JPH0659677A - Music signal processing method - Google Patents

Abstract

(57) [Summary] [Purpose] A smooth process is used to smooth the joints of looped waveforms without damaging the timbre. [Structure] FIG. 2 shows a process of looping a musical tone waveform input by the musical tone signal processing method in this embodiment. First, a musical tone waveform for a predetermined period (for example, one period) as sampling data is read from the storage device, and a musical tone waveform for almost one period is taken out (P12). Next, when the musical tone waveform of about one cycle as sampling data is repeated for an integer number of N cycles, an integer N that obtains the first sampling point and the last sampling point showing substantially the same phase is obtained (P13). Next, the tone waveform is oversampled by an integer N times (P14). Next, this musical tone waveform is repeated for an integer number N of times oversampled (P1
5). The tone waveform that is repeated N times is downsampled by the reciprocal of the integer (P16).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tone signal method for looping a tone waveform.

[0002]

2. Description of the Related Art Conventionally, when a digitally sampled tone waveform is formed into a loop, as shown in FIG.
Cut out approximately one cycle L of the musical sound waveform displayed on the display, and find points that are expected to be smoothly connected near both ends of the cut out musical sound waveform L,
The method of connecting the searched points together was used (Fig. 5 (b)). However, when the joints of the musical tone waveforms to be looped are misaligned, it was attempted to obtain a smooth loop waveform by reassembling them by a method such as subtly shifting the joining points.
The loop waveform of the musical tone thus obtained has been processed so as to be output to the outside through a low-pass filter when the musical tone is generated so that the joint which becomes a high frequency component is inconspicuous.

[0003]

However, according to such a conventional method, there is a problem that the tone color changes because the one-cycle waveform to be extracted is a waveform obtained by shifting the point of the joint. Therefore, for example, when other harmonics are overlaid with the obtained musical tone waveform as a fundamental tone, there is a problem that a desired musical tone waveform cannot be obtained because the harmonic overtone structure is different. When the sampling rate cannot be increased as the musical tone data due to the limitation of the memory capacity and the like, it is extremely rare that the sampling point indicates just one period of the musical tone waveform. For example, FIG. 5 (c)
In the case as shown in (3), it becomes very difficult to extract almost one cycle of the tone waveform from the sampling. Therefore, it is necessary to perform complicated post-processing such as shifting the sampling point or removing a joint which becomes a high frequency component by passing through a low pass filter.

The present invention solves the above problems,
The purpose is to make the joints of looped waveforms smooth without damaging the timbre with simple processing.

[0005]

The present invention has been made in order to achieve the above object, and as shown in FIG. 4, a method of processing a musical tone waveform in which a part of an inputted musical tone waveform is taken out and used as looped data. When the musical tone waveform of a predetermined cycle as the input sampling data is repeated for an integer number of N cycles, an integer N for obtaining the last sampling point showing substantially the same phase as the first sampling point is obtained, The musical tone waveform is oversampled by the integer N times, the musical tone waveform over a predetermined period that is oversampled by the integer N times is repeated by the integral number N times, and the musical tone waveform that is repeated by the integral N times is downsampled by the reciprocal of the integer N. A musical tone signal processing method, wherein the musical tone waveform down-sampled by the reciprocal of the integer N is used as loop data. The gist.

[0006]

In the tone processing method of the present invention, when the input musical tone waveform is looped, the musical tone waveform of a predetermined period (for example, one period) as sampling data is first oversampled by an integer N times. At that time, when the musical tone waveform of a predetermined cycle (for example, one cycle) is repeated N times, an integer N is obtained so that a final sampling point having almost the same phase as the initial sampling point can be obtained. The integer N thus obtained may be set so that the sampling point indicates almost a predetermined period of the musical tone waveform by N times oversampling. Next, the musical tone waveform oversampled by an integer N times is repeated the number of times N oversampled. Since the sampling point indicates almost a predetermined period, when a musical tone waveform repeated N times is downsampled by the reciprocal of the integer N, this sampling point indicates exactly the number obtained by multiplying the predetermined period by an integer N. become. Since the sampling point is a point obtained by multiplying the predetermined cycle by an integer N, the joint can be made smooth by using a musical tone waveform obtained by multiplying the predetermined cycle by an integer N as looped data. For example, in the case of a tone waveform for one cycle, it is possible to obtain a tone waveform as smooth looped data for N cycles which is oversampled and downsampled.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the arrangement of a device for executing the tone signal processing of this embodiment. The tone signal processing of this embodiment is executed using the computer 1, the input device 3, and the like.

The computer 1 includes a CPU 5, a RAM (random access memory) 7, a ROM (read only memory).
This is a well-known general-purpose computer including a display unit 11, a display unit 11, an operation unit 13, and the like, and has a data bus for transmitting data such as tone waveforms inside. The CPU 5 is a central processing unit for performing processing such as oversampling and undersampling on the tone waveform. The RAM 7 is a read-only memory for temporarily storing data such as a tone waveform to be processed. The ROM 9 is a read-only memory that stores the processing program of the computer 1 and the like. The display unit 11 is a display device that displays various types of information such as the tone waveform to be processed. The operation unit 13 is a device for inputting various types of processing for a musical tone waveform, and includes a keyboard, a mouse, and the like.

The input device 3 is a device which takes in a musical tone signal from a musical instrument such as a piano 14 and inputs it as digital data into the computer 1, and includes a microphone 15, an amplifier 16 and an A / D.
It is composed of a converter 17 and the like. The microphone 15 is a microphone that inputs a musical sound output from a sound source such as a piano and sends the musical sound to the amplifier 16 as an electric signal.
The amplifier 16 is an amplifier that electrically amplifies the tone signal as an analog signal sent from the microphone 15.
The A / D converter 17 is an analog / digital converter that converts a tone signal as an analog signal sent from the amplifier 16 into a digital signal.

The processed tone waveform stored in the RAM 7 is written in the memory 23 of the electronic musical instrument by the memory writer 21 or the like via the data bus. FIG. 2 shows a PCM (pulse code modulation) waveform as a musical tone waveform input by the tone signal processing method of this embodiment.
The process of the looping process which takes out a period and loops is shown.

The input musical tone waveform is a musical tone waveform sampled from a musical instrument such as the piano 14 and is stored in the RAM 7. When storing as musical tone data in a storage device of an electronic musical instrument, a musical tone waveform of a predetermined period is stored in consideration of the memory capacity, and a method of looping at the time of sound generation is adopted. The process of the musical tone waveform shown in FIG. 3 will be described below according to the steps shown in FIG.

First, a musical sound as a natural sound generated from a musical instrument such as the piano 14 is sampled by the input device 3 (P11). The sampled data is temporarily stored in the RAM 7 of the computer 1. Next, RAM
About one cycle is extracted from the tone waveform stored in 7 (P12). Almost one cycle of the extracted tone waveform is
It is displayed on the display unit 11. FIG. 3A shows a musical tone waveform for almost one cycle taken out. As shown in the figure, since the sampling rate is low, even if one cycle is taken out and looped, a smooth loop waveform cannot be obtained.

Then, by repeating the musical tone waveform of about one cycle taken out for N cycles, an integer N is obtained so as to obtain the last sampling point showing the substantially same phase as the first sampling point (P13). In this embodiment,
As shown in FIG. 3B, one cycle includes 2.25 sampling points. Therefore this 1
By repeating the tone waveform of a cycle four times, the last sampling point showing almost the same phase as the first sampling point can be obtained.

With the integer N thus obtained, the extracted musical tone waveform is oversampled N times (P1).
4). In the embodiment, the extracted musical tone waveform of approximately one cycle is oversampled four times. As shown in the figure, the first sampling point and the last sampling point that are oversampled have almost the same phase, and the wavelength between them is almost one cycle.

Next, the musical tone waveform oversampled N times in P14 is repeated N times (P15). In the embodiment, since the 4-fold oversampling is performed, the musical tone waveform obtained in P13 is repeated four times in this process. The waveform repeated four times is shown in FIG.

Next, the musical tone waveform repeated N times in P15 is downsampled by 1 / N (P16). In the embodiment, 1/4 times downsampling is performed.
The tone waveform is shown in (d). Here, by the sampling points S and E, approximately four cycles of the sampled tone waveform can be extracted.

Next, the musical tone waveforms for these four cycles are stored in the RAM 7 as looped data (P17). In the obtained four-tone musical tone waveform, the phases of the starting point S and the ending point E of the waveform are both zero, and the waveforms are substantially the same. The musical tone waveform of four cycles as the looped waveform data obtained as described above is written in the memory 23 of the electronic musical instrument using the memory writer 21 and the like (P18).

As described above, according to the tone signal processing method of this embodiment, it is possible to take out looped data for four cycles by a simple process without damaging the timbre.
The waveforms for four cycles to be taken out indicate the points at which the sampling points have substantially the same phase, and this musical tone waveform is looped so that no deviation occurs at the joints, and a smooth musical tone waveform can be obtained.

Further, even in the case where the sampling rate cannot be made high with an electronic musical instrument or the like, a smooth looped tone waveform can be obtained without increasing the sampling rate. In particular, in the loop waveform of a musical sound, since the sampled sound of a piano or the like is a natural sound, the phase slightly changes with time, and a smooth loop waveform cannot be obtained by simply repeating a few cycles. However, according to the method of this embodiment, the waveform for one cycle is extracted 4
Since the sampling data in which the phases of the first sampling point and the last sampling point are substantially the same is used by performing oversampling by a factor of 2, it is possible to easily obtain smooth loop waveform data for four cycles.

In the embodiment, the tone waveform before processing is 1
Although a tone waveform for a period is taken out, it may be a tone waveform having an integer period of two periods or more. Also, in this embodiment, 4 is used as N, but this is to obtain a more accurate musical tone waveform by using a larger integer depending on the required quality of the musical tone, the memory capacity of the electronic musical instrument, or the like. Is also possible.

For example, one tone of 440 Hz (A4)
If you want to take 024 points of data, simply think of it as a sampling rate of 1 second, 440 x 1
It should be 024 points. However, in this case, the sampling data becomes enormous, and it is necessary to reduce the sampling rate. 440 and 1024
It is conceivable to sample at the least common multiple of and, but this also results in enormous amounts of sampling data. As described above, although the sampling rate cannot be set too high, a situation in which a musical tone waveform with good sound quality (smooth musical tone waveform) is frequently required, and the method of the present embodiment is effective.

[0022]

As described in detail above, according to the tone signal processing method of the present invention, it is possible to smooth the joints of looped waveforms by a simple process without spoiling the tone color.

[Brief description of drawings]

FIG. 1 is a block diagram showing an apparatus configuration for executing a musical tone waveform processing of the present embodiment.

FIG. 2 is a block diagram showing a process of processing a musical tone waveform of this embodiment.

FIG. 3 is an explanatory diagram showing musical tone waveforms processed in the embodiment.

FIG. 4 is a diagram illustrating the configuration of the present invention.

FIG. 5 is an explanatory diagram showing a musical tone waveform as a processing step of a conventional technique.

[Explanation of symbols]

1 ... Calculator, 5 ... CPU, 7 ... RAM, 1
1 ... Display unit, 13 ... Operation unit, P13 ... Process of oversampling integer times (N times), P15 ...
The process of repeating the musical tone waveform N times, P17 ... The process of down-sampling the musical tone waveform by 1 / N times

Claims (1)

[Claims] 1. A musical tone waveform processing method in which a part of an input musical tone waveform is extracted and used as looped data, and when a musical tone waveform of a predetermined period as input sampling data is repeated for an integer number of N cycles, a first sampling point is obtained. The integer N that gives the last sampling point exhibiting the almost same phase as is obtained, the musical tone waveform for the predetermined period is oversampled by the integral N times, and the musical tone waveform for the predetermined period that is oversampled by the integral N times is defined as the above. A musical tone signal processing method characterized by repeating an integer N times, down-sampling the musical tone waveform repeating the integer N times by the reciprocal of the integer N, and using the musical tone waveform down-sampled by the reciprocal of the integer N as looped data. .