JPS62115499A - Fundamental cycle detector for voice signal - 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 (a) Field of Industrial Application The present invention relates to a fundamental period detection circuit device for audio signals.

(b) Conventional technology The fundamental period of an audio signal can be easily derived as the reciprocal of the fundamental frequency of the audio signal. The present applicant has published Japanese Patent Application Laid-Open No. 58-30 in connection with circuit means for extracting the fundamental frequency of an audio signal.
No. 795 (GIOH1100) (filed date August 1982)
May 17th) and JP-A No. 59-220794 (GIO
HIloo) (filed on May 30, 1988).

In Japanese Patent Application Laid-Open No. 58-30795, the audio signal is converted to a predetermined frequency (
In the example, it is 8 kHz>> Bling, convert to digital code, and select between samples where the autocorrelation function of the sampled main sequence is maximum: every other time,
Alternatively, the sample interval time when the difference function between specific sample values shows the minimum value is derived as the fundamental period of the audio signal.

In the example of JP-A-59-220794, JP-A-58-
In addition to the method for deriving the fundamental period of an audio signal disclosed in No. 30795, the audio signal is converted into a dintral signal of "1" and "0°" at the AC intersection point, and this is converted into a digital signal of "1" and "0°" at the AC intersection point, and this is automatically calculated based on the sample value sequence sampled based on a predetermined clock. This method calculates the correlation and derives the fundamental period.In these conventional devices,
In order to accurately derive the fundamental period of an audio signal, it is necessary to sample the audio signal (or the digital signal at the AC intersection point) at fine intervals and perform calculations to derive the fundamental period. In this case, (a) The sample value sequence to be calculated becomes large, and many means for storing it are required for calculation processing.

(b) As the sample value sequence becomes larger, the amount of calculation increases, and a high-speed calculation circuit is required.

It is convenient to use a microcomputer to store these calculations and the sample values for the calculations, but in this case, if a large number of storage means such as RAM are used, the circuit configuration becomes large, and In order to complete the calculation, it is necessary to keep the sample values within a predetermined number, which has the disadvantage that the detection accuracy of the fundamental period of the audio signal becomes rough.

(c) Problems to be Solved by the Invention In order to solve the above-mentioned drawbacks, the present invention aims to solve the fundamental period (or fundamental frequency) of the audio signal with high precision and without increasing the capacity of the storage means for arithmetic processing. ) is provided.

(d) Means for solving the problem The present invention converts an audio signal into a binary signal of "1" and "O",
a binarization circuit that outputs a binary signal of the converted audio;
, a clock circuit that generates a black/red signal of a predetermined frequency, a counting circuit that counts the output of the clock circuit and outputs a numerical value related to the timing of polarity reversal of the binary signal of the audio, and a binary signal of the audio. It is comprised of arithmetic means for inputting the signal and the output of the counting circuit and detecting the fundamental period of the input audio signal.

This calculation means detects the fundamental period of the audio signal according to the following procedure.

(1) Time series of polarity reversal of audio No. 46 [Ti, ri-+, Ti-2,...Tj-x÷
1 image (where Ii is the time of last capture), (2) Assuming the interval between the polarity reversal of N details as L(N), L(N)=l Ti-Ti-N1 , (L (N) is the absolute value), and (3) the value M times the L(N) (M = 2, 3, -
Find the timing (Tpn) with the closest interval from Ti in the time series of the polarity reversal between Mo) and the polarity reversal, and calculate the error E(NM).
E(NM) = l (ML(N) l Ti -T
PM I ) I, (4) This error E(NM) is calculated from M=2 to M=l'l
Calculate O by setting the cumulative value of errors accumulated up to o as 5 (N), and (5) find N when this cumulative value of errors, 5 (N), is the minimum.
L(N) corresponding to is detected as the fundamental period of the input audio signal.

(E) Effect Since the present invention is configured as described above, even if the oscillation frequency of the clock circuit is set high, the amount of polarity inversion time series data stored in order to calculate the fundamental period of the audio signal can be reduced. The increase is small, so this storage means can also be made small. In other words, the fundamental period of the audio signal can be detected with high accuracy.

Kube) Example Next, embodiments will be described with reference to the drawings.

FIG. 1 is a block diagram of the fundamental period detection circuit for an audio signal according to the present invention, in which (1) is an audio signal input terminal, (2) is a filter circuit, and (3) is a band limited by the filter circuit (2). A binarization circuit converts the input audio signal into a binary signal of "1" OII, (5) a clock generation circuit, (6
) is a counting circuit that divides the frequency of the clock, and (4) is an arithmetic circuit that inputs the audio binary signal and the output of the counting circuit, calculates the fundamental period of the audio signal, and outputs the result. The fundamental period of the audio signal calculated and detected by the calculation circuit (4) is output to the output terminal (0+ = Oe) of the calculation circuit (4), and when connected to an electronic musical instrument, etc., the electronic musical instrument can be played by voice. can be configured. Arithmetic circuit (4) is RA
It can be composed of a microcomputer with storage means such as M. Further, the clock generation circuit (5) and the counting circuit (6) can also be realized using a timer function of a microcomputer.

FIG. 2 is a waveform diagram for explaining the function of the binarization circuit (3) of FIG. 1. In the figure, (a) is an example of the audio signal waveform applied to the audio signal input terminal (1), and (
al) to (C2) are this fundamental period. In order to reduce fluctuations near the AC crossover point during this fundamental cycle, a filter (2) passes low frequency components. In the case of Fig. 2, the fundamental period of the waveform (c) obtained by converting this band-limited audio signal waveform (b> into a binary code by the binarization circuit (3)) is between (c+) (c s), (cz) between (C6),
It is clear that it is between (C3) and (C7).

When considering a human singing voice, the fundamental frequency of the voice for an adult male is 100H, although it varies depending on age and gender.
On the other hand, the duration of a scale is about 174 seconds to 178 seconds in a musical score with a sixteenth note length, so it is possible to expect an audio signal waveform in which the fundamental period of the audio does not change more than 10 times. For women and children, the fundamental period is even shorter, and therefore the number of times the fundamental period does not fluctuate is even longer. Considering these characteristics, the fundamental period of the audio signal is detected by detecting a periodically repeated pattern of binary numbers δ.A specific method will be described below.

FIG. 3(a) shows a diagram in which the input audio signal is converted into a 1ill14011 digital signal by the binarization circuit (3). Counting circuit (6)
The output of is stored as timing information. From this polarity reversal time series [Ti, Ti-+, . That is, this detection may be performed at each rising edge or every other rising edge.

Detection of the fundamental period when the polarity reversal timing (Ti) is stored will be described below.

Let the time interval from Ti to Ti-5 be L(N).

L (N)” I Ti -Ti-m lSince the two masters of this voice are band-limited by filter (2),
The basic period of the audio signal is within the range of every 2 to 6 polarity reversals (an even number). If L(N) is the fundamental period, there should be a polarity reversal (however, the same polarity as T1) at this M times. The distance from Ii is M times L(N) (M −2,
3. Find the polarity reversal point TPM closest to -・-・MO), and calculate the error ε(N) as E(NM)=I(ML(N)−l Ti−Tpn
The integrated value 5(N) of this error is determined as lN.

A^ In the case of Figure 3, if Mo5a4, S(1) = I lTi-Ti-4I -21Ti-1
i-+I l +11Ti-τi-a l -3I
Ti-Ti-+ I l +l I Ti-Ti-e
I-4lTi-Ti-+II. When N in 5(N) is an odd number, the polarity reversal is an odd number and cannot occur in the fundamental period, so for the case where N is 2.4.6, N when 5(N) is the minimum is called No. do.

S(No)=MinS(N) In the case of FIG. 3, No=6 is obtained. This L (No)
It is clear that is the fundamental period we are looking for.

In the above explanation, the counting circuit (6) is the clock circuit (5).
Although it has been explained that the clocks generated by the circuit are sequentially counted (counted up), the fundamental period of the audio signal can be determined by initializing the output of the counting circuit to 0 every time the polarity is reversed. In this case, the counting circuit output is the interval [J
i, Ji-+, . . . are output.

Therefore, L(N) becomes, and the value tL(N), which is M times L(N), and the inversion interval difference E
(NM) is assumed, and L(N) corresponding to N when the calculated error value 5(N)xc is the minimum is detected as the fundamental period of the input audio signal. J. T. In the above explanation, it was stated that the timing value series used for calculating the fundamental period should be memorized every time the polarity is reversed, but even if it is captured at every rising or falling edge, the calculation accuracy will decrease slightly. , the calculation speed is increased accordingly. Also, this fundamental period (L
(No)) need not necessarily be calculated every time the polarity is reversed, but may be calculated every rising edge or every other rising edge. As explained above, the Kn circuit (4) calculates the fundamental frequency (L(No)) of the audio signal and outputs the information corresponding to L(No) to the OI to Oe terminals. When driving, it is sufficient to quantize this in semitone units or scale units and output it. As described above, according to the configuration of the present invention, even if the frequency of the clock generated by the clock circuit (5) is set high and the time precision of the timing value at the time of polarity inversion is high, the time required for calculation and the capacity of the storage element are required. There's no need to make it any bigger.

(G) Effects of the Invention As described above, according to the present invention, when detecting the fundamental period of an audio signal, the time error can be made extremely small, and there is no need to increase the time required for calculation or the capacity of a storage element.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a fundamental period detection circuit for an audio signal according to the present invention, FIG. 2 is an explanatory diagram of a binarization circuit, and FIG. 3 is an example of a waveform of a binarization signal. (1) is an audio signal input terminal, (2) is a filter circuit,
(3) is a binarization circuit, (4) is an arithmetic circuit, (5) is a clock generation circuit, and (6) is a counting circuit.

Claims (3)

[Claims] (1) (a) A binarization circuit that converts the applied input audio signal into a binary signal and outputs it; (b) A clock circuit that generates a clock of a predetermined frequency; (c) A binarization circuit that converts the applied input audio signal into a binary signal and outputs the signal; (b) A clock circuit that generates a clock of a predetermined frequency; 2 of the audio signal
a counting circuit that outputs a numerical value related to the timing of polarity reversal of the value signal; (d) inputting the output binary signal of the binarization circuit and the output of the counting circuit to detect the fundamental period of the input audio signal; (d-1) When the polarity of the audio signal is reversed (only at the rising or falling time, or including the time when the polarity is reversed every predetermined number of times, this is referred to as the time of polarity reversal) ), a timing value sequence (Ti, Ti_-_1, Ti_-_
2,...Ti_-_K_+_1), (where Ti is the last timing value taken in, Ti_-_1 is the value taken one time ago, and Ti_-_2 is the value taken two times ago), and every time the polarity is reversed. (d-2) N pieces of the timing value series (N=1, 2,
...) Let the interval between the previous timing values be L(N), L(N)=|Ti-T(i_-_N)| (L(N) is the absolute value), and (d-3) M times the value of L(N) (M=2, 3...Mo
) and the timing value closest to Ti is the timing value T_P_M, and the error E(NH) is E(NM
)=|{M・L(N)−|Ti−T_P_M|}|, (d−4) Let the integrated value of this error E(NH) be S(N), S(N)=Σ＾M＾ o_M_=_2E(NH) is obtained, and (d-5) L(N) corresponding to N when the cumulative value S(N) of this error is minimized is detected as the fundamental period of the input audio signal. A device for detecting the fundamental period of an audio signal. (2) The calculation means stores the output of the counting circuit at the time of polarity inversion of the audio binary signal, and initializes the counting circuit to generate a numerical series corresponding to the polarity inversion interval.
(Ji, Ji_-_1,...Ji_-_K_+_1
) (where Ji is the last polarity reversal interval) and L(N) = Σ^N^-^1_j_=_0Ji-
j, and the error when the value M times this L(N) (M・L(N)) and the integrated value of the reversal interval Σ^P^M_j_=_0Ji-j is the closest value is E(NM). E(NM)=|{M・L(N)−Σ＾i_j_=_P_
MJj}|, and the integrated value of this error S(N)=Σ＾M＾
The basis of the audio signal according to claim 1, characterized in that L(N) corresponding to N when o_M_=_2E(NM) is minimum is detected as the basic period of the input audio signal. Period detection device. (3) The fundamental period detecting device for an audio signal according to claim 1 or 2, wherein the calculation means quantizes the fundamental period of the detected audio signal in scale units and outputs the quantized result.