound of an acoustic musical instrument such as a grand piano with a microphone is converted into an analog-to-digital signal, and the resulting digital musical tone data is stored in a memory and stored in a memory. A sound source system using a PCM (Pulse Code Modulation) system as a sound source is widely used.

The PCM sound source system has the advantage that it can produce musical tones that are extremely faithful to the tone of the original musical instrument, but in order to obtain musical tones with good sound quality, the sampling frequency at the time of analog / digital conversion is increased. Moreover, it is necessary to increase the number of quantization bits. However, in this case, there is a problem that the amount of digital musical tone data becomes enormous, the memory capacity increases, and the cost of the electronic musical instrument greatly increases.

In order to solve such a problem, there is a so-called loop waveform method. In the loop waveform method, the digital tone data of one pronunciation unit from the start of the tone generation to the mute is generally an attack tone section (or consonant section) in which the frequency characteristic largely changes and the periodicity is poor, Focusing on the fact that it consists of a continuous sound section (or a vowel section) in which the change in frequency characteristics over time is small and a constant waveform is repeated in synchronization with the pitch cycle, the digital musical sound of the attack sound section The data is stored as it is in the memory as sound source data, and regarding the digital musical tone data of the continuous tone section, only the digital musical tone data for one repetitive waveform unit of the repetitive waveform constituting the section (hereinafter, this is referred to as a loop waveform) It is stored in the memory as sound source data. Then, at the time of playing a musical sound, first, the digital musical sound data corresponding to the attack sound section is read from the memory as it is and D / A converted, and thereafter, the loop waveform data corresponding to the continuous sound section is instructed to be muted. It is repeatedly read from the memory and D / A converted. Such a reproduction method will be referred to as loop reproduction.

In the loop waveform method as described above, since it is sufficient to store the digital musical tone data corresponding to the attack tone section and the loop waveform representing the continuous tone section in the memory, the memory capacity is greatly reduced. be able to.

[0006]

In the loop waveform method,
It is necessary to cut out a loop waveform representing a continuous tone section together with the digital tone data of the attack tone section from the original digital tone data of one pronunciation unit.

When the loop waveform is cut out, a leading sampling point (hereinafter referred to as a loop start point) and a final sampling point (hereinafter referred to as a loop end point) of the digital musical sound data are determined. There is a need.

During loop reproduction, each sampling point is repeatedly reproduced in the loop section from the loop start point to the sampling point one sample before the loop end point. In this case,
Amplitude values need to be smoothly connected at the waveform connection. Therefore, the loop start point and the loop end point need to be at the time when the amplitude is zero, that is, when the waveform crosses zero.

However, in general, since the sampling point does not always coincide with the position where the waveform crosses zero, the loop start point and the loop end point cannot be perfectly matched with the waveform zero cross position.

Therefore, conventionally, as shown in FIG. 24 (a), a sampling point close to the zero-cross position of the waveform has to be selected as the loop start point and the loop end point. As shown in the rectangular part of, so-called loop noise occurs,
There has been a problem that the sound quality of the reproduced electronic musical instrument is deteriorated.

The object of the present invention is, based on a simple designation,
It is possible to generate a loop waveform from the digital waveform data such that the loop start point and the loop end point coincide with the zero-cross position of the waveform.

[0012]

According to the present invention, digital waveform data for one repeating waveform unit to be repeatedly reproduced (loop reproduction) from digital waveform data sampled at a first sampling period is generated as loop waveform data. It is assumed that the loop waveform generation device is

First, there is a loop section extracting means for extracting, as a loop section, a waveform section from an arbitrary first zero-cross position to an arbitrary second zero-cross position based on the digital waveform data. For example, the loop section extracting means first prompts the user to perform a sampling point immediately before the first zero-cross position which is the head of an arbitrary waveform section and a sampling point immediately before the second zero-cross position which is the end of the waveform section. Let the points be designated as the loop start initial point and the loop end initial point, respectively. Next, the loop section extraction means calculates the time from the loop end initial point to the first zero cross position immediately after that, and shifts the entire waveform by that time to match the loop end initial point with the first zero cross position. Then, the time from the loop end initial point corrected so as to be located immediately before the second zero-cross position to the second zero-cross position immediately after that is calculated,
Confirm the zero-cross position of.

Next, the digital waveform data of the loop section is added to the loop section such that the first zero-cross position at the beginning of the loop section and the second zero-cross position at the end of the loop section are included as sampling points. It has resampling means for generating loop waveform data by resampling at a second sampling period obtained by dividing the time length of 1 by a predetermined number of sampling points. In the resampling process by this means, for example, the sample value for each time position that advances in the second sampling cycle is determined by sampling the sampling points of the digital waveform data sampled in the first sampling cycle in the vicinity of the above-mentioned time position. It is a process of calculating by interpolation using a Lagrange's interpolation function or the like.

The present invention can also be realized as a loop waveform generating method for executing each process corresponding to the function of each means described above.

[0016]

According to the present invention, the section from the arbitrary first zero-cross position to the arbitrary second zero-cross position on the digital waveform data is the waveform section to be loop-reproduced, that is, based on the designation by the user. It is extracted as a loop section.

Then, the loop section length is determined by a predetermined sampling so that the loop section includes the first zero-cross position at the beginning of the loop section and the second zero-cross position at the end of the loop section as sampling points. It is resampled in a second sampling period obtained by dividing by the number of points.

As a result, loop waveform data consisting of "predetermined number of sampling points + 1" samples is generated, and the loop start point which is the start point and the loop end point which is the end point thereof are located at the beginning of the loop section. Zero-cross position of 1 and 2nd at the end
Exactly matches the zero-cross position of.

The loop waveform data for "the predetermined number of sampling points + 1" samples thus generated is saved in a memory or the like. In the saved loop waveform data, from the sampling point at the first zero-cross position at the beginning of the loop section to the sampling point one sample before the sampling point at the second zero-cross position at the end of the loop section, “predetermined By performing loop reproduction of the loop waveform data consisting of "the number of sampling points" of ", the musical tone containing no loop noise can be obtained.

[0020]

Embodiments of the present invention will now be described in detail with reference to the drawings. <Structure of Embodiment of the Present Invention> FIG. 1 is an external view of one embodiment of the present invention, and FIG. 2 is an overall structure diagram thereof.

When the control / processing unit 205 starts the control process for generating a loop waveform, first, PCM musical tone waveform data for one sound source unit serving as a source is stored in the waveform input / output unit 206 on a hard disk or The source waveform file 101 stored in the floppy disk is loaded into the RAM 204 in the personal computer main body 103, and the waveform is displayed on the display 102 of the display unit 202.

Next, the user uses the mouse 105, which is a pointing device, to specify the start and end positions of the waveform section to be looped on the displayed waveform. When this designation is made, the control / processing unit 205 starts arithmetic processing for generating a loop waveform, and as a result,
A desired loop waveform is generated, which is the waveform input / output unit 20.
The created waveform file 106 is stored in a hard disk or a floppy disk installed at No. 6.

In the ROM 203 of the control / processing unit 205,
A series of control programs relating to the loop waveform generation processing are stored, and the RAM 204 stores the above-described PCM tone waveform data and various variables used in the loop waveform generation processing. <First Operating Principle of the Present Invention> As the first operating principle of the present invention having the above-mentioned configuration, the operating principle when loop waveform data having a predetermined reference pitch is generated will be described.

The first operation principle is that, if the sampling cycle during reproduction is constant, the number of sampling points per basic cycle of a musical sound and the pitch at which the musical sound is reproduced are 1.
It makes use of the fact that it corresponds to one-to-one.

First, the user determines a reference pitch. Next, the user determines a sampling period T that divides one basic period corresponding to the reference pitch.

Next, when a musical tone having a reference pitch is sampled at the sampling period T, the number M of sampling points per basic period of the musical tone is calculated by the following equation.

[0027]

[Equation 1]

Subsequently, an analog tone signal having an arbitrary pitch is A / D converted at a sampling period T to obtain PCM tone waveform data. Next, the user, in the continuous sound section of the PCM musical tone waveform data obtained by A / D conversion,
The waveform section for one basic period starting from the zero-cross position and ending at the zero-cross position is registered, and the beginning and end of the waveform section are specified.

Based on this designation, the sampling point closest to the designated start position and immediately after the zero cross position of the waveform exists, and the sampling point closest to the designated end position and immediately after the zero cross position of the waveform. Sampling points are calculated as the loop start initial point and the loop end initial point, respectively.

On the basis of these calculated loop start initial point and loop end initial point, the loop end initial point is determined from the leading zero-cross position of the waveform section for one basic period located immediately after the loop start initial point. The section up to the end zero-cross position of the waveform section for one basic cycle located immediately after is extracted as a loop section, and the loop section length is calculated.

Then, in the sampling period T'calculated by the following equation 2, the above loop section is re-sampled (resampling) so that the leading zero-cross position and the trailing zero-cross position are included as sampling points. ) Will be done.

[0032]

[Equation 2]

As a result, loop waveform data consisting of M + 1 samples including sampling points at the zero cross positions at both ends of the loop section is generated, and the loop start point which is the start point and the loop end point which is the end point are waveforms. Exactly matches the leading zero-crossing position and the trailing zero-crossing position.

The loop waveform data for M + 1 samples thus generated is saved in a memory or the like.
A loop consisting of M samples from the sampling point at the beginning zero-cross position of the loop section to the sampling point one sample before the sampling point at the end zero-cross position of the loop section in the saved loop waveform data for M + 1 samples Since the waveform data is loop-reproduced at the sampling cycle T,
A musical tone that does not include loop noise and that exactly matches the reference pitch can be obtained. <Specific Operation (Part 1) of the Embodiment of the Present Invention> A specific operation No. 1 of the embodiment of the present invention for generating loop waveform data based on the first operation principle of the present invention will be described.

First, the user determines, as the reference pitch, the pitch of A4 having a fundamental frequency of 442.000 Hz, for example. Next, the user sets, for example, A4 as the sampling cycle T that divides one basic cycle corresponding to the reference pitch.
A sampling cycle T = 1/5304 [seconds] that divides 1/442 [seconds], which is one basic cycle corresponding to the pitch of, is determined. The user operates the key input unit 201 shown in FIG.
Set to 06. The sampling frequency in this case is 5
It becomes 304 [Hz].

Next, the control / processing unit 205 of FIG. 2 determines, based on the equation 1 described above, that one of the musical tones having the reference pitch is sampled at the sampling period T.
The number M of sampling points per basic cycle is calculated. For example, when a musical tone having a pitch of A4 is sampled at a sampling period T = 1/5304 [seconds], the number M of sampling points per basic period of the musical tone is calculated from the formula 1 as follows. To be done. M = (1/442) / (1/5304) = 12 [points] The number M of sampling points per basic period corresponding to the reference pitch calculated as described above is RA of FIG.
It is stored in M204.

Then, based on the user's operation on the key input unit 201, an analog tone signal having an arbitrary pitch is A / D converted at a sampling period T, and the PCM tone waveform data is converted into the waveform input / output shown in FIG. The source waveform file 101 is stored in a hard disk or a floppy disk installed in the unit 206.

Then, based on the user's operation on the key input unit 201, the control / processing unit 205 starts the control processing program for generating the loop waveform shown by the operation flowchart of FIG.

First, in step S301, PCM musical tone waveform data for one sound source unit serving as a source is stored in a hard disk or a floppy disk installed in the waveform input / output unit 206 from the source waveform file 101 in the personal computer main body 103. The waveform is displayed on the display 102 of the display unit 202 while being loaded into the RAM 204.

Next, when the user specifies the start (loop start) and end (loop end) of the waveform section to be loop-reproduced on the displayed waveform using the mouse 105, the determination in step S302 becomes YES. .

In the next step S303, the sampling point closest to the designated start position and immediately after the zero-cross position of the waveform exists, and the sampling point closest to the designated end position and immediately after the zero-cross position of the waveform exist. Sampling points to be calculated are calculated as a loop start initial point LSIP and a loop end initial point LEIP, respectively, as shown in FIG.
Each of these points is a PC loaded in the RAM 204
The leading sampling point of the M tone waveform data is numbered "0", and is represented by numbers (0, 1, 2, 3, ...) That increase sequentially for each subsequent sampling point.

By the processes of subsequent steps S304 to S308, based on the above-described calculated LSIP and LEIP, the position immediately after LEIP is determined from the leading zero-cross position of the waveform section for one basic period, which is positioned immediately after LSIP. The section up to the end zero-cross position of the waveform section for one cycle is extracted as a loop section.

First, in step S304, as shown in FIG. 4A, the loop start initial point LSIP is set.
The time Δt _LS from to the zero cross position immediately after is calculated.

Detailed operation of step S304 for calculating the time Δt _LS will be described with reference to FIGS. 5 to 9 and FIG.
A description will be given based on the operation flowchart of 0. In FIG. 10, first, in step S1001, the RAM2
The base time point b stored as a variable in 04 is initialized to the time point LSIP · T of the loop start initial point LSIP. However, T is a sampling period when the waveform data stored in the RAM 204 is A / D converted.

Next, in step S1002, the RAM 20
The value 2 is substituted into the variable m stored in No. 4, and in the subsequent step S1003, the time d stored as a variable in the RAM 204 is set to the value T / m. Therefore, d = T / 2.

Subsequently, in step S1004, a time point x = b + d when a time d = T / 2 has elapsed from the base time point b initialized to the loop start initial point LSIP is calculated. The time point x represents the elapsed time from the beginning of the musical tone waveform stored in the RAM 204, and x is the RAM.
These are variables stored in 204.

Next, in step S1005, the musical tone waveform interpolation value f (x) at the time point x is calculated using the Lagrange's interpolation formula described later. This interpolation value f (x)
Is also a variable stored in the RAM 204.

In step S1006, the interpolation value f (x)
Is determined to be "0" in terms of computer calculation accuracy. If this determination is NO, step S1007.
, The code of the interpolation value f (x) and the sample value SMP (L
It is determined whether the signs of (SIP) are the same.

Now, for example, as shown in FIG. 5, the zero cross position of the tone waveform is the loop start initial point L.
SIP and the next sampling point (LSIP +
Located between 1).

Then, as shown in FIG. 5, the sample value SMP at the loop start initial point LSIP.
When (LSIP) and the interpolation value f (x) at the time point x have the same sign, the zero-cross position exists at a time point after the time point x = b + d.

In this case, in step S1008, as shown in FIG. 6, the base time point b is moved to the time point LSIP · T + T / 2 when the time d = T / 2 has elapsed from the original base time point LSIP · T. Be done. Then, in step S1009, the value 2 of the variable m is doubled to be the value 4, and the time d is reset to a new time T / m in step S1003. In FIG. 6, the time d = is a new time T / corresponding to 1/2 of the original time T / 2.
It is reset to 4. Then, in step S1004, a time point x = b + when a new time point d = T / m = T / 4 has elapsed from the new base time point b = LSIP · T + T / 2.
d is calculated, and in the next step S1005, the interpolation value f
(X) is calculated. After the determination in step S1006, the sign of the interpolation value f (x) is determined in step S1007.

In the case of FIG. 6, the sample value SMP (LS
IP) and f (x) have opposite signs, and in this case, the zero-cross position exists at a time point before the time point x. In this case, step S1008 is not executed, so as shown in FIG. 7, the base time point b = LSIP.
・ T + T / 2 is not moved. Then, step S10
At 09, the value 4 of the variable m is doubled to be the value 8,
In step S1003, the time d is the new time T /
reset to m. In FIG. 7, the time d is the original time T /
From 4, the time is reset to T / 8, which is half the time. Then, in step S1004, a new time d = T / m = from the base time point b = LSIP · T + T / 2.
The time point x = b + d after T / 8 has been calculated, and the interpolation value f (x) is calculated in the next step S1005. After the determination in step S1006, step S10
At 07, the sign of the interpolation value f (x) is determined.

In the case of FIG. 7, the sampled value SMP (LS
IP) and f (x) have opposite signs, and in this case, the zero-cross position exists at a time point before the time point x. Also in this case, as in the case of FIG. 6, step S100.
8 is not executed, the base time point b = LSIP · T + T / 2 is not moved as shown in FIG. Then, in step S1009, the value 8 of the variable m is doubled to be 16 and the time d is reset to a new time T / m in step S1003. In FIG. 8, the time d is reset from the original time T / 8 to a time T / 16 corresponding to ½ thereof. Then, step S100
4, the base time point b = LSIP · T + T / 2, and a new time point d = T / m = T / 16, the time point x =
b + d is calculated, and in the next step S1005, the interpolation value f (x) is calculated. After the determination in step S1006, the sign of the interpolation value f (x) is determined in step S1007.

In the case of FIG. 8, the sample value SMP (LS
IP) and f (x) have the same sign, and in this case, the zero-cross position exists at a time point after the time point x. In this case, as in the case of FIG. 5, step S10
At 08, as shown in FIG. 9, the base time point b
From the original base time LSIP · T + T / 2, time d =
Time point when only T / 16 has elapsed LSIP T + T / 2 + T /
Moved to 16. Then, in step S1009, the value 16 of the variable m is doubled to a value 32, and the time d is reset to a new time T / m in step S1003. In FIG. 9, the time d is reset from the original time T / 16 to the time T / 32 corresponding to ½ thereof. Then, in step S1004, a new time d is calculated from the base time point b = LSIP · T + T / 2 + T / 16.
= T / m = T / 32 has elapsed, and the time point x = b + d is calculated, and in the next step S1005, the interpolation value f (x) is calculated. After the determination in step S1006, the sign of the interpolation value f (x) is determined in step S1007.

As described above, when the base time point b is sequentially moved and the time d added thereto is reduced, the interpolation value f (x) of the waveform signal gradually decreases, and finally the calculation accuracy of the computer. It becomes almost equal to "0" above, and the determination in step S1006 is YES. The time point x at this time is the time point of the zero cross position immediately after the loop start initial point LSIP.

Therefore, the loop start initial point LS
Time Δt from IP to the zero cross position immediately after that
_In step S1010, the _LS calculates Δt _LS = x−LS.
It can be obtained as IP · T.

As described above, the loop start initial point LSI
10 for calculating the interpolation value f (x) at the time point x in the operation of step S304 of FIG. 3 shown in the operation flowchart of FIG. 10 for calculating the time Δt _LS from P to the zero crossing position immediately thereafter. Step S1
The calculation of 005 will be described.

The interpolation value f (x) is calculated using the Lagrange's interpolation formula expressed by the following equation (3).

[0059]

[Equation 3]

The Lagrange's interpolation formula will be described below. FIG. 11 shows the linear interpolation which is the basis of the Lagrange's interpolation formula. The sampling point time points x ₀ and x ₁ of the original waveform f = f (x) and the respective sample values f (x ₀ ) and f From (x ₁ ), an equation of a straight line (linear equation) passing through two points is obtained, and x is substituted into the equation of the straight line to calculate the interpolated value f (x) at the time point x.

On the other hand, as shown in FIG. 12, the original waveform f
= Sampling point times x ₀ , x ₁ , on f (x),
And x ₂ and their respective sampled values f (x ₀ ), f (x
_{From 1} ) and f (x ₂ ), the equation of the quadratic curve shown by the thin line in FIG. 12 is obtained, and by substituting x into the equation, it is more faithful to the original waveform than the above linear interpolation. Point x
The interpolated value f (x) in is calculated.

As described above, the sample value on the original waveform is set to 2
By increasing the number of points to 3, 3, 4, ..., N points, more accurate interpolation data can be obtained. The Lagrange's interpolation formula is an interpolation formula in the case of using n-point sample values derived based on such a concept,
It is expressed by the formula

In the equation (3), at the interpolation position where x is obtained,
f (x) is the interpolation value to be obtained. Also, x ₀ ,
x ₁ , ..., X _n are sampling points of the original waveform, and f (x ₀ ), f (x ₁ ), ..., f (x
_n ) indicates the sample value at each sampling point. If n = 1 in this equation, the equation becomes a linear interpolation equation. That is, it can be said that the linear interpolation is two-point Lagrange interpolation.

FIG. 13 shows step S of FIG.
At 1005, when the interpolated value f (x) at the time point x is calculated, if n = 15 in the above-mentioned formula 3, the sampling point time points x ₀ , x ₁ , ..., X
₁₅ and sample values f (x ₀ ), f (x ₁ ), ..., f
The value to be substituted for (x ₁₅ ) is shown.

[0065] First of all, the time LSIP · T of the loop start initial point LSIP to the sampling point point x ₇
There is assigned, also from x ₀ from x ₇ 7 temae, to 16 points to x ₁₅ in the x ₇ after eight points, each sampling point time (LSIP-7) from · T (LSIP +
8) -Up to T are respectively substituted.

Next, sample values f (x ₀ ) to f (x ₁₅ )
At each sampling point (LSIP-7), (L
SIP-6), ..., Sample values SMP (LSIP-7), SMP (L) in (LSIP + 8)
SIP-6), ..., SMP (LSIP + 8) are substituted. It should be noted that 0 is substituted for the sample value corresponding to the negative sampling point.

[Mathematical formula-see original document] Equation 3 is calculated in this way, and FIG.
The interpolated value f (x) at the time point x obtained in step S1004 is obtained. As described above, in step S304 of FIG. 3, as shown in FIG. 4A, the time Δt _LS from the loop start initial point LSIP to the zero cross position immediately after that is calculated.

Next, in step S305 of FIG.
As shown in FIG. 4 (b), the PCM musical tone waveform data A for one pronunciation unit stored in the RAM 204 is
The time points of all the sampling points are shifted in the direction delayed by the time Δt _LS described above, and as a result, as shown in FIG.
Waveform data as indicated by B in FIG.

The process of step S305 of FIG. 3 described above will be described in more detail with reference to the operation flowchart of FIG. First, in step S1401, the sampling point k indicating the number of each sampling point from the beginning of the waveform data is initialized to 0. This point k is stored in the RAM 204 as a variable.

Next, in the PCM tone waveform data, the interpolated value at the time point delayed by the time Δt _LS from the time point kT at the sampling point and k is set as f (kT + Δt _LS ) based on the Lagrange's interpolation formula of the above-mentioned equation 3. The calculated interpolation value f (kT + Δt _LS ) is the sampling point k.
RAM204 as a new sample value SMP '(k) of
Memorized in.

FIG. 15 shows the above-mentioned interpolation value f (kT + Δt).
_LS ) is calculated, and when n = 15 in the above-mentioned formula 3, sampling point time points x ₀ , x ₁ , ...
.., x ₁₅ and sample values f (x ₀ ), f (x ₁ ),
.., the value to be substituted for f (x ₁₅ ) is shown.

First, the time point kT of the sampling point k is substituted for the sampling point time point x ₇ , and x
_For 16 points from x ₀ , which is ₇ to 7 points before, to x _15, which is 8 to ₇ points after, from each sampling point time (k−
7) · T to (k + 8) · T are respectively substituted.

Next, sample values f (x ₀ ) to f (x ₁₅ )
At each sampling point (k-7), (k-
6), ..., (k + 8), sample values SMP (k-7), SMP (k-6), ... Of the original PCM musical tone waveform data stored in the RAM 204.
SMP (k + 8) is substituted. It should be noted that 0 is substituted for the sample value corresponding to the negative sampling point.

In this way, the equation 3 is calculated, the interpolated value f (kT + Δt _LS ) is calculated, and the new sample value SM is calculated.
P '(k). Subsequently, in step S1403, the value of the sampling point k is incremented by 1, and in the next step S1404, the value of k is changed to the RAM 204.
It is determined whether or not the waveform end point WEP, which is the final sampling point of the original PCM musical tone waveform data stored in the.

If the determination is NO, step S
Returning to 1402, the interpolated value at the time point delayed by the time Δt _LS from the time point kT of the new sampling point k is f (kT +
Δt _LS ) and the interpolated value f (kT + Δ)
t _LS ) is the new sample value S at sampling point k
It is stored in the RAM 204 as MP ′ (k).

When the sampling point k exceeds the waveform end point WEP, the processing ends. In step S305 of FIG. 3 shown by the above processing, the RAM 20
For the PCM musical tone waveform data for one pronunciation unit stored in No. 4, the time points of all sampling points are time Δt.
It is shifted in the direction that can be delayed by _LS .

As a result of the processing in step S305 in FIG. 3 described above, as shown by B in FIG. 4 (b), in the waveform data shifted in the direction delayed by the time Δt _LS , the original loop start initial The sampling point corresponding to the point LSIP exactly matches the zero-cross position of the tone waveform.

On the other hand, in the original PCM tone waveform data, the loop end initial point LEIP was the sampling point immediately before the zero cross position of the waveform, but Δ
In the new waveform data obtained by waveform-shifting in the direction delayed by t _LS , the sampling point corresponding to the loop end initial point LEIP may be displaced immediately after the zero-cross position of the waveform. That is, Δt _LS is a time shorter than the sampling cycle T when the original tone waveform data is A / D converted, and
Loop end initial point LEIP on the original tone waveform
The time difference between the zero-cross position immediately after and the zero-cross position is also shorter than the sampling period T. Therefore, depending on the magnitude relationship between the two, in the new waveform data obtained by shifting the waveform in the direction delayed by Δt _LS , does the sampling point corresponding to the loop end initial point LEIP remain just before the zero cross position of the waveform? , Either immediately afterwards.

Therefore, in step S306 in FIG. 3, the sampling point immediately before the zero-cross position at the end of the loop section on the new tone waveform obtained by waveform shifting is corrected to the corrected loop end initial point LE.
A correction process for recalculating as IP 'is executed.

Now, the sample value SMP (LE of the loop end initial point LEIP on the original tone waveform data is obtained.
IP) sign and the original loop end initial point L on the new musical tone waveform data obtained by waveform shifting
Sample value S at the sampling point corresponding to EIP
The sign of MP '(LEIP) is discriminated.

If these codes are the same, the sampling point corresponding to the original loop end initial point LEIP stays immediately before the zero cross position of the waveform on the new musical tone waveform data obtained by waveform shifting. Therefore, LEIP is used as it is as the corrected loop end initial point LEIP ′.

On the other hand, if the above two codes are different, on the new musical tone waveform data obtained by waveform shifting,
Since the sampling point corresponding to the original loop end initial point LEIP is shifted immediately after the zero-cross position of the waveform, the sampling point (LEIP-1) immediately before the sampling point corresponding to the original loop end initial point LEIP is (LEIP-1). , The corrected loop end initial point LEIP '.

As described above, the corrected loop end initial point LEIP 'is newly obtained. next,
In step S307 of FIG. 3, as shown in FIG. 4B, the corrected loop end initial point LEI is obtained.
The time Δt _LE from P ′ to the zero cross position immediately thereafter is calculated.

The process for calculating the time Δt _LE is the same as the process for calculating the time Δt _LS from the loop start initial point LSIP to the zero cross position immediately after that in step S304 shown in the operation flowchart of FIG. However, the loop start initial point LSIP in step S1001 of FIG. 10 is replaced with the loop end initial point LEIP. Also, step S100
The sample value SMP (LSIP) of the original tone waveform data in LSIP of No. 7 is converted into the sample value SMP '(LEIP) of the waveform-shifted waveform data in LEIP,
Further, Δt _LS in step S1010 is replaced with Δt _LE .

When the time Δt _LE is calculated by the processing in step S307 in FIG. 3 described above, next, in step S308 in FIG. 3, the loop start time (loop start time) LST and the loop end time (loop end time) are calculated.
LET calculation is performed. The loop start time point LST means the leading zero-cross position of the loop section of the waveform data, and the loop end time point LET means the trailing zero-cross position of the loop section of the waveform data.

Here, the loop start time LST is, as shown in the upper part of FIG. 16, step S305 of FIG.
It coincides with the time point of the sampling point corresponding to the original loop start initial point LSIP in the waveform data newly obtained in the RAM 204 by the waveform shift processing of. That is, the loop start time LST can be obtained by the following equation.

[0087]

[Equation 4]

It is However, in T, the original waveform data is A
This is the sampling period when the / D conversion is performed. on the other hand,
As shown in the upper part of FIG. 16, the loop end time point LET is the time Δt _LE at the time point of the corrected loop end initial point LEIP ′ obtained in step S306 of FIG.
Is equal to the time when is added. That is, LE at the loop end
T can be calculated by the following equation.

[0089]

[Equation 5]

According to the equations (4) and (5) described above, in step S308 of FIG.
After the loop end time LET is calculated, the above-described <first operation principle of the present invention> is performed in step S309 of FIG.
The sampling period T ′ for performing resampling including LST and LET as sampling points is calculated by the following equation corresponding to the equation 2

[0091]

[Equation 6]

Here, M is one basic tone of the musical tone when the musical tone having the reference pitch (for example, A4) is sampled at the sampling period T, as described above in the <first operation principle of the present invention>. It is the number of sampling points per cycle, and as described above, it is calculated based on the equation 1 at the start of the loop waveform data generation processing, and the RAM 20 of FIG.
4 is stored in advance. For example, when a musical tone having a pitch of A4 is sampled at a sampling period T = 1/5304 [seconds], M = 12 as described above.

Then, in step S310 of FIG.
In the sampling period T ′ calculated based on the above equation 6, the loop section from the loop start time LST to the loop end time LET includes the leading zero-cross position and the trailing zero-cross position as sampling points. This results in being resampled to
Loop waveform data consisting of M + 1 samples is generated including sampling points at the zero cross positions at both ends of the loop section, and the loop start point that is the start point and the loop end point that is the end point thereof are the zero cross positions at the beginning of the waveform. Exactly matches the trailing zero-cross position. M + 1 generated in this way
Of the loop waveform data for samples, loop waveform data consisting of M samples from the sampling point at the beginning zero-cross position of the loop section to the sampling point one sample before the sampling point at the end zero-cross position of the loop section is sampled. By performing loop playback at T, it is possible to obtain a musical tone that does not include loop noise and that exactly matches the reference pitch.

However, in the embodiment of the present invention, it is possible to reproduce the attack sound section before the loop reproduction of the loop section,
Further, if necessary, for example, the playback of the release section is also possible after the loop section has been loop-played.
Of the waveform-shifted waveform data stored in M204, not only the loop section but the entire waveform data is resampled.

In this case, when the entire waveform data is resampled from the beginning of the waveform at the sampling cycle T ',
Normally, the loop start time point LST in FIG. 16 does not coincide with the sampling point. This is because the time from the beginning of the waveform data to the loop start time LST is not always divisible by the sampling period T '.

Therefore, in order to make the loop start time LST coincide with the sampling point, when the entire waveform data is resampled, the time point when the resampling is started is a predetermined time from the time point of the leading sampling point of the waveform data. It is staggered by time.

Step S3 of FIG. 3 including such processing
The resampling process of 10 will be described with reference to the detailed operation flowchart of FIG. First, in step S1701, the sampling point k indicating the number of each sampling point from the beginning of the waveform data is initialized to 0. This point k is stored in the RAM 204 as a variable.

In step S1702, the initial value i at the time when resampling is started is calculated. This initial value i is equal to the time value obtained by subtracting the integer part INT (LST / T ') of the value obtained by dividing the time value LST by the sampling period T'from the time value LST at the time of loop start. That is, the initial value i is calculated by the following equation.

[0099]

[Equation 7]

In the subsequent repetition of the processing of steps S1703 to S1707, the waveform value at each time point starting from the initial value i and advancing by the sampling period T'is calculated based on the Lagrange's interpolation formula of the above-mentioned equation 3, and Is sequentially set as a sampling value, whereby the resampling process is executed.

Steps S1703 to S1707 of FIG.
The process will be described with reference to the explanatory diagrams of FIGS. First, as shown in FIG. 18A, assuming that the sampling period T = 3, for example, in the waveform-shifted waveform data already stored in the RAM 204, each sampling point 0, 1, 2 ,. , 6, ... SMP ′ (0), SMP ′ corresponding to sample values
(1), SMP '(2), ..., SMP' (6),
.. are sampling points x = located at intervals of T
, 0, 3, 6, ..., 18, ...

Then, as shown in FIG. 18B, assuming that the sampling period T ′ = 4, for example, each sampling time point i = starting from the time point 1 which is deviated from the sampling time point 0 and located at the interval of T ′ = 1, 5, 9, 13,
Resampling is performed at 17, ..., At each sampling point k =
New sample values OUT (k) = OUT (0), OUT (1), OUT for 0, 1, 2, 3, 4, ...
(2), OUT (3), OUT (4), ... Are calculated.

At this time, the sampling value OUT (k) at the sampling point k corresponding to each sampling time point i located at the interval T'is 8 points before and after the sampling time point i, that is, a total of 16 points of the sampling period T. Using the sample values of the waveform data in the RAM 204 at the sampling points corresponding to the sampling times x located at the intervals of, the Lagrange's interpolation formula of the above-mentioned formula 3 is used for calculation.

Here, as shown in FIG. 19, of the sampling time points x located at intervals of T described above, T '
The sampling point j corresponding to the sampling time point immediately before each sampling time point i located at the interval of is an integer part INT (i / i of the value obtained by dividing the sampling time point i by the original sampling period T, as shown in the following equation. Equal to T).

[0105]

[Equation 8]

For example, in FIG. 18, for example, i = 13
Then, j = 4 is calculated. Therefore, the sampling point immediately before the sampling time i = 13 is j = 4, and the corresponding sampling time x is x = j · T =
4 × 3 = 12, and sampling point j =
The sample value of the waveform data stored in the RAM 204 corresponding to 4 is SMP '(4).

The sampling point j described above is the same as in FIG.
7 is calculated in step S1703. Next, after the determination in step S1704 in FIG. 17, which will be described later, in step S1705 in FIG. 17, as shown in FIG. 19, the interpolation value corresponding to the sampling time point i is converted into the Lagrange's interpolation formula of Equation 3 described above. Based on this, f (i) is calculated and stored in the RAM 204 as a new sample value OUT (k) at the sampling point k.

In FIG. 20, when the interpolated value f (i) is calculated, if n = 15 in the above-mentioned equation 3, the sampling point time points x ₀ , x ₁ , ..., X _{15 are set.} And sample values f (x ₀ ), f (x ₁ ), ..., f (x ₁₅ ).
The value to be substituted for is shown.

First, the time point j · T of the sampling point j is substituted for the sampling point time point x ₇ , and
From x ₀ from x ₇ 7 temae, x ₁₅ to from x ₇ after 8 points
Up to 16 points up to each sampling point (j
From −7) · T to (j + 8) · T are respectively substituted.

Next, sample values f (x ₀ ) to f (x ₁₅ )
At each sampling point (j-7), (j-
6), ..., (j + 8), sample values SMP ′ (j-7), SMP ′ (j-6), of the waveform-shifted waveform data stored in the RAM 204, respectively.
... SMP '(j + 8) is substituted. It should be noted that 0 is substituted for the sample value corresponding to the negative sampling point.

Thus, step S170 of FIG.
5, a new sample value OUT of one sampling point k corresponding to one sampling time i
After obtaining (k), the sampling point k is advanced by 1 in step S1706 of FIG. 17, and the sampling time point i is advanced by the sampling period T ′ in step S1707.

Thereafter, the procedure returns to step S1703, where the sampling point j corresponding to the sampling time point immediately before the new sampling time point i is calculated. Then, in step S1704, the value of j is R
It is determined whether or not the waveform end point WEP, which is the final sampling point of the waveform-shifted waveform data stored in the AM 204, has been exceeded.

If the determination is NO, step S1705.
Then, a new sample value OUT (k) corresponding to the new sampling time point i is calculated, and at the time point when the above determination is YES, the resampling process of step S310 in FIG. 3 ends.

As a result of the above resampling processing, FIG.
As shown in 6, waveform data including loop waveform data consisting of M + 1 samples including sampling points at the zero-cross positions at both ends of the loop section is generated, and a loop start point LSP which is a start point of the loop section and its end point. The loop end point LEP is exactly the same as the loop start time LST which is the leading zero-cross position of the loop section and the loop end time LET which is the trailing zero-cross position.

Finally, in step S311 of FIG. 3, the loop start point LSP and loop end point LEP are the waveform data OUT obtained in the RAM 204 by the resampling process in step S310.
Waveform data including the above-mentioned header data added to the head portion of (k) as header data in the next step S312 is the waveform input / output unit 2 of FIG.
The created waveform file 106 of FIG. 1 is saved in the hard disk or the floppy disk installed in 06, and the loop waveform generation process ends.

The waveform data containing the loop waveform data for M + 1 samples generated in this way is later stored in the ROM of the electronic musical instrument or the like and used as a sound source of a musical sound. In this case, for example, after the attack sound section is reproduced by reading the waveform data before the loop section from the memory as it is at the sampling cycle T and reproducing it, one sample before the loop end point LEP from the loop start point LSP. By loop-playing the loop waveform data consisting of M samples up to the sampling point of 1 at the sampling cycle T, it is possible to generate a musical tone that does not include loop noise and that exactly matches the reference pitch. <Second Operation Principle of the Present Invention> As a second operation principle of the present invention, an operation principle when loop waveform data having an arbitrary pitch is generated will be described.

First, the user previously sets a reference pitch and
The point that the sampling period T that divides one basic period corresponding to the reference pitch is determined is the same as in the case of the first operation principle described above. In the second operation principle, the user further specifies an arbitrary pitch.

Next, according to the above-mentioned first operation principle, when the musical tone having the reference pitch is sampled at the sampling period T, the number M of sampling points per basic period of the musical tone is calculated by the formula (1). Was done. On the other hand, in the second operation principle, the following calculation is performed.

As described above, since one basic period corresponding to the reference pitch is divisible by the sampling period T, a musical tone having a reference pitch can be obtained as calculated by the equation 1 in the first operation principle described above. The number M of sampling points per basic cycle of the musical sound when sampling is performed at the sampling cycle T is an integer. Therefore, as described above, if the loop waveform data for one basic cycle consisting of M points is loop-reproduced at the sampling cycle T, the pitch thereof exactly matches the reference pitch.

On the other hand, one basic period corresponding to a designated pitch is not necessarily the sampling period T described above.
It is not always divisible by. Therefore, even if the loop waveform data for one basic cycle consisting of integer points is loop-reproduced at the sampling cycle T, there may be a case where the pitch cannot be matched with the designated arbitrary pitch.

However, if the period is an integral multiple of one fundamental period corresponding to a designated arbitrary pitch, there is a case where the integral multiple is almost divisible by the sampling period T. For example, as described above, the reference pitch is A4 = 442.
[Hz], and the sampling period T that divides one basic period corresponding to the pitch is 1/5304 [sec]. Then, for example, the pitch of G4 is 393.777 [Hz], and one fundamental cycle corresponding to the pitch is not an integral multiple of the sampling cycle T as shown by the following equation. (1 / 393.777) / (1/5304) ≈13.47 However, twice the basic period corresponding to the pitch of G4 is approximately 27 times the sampling period T as shown by the following equation.
It is a multiple, that is, an integral multiple. {(1 / 393.777) × 2} / (1/5304) ≈26.94≈27 The above relationship is shown in FIG.

Therefore, if the loop waveform data for the two basic cycles consisting of the above 27 points is loop-reproduced at the sampling cycle T, the pitch thereof is calculated as shown by the following equation, and there is no problem in hearing. Within, the pitch of the designated G4 is approximately equal to 393.777. 1 / [{(1/5304) × 27} / 2] = 392.889 [Hz] Therefore, first, a sampling cycle that is an integral multiple of one fundamental cycle corresponding to a specified pitch T defines a cycle that is divisible within a predetermined allowable error range. Then, a loop waveform for the integral multiple period, which is composed of the number of sampling points obtained by dividing the integral multiple period of one basic period corresponding to the designated pitch by the sampling period T within a predetermined allowable error range. If the data is loop-reproduced at the sampling period T, the pitch of the data is substantially equal to the specified pitch within a range where there is no auditory problem.

That is, first, an integer n is determined so that the value of the following equation becomes an integer within a predetermined allowable error range. The allowable error is, for example, about ± 0.2.

[0124]

[Equation 9]

Next, using the above determined integer n, the integer closest to the operation result of the equation 9 is calculated by the following equation.

[0126]

[Equation 10]

The operation "INT" is an operation for extracting the integer part of the numerical value in the parentheses, and in the parentheses, the expression 9
By adding 0.5 to the numerical value corresponding to the expression and extracting the integer part, an integer value obtained by rounding off the numerical value corresponding to the expression 9 is obtained.

Integer value M'obtained as a result of the operation of Expression 10
Is the number of sampling points per n basic period of the musical tone having the specified pitch described above when the musical tone is sampled at the sampling period T.

Subsequently, the analog musical tone signal having an arbitrary pitch is A / D converted at the sampling period T to obtain PCM musical tone waveform data, as in the case of the above-mentioned first operating principle.

Further, the user estimates the waveform section of the n basic cycles which starts from the zero-cross position and ends at the zero-cross position in the continuous sound section of the PCM musical tone waveform data obtained by the A / D conversion. Specify the beginning and end of the section.

Subsequently, the loop start initial point and the loop end initial point are calculated corresponding to the above-mentioned designation, the loop section is extracted based on them, and the loop section length is calculated. It is similar to the case of the operation principle of.

Then, in the sampling period T'calculated by the following equation 11, the loop section for n basic periods described above includes the leading zero-cross position and the trailing zero-cross position as sampling points. Resampled.

[0133]

[Equation 11]

As a result, loop waveform data consisting of M '+ 1 samples including the sampling points at the zero-cross positions at both ends of the loop section for n basic cycles is generated, and the loop start point as the start point and the end point thereof are generated. A loop end point exactly matches the leading zero-crossing position and the trailing zero-crossing position of the waveform.

The loop waveform data for n basic cycles consisting of M ′ + 1 samples thus generated is saved in a memory or the like. Of the saved M ′ + 1 sample loop waveform data, M ′ samples from the sampling point at the beginning zero-cross position of the loop section to the sampling point one sample before the sampling point at the end zero-cross position of the loop section Since the loop waveform data for n basic cycles consisting of is reproduced at the sampling cycle T, a musical tone that does not include loop noise and that substantially matches the specified pitch is within a range that does not cause a hearing problem. can get. <Specific Operation (Part 2) of the Embodiment of the Present Invention> A specific operation No. 2 of the embodiment of the present invention for generating loop waveform data based on the second operation principle of the present invention will be described.

First, as in the case of the specific operation 1 described above, the user divides, for example, the reference pitch of A4 and one fundamental period corresponding to the reference pitch, for example, T = 1 /
In addition to determining the sampling period T of 5304 [seconds], an arbitrary pitch is designated.

Next, the user determines an integer n such that the value of the above-mentioned expression 9 becomes an integer within a predetermined allowable error range. In FIG. 22, when the reference pitch is A4 = 442 [Hz], and the sampling cycle T that divides one basic cycle corresponding to the pitch is 1/5304 [seconds], an accurate pitch of an arbitrary pitch is shown. A frequency, an example of an integer n, and a pitch frequency when the loop waveform data for the n basic cycles are loop-reproduced at the sampling cycle T are shown. Based on this figure, the user selects the integer n corresponding to the specified pitch.
Is determined and input from the key input unit 201 in FIG. Note that the table corresponding to FIG.
It may be stored in 03, and the integer n may be automatically calculated corresponding to the pitch specified by the user.

Next, the control / processing unit 205 in FIG. 2 determines, based on the specified pitch, the integer n, and the sampling period T as described above.
The number M ′ of sampling points per n basic cycles of a musical tone having a designated pitch is sampled based on the above-mentioned formula 10 when the musical tone having the designated pitch is sampled at the sampling period T. The number of sampling points M ′ is stored in the RAM 204 of FIG.

Then, as in the case of the first specific operation described above, an analog tone signal having an arbitrary pitch is A / D converted at the sampling cycle T based on the user's operation on the key input unit 201. , PCM tone waveform data is stored in the hard disk or floppy disk installed in the waveform input / output unit 206 of FIG.
It is stored as 01.

After that, as in the case of the specific operation 1 described above, the control / processing unit 205 generates the loop waveform shown by the operation flowchart of FIG. 3 based on the user's operation on the key input unit 201. To start the control processing program for.

The process of step S301 of FIG. 3 is the same as that of the specific operation 1 described above. At the timing when step S <b> 302 of FIG. 3 is executed, the user can display the P displayed on the display 102 of the display unit 202.
In the continuous tone section of the CM tone waveform data, the waveform section for n basic cycles starting from the zero-cross position and ending at the zero-cross position is registered, and the beginning and end of the waveform section are designated.

The processing of steps S303 to S308 of FIG. 3 is exactly the same as the case of the specific operation 1 described above. In the next step S309 of FIG. 3, resampling including the loop start point LST and the loop end point LET as sampling points is performed by the following equation corresponding to the equation 11 of <Second operation principle of the present invention> described above. The sampling period T'for performing is calculated.

[0143]

[Equation 12]

Here, M'is, as described above in the <2nd principle of operation of the present invention>, the musical tone having an arbitrary pitch (for example, G4) when it is sampled at the sampling period T. n is the number of sampling points per basic cycle, and as described above, it is calculated based on the equation 10 at the start of the loop waveform data generation process, and RA of FIG.
It is stored in advance in M204.

The subsequent processing of steps S310 to S312 of FIG. 3 is exactly the same as that of the specific operation 1 described above. As a result, the sampling points at the zero cross positions at both ends of the loop section for n basic cycles are included and M ′ + 1.
Waveform data including loop waveform data consisting of samples is generated, and the loop start point LSP which is the start point of the loop section and the loop end point LEP which is the end point thereof are, for example, as shown in FIG. Exactly match the zero-cross position of and the trailing zero-cross position.

The waveform data including the loop waveform data for n basic cycles consisting of M '+ 1 samples thus generated is later stored in the ROM of the electronic musical instrument and used as a sound source of musical sound. In this case, for example, after the attack sound section is reproduced by reading the waveform data before the loop section from the memory as it is at the sampling cycle T and reproducing it, the loop start point LSP
From the loop end point LEP to the sampling point immediately before the loop end point LEP, the loop waveform data for n basic cycles consisting of M'samples is loop-reproduced at the sampling cycle T, so that loop noise is not included and there is a hearing problem It is possible to generate a musical tone that substantially matches the specified pitch within a range without.

In the second specific operation of the above-described embodiment of the present invention, as can be seen from FIG. 22, the specified pitches are, for example, G3, A3, D4, E4, A4 (reference pitch), D.
In the case of 5, E5, A5, etc., since n = 1, the equations (10), (11), and (12) are based on the above-mentioned equations (1), (2), and (6), respectively. It becomes equal when the pitch is replaced with the specified pitch. So in this case,
Except for the addition of the pitch specifying operation, substantially the same operation as the specific operation 1 of the above-described embodiment of the present invention is executed.

[0148]

According to the present invention, the loop start point and the loop end point can be respectively adjusted to the zero-cross position by a simple operation in the process of creating the loop waveform for producing the continuous sound, and the loop noise can be adjusted. It is possible to obtain a musical sound that does not include.

[Brief description of drawings]

FIG. 1 is an external view of an embodiment of the present invention.

FIG. 2 is an overall configuration diagram of an embodiment of the present invention.

FIG. 3 is an operation flowchart of loop waveform generation processing.

FIG. 4 is a waveform diagram showing a relationship between a waveform before and after a waveform shift and a zero-cross position.

FIG. 5: Principle diagram of the method for calculating the time from the initial point of the loop start to the zero cross position immediately after that (part 1)
Is.

FIG. 6 is a principle diagram of a method for calculating a time from an initial point of a loop start to a zero cross position immediately after that (part 2).
Is.

FIG. 7: Principle diagram of the method for calculating the time from the initial point of the loop start to the zero cross position immediately after that (part 3)
Is.

FIG. 8: Principle diagram of the method for calculating the time from the initial point of the loop start to the zero cross position immediately after that (part 4)
Is.

FIG. 9: Principle diagram of the method for calculating the time from the initial point of the loop start to the zero cross position immediately after that (part 5)
Is.

10 is a detailed operation flowchart of step S304 of FIG.

FIG. 11 is an explanatory diagram of linear interpolation.

FIG. 12 is an explanatory diagram of Lagrange interpolation with three points.

FIG. 13 is a diagram (No. 1) showing values substituted into the equation (3).

14 is a detailed operation flowchart relating to the waveform shift processing of step S305 of FIG.

FIG. 15 is a diagram (No. 2) showing values substituted into the equation (3).

FIG. 16 is a waveform diagram showing the relationship between the waveform before and after resampling and the zero-cross position.

17 is a detailed operation flowchart of the resampling process in step S310 of FIG.

FIG. 18 is an operation timing chart showing timings of sample values before and after resampling.

FIG. 19 is a diagram showing an interpolation value f (i) and sample values of shifted waveform data before and after the interpolation value f (i).

FIG. 20 is a diagram (No. 3) showing the values substituted into the equation (3).

FIG. 21 is a waveform diagram when sounds other than A4 are sampled at the sampling cycle T.

FIG. 22 is a diagram showing an accurate pitch frequency for each pitch, a value of an integer n, and a pitch frequency during loop reproduction.

FIG. 23 is an explanatory diagram of a specific operation (No. 2) of the embodiment of the present invention.

FIG. 24 is an explanatory diagram of loop noise in the conventional example.

[Explanation of symbols]

 101 source waveform file 102 display 103 personal computer body 104 keyboard 105 mouse 106 generated waveform file 201 key input unit 202 display unit 203 ROM 204 RAM 205 control / processing unit 206 waveform input / output unit

Claims (4)

[Claims] 1. A loop waveform generation device for generating, as loop waveform data, digital waveform data for one repetitive waveform unit to be repeatedly reproduced from digital waveform data sampled at a first sampling period, A loop section extracting means for extracting a waveform section from an arbitrary first zero-cross position to an arbitrary second zero-cross position as a loop section, and the digital waveform data of the loop section based on the first section.
By re-sampling at a second sampling period obtained by dividing the time length of the loop section by a predetermined number of sampling points so that the zero crossing positions of the above and the second zero crossing positions are included as sampling points, Resampling means for generating the loop waveform data, and a loop waveform generating device. 2. A loop waveform generation method for generating, as loop waveform data, digital waveform data for one repetitive waveform unit to be repeatedly reproduced from digital waveform data sampled at a first sampling period, On the basis of this, a waveform section from an arbitrary first zero-cross position to an arbitrary second zero-cross position is extracted as a loop section, and the digital waveform data of the loop section is extracted from the first section.
By re-sampling at a second sampling period obtained by dividing the time length of the loop section by a predetermined number of sampling points so that the zero crossing positions of the above and the second zero crossing positions are included as sampling points, A loop waveform generation method, wherein the loop waveform data is generated. 3. The resampling process of the digital waveform data in the second sampling period, the sample value for each time position advanced in the second sampling period is the digital sampled in the first sampling period. The loop waveform generation device or the loop according to claim 1, wherein the sampling point of the waveform data is calculated by interpolation using a point near the time position. Waveform generation method. 4. The loop waveform generation device or the loop waveform generation method according to claim 3, wherein the interpolation calculation is an interpolation calculation using a Lagrange's interpolation function.