JPS63153600A - Pitch extractor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a pitch extraction device for acoustic signals such as various musical tones and voices.

Conventional technology 2ba/゛In recent years, with the advancement of digital technology, various pitch extraction techniques have been proposed, including a technique for calculating autocorrelation of time waveforms and a cepnutrum technique, but as a technique that does not require a multiplier, There is an integral pitch extraction technique (for example, the Acoustical Society of Japan/Speech Research Group material/material number 582-ots (
1982-4) P, P.

33-40).

The pitch extraction device described above will be explained below with reference to the drawings.

FIG. 3 shows the configuration of a conventional pitch extraction device. In Fig. 3, 1Q1 is a no 1 pass filter, 10
2 is a low-pass filter, 103 is an AD (analog-digital) converter, 104 is an integrator, and 105 is a determination section.

The operation of the pitch extraction device configured as described above will be described below.

An audio signal input from a microphone or the like is passed through a low-pass filter 102 after removing a DC component by a low-pass filter 101, thereby satisfying the sampling theorem.

Aging filtering is performed.

Next, the data is analog-to-digital converted by the AD converter 103 to become digital data. AD converter 10
The digital data outputted from the unit 3 is integrated by the integrator 104 and then outputs the integration result to the determination unit 105. The determination unit 105 detects a local minimum value regarding the integration result,
The pitch is calculated by counting the number of samples between the minimum values. That is, the digital data of the audio signal as shown in FIG. 4a, that is, the AD converter 10
The output of 3 is converted by the integrator 104 into an integration result as shown in FIG. 4C. The determination unit 105 detects minimum values as absolute values as shown by A, B, and C from the integration result of FIG. 4C, and determines the number of samples NA, NB, and N between the minimum values
c pitch periods are obtained. Note that in order to convert the pitch period Ni side to the so-called pitch f, it can be obtained by sampling.

In order to facilitate the detection of local minimum values, the integration results of the integrator 104 are subjected to moving average (smoothing) processing, as shown in FIG.
The influence of harmonic components on pitch period detection can be removed by inputting the signal to pitch period detection.

Problems to be Solved by the Invention However, with the above configuration, there is a problem in that the integration result diverges in the positive or negative direction due to the presence of frequency components lower than the pitch period.

In view of the above-mentioned problems, the present invention provides a pitch extraction device that has a simple configuration and can prevent divergence of integration results.

Means for Solving the Problems To achieve this objective, the pinch extractor of the present invention comprises:
A converting band-limited acoustic signals into digital data
D converter, an integrator that cumulatively adds the digital data output from the AD converter, and resets the integrator each time the cumulative result passes through the predetermined threshold twice. and a control determination section that detects each reset interval as a pitch period.

Operation According to the present invention, a band-limited acoustic signal is converted into digital data by an AD converter with this configuration.

The digital data output from the AD converter is sequentially
The integrator reset to the initial value O performs cumulative addition, and the results are sequentially output. The control determination section is
With respect to a predetermined threshold θ, the time interval from when the cumulative result output from the integrator once exceeds the threshold θ until it falls below the threshold θ again is detected, and this is output as a pinch period, and the integration Reset to device 0. By repeating the above operations, successively detected pitch periods will be output from the control determination section.

Embodiment One embodiment of the present invention will be described below with reference to the drawings.

6.7 FIG. 1 shows a block diagram of a pitch extraction device in one embodiment of the present invention.

In FIG. 1, 1o is an integrator, and 11 is a control determination section.

Note that 101 is a bypass filter, 102 is a low-pass filter, and 103 is an AD converter, which have the same configuration as the conventional example.

The operation of the pitch extraction device configured as described above will be described below.

First, the acoustic signal input to the bypass filter 101 contains frequency components considerably lower than the pitch frequency (for example, 5
After high-pass filtering is performed to remove frequencies (below 10 cHz), the signal is input to the low-pass filter 102 . The high-pass filtered acoustic signal input to the low-pass filter 102 is low-pass filtered so as to pass only fs/2 [Hz] or less with respect to the sampling frequency f8 [H2] so as to satisfy the so-called sampling theorem. Filter. In addition, in this example,
It is preferable to remove the influence of the high-frequency components by performing low-pass 7' overfiltering with a cutoff frequency of fc << f 8/2.

The acoustic signal that has passed through the bypass filter 1o1 and the low-pass filter 102 is a band-limited acoustic signal.
The data is converted into digital data by the AD converter 103 at a sampling frequency of f8CHz. The digital data output from the AD converter 103 is sequentially cumulatively added by the integrator 10. Here, it is assumed that the integrator 1o has been reset to an initial value of zero.

The control determination unit 11 holds a predetermined threshold value θ as a determination reference value, and compares it with the cumulative result output from the integrator 1o. As a result of the comparison, the cumulative result is the threshold value θ
After detecting that the value exceeds the threshold value, the integrator 1° is reset at the same time as the cumulative result becomes less than or equal to the threshold value. On the other hand, the control determination section 11 counts the number of digital data from when the integrator 10'ilJ is set until the next reset, and outputs the counted value as a pitch period detection value.

FIG. 2 shows the relationship between the above data.

Note that if you want to use the pinch period as a time value, you can multiply the detected value by 1/f6, and if you want to use it as a pitch frequency, you can divide f8 by the detected value.

Furthermore, in the above, regarding the comparison with the threshold value θ in the control determination unit 11, we have described the case where the cumulative result is a positive value, but when the cumulative result is a negative value, the determination is based on the absolute value or the magnitude determination with respect to the threshold value θ. You just have to change it as appropriate.

As described above, according to this embodiment, the integrator 1o is reset each time the control determination unit 11 detects a pinch period, so that it is possible to prevent the cumulative result from diverging in the positive or negative direction. Furthermore, smooth accumulation results can be obtained by comparing with the threshold value θ instead of requiring a complicated determination unit for determining the minimum value or the maximum value as in the conventional case.

Go to 9-2 Effects of the Invention The present invention sequentially cumulatively adds digital data obtained by converting a band-limited acoustic signal using an AD converter using an integrator, and then uses the result in a control determination section to set a predetermined threshold value θ. Since the pitch period is detected by comparison and judgment, and at the same time the cumulative result of the integrator is reset to zero, it is possible to prevent the cumulative result from diverging in the positive or negative direction.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a pitch extraction device according to an embodiment of the present invention, FIG. 2 is an exemplary waveform diagram of each data related to the same pitch extraction device, and FIG. 3 is a block diagram of a conventional pitch extraction device. Figure 4 is a signal waveform diagram of each part. 1o...Integrator, 11...Control determination section, 101...Bypass filter, 1o2...
...Low pass filter, 103...AD converter, 1o4...Integrator, 105...Judgment section. Name of agent: Patent attorney Toshio Nakao and 1 other person M
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Claims (1)

[Claims] A converting band-limited acoustic signals into digital data
A D converter, an integrator that sequentially cumulatively adds the digital data output from the AD converter, and compares the cumulative addition result output from the integrator with a predetermined threshold, and adds the digital data corresponding to the comparison result. a control determination unit that resets an integrator, and the control determination unit instructs the integrator to reset each time the cumulative addition result passes the threshold twice, and detects each reset interval as a pitch period. A pitch extraction device characterized by: