JP2555551B2 - Input waveform signal controller - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an input waveform signal control device in, for example, an electronic guitar.

[Background of the Invention]

Conventionally, a pitch (frequency) is extracted from a waveform signal generated by a performance operation of a natural musical instrument, and a sound source device composed of an electronic circuit is controlled to artificially obtain a sound such as a musical sound. Have been developed.

In this type of device, a typical method for performing pitch extraction is a zero-cross point detection method in which a time interval between waveform zero-cross points is detected and used as a cycle.

One example of this zero-cross point detection method is
This is shown in FIG. That is, FIG. 7A shows the case where the input signal is close to a sine wave. Then, when the zero cross point of this waveform is detected by a comparator or the like, the result is as shown in FIG. 7B, and the time interval between the rising edges or the falling edges of this waveform is measured.

By the way, although there is no particular problem with the waveform as shown in FIG. 10A, when the input waveform signal has overtones and cannot be removed by a low-pass filter or the like, that is, as shown in FIG. When a different waveform is given, the comparator output becomes as shown in FIG.

Therefore, if the pitch extraction is performed by the zero-cross point detection method, the extracted pitch has many errors, or complicated software processing (for example, processing such as checking the duty) is used to prevent such errors. Had to be extracted, and there was a technically difficult problem.

[Object of the Invention]

The present invention has been made in view of the above circumstances, and provides an input waveform signal control device capable of reliable pitch determination by performing pitch extraction that is not easily affected by harmonic components contained in an input waveform signal. The purpose is to

[Main points of the invention]

That is, in order to achieve the above object, the present invention detects at least one of the maximum value and the minimum value of the input waveform, and further detects each of the zero-cross points of the waveform generated immediately after the detection of the maximum / minimum value. The point is that the pitch of the input waveform signal is extracted by obtaining the time interval between the zero cross points.

〔Example〕

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

Overall Circuit Configuration FIG. 1 shows the overall circuit configuration of the same embodiment. In this embodiment, the present invention is applied to an electronic guitar,
The signals at the six input terminals 1 are signals from a pick-up provided on each of the six strings stretched on the electronic guitar body and converting the vibration of the strings into an electric signal.

The tone signals from the input terminals 1 ...
Is amplified, the high-frequency component is cut by the low-pass filter (LPF) 3 ... and the basic waveform is extracted, and the maximum peak detection circuit (MAX) 4 ... minimum peak detection circuit (MIN) 5 ...
And zero cross check output circuit (Zero) 6 ... The low pass filter 3 ...
The cutoff frequency is set to 4f, which is four times the vibration sound frequency f of the open string of each string. The maximum peak detection circuit 4 ... Detects the maximum peak point of the music signal, and at the rising edge of the detected pulse signal, the Q output of the flip-flop 14 ... The AND output of the output and the inverted output of the inverter 30 of the zero-cross point detection circuit 6 ... Is output as an interrupt command signal INT _{a1 to} INT _a6 via the AND gate 24.
Similarly, the minimum peak detection circuit 5 ... Is supplied to the CPU 100, the minimum peak point of the musical tone signal is detected, and the Q output of the flip-flop 15 ... The AND output of the outputs of the flip-flop 15 ... And the output of the zero-cross point detection circuit 6 ... Is given to the CPU 100 as interrupt command signals INT _{b1 to} INT _b6 via the AND gate 25.

That is, the maximum peak point is detected and the flip-flop 14
When the waveform is crossing from positive to negative, the interrupt signals INT _{a1 to} INT _a6 are given to the CPU100, and conversely the minimum peak point is detected and the flip-flop 15
The interrupt signals INT _{b1 to} INT _b6 are input to the CPU 100 when the waveform changes from negative to positive while is at the High level.

Immediately after receiving these interrupt signals, the CPU 100 resets by generating clear signals CL _{a1 to} CL _a6 and CL _{b1 to} CL _b6 for the corresponding flip-flops 14 ..., 15 ... Therefore, even if the zero-cross point is passed many times until the next maximum peak point or minimum peak point is detected, the corresponding flip-flops 14 ..., 15 ... are in the reset state, so the CPU 100 is not interrupted. Become.

By the way, in the CPU 100, among the above interrupt command signals, the interrupt command signal of the zero crossing point immediately after the maximum peak point detection is performed.
When INT _{a1 to} INT _a6 is given, the difference from the counter value at the zero cross point immediately after the maximum peak point detected in the same way as before is calculated, and the interrupt at the zero cross point immediately after the minimum peak point is detected. When the command signals INT _{b1 to} INT _{b6 are} generated, the difference from the counter value similarly detected before that is obtained. Each time these two signals INT (INT _a1 to _a6 , INT _b1 to _b6 ) are given, the count value of the counter 7 is stored in the corresponding maximum time memory 101 and minimum time memory 102, respectively.

The time count data of the obtained difference in the count values of the counter 7 is sent from the CPU 100 to the frequency ROM 8 and
Frequency data indicating a frequency having one cycle of this count data is read out, sent to the tone generator circuit 9 to generate a tone signal, and sound output from the sound system 10.

The six tone signals from the low pass filter 3 ... Are respectively transferred to the A / D converter 1 via the transfer gate T.
It is given to 1, converted into digital data according to the waveform level, and given to the CPU 100. In the CPU 100, when the absolute value of the data indicating the waveform level given by the A / D converter 11 exceeds a predetermined fixed value, the data obtained from the value of the counter 7 is sent to the frequency ROM 8 to start sound emission. Then, when this data becomes equal to or less than the predetermined value, a mute instruction is given and the sound emission is ended. The data indicating the waveform level is also given from the CPU 100 to the tone generator circuit 9 to control the tone emission level (volume) of the musical sound.

Channel timing signals t _{1 to} t ₆ whose timings are sequentially shifted are given to the transfer gate T, respectively.
The sound emission level control of the 6 tone signals (corresponding to 6 strings) is performed in time series, and in response to this, the 6-channel tone generation system is formed in the frequency ROM 8 and the tone generator circuit 9 by time division processing. .

Configuration of Maximum Peak Detecting Circuit 4 and Minimum Peak Detecting Circuit 5 Zero Crossing Point Detecting Circuit 6 FIG. 3 shows a specific configuration of the maximum peak detecting circuit 4. The tone signal from the low-pass filter 3 is an operational amplifier 4-1. Of the operational amplifier 4-1 is connected to the anode side of the diode D1 and the cathode side of the diode D1 is connected in parallel.
And grounded via a resistor R1 and the operational amplifier 4
-1 - is connected to the terminal, the output of the operational amplifier 4-1 through the resistor R2, through the amplifier 4-2 and is output as an interrupt command signal INT _a1 to INT _a6 of the maximum peak point detection.

Assuming that a waveform as shown in FIG. 4A is given to the + terminal of the operational amplifier 4-1, the capacitor C is charged when the waveform level rises and discharged when the waveform level falls. The waveform shown in b) is the operational amplifier 4-
Is input to the terminal, when elevated waveform level only, + terminal and - - 1 of the difference value of the terminal is output, which is output as an interrupt command signal INT _a shown in FIG. 4 (c). Interrupt processing is started at the trailing edge of the pulsed signal shown in (c).

Further, the maximum peak detection circuit may be as shown in FIG. The same parts as those in FIG. 3 are designated by the same reference numerals. That is, there is a diode D2 connected in the opposite direction to the diode D1 in FIG. 3, and the operational amplifier 4-3 is connected to the + terminal of the operational amplifier 4-1.
The input signal in is given to the-terminal of the operational amplifier 4-3 via the resistor R4, and its output is also connected to the resistor R3.
Have returned through. The operation of the maximum peak detection circuit 4'in FIG. 5 is almost the same as the operation of the minimum peak detection circuit 5 described below, and the operational amplifier 4 for signal inversion is provided on the input side.
-3 is only connected, and therefore omitted.

FIG. 6 shows a specific configuration of the minimum peak detecting circuit 5, and this minimum peak detecting circuit 5 is a maximum peak detecting circuit 4.
However, the direction of the diode D2 is reversed, and the capacitor C repeatedly charges and discharges in the reverse direction as shown in FIG. 4 (d) to generate an interrupt as shown in FIG. 4 (e). The command signal INT _b will be obtained.

Further, FIG. 7 shows a specific configuration of the zero-cross point detection circuit 6, in which the tone signal from the low pass filter 3 is given to the + terminal of the operational amplifier 6-1, and the ground level is connected to the-terminal. The output of the operational amplifier 6-1 is a resistor
Output via R5 and amplifier 6-2. Therefore, when there is a positive level input signal, the amplifier 6-2 outputs Hign, and when there is a negative level input signal, the amplifier 6-2 outputs
Low output. That is, the output level is inverted every time the signal passes through the zero cross point.

Operation Next, the operation of this embodiment will be described. Figure 8 shows CPU1
In the main flow of 00, first perform the initial setting in step A1, then read the value of the A / D converter 11 in step A2, and continue the tone off processing unless it reaches a certain level (steps A3, A4 ). Now, when a string performance operation is performed, a tone signal of a certain level or higher as shown in FIG.
If it is input to the D converter 11 (step A3), the process proceeds to step A5, where frequency control processing, that is, tone emission processing for giving the data from the counter 7 to the frequency ROM 8 is performed, as long as the tone signal level is above a certain level. Continue sound emission processing (steps A2, A3, A5). The count data of the counter 7 is set in the interrupt processing described below.

Next, if the musical tone waveform rises by the string operation and the waveform level reaches the first maximum peak point (MAX1 in the figure) shown in MAX1 of FIG. 9 (a), the maximum peak detection circuit 4 causes A signal as shown in FIG. 9B is generated, and the flip-flop 14 is set to High level (see FIG. 9D). Then, from the zero-cross point detection circuit 6 to Zero of FIG.
The zero-cross point detection output is inverted at point 1 ((c) in the same figure).
A reference), the interrupt command signal INT _a is supplied to the CPU 100 from the AND gate 24, CPU 100 starts the interrupt processing of FIG. 10. First, the CPU 100 reads the count value of the counter 7 at step B1 and determines whether or not the waveform is the first wave (step B2). Right now, the tone waveform has just started,
Since it is the first wave, the routine proceeds to step B5, the flag "1" is set, and the count value of the counter 7 read to the step B1 is set in the maximum memory 101. This flag "1"
Is a flag indicating that the zero-cross point next to the maximum peak point has already been detected. If this flag is cleared, it means that the minimum peak point has been detected. The function of this flag is as described later.

When a waveform as shown in Fig. 9 (a) is input, each time the zero-cross points Zero2 and Zero3 are continuously detected, the zero-cross point detection circuit 6 outputs an inverted output as shown in Fig. 9 (c). Is obtained.

However, the output of flip-flop 14 has been reset (at step B1) and no interrupt signal INT _a
Does not occur. Since remains of course flip flop 15 is also reset, interrupt signal INT _b is not generated.

Then, when the minimum peak point indicated by MIN1 in FIG. 9 (a) is reached, a peak detection signal is output from the minimum peak detection circuit 5 and the flip-flop 15 is set.
Then, at the next zero cross point (ZERO4), zero-cross point detection circuit 6 outputs is inverted, the result from the AND gate 25 to CPU100 given interrupt command signal INT _b, CPU 1
00 starts the interrupt processing shown in FIG. First, the CPU 100 resets the flip-flop 16 at step C1 and further reads the count value of the counter 7 to determine whether the waveform is the first wave (step C2). However, the zero cross point next to the minimum peak point is the current one. In the case of the first wave, the flow proceeds to step C5 to clear the flag to "0", and the count value of the counter 7 read at step C1 is set in the minimum time memory 102.

Whether or not it is the first wave of step C2 and step B2 is determined by setting the first wave flags A and B, for example, when the waveform level data from the A / D converter 11 exceeds a certain level.
Before step B5 after when step B2 an interrupt command signal INT _a zero-cross point detection immediately after the maximum peak point is given, clears the first wave-th flag A, an interrupt command for the zero-cross point detection immediately after the minimum peak point before step C5 after step C2 when the signal INT _b is given, it clears the first wave-th flag B, step B2, C2 in first wave-th flag a, B
It is achieved by judging whether or not is standing.

Then, upon reaching the zero-cross point following the maximum peak point shown in MAX2 of FIG. 9 (a) (Zero5), given interrupt command signal INT _a zero-cross point detection immediately after the maximum peak point, CPU 100 is a counter at step B1 The count value of 7 is read, it is determined in step B2 that the waveform is not the first waveform, and it is determined in step B3 whether the flag is "0".
The flag is set to "0" at the next zero cross point (Zero4) of the immediately preceding minimum peak point MIN1, so the CPU 100 proceeds to step B4 and immediately after the maximum peak point MAX1 one cycle before (Zero1). At this time, the time count data set in the maximum time memory 101 is read and subtracted from the current time count data read at step B1 to obtain the result data. As a result, in the above step A5, the above result data is given to the frequency ROM8 and the zero cross point (Zero
Control is performed so that a musical tone of a frequency having a period of time from 1) to the zero-cross point (Zero5) as one cycle is emitted. Following the above processing, the CPU 100 sets a flag "1" and sets the current time count data value in the maximum memory 101 (step B5).

In this way, the zero crossing point immediately following the maximum peak point is determined in steps C5 and B5, the time (t ₁ ) between these zero crossing points is measured, and the period calculation is performed in step B4.

Similarly, the zero-cross points (Zero6, Zeto7) are ignored and the interrupt signal from the AND gate 25 generated by the detection of the zero-cross point (Zero8) immediately after the minimum value is detected.
In response to the input of INT _b , the CPU 100 performs the processing shown in FIG. 11, and this time, the time interval (t ₂ ) from the previous zero cross point (Zero4) to the current zero cross point (Zero8) is extracted by pitch. It becomes data.

Therefore, in this embodiment, the time interval between the zero-cross points that occurs immediately after the maximum value is detected (t ₁ : that is, Zero ₁ → Zero 5).
And the time interval between zero-cross points (t ₂ :: Zero 4 → Zero 8) that occurs immediately after the minimum value is detected, frequency change processing can be performed twice in one cycle, and it can respond to the frequency change of the input signal. It has become.

By the way, in the present embodiment, FIG.
Even if the waveform shown in Fig. 12 is input by the flag function of the flow in Fig. 11, the zero-cross points Zero12, Zero in the diagram
14 will be ignored.

In other words, the zero-crossing point as an interrupt signal INT _a Zero1
2, even if the signal corresponding to Zero14 comes in, the flag is
One set is made at the arrival of the zero-cross points Zero11 and Zero13 (step B3). Therefore, the jersey at step B3 becomes NO and no cycle calculation is performed. In this way, in this embodiment, even if the zero-cross point is detected a plurality of times consecutively after the maximum value is detected or the minimum value is detected by this flag, it is ignored to further remove the influence of the overtone. It is possible.

As the processing in step A5 of FIG. 8, the average value of the previously stored time count data and the time count data obtained this time is output and output, or when the data difference from the previous time is large, for example, 20% If there is a difference above, if the previous one is output, frequency stability can be achieved. In addition, if the starting point of the tone waveform is a rising waveform, the cycle calculation based on the zero-cross point detection immediately after the maximum peak point and the cycle calculation based on the zero-cross point detection immediately after the minimum peak point are set to the zero-cross point immediately after the maximum peak point. If the start point of the tone waveform is a falling waveform, the cycle calculation may be selectively executed so that the cycle calculation is performed based on the zero-cross point immediately after the minimum peak point. In this way, the response speed at the start of sound generation is increased.

As described above, in this embodiment, the CPU 100 can execute an appropriate process as step A5 shown in FIG.
Moreover, since this process change can be performed by simply changing the program of the CPU 100 without changing the external circuit of the CPU 100, the versatility is increased, and it is suitable for the intelligentization.

In the above embodiment, both the time interval (t ₁ ) between the zero cross points immediately after the detection of the maximum peak point and the time interval (t ₂ ) between the zero cross points immediately after the detection of the minimum peak point are obtained. It is not always necessary to calculate both, and if the circuit configuration is made up of only one, the maximum peak detection circuit 4, flip-flop 14, AND gate shown in FIG.
The circuit can be simplified because one of the set of 24 and the inverter 30 or the set of the minimum peak detection circuit 5, the flip-flop 15 and the AND gate 25 is unnecessary.

In the above embodiment, the present invention was applied to an electronic guitar, but the present invention is not necessarily limited to that.Pitch extraction is performed from a voice signal or an electric vibration signal input from a microphone or the like, Any form may be used as long as it is a system that generates an acoustic signal different from the original voice signal at the corresponding pitch or scale frequency. Specifically, the present invention can be similarly applied to those having a keyboard, for example, an electronic piano, an electronic wind instrument, and a stringed instrument, for example, an electronic version of a violin or a koto.

〔The invention's effect〕

As described in detail above, the present invention, for example, detects the frequency of a signal of a natural sound, creates an artificial sound by digital data processing of a musical sound corresponding to the frequency, and emits the artificial sound. Detect at least one of the time interval between the zero cross points immediately after the peak point (t ₁ ) and the time interval between the zero cross points immediately after the consecutive minimum peak points (t ₂ ), and process the resulting time interval appropriately. Since the pitch extraction is performed in this manner, the frequency data can be obtained more accurately and speedily, and the circuit configuration with versatility can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing the overall circuit configuration of an embodiment of the present invention,
FIG. 2 is a diagram showing the cutoff frequency of the low-pass filter in FIG. 1, and FIG. 3 is a block diagram of the maximum peak detection circuit.
FIG. 4 is a diagram showing operation waveforms of respective parts of the maximum peak detection circuit and the minimum peak detection circuit, FIG. 5 is a circuit configuration diagram showing another example of the maximum peak detection circuit, and FIG. 6 is a diagram showing the minimum peak detection circuit. Configuration diagram, FIG. 7 is a configuration diagram of a zero-cross point detection circuit,
FIG. 8 is a diagram showing the main flow chart of the CPU, FIG. 9 is a time chart showing the input waveform and the operation of each part accompanying it, and FIG. 10 is an interrupt processing flow chart at the time of detecting a zero-cross point immediately after the maximum peak point. Fig. 11, Fig. 11 is a diagram showing an interrupt processing flow chart when a zero-cross point is detected immediately after the minimum peak point, and Fig. 12 is a time chart showing another input waveform and the operation of each part accompanying it, Fig. 13 [Fig. 6] is a state diagram by detecting a zero-cross point in a conventional example. 1 ... Input terminal, 4 ... Maximum peak detection circuit, 5 ... Minimum peak detection circuit, 6 ... Zero-cross point detection circuit, 7 ...
… Counter, 8… Frequency ROM, 9… Sound source circuit, 10…
… Sound system, 14, 15 …… Flip flop, 10
0 …… CPU, 101 …… Maximum memory, 102 …… Minimum memory.

Claims (1)

(57) [Claims] 1. A maximum / minimum value detecting means for detecting a maximum value and a minimum value of a waveform of an input waveform signal, a zero-cross point detecting means for detecting a zero-cross point of the waveform, and a maximum / minimum value detecting means. Based on the detection information of the zero-cross point detection means, at least a zero-cross point immediately after detection of the maximum value (or minimum value) of the first and second waveforms and a minimum value of the first waveform ( Or a maximum value) and a zero-crossing point immediately after detection, and an input waveform signal control device comprising: a pitch extraction means for detecting a first maximum value (or minimum value). Starting from the zero cross point a immediately after, the zero cross point b immediately after detecting the first minimum value (or maximum value) and the zero cross point c immediately after detecting the second maximum value (or minimum value) Termination, ac And the zero cross point e immediately after the first maximum value (minimum value) is detected starting from the zero cross point d immediately after the first minimum value (or maximum value) is detected, and the second minimum An input waveform signal control device characterized by extracting at least one of a pitch between d and f, which terminates at a zero-cross point f immediately after a value (or maximum value) is detected.