JP2000105589A - Trigger detecting device and method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the detecting accuracy of a trigger in a base synthesizer or the like. SOLUTION: When the level of peak reaches a reject level just as peaks P1, P2, P3, it is adopted as an envelope level to renew the reject level, and simultaneously a timer timing up in a fixed time TO is started. By time up of the timer, a peak P4 of the maximum level is adopted as the envelope level from peak data after the peak lastly adopted as the envelope level within peak data stored in a peak memory part. In addition to renew the reject level by the level of the peak P4, the value of the counter of the timer is set as the value regarded to be started at the timing 14 of the peak P4. The envelope level is followed to peaks P4, P5 of signal waveform attenuating the envelope level. By being the level A of a peak P6 over 1.2 times the reject level R, a trigger is judged to be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a trigger detecting device and a trigger detecting method for detecting a trigger corresponding to a new performance event from a signal waveform caused by vibration of a vibrating body such as a string of a bass guitar.

[0002]

2. Description of the Related Art Conventionally, a pickup detects a vibration of a string played on a bass guitar, detects a signal waveform, detects a trigger or a pitch from the signal waveform, and detects a sound source based on the detected trigger timing or detected pitch. There is known an electronic musical instrument called a bass synthesizer, which is configured to generate a musical tone according to the vibration of a played string by driving a musical instrument.

FIG. 3 is a diagram for explaining a trigger detection method in a conventional bass synthesizer. Conventionally, a trigger is detected from a sudden change in signal level using an envelope follower. The envelope follower detects an envelope level forming an envelope of the signal waveform. For example, when a signal waveform as shown in FIG. 3 (A) is detected by a pickup, the peak of the currently detected signal level is calculated from the peak of the currently detected signal level. By reducing the value based on a predetermined time constant, a threshold value (broken line) called a reject level is used. When a peak exceeding this reject level is detected, the peak is adopted.

Next, the value of the adopted peak is reduced based on a predetermined time constant to obtain a reject level, and thereafter, by performing the same operation, the envelope level is detected from the sequentially adopted peak value. ing. Then, a point where the envelope fluctuates rapidly, such as a peak a in FIG. 3A, is detected as a new trigger.

Incidentally, it is preferable that the envelope follower detects the peak having the maximum signal level only once for one waveform of one cycle corresponding to the pitch, and does not detect the signal level of a small vibration in one waveform. The reject level time constant is increased. That is, FIG.
As shown in (A), if a reject level with a short time constant is used, a peak with a small level is also adopted, so a reject level with a long time constant is skipped so as to skip the peak and adopt the next valid peak. I use it. In particular, the time constant of the reject level needs to be increased as the frequency range (pitch) of the vibration becomes lower as in a bass guitar.

[0006]

However, in the above-described conventional trigger detection method using an envelope follower,
The trigger can be detected if there is a peak having a large rise like the peak a in FIG. 3A, but the trigger may be missed because the time constant of the reject level is long. For example, part (A) of FIG. 3 (B) shows a state in which the finger is touching the string and the signal is attenuated. Since the signal level during this time does not reach the reject level, it is not set to the envelope level, and the reject level before attenuation is maintained.

However, as in the case of the peak b, the signal level when the string is actually struck is small and may not reach the reject level, and the trigger at the time of the peak b may be missed. Also, even if the peak reaches the reject level as shown by the dashed line in FIG. 3 (B), a step between the reject level and the signal level of the peak cannot be obtained, that is, if the envelope level sharply increases. Change may not be obtained and the trigger may be missed.

As described above, especially in the case where the pitch is low as in a bass guitar, in the conventional trigger detection method, a positive step in the signal level cannot be formed unless the player plays the sound stronger than the previous sound, and the detection sensitivity of the trigger is high. Is low.
SUMMARY OF THE INVENTION It is an object of the present invention to improve the detection accuracy of a trigger even for a signal waveform having a low pitch, such as a bass guitar.

[0009]

According to a first aspect of the present invention, there is provided a trigger detecting apparatus for detecting a peak of a predetermined vibration element in a signal waveform corresponding to the vibration of a vibrating body, and the level of the peak is currently set. When the current reject level is reached, the peak is adopted as the envelope level, and a value near the peak value or less is updated as the reject level to update the current reject level, and the peak is adopted based on the reject level. A peak detecting means for detecting a trigger from a sudden change in an envelope level, wherein the peak is detected in time series, and a timer for measuring a predetermined time longer than a period of a pitch of the signal waveform. Means, and the peak is adopted as an envelope level within the predetermined time measured by the timer means. If not, the peak having the highest level among the peaks after the peak that was last adopted as the envelope level among the past peaks stored in the peak storage means is adopted as the envelope level, and Control means for updating the reject level based on the peak, and restarting the timer means as if it had been started when the peak was detected.

Note that the extreme value of the signal level can be adopted as the peak of the predetermined vibration element in the signal waveform. Generally, when the slope of the zero-cross point of the signal waveform is large, the signal level immediately after that becomes large, and the zero-cross point becomes large. When the slope is small, the signal level immediately after that is also small, so
The value of the slope of the zero cross point of the signal waveform may be adopted as the peak. Further, an extreme value of a differential waveform of the signal waveform may be adopted. Further, the integrated value of the waveform between the zero cross points (the area of the portion surrounded by the waveform) may be adopted as the peak.

The signal waveform has at least one peak within the period of the pitch. Therefore, in the trigger detecting device according to the first aspect of the present invention, since the timer means measures a predetermined time longer than the pitch cycle of the current signal waveform, at least one peak is detected within the measured predetermined time. You. In addition, when a string is played on a bass guitar or the like, the finger touches the string, so that the signal waveform of the sound before the trigger is often attenuated. Therefore, if the detected peak does not reach the reject level and is not adopted as the envelope level, the signal waveform is attenuated. However, the detected peak is stored in a peak storage unit, and the control unit controls the past peaks stored in the peak storage unit in the peaks after the peak that was last adopted as the envelope level. And the maximum level peak is adopted as the envelope level, the reject level is updated based on the adopted peak, and the timer is restarted as if it had been started when the peak was detected. Therefore, the envelope level is adopted based on the peak and the reject level of the attenuated portion, and if there is a trigger thereafter, it appears as a rapid change in the envelope level, so that even a small peak trigger can be detected with high accuracy.

According to a second aspect of the present invention, there is provided a trigger detecting method for detecting a peak of a predetermined vibration element in a signal waveform corresponding to the vibration of a vibrating body, and the level of the peak reaches a currently set reject level. In this case, the peak is adopted as the envelope level, and the current reject level is updated by using a value near the peak value or less as the reject level, and the sharpness of the envelope level adopted based on the peak and the reject level is increased. A trigger detection method for detecting a trigger from a change, wherein the step of storing the detected peak in time series, the step of measuring a predetermined time longer than a pitch cycle of the signal waveform, and the step of measuring the predetermined time If the peak is not adopted as the envelope level within the Among the peaks, the peak of the maximum level is adopted as the envelope level from among the peaks after the peak that was last adopted as the envelope level, and the reject level is updated based on the adopted peak, and the predetermined time is updated. Restarting the timing step as if it had been started when the peak was detected. According to the trigger detecting method of the second aspect, the same operation and effect as those of the first aspect can be obtained.

[0013]

Embodiments of the present invention will be described below. FIG. 2 is a main block diagram of a bass synthesizer to which the trigger detection device and the trigger detection method according to the embodiment of the present invention are applied. An electric bass guitar (not shown) is connected to the bass synthesizer.
The electric bass guitar has any number of strings of 4 to 6, each string is stretched between a bridge and a head, and its body is provided with a pickup 1 corresponding to each string. .

The mode of the bass synthesizer is set according to the number of strings of the electric bass guitar to be connected. The pickup 1 independently detects the vibration of each string, and the vibration waveform detected by the pickup 1 is converted by the AD converter 2 Supplied to The AD converter 2 converts the input vibration waveform of each string into digital data indicating the amplitude value of the vibration waveform of each string by time division processing according to the number of strings, and outputs the digital data. That is, this digital data is
It is output for each conversion cycle (sampling timing) and input to the pitch detection unit 3 and the peak detection unit 4.

The pitch detecting section 3, peak detecting section 4, envelope detecting section 6, quantizer 8 and MIDI output section 9 perform time division processing corresponding to each string in synchronization with the time division processing of the AD converter 2. The timer 7 has a number of counters corresponding to the time-division processing slots corresponding to the respective strings, and each counter is set so as to measure a time slightly longer than the pitch cycle of the open strings of the respective strings. ,Also,
When the performance pitch of each string is determined, it is set so that a time slightly longer than the pitch cycle is measured. Then, a time-up signal is output when the counting of the set time is completed. In the following description, processing of one time slot of the time division processing, that is, processing corresponding to one string will be described.

The pitch detecting section 3 obtains one signal pattern of the signal waveform from the output of the AD converter 2, and detects the pitch from the repetition period of this pattern. Then, the detected pitch is input to the quantizer 8, and the quantizer 8 quantizes the detected pitch when the fluctuation of the detected pitch is equal to or smaller than the minimum pitch change assumed in the pitch bend. The detected pitch is output to the MIDI output unit 9 as it is. Thus, when the pitch changes due to a pitch bend that is not intended by the player, an accurate pitch is obtained, and when the pitch bend is intended by the player, a natural pitch change is obtained.
Note that the pitch detected by the pitch detection unit 3 is also input to the envelope detection unit 6 and used for determining the set time of the timer 7.

The peak detector 4 detects, from the output signal of the AD converter 2, data having a maximum value at a level equal to or higher than a noise component and a predetermined value or more, and converts the detected data and the data of the timing at that time into one. Output as peak data. The peak data is sequentially stored in the peak storage unit 5 and sequentially output to the envelope detection unit 6. In the peak storage unit 5, buffers for storing a plurality of peak data are set by the number corresponding to the time-division processing slots corresponding to the respective strings. Is sufficient to store the peak data generated at the pitch of the highest note of each string. The peak detection unit 4 and the envelope detection unit 6 write and read from and to each buffer as needed by controlling the pointer.

The envelope detector 6 determines the envelope level of the signal waveform based on the peak data input from the peak detector 4 and the peak data stored in the peak storage 5, as will be described later. A note-on is output to the MIDI output unit 9 by detecting a trigger from a rapid change in Further, note off and velocity are detected from the envelope level, and the detected information is supplied to the MIDI output unit 9. The MIDI output unit 9 generates MIDI data of a musical tone to be generated based on the pitch information input from the quantizer 8 and the note-on / note-off and velocity information input from the envelope detection unit 6. 1
Output to 0 to generate a musical tone.

The pitch detector 3, the peak detector 4,
The peak storage unit 5, the envelope detection unit 6, the timer 7, the quantizer 8, and the MIDI output unit 9 include, for example, a CP.
It can also be constituted by a microcomputer and software provided with U, RAM, ROM, I / O.

Next, the configuration and operation of the envelope detector 6 will be described. The envelope detector 6 has a register for setting a reject level, and the reject level of this register is set to an initial value “0” by turning on the power or turning off the note. Then, the level of the peak data input from the peak detector 4 is compared with the reject level set in this register, and when the level of the peak data has reached the reject level, the level of the peak data is set as the envelope level. Adopt and set in register to update reject level. Note that the value of this register is reduced by a predetermined time constant, thereby setting a reject level that is reduced by the predetermined time constant. As a result of the comparison, if the level value of the input peak data is 1.2 times or more the reject level value, it is determined that “trigger detection” has occurred, and a trigger detection signal is output to the MIDI output unit 9.

The envelope detector 6 includes a timer 7
A predetermined time slightly longer than the pitch of the open string is set as an initial value by turning the power on and off, and when the pitch detected from the pitch detection unit 3 is input, the predetermined time is slightly longer than the pitch of the pitch. Set the time. Each time the peak data is adopted as an envelope level as described above, a timer 7 (a counter corresponding to a string) is used.
Reset and start.

On the other hand, when the timer 7 times out without detecting a peak exceeding the reject level, the peak data is read from the peak storage section 5 from the peak next to the peak last adopted as the envelope level.
The maximum level of the peak data is adopted as the envelope level. Then, the time when this peak is detected is determined based on the timing of the peak data, and the timer 7 is set and started as if started at that time.

With the above configuration, the envelope detecting section 6 detects a trigger by the following operation, for example. FIG. 1 is a diagram for explaining the operation of the envelope detector 6 and the timer 7. Since the timer 7 is set longer than the period of the string pitch, the time interval between the peaks P1, P2, and P3 is within the set time TO of the timer 7. Since the peaks P1, P2, and P3 are hardly attenuated, they are adopted as envelope levels at timings t1, t2, and t3, the reject level is updated, and the timer 7 is reset. Note that the small peaks p1, p2, p3, etc. do not reach the reject level and are not adopted as envelope levels.

When the signal waveform attenuates to peaks P4 and P5, the peak P4 does not reach the reject level, so that the timer 7 times out at timing t41. Due to this time-up, the peak data of the peaks p3, P4, and p4 after the peak which was lastly adopted as the envelope level among the peaks stored up to the present time from the peak storage unit 5 are read out, and these peaks are read out. Of the peak P4, ie, the level of the peak P4, is adopted as the envelope level. Also, the reject level is a value obtained by attenuating the level of the peak P4 until the timing t41, and furthermore, the value of the counter of the timer 7 is set to a value regarded as being started at the timing t4 of the peak P4. As a result, before the timer 7 times out, at timing t5, the peak P5 reaches the reject level and is adopted as the envelope level, and the reject level is updated by the level of this peak P5.

Then, at timing t6, a peak P6 due to new picking is detected. If the level of this peak P6 has reached the reject level, it is adopted as the envelope level. In the case of the figure, since the level A of the peak P6 has reached the reject level R, it is adopted as the envelope level. Also, since the level A is 1.2 times or more the reject level R, it is determined that a trigger has been detected. If the trigger is determined, the predetermined time measured by the timer 7 until the next pitch is detected is set to a time slightly longer than the pitch cycle of the open string.

This peak P6 corresponds to the peak b in FIG.
The trigger is detected at the reject level that follows the envelope level based on the attenuated peak, such as peak P5, so a sudden change in the envelope level (difference between reject level and peak level) As a result, a trigger that could not be detected conventionally can be detected.

In the above-described embodiment, a reject level whose value is reduced by a time constant is used. For example, the reject level may be 0.8 times the peak level used as the envelope level. A fixed value (a value that is not reduced by a time constant) that is a multiple of the level may be used. That is, both the reject level whose value decreases due to the time constant and the reject level having a fixed value that is a multiple of a few times the level of the peak correspond to a value close to or less than the peak value adopted as the envelope level.

In the embodiment, the level (extreme value) of the signal waveform itself is adopted as a peak for detecting the envelope level. The peak includes the slope of the zero-cross point of the signal waveform and the differential waveform of the signal waveform. And the integrated value of the waveform between the zero cross points.

In the above embodiment, a bass synthesizer has been described, but it goes without saying that the present invention can be applied to a guitar synthesizer or the like. In addition, the present invention can be applied not only to stringed instruments but also to other instruments.

[0030]

As described above, according to the first aspect of the present invention,
According to the trigger detecting device of the first aspect or the trigger detecting method of the second aspect, the envelope level is adopted based on the peak and the reject level of the attenuated portion of the signal waveform, and if there is a trigger thereafter, the envelope level suddenly changes. Therefore, even a trigger having a small peak can be detected with high accuracy, and the detection accuracy of the trigger can be improved even for a signal waveform having a low pitch such as a bass guitar.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of an operation of an envelope detection unit and a timer according to an embodiment of the present invention.

FIG. 2 is a main block diagram of a base synthesizer to which the trigger detection device and the trigger detection method according to the embodiment of the present invention are applied.

FIG. 3 is a diagram illustrating a conventional trigger detection method.

[Explanation of symbols]

3 pitch detector, 4 peak detector, 5 peak storage unit, 6 envelope detector, 7 timer.

Claims (2)

[Claims] 1. A peak of a predetermined vibration element in a signal waveform corresponding to vibration of a vibrating body is detected, and when the level of the peak reaches a currently set reject level,
The current reject level is updated by using the peak as an envelope level and a value near the peak value or less as a reject level, and the signal is obtained from a sudden change in the envelope level adopted based on the peak and the reject level. A trigger detection device that detects a trigger in a waveform, a peak storage unit that stores the detected peaks in a time series, a timer unit that measures a predetermined time longer than a pitch cycle of the signal waveform, and the timer unit. If the peak is not adopted as the envelope level within the predetermined time measured in the above, the peak after the peak last adopted as the envelope level among the past peaks stored in the peak storage means. The maximum level peak is the envelope level Control means for renewing the reject level based on the adopted peak and restarting the timer means as if it were started when the peak was detected. Trigger detection device. 2. A peak of a predetermined vibration element in a signal waveform corresponding to vibration of a vibrating body is detected, and when the level of the peak reaches a currently set reject level,
The peak is adopted as an envelope level, and the current reject level is updated with a value near the peak value or less as a reject level, and a trigger is generated from a sudden change in the envelope level adopted based on the peak and the reject level. A trigger detecting method for detecting, wherein the step of storing the detected peak in a time series; the step of measuring a predetermined time longer than a pitch cycle of the signal waveform; and the step of measuring the peak within the measured predetermined time. When is not adopted as the envelope level, the peak of the maximum level among the peaks after the last adopted as the envelope level among the stored past peaks is adopted as the envelope level, and Update reject level based on peak employed As well as, the trigger detection method characterized by comprising the steps of: restarting to the step of counting a predetermined time is started when the said peak is detected.