JPH0687197B2 - Tempo display - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tempo display device used in a sound reproducing device.

2. Description of the Related Art As a device for extracting the tempo of music, there is a device related to an electronic musical instrument, particularly a keyboard.

However, this is not to extract the tempo from the music signal purely, but to detect the touch of a key on the keyboard (the moment when the player strikes the key) and extract the tempo from this information.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in an electronic musical instrument or the like, there is one that displays the tempo of the music when it is automatically played, but this also does not purely extract the tempo from the music signal, The tempo was created from the synchronized clock when playing automatically, and it was only displayed.

Further, as a device for extracting the rhythm of music, there is a device that performs extraction by looking at the sharpness of the rising slope of the amplitude of the music signal. This is for extracting only the rhythm of music and displaying it. Could not extract and display the tempo of.

SUMMARY OF THE INVENTION The present invention provides a tempo display device capable of extracting and displaying a tempo in a normal music signal, which is possible only in the performance by the electronic musical instrument and the automatic performance by the electronic musical instrument as described above.

Means for Solving the Problems In order to solve the above problems, the present invention extracts a rhythm component in a music signal input from an input terminal, and outputs a certain signal when the rhythm is extracted. Means and
The output signal of the rhythm extraction means is input, the tempo of the music is extracted by calculating the signal, and the tempo calculation means for outputting the tempo, and the tempo signal output by the tempo calculation means and the rhythm extraction means are extracted. A structure provided with a synchronization means for controlling the tempo calculation means so as to synchronize the tempo with the music by comparing and calculating the rhythm, and a display means for performing a display corresponding to the tempo signal output from the tempo calculation means. Has become.

Operation According to the present invention, with the above-described structure, first, the rhythm extracting means calculates the rising and falling slopes of the amplitude of the input signal to form a rhythm represented by a percussion instrument included in the input music signal. Is extracted, and the rhythm of music is extracted.

Next, the rhythm signal extracted by the rhythm extraction means is
By inputting to the tempo calculating means and calculating the time interval of the input signal in this tempo calculating means,
The tempo of the input music signal is extracted. The tempo calculation means starts the tempo display from the moment the rhythm is first extracted by the rhythm extraction means after the tempo is extracted.

When the tempo display is started, the rhythm signal extracted by the rhythm extraction means in the synchronization means and the tempo signal output from the tempo display means are temporally compared with each other to control the tempo calculation means, and the music and tempo Synchronous control and
The tempo is corrected so that accurate tempo display control is performed.

Further, the tempo signal output from the tempo calculation means is input to the display means, and external display corresponding to this signal is performed on the display means, and the tempo display synchronized with the music is performed.

Embodiment One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a tempo display device according to an embodiment of the present invention.

In FIG. 1, 1 is an input terminal for inputting a music signal or the like,
2 is a band pass filter that passes only the signal in a certain band, 3 and 4 are rectified input signals, then integrate the signals with different time constants, and calculate the energy of the signal within a certain time. A rectifying circuit composed of a capacitor or the like (however, the integration time constant in the rectifying circuit 4 is set larger than that in the rectifying circuit 3), 5 is an amplifying circuit for amplifying the level of the output signal of the rectifying circuit 3, 6 Is a differentiating circuit consisting of a resistor and a capacitor that detects the rising edge of the signal, 7 is the input of two signals, and the levels of those signals are compared. When one signal is larger than the other signal, a pulse is output. A comparator circuit that outputs a signal, 11 passes the first input signal,
After that, a gate circuit that does not allow the input signal to pass within a fixed time, 8 a tempo calculation circuit that extracts the tempo by calculating the time interval of the input signal, and 9 performs a comparison calculation of the two input signals. Thus, a synchronizing circuit for synchronizing the music signal with the extracted tempo, and a sounding circuit 10 for sounding with the input signal as a trigger.

A portion A surrounded by a broken line is a rhythm extraction unit that extracts a rhythm component in the input music signal.

FIG. 2 shows a signal waveform in each block of the rhythm extraction section A of FIG.

In FIG. 2, (a) is an input signal, (b) is an output signal of the bandpass filter 2 (in this case, a low-frequency signal is passed), and (c) is a rectifier circuit. 3, the signal output from the amplifier circuit 5, (d) is the output signal of the rectifier circuit 4, and (e) is the output signal of the differentiating circuit 6, and the signal of (d) is shown in a superposed manner by a broken line. Further, (f) shows the output signal of the comparison circuit 7, and (g) shows the output signal of the gate circuit 11.

The operation of this embodiment will be described below with reference to the drawings.

The signal (a) input to the input terminal 1 is input to the bandpass filter 2 and the signal (b) of only a certain band is extracted. (In this case, the case where a low-frequency signal is extracted is shown.) With this, the rhythm instrument signal in the input music signal can be emphasized. The output signal (b) of the band-pass filter 2 obtains the average energy of the input signal within a certain time, and therefore the rectifier circuits 3 and 4 having different integration time constants are used.
(The rectifier circuit 4 has a larger integration time constant.). Next, the output signal of the rectifier circuit 3 is input to the amplifier circuit 5 and amplified with a certain degree of amplification (signal (c)).
This is because the signal is attenuated in the next differentiating circuit 6, and this is compensated. (If in the differentiating circuit 6,
If the signal attenuation can be compensated, the amplifier circuit 5 is not necessary. The output signal (c) of the amplifier circuit 5 is input to the differentiating circuit 6 and the rising edge of the signal is detected (signal (e)). The signal (e) and the output signal (d) of the rectifier circuit 4 are input to the comparison circuit 7, and their amplitude levels are compared. If the signal (e) is larger than the signal (d), the pulse signal (h) is output. The signal (d) has a value proportional to the level of the signal input to the input terminal 1 and is a signal that slowly changes, and the signal (e) detects the sharp rising edge of the input signal. By comparing the signal (e) with the signal (d) as a reference, it is possible to accurately extract a signal (rhythm musical instrument sound) having a sharp rising edge in accordance with the varying level of the input signal.

Next, the output signal (f) of the comparison circuit 7 is input to the gate circuit 11, and at a certain time T, the input signal is gated and output (signal (g)). (Here, the gate is
This means that the first pulse input is passed as it is, and then the signal input during the time T from that signal is not passed. By thus providing the gate circuit, it is possible to prevent variations in the pulse signal due to signals other than the rhythm musical instrument, or slow fluctuations (beats) in the levels of noise and rhythm musical instrument signals. By the above, the rhythm component contained in the music signal which is the input signal can be accurately extracted.

Next, the output signal (g) of the gate circuit 11 is input to the tempo calculation circuit 8, and the tempo is obtained from the time interval at which the signal is input.

Here, an example of an algorithm for obtaining the tempo in the tempo calculation circuit 8 will be described with reference to the flowchart of FIG. 3 and FIG.

FIG. 3 shows one of the tempo calculation algorithms. The tempo calculation circuit 8 within a certain time (in this case, 2 seconds) has a process of obtaining the minimum value of the time intervals of the input signals. A method of repeating the number of times (in this case, four times), comparing each minimum value obtained by this processing, and if there is a number of equal values (two in this case), the value is used as the tempo Is.

In FIG. 3, TMPMIN is the minimum value of the measured time intervals T of the input signal, MAX is the maximum value T of the time intervals T of the input signal, which is the time interval of the input signal. Value, TMIN is the minimum value that limits the value of T, and TMAX is T
The maximum value that limits the value of TIME, TIME is the time to extract one TMPMIN (in this case, 2 seconds), and COUNT is the number of times to extract TMPMIN (in this case, 4 and the initial value is 1). .),
Ti (T1, T2, T3, T4) is a buffer that stores the extracted TMPMIN.

First, the maximum possible value of T is set in TMPMIN, and the input signal pulse is waited for (steps 31, 32). When the pulse is input, T becomes "0" (step 33), time counting is started, and the time is set to T (step 34). This time counting process is repeated until the next pulse arrives (step 3
Five).

When the next pulse is input, T at that time is the time interval between the two first input signals. Next, it is checked whether the value of T is larger than TMIN and smaller than TMAX, and if not, the value of T extracted at that time is deleted, and the process returns to the process of waiting for the next pulse again ( Steps 36-4
0). By this processing, it is possible to prevent extraction of an abnormally fast tempo or an abnormally slow tempo. The value of T is
If included between TMIN and TMAX, the T and TMPM
A comparison with IN is performed, and if T is smaller than TMPMIN, T is set to TMPMIN (step 39), and if not, the process proceeds to the next process. As a result, the minimum time width between the input signals is extracted.

After this, seeing the value of TIME, 2 after the above processing is started
It is checked whether seconds have passed (step 40). If 2 seconds have not passed, the above process is repeated. If 2 seconds have passed, TMPMIN is set to Ti (i is the value of COUNT) ( In step 41), the value of COUNT is checked to see if the above process has been performed four times (step 42). (here,
The value of TIME is set to 2 seconds, because the tempo of music is about 1 second, and at least 2 seconds are required to extract the tempo, so this value is set. . )
If it has not been performed four times, the value of COUNT is increased (step 43) and the process returns to the process of extracting the next TMPMIN again. If it has been performed four times, the value of COUNT is decreased (step 44) and the values of T1 to T4 are compared (step 45). Here, if there are two equal ones from T1 to T4 (for example, T1 = T2, T1 = T3, etc.), the value is determined as the tempo, and the tempo calculation processing is terminated (step 47). . At this time, if there are not two equal items, T1 is set to T2, T2 is set to T3, T3 is set to T4, and the process returns to the above process for obtaining the next TMPMIN (step 46). Here, when comparing T1 to T4, the difference between the respective values is Δt.
In such a case, Δt = 0 is actually rare.
Therefore, Δt is not considered to be equal only when Δt = 0.
If they fall within a percentage of each value, they are considered equal. Further, in this case, when it is considered that the values are equal to each other, an accurate value can be obtained by setting the average value of the two values as the original value.

Although the tempo is extracted by the above processing, this algorithm is based on the idea that the minimum value of the rhythm width of a rhythm in music is the tempo. This concept will be described with reference to FIG.

Figure 4 shows the rhythmic part of a piece of music,
The rhythm is composed of quarter notes and eighth notes. Further, it is assumed that one bar is 2 seconds. Assuming that the rhythm shown in FIG. 4 has been accurately extracted in the rhythm extraction section A, the values extracted as T at the first bar are t1, t2, t3, t4, t5, t6, and TMPMIN As a result, the extracted value is t5. Also, this value is a value of eighth note. Similarly, in the second measure, TMPMIN is t7, the third
At the bar, t8, at the fourth bar, t9, T1 = t5, T2 = t
7, T3 = t8, T4 = t9. In addition, the value is the value of an eighth note in both cases.

Therefore, in this case, the value of the eighth note is determined as the tempo. Actually, the value of the quarter note is the tempo of this music (rhythm), but since the eighth note is twice as fast as the quarter note, it does not matter even if it is the tempo (shown in the score. The tempo that is being felt and the tempo that humans actually feel are often different, because some people may take the tempo faster or slower).

Although the rhythm shown in FIG. 4 is very simple, it can be understood that the minimum unit of the rhythm of music can be extracted by using the above algorithm. That is, the minimum unit that constitutes the rhythm of the input music is 4
If it is a quarter note, a quarter note is used. If the minimum unit of the rhythm is an eighth note, the eighth note is the minimum unit of rhythm.
If it is a 16th note, the 16th note is extracted as the tempo value. From the above, it is understood that the above algorithm can extract the tempo of music (actually, it may be a multiple of 2 on the score).

Next, when the tempo is calculated in the tempo calculation circuit 8, the tempo calculation circuit 8 then outputs a pulse signal (tempo signal) from the moment when the input signal comes from the gate circuit 11 for the first time.
Is output to the synchronizing circuit 9 and the tone generating circuit 10. Pronunciation circuit 10
In, sound is produced in response to the input signal. Here, the timing of starting sound generation (outputting the tempo signal from the tempo calculation circuit 8) becomes a problem, but as described above, the extracted tempo is the minimum unit of the rhythm of the music that is the input signal. Therefore, if the tempo display is started from the moment the rhythm is extracted, the music can always be synchronized at that time. (When the length of the quarter note is set to 1, the extracted tempo is the minimum unit of the rhythm of the music, and it is a multiple of 2, so that the actual tempo is It is obvious that the output signal from the gate circuit 11 and the tempo calculation circuit 8 is input to the synchronizing circuit 9 and the deviation of these signals is monitored. By controlling, the tempo and music are synchronized and the tempo is corrected.

Here, the necessity of synchronization and tempo correction will be described. It is natural to think that the rhythm and tempo of music played by human beings are not constant but change momentarily, and conversely, it is difficult to perform the tempo constant. This can be seen from the fact that the automatic performance of electronic musical instruments and the performance of robots are mechanical and constant, which is not interesting.

Moreover, in actual music, the tempo is often changed intentionally. Furthermore, it can be said that the rhythm and tempo are not constant due to the influence of time fluctuations that occur during reproduction due to wow and flutter of a tape recorder or a reproducing device such as a record player. Therefore, it becomes necessary to synchronize with the temporal change of music and to correct the tempo itself. On the contrary, without this synchronization and tempo correction function, the tempo itself will be maintained, but the tempo will be out of sync with the music.

Regarding the method of synchronizing and the method of correcting the tempo, Part 5
It will be described with reference to the drawings.

In FIGS. 5 (a) and 5 (b), the waveform of the tempo is shown at the top, T is one tempo, and is shown as a rectangular wave that becomes a high level for 1 / 2T, and the rhythm is shown at the bottom with a certain width. The pulse waveform is shown, with the solid line showing the state before correction and the broken line showing the state after correction.

Further, FIG. 5 (a) shows a case where the tempo is ahead of the rhythm of music, and FIG. 5 (b) shows a case where it is behind. In both cases, the deviation between the tempo and the rhythm is X.

First, when the rhythm signal is high when the tempo signal is at a high level, it is considered that the tempo is advanced (state as shown in FIG. 5A), and the tempo signal becomes high. From the moment, the time X when the rhythm signal becomes high is measured, and when the value of the X is smaller than a certain value, the value X is added to the time 1 / 2T when the tempo signal is high level. As a result, the time of the entire tempo becomes T + X, and the deviation X between the tempo and the rhythm can be absorbed when the next tempo signal becomes high. (State of broken line in FIG. 5 (a)).

Also, when the tempo signal is at the low level,
When the rhythm signal becomes high, it is considered that the tempo is delayed (state as shown in FIG. 5 (b)), and from the moment the rhythm signal becomes high, the time X at which the tempo signal becomes high is measured, When the value of X is smaller than a certain value, the value X is subtracted during 1 / 2T when the tempo signal is at the high level. As a result, the time of the entire tempo becomes T−X, and the deviation X between the tempo and the rhythm can be absorbed when the next tempo signal becomes high (state of broken line in FIG. 5B).
In the above process, the limitation on X is that the value of X is
This is because it is processed according to whether it is the actual shift on the score or the shift that has occurred due to the loss of synchronization.

By sequentially repeating the above processing, the tempo and the music can be synchronized.

The value X that is added to or subtracted from the tempo T is 1 / 2X
By setting it to 1 / 4X or 1 / 4X, you can prevent sudden changes in tempo, which is even more effective.

In addition, the rhythm extraction section is configured to perform the above process when the tempo is advanced or the tempo is delayed, not when the above processes are sequentially performed. , It is possible to prevent a malfunction when a wrong rhythm is extracted. This is because the probability of repeatedly performing erroneous rhythm extraction is small.

The method of correcting the tempo is to extract the X (calculated separately for the case where the tempo is advanced and for the case where it is delayed) several times, and add the average value of these to the tempo (or Method). In other words, if the tempo is advanced, T = T + (X1 + X2 + ~ + XN) / N (X1, X2-XN are the respective values of X), and if the tempo is delayed, T = T- (X1 + X2 + ~ + XN) / N is calculated. By repeating this process, the deviation between the tempo and the actual rhythm can be sequentially corrected, so that a more accurate tempo can be obtained.

In addition, there may be no rhythm (musical instrument signal extracting the rhythm) in the music between music pieces, and in such a case, it is impossible to synchronize with the music only by the above processing. Become. In particular, if the rhythm does not exist for a long time, the synchronization may be lost.

To prevent this, the synchronization circuit 9 also performs the following processing.

When the above-mentioned deviation X between the tempo signal and the rhythm signal is larger than a certain value, it is considered that the synchronization of the tempo and the rhythm of the music is out of sync, the tempo calculation circuit 8 is controlled, and the output of the tempo signal is stopped. Then, the tempo calculation circuit 8
After that, the pulse signal is controlled to be output to the synchronizing circuit 9 and the tone generating circuit 10 again from the moment when the input signal comes from the gate circuit for the first time. By doing so, even if the tempos of the songs are out of sync, it is possible to instantly correct the out-of-sync.

It should be noted that in this processing, when the value of X is larger than a certain value,
If the rhythm extraction section extracts the wrong rhythm, the rhythm extraction section can prevent a malfunction when the rhythm extraction section performs the wakeup several times. This is because the probability of repeatedly performing erroneous rhythm extraction is small.

By the processing of the synchronization circuit 9 as described above, the tempo calculation circuit 8 is controlled, and the tempo can be synchronized and the tempo can be corrected.

As described above, according to the present embodiment, the tempo of a normal music signal can be accurately extracted, and the tempo display synchronized with music can be displayed.

It should be noted that the tempo extraction algorithm of the tempo calculation circuit 8 in the present embodiment is an embodiment, and the tempo calculation circuit 8
In the case where there are a number of input signals having the same value within a certain time, the tempo can be accurately extracted by using an algorithm that uses the value as the tempo. This algorithm is based on the fact that the minimum unit of rhythm of music can be regarded as the tempo as described above, but the minimum unit of rhythm tends to appear frequently in music. On the contrary, the rhythm that often appears in music (the rhythm here means the time interval between rhythm signals) is the center of the rhythm of the music, so this is called the tempo. Can be considered

Further, when signals having the same time interval of the inputted signals are continuously inputted a certain number of times, the tempo can be accurately extracted even by using an algorithm which uses the value as the tempo. This is also based on the same principle as the algorithm described above.

Furthermore, the effect of tempo extraction can be improved by combining the three algorithms described above.

Further, the sounding circuit described in the present embodiment is configured to automatically change the sounding level in proportion to the amplitude level of the music signal input to the input terminal 1,
It becomes possible to display the tempo more in harmony with music.

Advantageous Effects of Invention The present invention extracts a rhythm component in a music signal input from an input terminal, inputs a rhythm extraction means for outputting a certain signal at the time of extracting a rhythm, and an output signal of the rhythm extraction means, The tempo of music is extracted by calculating the signal, and a tempo calculation means for outputting a certain signal in accordance with the tempo is compared with the tempo signal output by the tempo calculation means and the rhythm extracted by the rhythm extraction means. By providing a synchronization means for controlling the tempo calculation means so as to synchronize the tempo with the music by calculation and a display means for displaying the tempo signal output from the tempo calculation means The tempo in the signal can be extracted and displayed in sync with the music.

[Brief description of drawings]

FIG. 1 is a block diagram of a tempo display device according to an embodiment of the present invention, FIG. 2 is a waveform diagram of signals corresponding to each block of a rhythm extraction section of the tempo display device, and FIG. FIG. 4 is a flowchart showing the tempo calculation algorithm, FIG. 4 is a principle diagram showing the tempo calculation algorithm of the tempo calculation circuit, and FIG. 5 is a waveform diagram showing the principle of synchronization in the synchronization circuit. 1 ... Input terminal, 2 ... Band pass filter, 3,4 ... Rectifier circuit, 5 ... Amplification circuit, 6 ... Differentiation circuit, 7 ... Comparison circuit, 8 ... Tempo operation circuit, 9 ... Synchronization Circuit, 10 ...
Sounding circuit, 11 ... Gate circuit, A ... Rhythm extraction section.

Claims (14)

[Claims] 1. Rhythm extracting means for extracting a rhythm component from a music signal input from an input terminal and outputting a predetermined signal at the time of extracting the rhythm component; and an input signal of the rhythm extracting means. , A tempo calculation means for extracting the tempo of music by calculating the signal and outputting a tempo signal corresponding to the tempo, a tempo signal output by the tempo calculation means, and a rhythm extracted by the rhythm extraction means. A tempo including a synchronization means for controlling the tempo calculation means so as to synchronize the tempo with music by performing a comparison calculation, and a display means for displaying the tempo signal output from the tempo calculation means. Display device. 2. The rhythm extracting means extracts a signal of a musical instrument mainly responsible for a rhythm part such as a percussion instrument in a music signal by calculating a rising or falling slope of an amplitude of an input signal. The tempo display device according to claim 1. 3. The tempo calculation means monitors the time interval of an input signal for a certain period of time, and detects the minimum time interval within that time as the tempo of the music. The tempo display device according to item 1. 4. The tempo calculation means monitors the time interval of an input signal for a certain period of time, and detects the time interval as the tempo of the music when the same time interval is continuously present a certain number of times. Claim 1 characterized by
The tempo display device according to the item. 5. The tempo calculation means monitors a time interval of an input signal for a certain fixed time, and if the same time interval exists a certain number of times within the fixed time, the time interval is detected as the tempo of the music. The tempo display device according to claim 1, wherein: 6. The time interval used by the tempo calculation means when detecting the tempo, by ignoring the time interval of the input signal when the time interval is smaller than a certain time and when the time interval is larger than the certain time. The tempo display device according to claim 1, characterized in that the tempo display is held within a certain time. 7. The tempo display according to claim 1, wherein the tempo calculation means starts the tempo display from the moment when the rhythm is first extracted by the rhythm extraction means after detecting the tempo. apparatus. 8. The synchronizing means obtains the difference between the time when the tempo signal is output from the tempo calculating means and the time when the rhythm is first extracted by the rhythm extracting means after the tempo signal is output. When the time is smaller than a certain time, the tempo calculation means is controlled so as to synchronize the music signal with the tempo by adding the difference to the tempo obtained by the tempo extraction means.
The tempo display device according to the item. 9. The synchronizing means calculates the difference between the time when the rhythm is extracted by the rhythm extracting means and the time when the tempo signal is output from the tempo calculating means for the first time after the rhythm is extracted, and there is the difference. When the time is smaller than the time, the tempo calculation means is controlled so as to synchronize the music signal and the tempo by subtracting the difference from the tempo calculated by the tempo calculation means. The tempo display device according to item 1. 10. The synchronizing means obtains a difference between the time when the tempo signal is output from the tempo calculating means and the time when the rhythm is first extracted by the rhythm extracting means after the tempo signal is output, and the difference is obtained. If the time is smaller than a certain time, the average for the number of times of the difference is calculated, and the tempo calculation unit is controlled to correct the tempo by adding the average value to the tempo calculated by the tempo calculation unit. The tempo display device according to claim 1, wherein 11. The synchronizing means comprises: after the rhythm is extracted by the rhythm extracting means and after the rhythm is extracted,
The difference from the time when the tempo signal was first output from the tempo calculator was calculated, and when the difference was smaller than the time, the average for the number of times of the difference was calculated, and the average value was calculated by the tempo calculator. The tempo display device according to claim 1, wherein the tempo calculation means is controlled so as to correct the tempo by drawing the tempo. 12. The synchronizing means comprises a difference between a time when the tempo signal is output from the tempo calculating means and a time when the rhythm is first extracted by the rhythm extracting means after the tempo signal is output, and the rhythm extraction. The time difference between the time when the rhythm is extracted by the means and the time when the tempo signal is output from the tempo calculation means for the first time after the rhythm has been extracted is calculated. If the tempo display is stopped, the tempo display is stopped, and then the tempo calculation means is controlled so as to restart the tempo display from the moment the rhythm is extracted by the rhythm extraction means for the first time. The tempo display device according to claim 1. 13. A display according to claim 1, wherein the display is performed by sound, light, vibration, or an image.
The tempo display device according to the item. 14. The tempo display device according to claim 1, wherein the display means controls the display level in accordance with the amplitude level of the music signal input to the input terminal.