JPH0769716B2 - Pitch extractor - Google Patents

Abstract

PURPOSE:To execute a pitch extraction with high accuracy by a simple constitution by converting the acoustic signal of an input to a digital signal and clocking a period, storing a timer value in a storage means, and also, comparing it with the result of clocking in the past. CONSTITUTION:An acoustic signal of an input is converted to a digital signal by a binarization means 2, and the period is clocked by a timer means 3. A timer value being the result of clocking is stored in a storage means 4, and also, the timer values of a high level and a low level are compared successively with each timer value corresponding to a high level and a low level in the past, respectively by a first comparing means 5. Subsequently, the signal which is read out successively from the storage means 4 is accumulated and added by an adding means 6 until a coincidence signal is outputted by a first comparing means 5, the accumulated and added value and a latch 7 in which an accumulated and added value in the past is held are compared, and when a roughly equal result is obtained, the accumulated and added value of the adding means 6 is outputted as a pitch period. In such a manner, the pitch extraction of high accuracy can be executed without necessitating a high speed operation processing, and also, by a simple constitution.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pitch extraction device for audio signals such as various musical sounds and voices.

2. Description of the Related Art In recent years, with the progress of digital technology, various pitch extraction techniques for extracting a pitch from an acoustic signal have been proposed, and a technique for obtaining an autocorrelation of a time waveform, a cepstrum technique, etc. are known. A pitch extraction technique based on polarity reversal detection is considered as a pitch extraction technique for reducing the amount of calculation or for high-speed processing.

Hereinafter, the pitch extraction device described above will be described with reference to the drawings.

FIG. 3 shows the structure of a conventional pitch extracting device.

In FIG. 3, 11 is an acoustic signal input terminal, 12 is a high-pass filter, 13 is a low-pass filter, 14 is an A / D converter for converting an analog acoustic signal into digital data, and 15 is an A / D converter.
/ D converter 14 detects the polarity inversion of the digital data output polarity inversion detection unit that outputs a polarity inversion detection signal, 16 is the polarity inversion detection signal output from the polarity inversion detection unit 15 A control unit 17 outputs a time measurement instruction signal for instructing start or end, a time measurement unit 17 for measuring a pitch period of digital data according to the time measurement instruction signal, and an output terminal 18.

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

The acoustic signal input to the acoustic signal input terminal 11 from the microphone or the like is subjected to antialiasing filtering that satisfies the sampling theorem by passing through the lowpass filter 13 after the direct current component is removed by the highpass filter 12, and A / The D converter 14 sequentially performs analog-digital conversion to obtain digital data.

Next, the polarity inversion detection unit 15 detects the polarity inversion of the digital data sequentially output from the A / D converter 14, and then outputs the polarity inversion detection signal to the control unit 16. The control unit 16 outputs to the timing unit 17 a timing instruction signal for instructing the start or end of the timing of the pitch period according to the polarity inversion detection signal. When the control section 16 outputs a timing instruction signal for instructing to start timing, the timing section 17 starts counting the number of samples of digital data, that is, counting the pitch period.

Further, when the control section 16 outputs a time measurement instruction signal for instructing the end of time measurement, the time measurement section 17 outputs the number of samples up to that time, that is, the time measurement result to the control section 16 as a pitch cycle, and then resets the time measurement result.

By repeating the above operation according to the polarity inversion detection signal of the polarity inversion detection unit 15, the pitch cycle of the digital data sequentially output from the A / D converter 14 can be obtained.

In order to convert the Ni pitch periods into the so-called pitch Fi [Hz], the sampling frequency Fs [Hz] can be used and Fi [Hz] = Fs / Ni (1) can be obtained.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-mentioned configuration, not only the accuracy of the pitch period obtained by the sampling frequency changes as is clear from the equation (1), but the sampling frequency must be increased in order to improve the accuracy. Therefore, there has been a problem that high-speed arithmetic processing is required and an expensive device is required.

In view of the above problems, the present invention provides a pitch extraction device that does not require high-speed arithmetic processing and has a simple configuration and high accuracy.

Means for Solving the Problem In order to achieve this object, a pitch extraction device according to the invention of claim 1 of the present application, a binarizing means for binarizing an acoustic signal, and a binarizing means for binarizing the same. The clocking means for timing the period of the generated acoustic signal, the storage means for sequentially storing the clocked values clocked by the clocking means, and the storage means for storing at least two clocked values; and the clocking means. First comparing means for sequentially comparing the measured time value and the past measured value stored in the storage means, and outputting a coincidence signal when the ratio of the two measured values is within a predetermined value range; An adding means for accumulatively adding the time count values stored in the storage means until the coincidence signal is output by the first comparing means, a latch for holding the cumulative addition result of the count values from the adding means, and the addition. The output of the means The second addition means compares the product addition result with the past cumulative addition result held in the latch, and outputs a coincidence signal when the ratio of the two cumulative addition results is within a predetermined value. When the coincidence signal is obtained from the second comparing means, the cumulative addition result which is the output of the adding means is output as the pitch period of the acoustic signal. Further, in addition to the above configuration, the pitch extracting apparatus according to the invention of claim 2 of the present application holds the accumulated addition result which is the output of the adding means and the latch in the case where the coincidence output is obtained from the second comparing means. Has the averaging means for calculating the average value of the past cumulative addition results, and has the latest timing result for each of the high level and the low level of the binarized acoustic signal obtained by the binarizing means. The cumulative addition value of the timing results up to the past timing result, which is almost the same as the above, is obtained, and the average value of the two cumulative addition results is output as the pitch period.

Operation According to the above configuration, the input acoustic signal is converted into a digital signal by the binarizing means, and the period is timed by the time counting means. The time value which is the time measurement result is stored in the storage means, and the time values of the high level and the low level are sequentially compared with the time values corresponding to the past high level and low level respectively by the first comparing means, It is compared whether the ratio is within a predetermined range. Then, the signals sequentially read from the storage means are cumulatively added by the adding means until the coincidence signal is output by the first comparing means, and the cumulative addition value is compared with the latch holding the past cumulative addition value, When almost equal results are obtained, the cumulative addition value of the adding means is output as the pitch cycle.

Further, in the invention of claim 2 of the present application, the average of the cumulative addition value thus obtained and the cumulative addition value held in the latch is output as the pitch cycle.

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

FIG. 1 is a block diagram of a pitch extracting device according to an embodiment of the present invention, and FIG. 2 is operation waveforms of the block diagram shown in FIG.

In FIG. 1, 1 is an acoustic signal input terminal, 2 is a binarizing means for binarizing an acoustic signal, 3 is a timing means, which is controlled by the output of the binarizing means 2 and has an output latch (not shown). No). Reference numeral 4 is a storage means for storing the time count value output from the time count means 3. Reference numeral 5 is a first comparing means, which is a clocking means 3
And the time values read from the storage means 4 are compared, and a coincidence signal is output when the ratio of both time values is within a predetermined range. Reference numeral 6 denotes an adding means with an output latch (not shown), which cumulatively adds the time count values read from the storage means 4. A latch 7 temporarily holds the output of the adder 6. Reference numeral 8 is an averaging means, which averages the data held in the latch 7 and the output data of the adding means 6, that is, the cumulative addition results corresponding to the high level and the low level, respectively. 9
Is a second comparing means for comparing the input and output of the latch 7, that is, the cumulative addition results corresponding to the high level and the low level, respectively. 10 is an output terminal.

Next, the operation of this embodiment will be described. When the acoustic signal shown in FIG. 2 (a) is input to the acoustic signal input terminal 1, 2
The output signal of the digitizing means 2 has the waveform shown in FIG. The time measuring means 3 measures time by a clock signal (not shown), and the high level and low level times T _U-4 , T _L-4 , T _U-3 , T of the waveform of the output signal of the binarizing means 2 _L-3 , T _U-2 , T _L-2 ...
・ T _U0 and T _L0 are sequentially counted and latched in the output latch (not shown). FIG. 2 (c) shows the contents of the signal of the output latch of the timing means 3. The storage means 4 stores the measured value T _Un or
After storing T _Ln, as shown in FIG. 2 (d), the measured value T _L-1
The sequentially measured values are read from. The current high level time value
If T _U0 is stored in the storage means 4, these past measured values T _Ln-1 , T _Un-1 , T _Ln-2 , T _Un-2 , ... _Are stored in the storage means 4.
From the storage means 4 is sequentially sent to the comparing means 5 from the storage means 4, and the latest time value T _U0 is compared, and when the ratio of both time values is within a predetermined range, FIG. 2 (e). The coincidence signal shown in (1) is output, and the storage means 4 stops reading the measured value. At this time, if the latest time-measured value is of high level or low-level, the comparison by the comparison means 5 is compared only with the time-measured value of the past high-level or low-level. Further, the past time count values sequentially read from the storage means 4 are cumulatively added by the addition means 6. The cumulative addition result is shown in FIG. This cumulative addition result (T _L-1 ) + (T _U-1 ) +
(T _L-2 ) + (T _U-2 ) is the cumulative addition result (T _U-1 ) + obtained from the past timing result stored in the latch 7.
(T _L-2 ) + (T _U-2 ) + (T _L-3 ) is compared by the comparison means 9 and both cumulative addition results are within a predetermined range. The matching signal shown in g) is output.
If a coincidence signal is obtained from the comparison means 9, the averaging means 8
The latest cumulative addition result (T
_L-1 ) + (T _U-1 ) + (T _L-2 ) + (T _U-2 ) and the past cumulative addition result (T _U-1 ) + (T _L-2 stored in the latch 7 ) +
Average of (T _U-2 ) + (T _L-3 ), that is, P ₀ = {(T _L-1 ) +2 (T _U-1 ) +2 (T _L-2 ) +2 (T _U-2 ) + (T _L-3 )} / 2 is calculated by the averaging means 8 and output from the output terminal 10 as the pitch period P ₀ of the acoustic signal as shown in FIG. 2 (h). When the pitch period P ₀ is output from the output terminal 10, the latch 7 stores the latest cumulative addition result which is the output of the adder 6.

The pitch period P ₀ is a signal corresponding to the pitch period of the acoustic signal, and has a relationship with the clock signal CK input to the timing means 3. Therefore, it is understood that if the pitch period P ₀ is to be obtained with high accuracy, the frequency of the clock signal CK should be increased. From FIG. 2 (a, b), the pitch period P ₀ is (T _L-1 ) + (T _U-1 ) + (T _L-2 ) + (T _U-2 ), (T _U-1 ) + (T _L-2 ) + (T _U-2 ) + (T _L-3 ), (T _L-2 ) + (T _U-2 ) + (T _L-3 ) + (T _U-4 ) Therefore, it is possible to prevent erroneous extraction of pitch due to harmonics of the acoustic signal.

According to the inventions of claims 1 and 2, the input acoustic signal is converted into a digital signal by the binarizing means, and the period is timed by the timekeeping means. The measured value, which is the measured result, is stored in the storage means and is compared with the past measured result by the comparison means. If there is a result that is almost equivalent to the past time measurement result, the cumulative addition value of the past time measurement values that is the target of comparison is a value corresponding to the pitch period of the input acoustic signal. Is performed for both the high level and the low level of the binarized acoustic signal to prevent erroneous extraction of the pitch period. As described above, according to the present invention, it is possible to perform highly accurate pitch extraction with a simple configuration and prevent pitch period extraction errors due to harmonics or noise of an acoustic signal.

Further, there is an effect that it is not necessary to perform high-speed arithmetic processing in order to improve the pitch period extraction accuracy, and it can be realized by inexpensive hardware.

Further, in addition to this effect, the invention of claim 2 of the present application takes an average of the obtained cumulative addition value of the adding means and the pitch period held by the latch, so that a more accurate pitch period can be obtained. The effect of being able to do is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a pitch extracting device according to one embodiment of the present invention, FIG. 2 is an exemplary waveform diagram of each data according to one embodiment of the present invention, and FIG. 3 is a pitch extracting device of a conventional technique. It is a block diagram. 1 ... Acoustic signal input terminal, 2 ... Binarization means, 3 ... Timekeeping means, 4 ... Storage means, 5 ... Comparison means, 6 ... Addition means, 7 ... Latch, 8 ... Averaging Means, 9 …… Comparison means, 10 …… Output terminal, 11 …… Sound signal input terminal, 12 ……
High pass filter, 13 …… Low pass filter, 14 …… A /
D converter, 15 ... polarity reversal detection unit, 16 ... control unit, 1
7 …… Timer, 18 …… Output terminal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Nakanishi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yuko Shinada, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. A binarizing means for binarizing an audio signal, a clocking means for clocking high level and low level times of the audio signal binarized by the binarizing means, and the clocking means. Storage means for sequentially storing the clocked values clocked by, and a storage means capable of storing at least two clocked values; a clocked value clocked by the clocking means and a clocked value stored in the storage means, which are sequentially read out. First comparing means for sequentially comparing the timer values corresponding to the high level and the timer values corresponding to the low level, and outputting a coincidence signal when the timer value ratio is within a predetermined value range; The adder means for cumulatively adding the clock values sequentially read from the storage means until the coincidence signal is output by the comparator means 1, the latch for temporarily holding the output of the adder means, and the output of the adder means. Ah A second comparison means for comparing the cumulative addition result with the cumulative addition result held in the latch, and the cumulative addition which is the output of the addition means when there is a coincidence signal from the second comparison means. A pitch extraction device which outputs a result as a pitch cycle of an acoustic signal. 2. A binarizing means for binarizing an audio signal, a clocking means for timing the high level time and the low level time of the audio signal binarized by the binarizing means, and the clocking means. Storage means for sequentially storing the time-measured values by means of the storage means capable of storing at least two time-measured values, and the time-measured values measured by the time-measurement means and the time-measured values stored in the memory means are sequentially read. First comparing means for sequentially comparing the timer values corresponding to the high level and the timer values corresponding to the low level, and outputting a coincidence signal when the timer value ratio is within a predetermined value range; Addition means for accumulatively adding the time count values sequentially read from the storage means until the coincidence signal is output by the first comparison means, a latch for temporarily holding the output of the addition means, and an output of the addition means. And The second comparison means further comprises: second comparison means for comparing the cumulative addition result with the cumulative addition result held in the latch; and averaging means for outputting an average value of the two cumulative addition results. When there is a coincidence signal from the means, the average value of the cumulative addition results corresponding to the high level and the low level held in the latch and the adding means is output as the pitch period of the acoustic signal. apparatus.