JPH03288200A - Pitch detecting device - Google Patents

Abstract

PURPOSE:To accurately find a pitch period in a short processing time by finding one pitch period according to the time interval between a zero-cross position and a peak position. CONSTITUTION:A zero-cross position detecting means 8 which detects the zero- cross position of a period signal which is inputted from an input means 2 and a peak position detecting means 10 detects the peak position. A means 12 which finds the pitch period measures the time interval between the peak position and an adjacent zero-cross point which is generated precedently and also measures the time interval between the peak position and an adjacent zero-cross position which is generated after in order. Then the means 14 compares the time intervals of the same characteristics with each other and decides one period when they are equal to obtain one period of the period signal. Consequently, the pitch detection which is accurate and short in processing time becomes possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pitch detection device for detecting the pitch of an audio signal.

[Conventional technology]

Techniques for detecting the pitch of audio signals have been developed in the past, for example, in Japanese Patent Application Laid-open No. 1-310400
An apparatus has been disclosed that sequentially detects zero-crossing positions of an audio signal, sequentially determines the areas of the audio signal existing between the zero-crossing positions, and detects the pitch of the audio signal based on these areas.

[Problem to be solved by the invention]

Such pitch detection devices are sometimes used in electronic musical instruments that detect the pitch of a periodic signal and generate new musical tones based on that pitch or add effects corresponding to the pitch. For example, guitar synthesizers and This electronic musical instrument detects the pitch of the vibration of a guitar string and generates a new musical tone with a pitch corresponding to the detected pitch.

With electronic instruments like this guitar synthesizer, musical sounds must be generated immediately when the performer plucks the strings.
Reducing the time required for pitch detection is an important issue. In addition to the pitch detection device described above, pitch detection techniques using methods such as Fourier analysis have been proposed, but the reality is that they cannot be put to practical use with current electronic musical instruments, and a simple zero-cross method has been proposed. Pitch is detected by comparing sections. However, this is insufficient in terms of accuracy and may result in the detection of incorrect pitches.

The present invention solves the above problems.In addition to detecting and comparing zero cross positions, the present invention also detects and compares peak positions and peak heights of waveforms, thereby providing an accurate pitch detection device with short processing time. The purpose is to provide

[Means for solving problems]

In order to solve the above problems, a first invention provides means for inputting a periodic signal, means for detecting a zero-crossing position of the periodic signal input from the input means, and a peak of the periodic signal from the input means. The apparatus includes means for detecting the position and means for determining the pitch period of the periodic signal based on the time interval between the detected zero-crossing position and the peak position.

Further, the second invention provides one or more features in addition to the input means, zero-crossing position detecting means, and peak position detecting means in the first invention.
Means for detecting the peak height of the periodic signal is provided, and means for determining the pitch period is configured to determine the pitch period based on the time interval between the zero cross position and the peak position and the peak height.

[For production]

According to the first invention, for example, as shown in FIG. 3, zero cross positions Z1, Z2, Z3, . . . are detected by the zero cross position detection means, and peak positions PPI, PP2,
PP3... is detected by the peak position detection means. The means for determining the pitch period is the time interval between the peak position and the previous zero-crossing position adjacent to it,
For example, the time interval al between PPI and 21, the time interval a2 between PP2 and 22, etc. are sequentially measured, and the time interval between the peak position and the adjacent zero cross position that occurs later, for example, the time interval between PPI and 22. The time interval bl between PP2 and Z3, the time interval b2 between PP2 and Z3, etc. are sequentially measured. The means for determining the pitch period is to compare the time intervals of the same I wave, for example, al and a2, and bl and b2, so that al and a2 are approximately equal, and bl and b2 are approximately equal. If they are equal, the period from zero cross position Z1 to zero cross position Z3 is determined to be one period, and the time interval 1, for example, time interval al+ bl+ a2+
Let b2 be one period of this periodic signal.

According to the second invention, the time intervals a1, a2, . . . , bl, b2, .
P... is detected. The pitch period determining means not only compares al and a2 and bl and b2 similarly to the pitch period determining means according to the first invention, but also compares the peak heights PI and PP. Then, al and a2 are almost equal, and bl and b2 have the second
In the invention, three values are compared, but in addition to the above, these three values include (a) comparison between al and a2, comparison between al+bl and a2+b2, and PI
Comparison of and PP, (o) bl g b2. ! = (7) Comparison, Comparison of al + bl and a2 + b2, Comparison of Pl and 22, (n) Comparison of PI and 22, Comparison of PP and 23, Comparison of bl + a2 and b2 + a3 You may do so.

In the case of (a) and (rl), the pitch period is the time interval between zero cross positions Z1 and Z3 al+ bt+ a2+ b
In the case of (c), peak position PPI, time interval bl+ a2+b2+ of PP2
It can be determined by a3.

[Embodiment] In this embodiment, the present invention is applied to an electronic musical instrument such as a guitar synthesizer. In FIG. Convert a periodic signal as shown in the figure into an electrical signal. This electrical signal is sequentially converted into a digital signal at a predetermined sampling frequency in the A/D converter 4,
It is stored in a memory (not shown) attached to the microcomputer 6.

As is well known, the microcomputer 6 includes a CPU,
It is composed of RAM, ROM, etc. s
In Figure 1, the microcomputer 6 is shown by blocks for each function that it performs, and the following explanation is also as follows:
The explanation will be based on this functional block.

Each of the above digital signals sequentially indicates the time at which the sign representing the zero crossing position inverts from positive to negative or from negative to positive.
Fi! Zero cross positions z1, Z2, z3 as shown in i
Detected as...

While detecting the zero cross position in this way, the peak height and position detection means 10 detects the maximum value (peak height) PI, PP, P3, etc. in each digital signal, and also detects the maximum value (peak height) PI, PP, P3, etc. The time of occurrence of the maximum value is the peak position PPI
, PP2, PP3...

In this way, zero cross positions Z1, Z2, Z3...
and peak positions PPI, PP2, PP3...
In parallel with the detection of the zero cross position and the peak position, the time calculation means 12 calculates each zero cross position 21.2.
2, z3... and peak positions PPI, PP2,
Time with PP3... al, bl, a2, b2, a3
, b3... are sequentially calculated.

The comparison means 14 compares the times calculated in this way. This comparison is performed as follows.

The most recent time interval (the first half of the peak) between each peak position and a zero-crossing position that occurs adjacent to and before the peak position, for example, al and a2 are compared. Similarly, the most recent time interval (second half of the peak) between each peak position and a zero crossing position that occurs adjacent to and after this, for example, bl
and b2. For example, if al and a2 match, and bl and b2 match, the zero cross position Z
The comparing means 14 determines that the period from 1 to Z3 is one pitch period. Note that a match is not limited to a complete match, but is considered to be a match if one of the two values to be compared, for example al, is a certain percentage of the other, for example 95% or more. If it is determined that they match in this way, the time interval between the zero-crossing position of the first half of the peak, for example Zl, and the zero-crossing position of Z3 after the second half of the peak, for example al+bl+a2+b2, is output as one pitch period. do.

In order to improve the accuracy of the l pitch period, in addition to comparing the first half of the peak and the second half of the peak described above, also compare the peak height, for example, Pl and 22, and check if these three values match each other. In some cases, the comparing means 14 may be configured to determine that it is one pitch period.

When comparing three values in this way, in addition to the above, the comparing means is used to compare the first half of the peak, compare the peak height, and compare the time interval between zero cross positions, for example, compare al+bl and a2+b2. 14 may be configured,
Furthermore, the comparison means 14 may be configured to compare the latter half of the peak, the peak height, and the time interval between zero crosses.
and PP, PP and P3, and the comparison means 14 may be configured to compare the time interval between the peak positions, for example, bl+a2 and b2+a3. In this case, the l pitch period is determined by bl+a2+ b2+ a3. .

When comparing three values in this way, it is desirable for each value to match completely, but for two values, for example, the peak height and the first half of the peak, it is difficult to
For example, it may be determined that a match is reached at 99%, and another value, for example, at a slower rate for the second half of the peak, such as 95%.

Also, when comparing two values, it is not limited to comparing the first half of the peak and the second half of the peak, but also comparing the first half of the peak and comparing the peak height, or comparing the second half of the peak and comparing the peak height. A comparison may be made.

In the embodiments described above, the present invention is applied to a guitar synthesizer, but the present invention is not limited to this, and can also be applied to, for example, an audio pitch detection device. In that case, a microphone may be used instead of the pickup 2.Also, although the microcomputer 6 was used in the above embodiment, a digital signal processing device (DSP) may be used instead.

〔Effect of the invention〕

As described above, in the 4i pitch detection device according to the present invention, l pitch period is determined based on the time interval between the zero cross position and the peak position, or based on the time interval between the zero cross position and the peak position and the peak height. Therefore, the pitch period can be accurately determined in a short processing time.

[Brief explanation of drawings]

Fig. 1 is a block diagram of one embodiment of the pitch detection device according to the present invention, Fig. 2 is a diagram showing a periodic signal detected by the pickup of the same embodiment, and Fig. 3 is a zero-crossing position of the periodic signal of Fig. 2. , a diagram showing peak positions and peak heights. 2...Pickup (input means), 8...Zero cross position detection means, lO-...Peak height and position detection means, 12...Time calculation means for zero cross position and peak position, 14...Comparison means.

Claims (2)

[Claims] (1) means for inputting a periodic signal; means for detecting the zero-crossing position of the signal input from the input means;
Pitch detection comprising: means for detecting the peak position of the signal input from the input means; and means for determining the pitch period of the signal based on the time interval between the detected zero-crossing position and the peak position. Device. (2) means for inputting a periodic signal; means for detecting the zero-crossing position of the signal input from the input means;
means for detecting the peak position of the signal input from the input means; means for detecting the peak height of the signal input from the input means; and the time between the detected zero-crossing position and the peak position. and means for determining the pitch period of the signal based on the interval and the peak height.