JPS63169525A - Pitch extracting device - Google Patents

Abstract

PURPOSE:To obtain a pitch period without varying an accumulation result with the starting point of processing by detecting the polarity inversion of digital data by a polarity monitoring part and sending a polarity inversion signal an integrator. CONSTITUTION:A band-limited acoustic signal is converted by an A/D converter 103 into digital data and the output data of a comparator 103 is sent out to the polarity monitoring part 12 and integrator 10 in order. The polarity monitoring part 12 detects the polarity inversion of the digital data and outputs a signal indicating the start of cumulative addition to the integrator 10, then the digital data are integrated by the integrator 10, and the result is outputted successively. Then a control decision part 11 detects the time interval from the starting point of the integration to the point where the integration result from the integrator 10 decreases below a threshold value theta again after exceeding the threshold value theta once, and outputs it as a pitch period. Said operation is repeated and the detected pitch period is outputted from the control decision part 11 in order.

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 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 integral pitch is a technique that does not require a multiplier. There is an extraction technique (Acoustical Society of Japan/Speech Research Group material/material number 882-06 (1982)
-4) p, p, 33-40).

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

FIG. 3 shows the configuration of a conventional pitch extraction device.

In FIG. 3, 1o1 is a bypass filter, 102 is a low-pass filter, 103 is an A/D (analog to digital) converter, 104 is an integrator, and 106 is a determination section.

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

An audio signal input from a microphone or the like has its direct current component removed by a high-pass filter 101, and then passes through a low-pass filter 102 to undergo anti-aliasing filtering that satisfies the sampling theorem.

Next, the data is analog-to-digital converted by the A/D converter 103 to become digital data.

The digital data output from the A/D converter 103 is integrated by an integrator 104, and then the integration result is output to the determination section 105. The determination unit 106 calculates the pitch by detecting the minimum value of the integration result and counting the number of samples between the minimum values. That is,
The digital data of the audio signal as shown in FIG. 4(,), that is, the output of the A/D converter 103, is converted by the integrator 104 into an integration result as shown in FIG. 4(c)K. The determination unit 105 determines A for the integration result in FIG. 4(C).
,B.

A minimum value as an absolute value as shown by C is detected, and the number of samples Na, Nb, NC between the minimum values is obtained as a pitch period. In addition, in order to convert the pitch period Ni side to the so-called pitch f1, the sampling frequency F, CH2)
can be obtained as f i (Hz 'J = Fs / Ni.

In addition, in order to facilitate the detection of local minimum values, the results of moving average (smoothing) the integration results of the integrator 104 are
As shown in Figure (b), the results of this moving average processing are
05, it is possible to eliminate the influence of harmonic components on pitch period detection.

Problems to be Solved by the Invention However, with the above configuration, the cumulative result obtained fluctuates due to the starting point of the process (pitch extraction) as shown in FIG. , ) , (b)
), therefore, there was a problem in that it was difficult to detect the minimum value.

In view of the above-mentioned problems, the present invention provides a pitch extraction device that can obtain a pitch period with a simple configuration and without changing the cumulative result depending on the starting point of processing.

Means for Solving the Problem In order to achieve this object, the pinch extraction device of the present invention includes an A/D converter that converts a band-limited acoustic signal into digital data, and an A/D converter that converts a band-limited acoustic signal into digital data. an integrator that cumulatively adds digital data; a polarity monitor unit that outputs a signal indicating an instruction to start cumulative addition to the integrator by inverting the j-character of the digital data output from the A/D converter; It is comprised of a control determination unit that detects the interval from the start of addition until the cumulative addition result passes a predetermined threshold twice as a pitch period.

Operation: With this configuration, the band-limited acoustic signal is converted into digital data by the A/D converter. A/D
Digital data output from the converter is sequentially sent to a polarity monitor section and an integrator. At this time, the readability monitor section detects the polarity reversal of the digital data and outputs a signal instructing the start of cumulative addition to the integrator.Then, the digital data is cumulatively added by the integrator and the results are sequentially output. The control determination unit determines, with respect to a predetermined threshold θ, that the cumulative addition result outputted from the integrator once exceeds the threshold θ and then becomes less than or equal to the threshold θ from the time when the cumulative addition starts. Find the time interval up to the point in time,
This is output as a pitch period. By repeating the above operations, the sequentially detected pitch periods are output from the control determining section.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

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, 11 is a control determination section, 1
2 is a polarity monitor section. Note that 101 is a high-pass filter, 1o2 is a low-pass filter, and 103 is an A/D converter, which are the same as the conventional configuration.

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

First, the acoustic signal input to the bypass filter 01 contains frequency components considerably lower than the pitch frequency (for example, 6o
After being subjected to high-pass filtering that removes the frequency (below [cHz]), the signal is output to the low-pass filter 02.

The high-pass filtered acoustic signal input to the low-pass filter 02 has a sampling frequency f (:H2) so as to satisfy the so-called sampling theorem.
Low-pass filtering is performed so that only frequencies below f8/2 [H2] are allowed to pass.

In this embodiment, it is preferable to remove the influence of high-frequency components by performing low-pass filtering with a cutoff frequency of fo<f, /2.

The acoustic signal that has passed through the bypass filter 01 and the low-pass filter 02 is a band-limited acoustic signal.
The digital data is A/D converted by the A/D converter 03 at a sampling frequency of fsCHZ. Digital data output from the A/D humbator 103 is sent to the polarity monitor section 12 and the integrator 10.

Next, when the polarity monitor section 12 detects the reversal of the polarity of the digital data, that is, the zero crossing point of the band-limited acoustic signal, the polarity monitor section 12 detects the inversion of the polarity of the digital data, in other words, the zero crossing point of the band-limited acoustic signal. If not, a signal instructing the integrator 10 to start cumulative addition is output, and if cumulative addition is not in progress, a signal to start cumulative addition is not output until the cumulative addition is completed.

Here, when the integrator 1o receives a signal instructing the start of cumulative addition, it temporarily sets the cumulative value at that point to 0 before starting cumulative addition.
Cumulative addition starts after being reset to . Control determination unit 1
1 holds a predetermined threshold value θ as a determination reference value, and compares it with the cumulative addition result output from the integrator 1o when cumulative addition is started. As a result of the comparison, after detecting that the cumulative addition result exceeds the threshold θ for the first time,
The number of digital data from the time when the cumulative addition result becomes equal to or less than the threshold value θ and the cumulative addition is started at the same time as the time when the cumulative addition result becomes equal to or less than the threshold value θ is counted, and the counted end is outputted as a pitch period detection value. Thereafter, the control determination section 11 outputs a signal to the polarity monitor section 12 indicating that the cumulative addition result has been completed. The relationship diagram of each data above is shown in the second
As shown in the figure.

Note that when the pitch period is expressed as a time value, the detected value may be multiplied by 1/f8, and when the pitch frequency is expressed as a pitch frequency, f8 may be divided 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 addition result is a positive value, but when the cumulative addition result is a negative value, the determination based on the absolute value or the threshold value θ is performed. The size determination may be changed as appropriate. Furthermore, in order to prevent the cumulative addition result from taking a negative value, it is also possible to start the cumulative addition using a polarity inversion signal when the digital data takes a positive value.

As described above, according to this embodiment, the polarity monitor section 12 resets the integrator 1o before starting cumulative addition using a signal indicating polarity inversion, so that the cumulative addition result does not diverge in the positive or negative direction. It can be prevented. Furthermore, the determination can be made by comparison with the threshold value θ, without requiring a complicated determination unit for determining the local minimum value or maximum value as in the conventional case.

Also, the cutoff frequency fC of the low-pass filter 102
By setting fo(fC/2), smooth accumulation results can be obtained.

Effects of the Invention In the present invention, the polarity monitor section detects polarity reversal of digital data obtained by converting a band-limited acoustic signal by an A/D converter, and sends a polarity reversal signal to an integrator, thereby starting cumulative addition. Since it can be synchronized with the zero crossing of the acoustic signal, the cumulative addition result does not vary depending on the processing start point, and therefore, the pitch can be extracted without changing the setting of the threshold value θ each time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a pitch extraction device according to an embodiment of the present invention, and FIG. 2 is a signal waveform diagram according to an embodiment of the present invention. 10... Integrator, 11... Control judgment section,
12...Polarity monitor section, 101...Bypass filter, 102...Low pass filter, 1
03... A/D converter, 104... Integrator, 105... Judgment section. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure n1η hazy, ・Sitoto both t≧ 8 15°2 Figure 4 □Poetry Figure 5

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 A/D converter, and an integrator that receives the digital data output from the A/D converter, and by reversing the polarity of the digital data. A polarity monitor section that outputs a reset signal to the integrator for instructing the start of cumulative addition, and a control determination section that compares the cumulative addition result output from the integrator with a predetermined threshold, A pitch extraction device characterized in that a control determination unit detects an interval from a time when the cumulative addition is started to a time when the cumulative addition result passes the threshold twice as a pitch period.