JP2007052394A - Tempo detector, code name detector and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tempo detector capable of detecting a section for detecting an average tempo and an accurate beat position of the entire melody, a rhythm of the melody and a first beat position of the melody from signals of performance with a fluctuating tempo. <P>SOLUTION: A tempo detector comprises: an input part 1 for inputting a sound signal; a scale sound level detecting part 2 for determining a sound level of each scale at every prescribed time interval by performing an FFT operation on the sound signal; a beat detecting part 3 for detecting an average beat interval and the position of each beat by summing up increments in sound level for each scale note at prescribed time intervals and determining the total increment in level indicative of a degree of variation in all sounds at the above time intervals; and a bar detecting part 4 for calculating the average sound level of each scale note for every beat, and summing up an increment in average level for all scale notes for every beat and thereby determining a value indicative of a degree of variation in all sounds for every beat, and detecting the rhythm and the position of a bar line position from the value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tempo detection device, a code name detection device, and a program.

  In a conventional automatic accompaniment apparatus, a user sets a tempo for performance in advance, and automatic performance is performed according to this tempo. Therefore, when a performer performs in accordance with the automatic accompaniment, it is necessary to perform in accordance with the tempo of the automatic accompaniment, which is very difficult especially for beginners of performance. Therefore, an automatic accompaniment apparatus that automatically detects the tempo from the performance sound of the performer and performs automatic accompaniment in accordance with this tempo has been desired.

  Further, in a music transcription device that detects chord names and note information from a sound source such as a music CD on which performance sounds are recorded, the function of detecting the tempo from the performance sounds is indispensable as the previous process.

  As such a tempo detection device, for example, there is a tempo detection device disclosed in Patent Document 1 below.

  The tempo detection device of Patent Document 1 is based on performance information representing the pitch, volume, and sounding timing of each performance sound input from the outside, and an accent caused by the volume and music elements other than the volume. Is a tempo detection device comprising a tempo changing means for detecting an accent caused by a tempo, predicting a change in the tempo of performance information based on both of these accents, and causing the internally generated tempo to follow the predicted tempo. Therefore, note information must be detected in order to detect the tempo, and this can be easily obtained when played by a musical instrument having a function of outputting note information such as MIDI. When the performance is performed with a general musical instrument that does not have a musical notation, it is necessary to have a music transcription technique of detecting note information from the performance sound.

  As an example of a tempo detection device that receives a performance sound of a general musical instrument that does not have a function of outputting note information such as MIDI, that is, an acoustic signal, there is a configuration shown in Patent Document 2 below.

  In the configuration shown in Patent Document 2, the input acoustic signal is digitally filtered in a time-sharing manner to extract the scale, the scale sound generation period is detected based on the detected envelope value of the scale sound, The tempo is detected based on the generation period of the scale sound and the time signature of the input acoustic signal designated in advance. Since this tempo detection device does not detect note information, it can also be used as preprocessing for a music transcription device that detects chord names and note information.

  As a similar tempo detection device, there is Non-Patent Document 1 described later.

  On the other hand, chords are a very important element in popular music, and when playing music of such a genre in a small band, do not use the score on which the individual notes to be played are written, It is common to use a score written only with a melody and chord progression called a chord score or lead sheet. Therefore, it is necessary to record the chord progression of a song in order to perform a song such as a commercial CD in a band, but this work can only be performed by an expert with special musical knowledge. It was impossible. Therefore, there has been a demand for an automatic music transcription device that detects a chord name from a music acoustic signal using a commercially available personal computer or the like.

  As an apparatus for detecting a chord from such a music sound signal, there is a configuration of Patent Document 3 below. In the configuration of this document, a fundamental frequency candidate is extracted from the calculation result of the power spectrum, and what is considered to be a harmonic is removed from the fundamental frequency candidate to detect note information, and a chord is detected from this note information. .

  However, in the configuration shown in Patent Document 3, the operation of removing the above harmonics includes the difference in the harmonic structure depending on the type of the instrument, the difference in how the harmonics are generated due to the keystroke strength, the power change of the harmonic over time, and the harmonics of the same frequency. It is known that it is very difficult due to the problem of phase interference between sounds possessed as components. That is, it is not considered that the step of detecting the note information functions correctly with a sound source such as a general music CD in which many musical instruments and singing are mixed.

Similarly, as a device for detecting a chord from a music acoustic signal, there is a configuration of Patent Document 4 described later. In the configuration of Patent Document 4, digital filtering processing with different characteristics is performed on input acoustic signals in a time-sharing manner to detect the level of each scale sound, and the same scale relation within the octave is detected among the detected levels. The chords are detected by using a predetermined number having a large value among the integrated levels by integrating certain levels. Since this method does not detect individual note information included in the acoustic signal, the problem described in Patent Document 3 does not occur.
Japanese Patent No. 3231482 Japanese Patent No. 3127406 Real-time beat tracking system by Masataka Goto (Kyoritsu Publishing Computer Science magazine bit Vol.28 No.3 1996) Japanese Patent No. 28768861 Japanese Patent No. 3156299

  However, in the tempo device disclosed in Patent Document 2, the part that detects the scale sound generation period from the envelope of the scale sound detects the maximum value of the envelope value, and detects the part that exceeds a predetermined ratio with respect to the maximum value. It is the structure performed by doing. However, if the predetermined ratio is uniquely determined in this way, the sound generation timing may not be detected depending on the volume level, which may have a great influence on the final tempo determination. I have it.

  The beat tracking system disclosed in Non-Patent Document 1 also extracts the rising component of the sound from the frequency spectrum obtained by performing FFT on the acoustic signal. Whether it can be done will have a big impact on the final tempo decision.

  What is common to these two tempo detection devices is which scale sound or frequency is used to detect the rising of this sound. If there is a song that has a fine rhythm in the scale sound (frequency) that happens to be detected, there is a problem that a fast tempo is detected by mistake.

  On the other hand, in the configuration shown in Patent Document 4 for detecting a chord from a music acoustic signal, the levels of the scales are integrated for each of the 12 pitch names having the same scale relationship within the octave. A plurality of chords composed of the same constituent sound, for example, Am7 composed of la, de, mi and so, and C6 composed of de, mi, so and la cannot be discriminated.

  Further, the chord detection device of Patent Document 4 does not have a tempo or measure detection function, and the chord detection is performed at predetermined timings. In other words, it is assumed that the tempo of the song is set in advance and the performance is performed in accordance with a metronome that produces the tempo. The chord name can be detected, but the tempo and measure are not detected, so it cannot be output in the form of a score in which the chord name of each measure such as a chord score or lead sheet is written. .

  Even if the tempo of the song is given, the tempo of the performance recorded on the music CD is generally not constant and slightly fluctuates, so that the chord for each measure cannot be detected correctly.

  Also, it is very difficult for beginners to perform at an accurate tempo that matches a metronome that is pronounced at a constant tempo, and generally the performance tempo usually fluctuates. .

  Furthermore, in the configuration of Patent Document 4, a configuration in which digital filtering processing with different characteristics is performed in a time-division manner on the input acoustic signal is adopted. The frequency resolution is bad. However, it is possible to obtain a certain level of frequency resolution even at low frequencies by down-sampling the input acoustic signal and performing FFT, and the digital filtering process requires an envelope extraction unit to determine the level of the filter output signal On the other hand, in FFT, the power itself after the FFT represents the level at each frequency, so that is not necessary, and the frequency resolution can be selected by appropriately selecting the parameters of the number of FFT points and the shift amount. And the time resolution can be set freely.

  The present invention was devised in view of the above-described problems. From an acoustic signal of a performance performed by a human to change the tempo, the average tempo of the entire song, the exact beat position, and the song It is intended to provide a tempo detection device capable of detecting the time signature and the position of the first beat.

  Further, another configuration of the present invention is that a chord name (chord name) can be obtained from a music acoustic signal (audio signal) in which a plurality of instrument sounds such as a music CD are mixed, even if it is not an expert having special musical knowledge. It is an object of the present invention to provide a code name detection device capable of detecting the above.

  More specifically, it is an object of the present invention to provide a chord name detection device that can determine chords from the overall sound without detecting individual note information for an input acoustic signal.

  In addition, a chord that can be detected even with the same chord and can detect chords for each measure even if the performance tempo fluctuates or, on the other hand, a sound source that intentionally fluctuates the tempo An object is to provide a name detection device.

  As described above, in the configuration of the present invention, processing that requires time resolution of beat detection with the simple configuration only (same as the configuration of the tempo detection device) and processing that requires frequency resolution of chord detection (the tempo detection device described above) It is an object of the present invention to provide a chord name detection apparatus capable of simultaneously performing a chord detection based on the above configuration.

  In addition, a computer program for tempo detection and code name detection that can implement these devices on a computer is also provided.

Therefore, the tempo detection device according to the present invention is
An input means for inputting an acoustic signal;
A scale sound level detection means for performing an FFT operation at a predetermined time interval from an input acoustic signal and obtaining a level of each scale sound for each predetermined time;
The increment value of each scale sound level for each predetermined time is summed for all the scale sounds to obtain a total of level increment values indicating the degree of change in the overall sound for each predetermined time. Beat detection means for detecting the average beat interval and the position of each beat from the sum of the incremental values of the level indicating the degree of change in the overall sound for each,
The average value of the scale level for each beat is calculated, and the increment value of the average level of each scale sound for each beat is added for all the scale sounds to indicate the degree of change in the overall sound for each beat. The basic feature is to have a bar detection means for detecting a time signature and a bar line position from a value indicating the degree of change in the overall sound for each beat.

  According to the above configuration, the scale level for each predetermined time is obtained from the acoustic signal input to the input means by the scale level detecting means, and the beat detection means determines the scale sound for each predetermined time. The level increment values are summed for all scales to obtain the total level increment value indicating the degree of change in the overall sound for each predetermined time, and the beat detection means also performs the overall sound for this predetermined time. The average beat interval (that is, tempo) and the position of each beat are detected from the sum of the level increments indicating the degree of change in the level, and then the measure detection means measures the tone of each scale note for each beat. The average value of the level is calculated, and the increment value of the average level of each scale sound for each beat is summed up for all the scale sounds, and the above value indicating the degree of change in the overall sound for each beat is obtained, and for each beat. all From a value that indicates the degree of change in tone, thereby detecting the beat and measure line position (first beat position).

  That is, the level of each scale sound for each predetermined time is obtained from the input sound signal, and the average beat (beat) interval (that is, tempo) and each beat are determined from the change in the level of each scale sound for each predetermined time. Next, the time signature and bar line position (position of the first beat) are detected from the change in the level of each scale tone for each beat.

The configuration of the code name detection device is
An input means for inputting an acoustic signal;
First scale sound level detection means for performing FFT calculation using a parameter suitable for beat detection at predetermined time intervals from the input acoustic signal, and obtaining the level of each scale sound for each predetermined time;
The increment value of each scale sound level for each predetermined time is summed for all the scale sounds to obtain a total of level increment values indicating the degree of change in the overall sound for each predetermined time. Beat detection means for detecting the average beat interval and the position of each beat from the sum of level increments indicating the degree of change in the overall sound for each,
The average value of the scale level for each beat is calculated, and the increment value of the average level of each scale sound for each beat is added for all the scale sounds to indicate the degree of change in the overall sound for each beat. A bar detecting means for obtaining a value and detecting a time signature and a bar line position from a value indicating a change degree of the whole sound for each beat;
From the input acoustic signal, an FFT operation is performed using a parameter suitable for chord detection at a predetermined time interval different from that at the time of the previous beat detection, and the level of each scale sound for each predetermined time is calculated. Second scale level detection means to be obtained;
Bass sound detection means for detecting a bass sound from the level of the low-frequency scale sound in each measure out of the detected scale levels,
It has a chord name determining means for determining the chord name of each measure from the detected bass sound and the level of each scale sound.

  In the bass sound detecting means, when a plurality of bass sounds are detected in a measure, the chord name determining means divides the measure into several chord detection ranges according to the bass sound detection result. The chord name in each chord detection range is determined from the base sound and the level of each scale sound in each chord detection range.

  According to the above configuration, the first acoustic scale level detection means first performs an FFT operation with a parameter suitable for beat detection on the input sound signal input from the input means at a predetermined time interval. The level of each scale sound for each time is obtained, and the beat detection means detects the average beat interval and the position of each beat from the change in the level of each scale sound for each predetermined time. Next, the measure and the bar line position are detected from the change in the level of each scale sound for each beat by the measure detecting means. Furthermore, the chord name detection apparatus according to the present invention is suitable for chord detection at a predetermined time interval different from the time of the previous beat detection with respect to the input acoustic signal by the second scale sound level detection means. An FFT operation is performed with the parameters, thereby obtaining the level of each scale sound for each predetermined time. The bass sound detecting means detects the bass sound of each measure from the scale sound level on the low frequency side, and the chord name determining means detects the bass sound and the level of each scale sound. The chord name of each measure will be determined from

  In addition, as described above, when a plurality of bass sounds are detected in the measure by the bass sound detecting means, the chord name determining means determines that the measure is divided into several chord detection ranges according to the bass sound detection result. The chord name in each chord detection range is determined from the bass sound and the level of each tone in the chord detection range.

  Further, in order to cause a computer to execute the configuration according to claim 1, the configuration according to claim 9 defines a program itself that can be executed by the computer. In other words, as a configuration for solving the above-described problems, the above-described means is realized by using the configuration of a computer, and is a program that can be read and executed by the computer. In this case, the computer may include a general-purpose computer configuration including the configuration of the central processing unit, or may include a dedicated machine directed to a specific process, and the configuration of the central processing unit. If it accompanies, there will be no limitation in particular.

  When a program for realizing each of the above means is read by the computer, the same function realizing means as the function realizing means defined in claim 1 is achieved.

A more specific configuration of claim 9 is:
Computer
An input means for inputting an acoustic signal;
A scale sound level detection means for performing an FFT operation at a predetermined time interval from an input acoustic signal and obtaining a level of each scale sound for each predetermined time;
The increment value of each scale sound level for each predetermined time is summed for all the scale sounds to obtain a total of level increment values indicating the degree of change in the overall sound for each predetermined time. Beat detection means for detecting the average beat interval and the position of each beat from the sum of the incremental values of the level indicating the degree of change in the overall sound for each,
The average value of the scale level for each beat is calculated, and the increment value of the average level of each scale sound for each beat is added for all the scale sounds to indicate the degree of change in the overall sound for each beat. A program for detecting a tempo, characterized in that a value is obtained and functioned as a bar detecting means for detecting a time signature and a bar line position from a value indicating the degree of change in the overall sound for each beat.

  Further, in order to cause a computer to execute the configuration according to claim 7, the configuration according to claim 10 defines a program itself that can be executed by the computer. That is, when a program for causing a computer to realize each of the above means is read out by the computer, function realizing means similar to the function realizing means defined in claim 7 are achieved.

A more specific configuration of claim 10 is:
Computer
An input means for inputting an acoustic signal;
First scale sound level detection means for performing FFT calculation using a parameter suitable for beat detection at predetermined time intervals from the input acoustic signal, and obtaining the level of each scale sound for each predetermined time;
The increment value of each scale sound level for each predetermined time is summed for all the scale sounds to obtain a total of level increment values indicating the degree of change in the overall sound for each predetermined time. Beat detection means for detecting the average beat interval and the position of each beat from the sum of the incremental values of the level indicating the degree of change in the overall sound for each,
The average value of the scale level for each beat is calculated, and the increment value of the average level of each scale sound for each beat is added for all the scale sounds to indicate the degree of change in the overall sound for each beat. A bar detecting means for obtaining a value and detecting a time signature and a bar line position from a value indicating a change degree of the whole sound for each beat;
From the input acoustic signal, an FFT operation is performed using a parameter suitable for chord detection at a predetermined time interval different from that at the time of the previous beat detection, and the level of each scale sound for each predetermined time is calculated. Second scale level detection means to be obtained;
Bass sound detection means for detecting a bass sound from the level of the low-frequency scale sound in each measure out of the detected scale levels,
A chord name detection program that functions as chord name determining means for determining the chord name of each measure from the detected bass sound and the level of each scale sound.

  With the program configuration as described above, by using this program using the existing hardware resources, each device of the present invention as a new application can be easily realized with the existing hardware. Become.

  In the aspect of this program, it becomes possible to easily use, distribute, and sell it using communication or the like. In addition, by using this program using existing hardware resources, the apparatus of the present invention as a new application can be easily executed with the existing hardware.

  It should be noted that some of the functions realizing means according to claims 9 and 10 may be functions built into a computer (functions built into the computer in hardware or operating functions built into the computer). It may be a function realized by a system or other application program), and the program may include an instruction for calling or linking a function achieved by the computer.

  This is because part of each function realization means defined in claims 1 and 7 is substituted for part of the function achieved by, for example, an operating system, and the program or module for realizing the function is directly Although it does not exist, if a part of the function of the operating system that achieves these functions is called or linked, the configuration is substantially the same.

  According to the tempo detection device according to claims 1 to 6 of the present invention and the program according to claim 9, the average tempo of the entire song and the accurate tempo are accurately obtained from the sound signal of the performance of the tempo performed by a human. An excellent effect can be obtained that the position of the beat (beat), the time signature of the song, and the position of the first beat can be detected.

  Further, according to the chord name detection apparatus according to claim 7 and claim 8 and the program according to claim 10, a plurality of musical instrument sounds such as music CDs are mixed even if not an expert having special musical knowledge. It is possible to detect a chord name (chord name) from the entire sound without detecting individual note information for an input music sound signal (audio signal).

  Furthermore, according to this configuration, even if the constituent sound is the same chord, even if the tempo of the performance has fluctuated, or conversely the sound source that is performing intentionally fluctuating the tempo, the chord for each measure Can be detected.

  In particular, in the latter configuration of the code name detection device according to claim 7 and claim 8 and the program according to claim 10, processing that requires time resolution of beat detection with only a simple configuration (the same as the configuration of the tempo detection device). ) And processing that requires a frequency resolution of chord detection (configuration that can further detect chords based on the configuration of the tempo detection device) can be performed simultaneously.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall block diagram of a tempo detection apparatus according to the present invention. According to the figure, the configuration of the tempo detection device includes an input unit 1 that inputs an acoustic signal, and performs an FFT operation at a predetermined time interval from the input acoustic signal, and each scale sound for each predetermined time. A level indicating the degree of change in the overall sound per predetermined time by summing up the increment value of the level of each scale sound per predetermined time for all scale sounds A beat detector 3 for detecting an average beat interval and the position of each beat from the sum of the incremental values of the level indicating the degree of change of the entire sound for each predetermined time, A value that indicates the degree of change in the overall sound for each beat by calculating the average value of the level of each scale sound for each beat, and adding up the increments of the average level of each scale sound for each beat for all scale sounds. Change the overall sound for each beat From the value indicating the fit, and a bar detection unit 4 that detects the time signature and bar line position.

  The input unit 1 for inputting a music sound signal is a part for inputting a music sound signal to be subjected to tempo detection. An analog signal input from a device such as a microphone may be converted into a digital signal by an A / D converter (not shown). In the case of digitized music data such as a music CD, it is directly taken in as a file ( Ripping), it may be specified and opened. When the input digital signal is stereo, it is converted to monaural in order to simplify subsequent processing.

  This digital signal is input to the scale sound level detector 2. This scale sound level detection unit is composed of each unit shown in FIG.

  Among them, the waveform preprocessing unit 20 is configured to downsample the sound signal from the input unit 1 of the music sound signal to a sampling frequency suitable for future processing.

  The downsampling rate is determined by the range of the instrument used for beat detection. In other words, in order to reflect the performance sound of high-frequency rhythm instruments such as cymbals and hi-hats in beat detection, it is necessary to set the sampling frequency after down-sampling to a high frequency, but bass sounds, bass drums, snare drums, etc. When beat detection is mainly performed from instrument sounds and middle instrument sounds, the sampling frequency after downsampling need not be so high.

  For example, when the highest sound to be detected is A6 (C4 is in the middle), the basic frequency of A6 is about 1760 Hz (when A4 = 440 Hz), so the sampling frequency after downsampling is a Nyquist frequency of 1760 Hz or higher. It may be 3520 Hz or higher. From this, the downsampling rate may be about 1/12 when the original sampling frequency is 44.1 kHz (music CD). At this time, the sampling frequency after downsampling is 3675 Hz.

  In the downsampling process, data is skipped after passing through a low-pass filter that cuts off components above the Nyquist frequency (1837.5 Hz in this example), which is usually half the sampling frequency after downsampling (now In this example, 11 out of 12 waveform samples are discarded).

  The purpose of downsampling in this way is to reduce the FFT computation time by lowering the number of FFT points necessary to obtain the same frequency resolution in the subsequent FFT computation.

  When a sound source has already been sampled at a fixed sampling frequency, such as a music CD, such downsampling is necessary. However, the music acoustic signal input unit 1 is input from a device such as a microphone. When an analog signal is converted into a digital signal by an A / D converter, the waveform pre-processing unit is naturally set by setting the sampling frequency of the A / D converter to the sampling frequency after downsampling. It can be omitted.

  When the downsampling by the waveform preprocessing unit 20 is completed in this manner, the output signal of the waveform preprocessing unit is subjected to FFT (Fast Fourier Transform) by the FFT calculation unit 21 at predetermined time intervals.

  The FFT parameters (the number of FFT points and the shift amount of the FFT window) are values suitable for beat detection. In other words, if the number of FFT points is increased in order to increase the frequency resolution, the size of the FFT window increases, and one FFT is performed from a longer time, resulting in the FFT characteristic that the time resolution decreases. (In other words, it is better to increase the time resolution at the expense of the frequency resolution when detecting beats.) There is a method in which the time resolution is not deteriorated even if the number of FFT points is increased by setting the waveform data to only a part of the window and filling the rest with 0 without using the waveform as long as the window size. However, a certain number of waveform samples is necessary to correctly detect the power on the bass side.

  Considering the above, in this embodiment, the number of FFT points is 512, the window shift is 32 samples, and no zero padding is set. When FFT calculation is performed with such settings, the time resolution is about 8.7 ms and the frequency resolution is about 7.2 Hz. It can be seen that the time resolution of about 8.7 ms is a sufficient value considering that the tune has a tempo of quarter note = 300 and the length of the 32nd note is 25 ms.

  In this way, the FFT operation is performed at predetermined time intervals, the power is calculated from the square root of the sum of the squares of the real part and the imaginary part, and the result is sent to the level detector 22.

  The level detector 22 calculates the level of each scale sound from the power spectrum calculated by the FFT calculator 21. Since the FFT only calculates the power of a frequency that is an integer multiple of the sampling frequency divided by the number of FFT points, in order to detect the level of each scale tone from this power spectrum, the following processing is performed. I do. In other words, for all the sounds (C1 to A6) for which the scale sound is calculated, the maximum power in the power spectrum corresponding to the frequency in the range of 50 cents above and below the fundamental frequency of each sound (100 cents is a semitone) is obtained. Let the power of the spectrum it has be the scale level.

  When the levels are detected for all the scale sounds, this is stored in the buffer, the waveform reading position is advanced by a predetermined time interval (32 samples in the previous example), and the FFT calculation unit 21 and the level detection unit 22 are moved to the waveform. Repeat until the end.

  As described above, the level of each scale sound for each predetermined time of the acoustic signal input to the music acoustic signal input unit 1 is stored in the buffer 23.

  Next, the configuration of the beat detection unit 3 in FIG. 1 will be described. The beat detection unit 3 is executed in the process flow as shown in FIG.

  The beat detection unit 3 uses an average beat (beat) interval (based on a change in the level of each scale sound for each predetermined time (hereinafter, this one predetermined time is referred to as one frame) output from the scale sound level detection unit. That is, the tempo) and the beat position are detected. For this purpose, first, the beat detection unit 3 sums up the level increment values of each scale sound (the sum of the level increment values from the previous frame for all the scale sounds. When the level is reduced from the previous frame Is added as 0) (step S100).

That is, when the level of the i-th scale sound at the frame time t is L _i (t), the level increment value L _addi (t) of the i-th scale sound is as shown in the following equation 1, Using L _addi (t), the sum L (t) of the level increments of each scale tone at the frame time t can be calculated by the following equation (2). Here, T is the total number of scale sounds.

  The total L (t) value represents the degree of change in sound for each frame. This value suddenly increases at the beginning of sounding, and becomes larger as more sounds begin to sound at the same time. Since music often starts to sound at the beat position, there is a high possibility that the place where this value is large is the beat position.

  As an example, FIG. 4 shows a diagram of the sum of the waveform of a part of a certain song, the level of each musical note, and the level increment value of each musical note. The upper row is the waveform, the middle is the tone level of each scale in each frame (lower is lower, the upper is higher. In this figure, the range is C1 to A6), and the lower is each scale. Shows the sum of level increments. Since the level of each scale sound in this figure is output from the scale sound level detector, the frequency resolution is about 7.2 Hz, and the level cannot be calculated for some scale sounds below G # 2. In this case, since the purpose is to detect beats, it is not a problem that the level of a part of the lower tone cannot be measured.

  As seen in the lower part of the figure, the sum of the level increments of each scale sound has a peak periodically. This regular peak position is the beat position.

  In order to obtain the beat position, the beat detector 3 first obtains the periodic peak interval, that is, the average beat interval. The average beat interval can be calculated from the autocorrelation of the total level increment value of each scale note (FIG. 3; step S102).

  When the total level increment value of each scale tone in a certain frame time t is L (t), this autocorrelation φ (τ) is calculated by the following equation (3).

ここで、Ｎは総フレーム数、τは時間遅れである。

Here, N is the total number of frames, and τ is a time delay.

  A conceptual diagram of autocorrelation calculation is shown in FIG. As shown in this figure, when the time delay τ is an integral multiple of the peak period of L (t), φ (τ) takes a large value. Therefore, if the maximum value of φ (τ) is obtained for a certain range of τ, the tempo of the music can be obtained.

  The range of τ for obtaining the autocorrelation may be changed according to the assumed tempo range of the song. For example, if the range of quarter note = 30 to 300 is calculated with a metronome symbol, the range for calculating the autocorrelation is 0.2 second to 2 seconds. The conversion formula from time (seconds) to frame is as shown in the following equation (4).

  Τ with the maximum autocorrelation φ (τ) in this range may be set as the beat interval, but τ when autocorrelation is maximum in all songs is not necessarily the beat interval, so the autocorrelation is the maximum value. It is preferable to obtain beat interval candidates from τ at a certain time (FIG. 3; step S104), and let the user determine the beat interval from these multiple candidates (FIG. 3; step S106).

When the beat interval is determined in this way (the determined beat interval is set to τ _max ), the head beat position is first determined.

A method for determining the first beat position will be described with reference to FIG. The upper part of FIG. 6 is a total L (t) of the level increment values of each tone at the frame time t, and the lower part M (t) is a function having a value at the determined beat interval τ _max . This is expressed by the following equation (5).

The cross correlation between L (t) and M (t) is calculated while shifting this function M (t) in the range of 0 to τ _max −1.

  The cross-correlation r (s) can be calculated by the following equation 6 from the characteristic of M (t).

  In this case, n may be determined appropriately according to the length of the first silent portion (n = 10 in the example of FIG. 6).

If r (s) is obtained in the range of s from 0 to τ _max −1, and s at which r (s) is maximized is obtained, this s frame is the first beat position.

  When the first beat position is determined, the subsequent beat positions are determined one by one (FIG. 3; step S108).

The method will be described with reference to FIG. Assume that the first beat is found at the position of the triangle in FIG. The second beat position is determined from a position where L (t) and M (t) are most correlated in the vicinity of the temporary beat position at a position separated by a beat interval τ _max from the first beat position. That is, when the leading beat position is b ₀ , the value of s is determined so that r (s) in the following expression is maximized. In this equation, s is a deviation from the temporary beat position, and is an integer in the range of Equation 7 below. F is a fluctuation parameter, and a value of about 0.1 is appropriate. However, a larger value may be used for a song with a large tempo fluctuation. n may be about 5.

  k is a coefficient that changes in accordance with the value of s, and has a normal distribution as shown in FIG. 8, for example.

If the value of s that maximizes r (s) is obtained, the second beat position b ₁ is calculated by the following equation (8).

  Thereafter, the third and subsequent beat positions can be obtained in the same manner.

  For songs with almost no change in tempo, the beat position can be obtained to the end of the song in this way, but the actual performance often fluctuates slightly or becomes partly slower.

  Therefore, the following method was considered so as to cope with these fluctuations in tempo.

That is, the function of M (t) in FIG. 7 is changed as shown in FIG.
1) is a conventional method, and when the intervals of each pulse are τ1, τ2, τ3, and τ4 as shown in the figure,
τ1 = τ2 = τ3 = τ4 = τ _max
It is.
In 2), τ1 to τ4 are uniformly increased or decreased.
τ1 = τ2 = τ3 = τ4 = τ max + s (-τ max · F ≦ s ≦ τ max · F) Thus, it corresponds to the case where sudden tempo changes.
3) rit. (Ritardando, gradually) or accele. (Accelerando, gradually faster), each pulse interval is
τ1 = τ _max
τ2 = τ _max + 1 · s
τ3 = τ _max + 2 · s (−τ _max · F ≦ s ≦ τ _max · F)
τ4 = τ _max + 4 · s
Calculated by
The coefficients 1, 2, and 4 are merely examples, and may be changed depending on the magnitude of tempo change.
4) is a rit. And accel. In this case, the position of the five pulses is changed where the current beat is to be obtained.

  By combining all of these, calculating the correlation between L (t) and M (t), and determining the beat position from the maximum of them, it is possible to determine the beat position even for a song whose tempo fluctuates. In the case of 2) and 3), the value of the coefficient k when calculating the correlation is also changed according to the value of s.

  Furthermore, although the five pulses are all the same in size, only the pulse at the position where the beat is calculated (the temporary beat position in FIG. 9) is increased, or the value is decreased as the distance from the position where the beat is determined is increased. The sum of the level increments of each scale tone at the position where the beat is sought may be emphasized [5) in FIG.

  As described above, when the position of each beat is determined, the result is stored in the buffer 30, and the detected result is displayed, and the user is asked to confirm and correct the wrong part. Also good.

  An example of a confirmation screen for beat detection results is shown in FIG. The position of the triangle mark in the figure is the detected beat position.

  When the “play” button is pressed, the current music sound signal is D / A converted and played from a speaker or the like. Since the current playback position is displayed with a playback position pointer such as a vertical line as shown in the figure, it is possible to confirm an error in the beat detection position while listening to the performance. Furthermore, if a sound such as a metronome is played at the beat position timing simultaneously with the reproduction of the original waveform of the detection, it is possible to check not only with the eyes but also with the sound, and it is possible to judge the false detection more easily. . As a method for reproducing the sound of the metronome, for example, a MIDI device can be considered.

The beat detection position is corrected by pressing the “correct beat position” button. When this button is pressed, a cross cursor appears on the screen. Click the correct beat position where the first beat detection is wrong. All beat positions after a position slightly before the clicked position (for example, half the position of _τmax ) are cleared, and the subsequent beat positions are detected again with the clicked position as the temporary beat position.

  Next, the detection of time signature and measure will be described.

  Since the position of the beat has been determined by the processing so far, the degree of change in sound for each beat is obtained next time. The degree of change in sound for each beat is calculated from the level of each scale sound for each frame output from the scale sound level detector.

When the number of frames of the j-th beat is b _j and the frames of the beats before and after the j-th beat are b _j−1 and b _{j + 1} , the degree of change in sound for each beat of the j-th beat is from the frame b _j−1. The average of the levels of each scale in the frames up to b _j −1 and the average of the levels of each scale in the frames from b _j to b _{j + 1} −1 are calculated. The degree of change of sound can be obtained and calculated by summing up all the scales.

That is, when the level of the i-th scale sound at the frame time t is L _i (t), the average level L _avg i (j) of the i-th scale sound level of the j-th beat is expressed by the following equation (9). Therefore, the sound change degree B _addi (j) for each beat of the i-th tone of the j-th beat is expressed by the following equation (10).

  Therefore, the sound change degree B (j) for each beat of the j-th beat is as shown in the following equation (11). Here, T is the total number of scale sounds.

  The bottom row in FIG. 11 shows the degree of change in sound for each beat. The time signature and the position of the first beat are obtained from the degree of change in sound for each beat.

  The time signature is obtained from the autocorrelation of the degree of sound change for each beat. In general, it is considered that the sound often changes in the first beat, so the time signature can be obtained from the autocorrelation of the sound change degree for each beat. For example, the autocorrelation φ (τ) of the sound change degree B (j) for each beat is determined in the range of 2 to 4 from the formula for obtaining the autocorrelation φ (τ) shown in the following equation (12). The delay τ that maximizes the autocorrelation φ (τ) is defined as the number of beats.

  N is the total number of beats, and φ (τ) is calculated in the range of τ = 2 to 4, and τ at which φ (τ) is the maximum is the number of beats.

Next, the first beat is obtained. This is the position where the sound change degree B (j) for each beat is the largest. That is, when phi (tau) is maximum tau and tau _max, the k of X (k) is maximum the following equation number 13 and _{k max, k max} th beat becomes the position of the first first beat Thereafter, the beat position obtained by adding τ _max is the first beat.

ｎ_ｍａｘは、τ_ｍａｘ・ｎ＋ｋ＜Ｎの条件で最大となるｎ

n _max is the _maximum n under the condition of τ _max · n + k <N

  As described above, when the time signature and the position of the first beat (bar line position) are determined, the result is stored in the buffer 40, and the detected result is displayed on the screen so that the user can change it. Is desirable. In particular, music with odd time signatures cannot be handled by this method, so it is necessary to have the user specify the location of odd time signatures.

  With the configuration of the above embodiment, the average tempo and accurate beat (beat) position of the entire song, as well as the time signature and the first beat position are detected from the acoustic signal of the performance of the tempo performed by a human. It becomes possible.

  FIG. 12 is an overall block diagram of the code detection apparatus of the present invention. In the figure, the configuration of beat detection and measure detection is basically the same as that of the first embodiment, and in the same configuration, the tempo detection and chord detection configurations are different from those of the first embodiment. Therefore, the same description overlaps except for mathematical formulas and the like, and is shown below.

  According to the figure, the configuration of the code detection device performs an FFT operation using parameters suitable for beat detection at predetermined time intervals from the input unit 1 for inputting an acoustic signal and the input acoustic signal. , A beat detection scale level detector 2 for obtaining the level of each scale sound for each predetermined time, and the increment value of each scale sound level for each predetermined time is summed for all the scale sounds, The sum of the level increments that indicate the degree of change in the overall sound over time is obtained, and the average beat interval and each beat are calculated from the sum of the level increments that indicate the degree of change in the overall sound over a given time period. The beat detection unit 3 for detecting the position of the sound, and the average value of the level of each scale sound for each beat are calculated, and the increment value of the average level of each scale sound for each beat is summed for all the scale sounds. Change in overall sound for each beat And a measure detecting unit 4 for detecting the time signature and the position of the measure line from the value indicating the degree of change in the overall sound for each beat, and the time of the previous beat detection from the input acoustic signal. A chord detection scale sound level detection unit 5 that performs an FFT operation using a parameter suitable for chord detection at a predetermined time interval different from the above and obtains the level of each scale sound for each predetermined time; Among the levels of each scale, the bass sound detection unit 6 that detects a bass sound from the level of the low-frequency scale sound in each measure, and the chord name of each measure from the detected bass sound and the level of each scale sound And a code name determination unit 7 for determination.

  The input unit 1 for inputting a music acoustic signal is a part for inputting a music acoustic signal to be subjected to chord detection, but the basic configuration is the same as that of the input unit 1 of the first embodiment. Description is omitted. However, if vocals normally localized at the center are disturbed by later code detection, vocal cancellation may be performed by subtracting the waveform of the right channel and the waveform of the left channel.

  This digital signal is input to the beat detection scale level detector 2 and the chord detection scale level detector 5. Each of these scale sound level detection units is composed of the respective units shown in FIG. 2 and has the same configuration. Therefore, the same components can be reused by changing only the parameters.

  The waveform pre-processing unit 20 used as the configuration has the same configuration as described above, and down-samples the acoustic signal from the input unit 1 of the music acoustic signal to a sampling frequency suitable for future processing. However, the sampling frequency after downsampling, that is, the downsampling rate, may be changed for beat detection and chord detection, or may be the same in order to save time for downsampling.

  In the case of beat detection, the downsampling rate is determined by the range used for beat detection. In order to reflect the performance sound of high-frequency rhythm instruments such as cymbals and hi-hats in beat detection, the sampling frequency after down-sampling needs to be set to a high frequency, but the bass sound and instrument sounds such as bass drum and snare drum In the case of detecting beats mainly from instrument sounds in the middle range, the same downsampling rate as that in the following chord detection may be used.

  The down-sampling rate of the chord detection waveform pre-processing unit varies depending on the chord detection range. The chord detection tone range is a tone range used when chord detection is performed by the chord name determination unit. For example, if the chord detection sound range is C3 to A6 (C4 is the center), the basic frequency of A6 is about 1760 Hz (when A4 = 440 Hz), so the sampling frequency after downsampling is a Nyquist frequency of 1760 Hz or higher. It may be 3520 Hz or higher. From this, the downsampling rate may be about 1/12 when the original sampling frequency is 44.1 kHz (music CD). At this time, the sampling frequency after downsampling is 3675 Hz.

  In the downsampling process, data is skipped after passing through a low-pass filter that cuts off components above the Nyquist frequency (1837.5 Hz in this example), which is usually half the sampling frequency after downsampling (now In this example, 11 out of 12 waveform samples are discarded). This is for the same reason as described in the first embodiment.

  When the downsampling by the waveform preprocessing unit 20 is completed in this manner, the output signal of the waveform preprocessing unit is subjected to FFT (Fast Fourier Transform) by the FFT calculation unit 21 at predetermined time intervals.

  The FFT parameters (the number of FFT points and the shift amount of the FFT window) are different values at the time of beat detection and code detection. This is because if the number of FFT points is increased to increase the frequency resolution, the size of the FFT window increases, and one FFT is performed from a longer time, resulting in a decrease in time resolution. (In other words, it is better to increase the time resolution at the expense of frequency resolution when detecting beats). A method that does not deteriorate the time resolution even if the number of FFT points is increased by setting waveform data to only a part of the window and filling the rest with 0 without using a waveform with the same length as the window size. However, in the case of the present embodiment, a certain number of waveform samples are necessary in order to correctly detect the power on the bass side.

  In consideration of the above, in this embodiment, the number of FFT points is 512 at the time of beat detection, the window shift is 32 samples, 0 padding is not performed, the number of FFT points is 8192 at the time of code detection, and the window shift is 128 samples. Then, 1024 samples were used for the waveform sample in one FFT. When FFT calculation is performed with such a setting, the time resolution is about 8.7 ms and the frequency resolution is about 7.2 Hz when the beat is detected, and the time resolution is about 35 ms and the frequency resolution is about 0.4 Hz when the code is detected. Since the scale tone for which the level is to be obtained is in the range from C1 to A6, the frequency resolution of about 0.4 Hz at the time of detecting the chord is the difference between the basic frequency of C1 and C # 1 having the smallest frequency difference, about 1 .9 Hz is also supported. Considering that the length of a 32nd note is 25 ms in a song with a tempo of quarter note = 300, it can be seen that the time resolution of about 8.7 ms at the time of beat detection is a sufficient value.

  In this way, the FFT operation is performed at predetermined time intervals, the power is calculated from the square root of the sum of the squares of the real part and the imaginary part, and the result is sent to the level detector 22.

  The level detector 22 calculates the level of each scale sound from the power spectrum calculated by the FFT calculator 21. Since FFT only calculates the power of a frequency that is an integer multiple of the value obtained by dividing the sampling frequency by the number of FFT points, in order to detect the level of each scale tone from this power spectrum, the same as in the first embodiment. Perform proper processing. That is, for all the sounds (C1 to A6) for which the scale sound is calculated, the maximum power in the power spectrum corresponding to frequencies in the range of 50 cents above and below the fundamental frequency of each sound (100 cents is a semitone) is obtained. Let the power of the spectrum it has be the scale level.

  When the levels are detected for all the scale sounds, this is stored in the buffer, and the waveform read position is advanced by a predetermined time interval (32 samples at the time of beat detection and 128 samples at the time of chord detection in the previous example), and FFT is performed. The calculation unit 21 and the level detection unit 22 are repeated until the end of the waveform.

  As described above, the level of each scale sound of the sound signal input to the music sound signal input unit 1 for each predetermined time is stored in the two types of buffers 23 and 50 for beat detection and chord detection.

  Next, since the configurations of the beat detection unit 3 and the bar detection unit 4 in FIG. 12 are the same as those of the beat detection unit 3 and the bar detection unit 4 of the first embodiment, detailed description thereof is omitted here.

  Since the position of the bar line (the frame number of each bar) is determined by the same configuration and procedure as in the first embodiment, the bass sound of each bar is detected this time.

  The bass sound is detected from the scale level of each frame output by the chord detection scale level detector 5.

  FIG. 13 shows the scale level of each frame output by the chord detection scale level detector 5 of the same part of the same song as FIG. 4 of the first embodiment. As shown in this figure, since the frequency resolution in the chord detection scale sound level detector 5 is about 0.4 Hz, the levels of all the scale sounds C1 to A6 are extracted.

  Since the bass sound may be different between the first half and the second half of the measure, the bass sound detection unit 6 detects the first half and the second half of each measure. When the first half and the second half are the same, this is confirmed as the bass of the measure, and the chord is also detected in the entire measure. When different bass sounds are detected in the first half and the second half, the chord is also detected separately in the first half and the second half. In some cases, the range to be divided may be further reduced to half (up to a quarter of the bar).

  The bass sound is obtained from the average intensity of the scale sound level in the bass detection range during the bass detection period.

When the level of the i-th note in the scale at frame time t and _L i (t), the average level of the i th scale notes of _{f e} from the frame _{f s L avgi (f s,} f e) is the following formula It can be calculated by Equation 14.

  This average level is calculated in the bass detection range, for example, in the range from C2 to B3, and the bass sound detection unit 6 determines the scale tone having the highest average level as the bass sound. An appropriate threshold is set to prevent the bass sound from being erroneously detected in songs or silences that do not include sound in the bass detection range, and if the average level of the detected bass sound is below this threshold, Sound may not be detected. In addition, when the bass sound is important in later chord detection, it is checked whether the detected bass sound keeps a certain level or more continuously during the base detection period, so that only the more reliable ones are checked. You may make it detect as a bass sound. Further, instead of determining the scale tone having the highest average level in the bass detection range as the base tone, the average level of each pitch name is averaged for every 12 pitch names, The pitch name having the highest level may be determined as the bass pitch name, and the scale tone having the highest average level among the scale sounds in the bass detection range having the pitch name may be determined as the bass tone.

  When the bass sound is determined, the result may be stored in the buffer 60, and the bass detection result may be displayed on the screen so that the user can correct it if it is incorrect. Further, since the bass range may be changed depending on the song, the user may be able to change the bass detection range.

  In FIG. 14, the example of a display of the bass detection result by the bass sound detection part 6 is shown.

  Next, the chord detection process by the chord name determination unit 7 is also determined by calculating the average level of each tone in the chord detection period.

  In this embodiment, the code detection period and the base detection period are the same. The average level in the chord detection period, for example, the C3 to A6 scales in the chord detection period is calculated, and several pitch names are detected in order from the scale that has the largest value, and the pitch names of the bass sounds Extract code name candidates from.

  At this time, since a sound with a high level is not necessarily a chord component sound, for example, five sounds having a plurality of pitch names are detected, and two or more of them are extracted in all combinations, and this is used as a base. Extract chord name candidates from the pitch names of the sounds.

  As for the code, the code whose average level is less than or equal to the threshold value may not be detected. Also, the chord detection range may be changed by the user. Further, the chord constituent sound candidates are not extracted in order from the scale sound having the highest average level in the chord detection range, but the average level of each pitch name in the chord detection range is set for every 12 pitch names. On average, chord constituent sound candidates may be extracted in order from the sound name having the largest level for each sound name.

  The chord name candidates are extracted by searching the chord name determination unit 7 for a chord name database storing the chord type (m, M7, etc.) and the pitch from the root tone of the chord constituent sound. In other words, all two or more combinations are extracted from the five detected pitch names, and whether or not the pitch between these pitch names is related to the pitch of the chord constituent pitches of this chord name database. If the same pitch relation is found, the root sound is calculated from any one of the chord constituent sounds, the chord type is added to the pitch name of the root sound, and the chord name is determined. At this time, the chord root sound (five tone) and the fifth sound may be omitted in the musical instrument playing the chord, so that even if they are not included, they are extracted as chord name candidates. When a bass tone is detected, the pitch name of the bass tone is added to the chord name of this chord name candidate. In other words, if the chord root sound and the bass sound have the same pitch name, they can be left as they are.

  In the above method, when there are too many code name candidates to be extracted, limitation by bass sound may be performed. That is, when a bass sound is detected, chord name candidates whose root sound is not the same as the base sound are deleted.

  When a plurality of code name candidates are extracted, the code name determination unit 7 calculates likelihood (likelihood) in order to determine one of them.

The likelihood is calculated from the average level intensity of all chord constituent sounds in the chord detection range and the level intensity of the chord root tone in the base detection range. That is, the average level of the average value L _avgC in code detection periods for all constituent notes of a chord name candidates _extracted, when the average level at the base detection period route of the chord and L _AVGR, the following equation number 15 Thus, the likelihood is calculated by the average of the two.

  At this time, when a plurality of sounds having the same pitch name are included in the chord detection range and the bass detection range, the one with the stronger average level is used. Alternatively, in each of the chord detection range and the bass detection range, the average level of each scale sound may be averaged for every 12 pitch names, and the average value for each pitch name may be used.

  Further, musical knowledge may be introduced into the likelihood calculation. For example, the level of each musical note is averaged over all frames, and is averaged for every 12 pitch names to calculate the strength of each pitch name, and the key of the song is detected from the distribution of the strength. Then, the key diatonic chord is multiplied by a certain constant so that the likelihood is increased, or the chord that includes the sound deviating from the sound on the key diatonic scale depends on the number of the deviated sounds. For example, the likelihood may be reduced. In addition, by storing a pattern of common chord progressions as a database and comparing it with the ones that are frequently used among chord candidates, a certain constant is applied to increase the likelihood. Also good.

  The code having the highest likelihood is determined as the code name. However, the code name candidates may be displayed together with the likelihood to be selected by the user.

  In any case, when the code name is determined by the code name determination unit 7, the result is stored in the buffer 70 and the code name is output to the screen.

  FIG. 15 shows a display example of the code detection result by the code name determination unit 7. In addition to displaying the detected code name on the screen in this way, it is desirable to reproduce the detected code and bass sound using a MIDI device or the like. This is because it is generally not possible to determine whether the code is correct just by looking at the code name.

  According to the configuration of the present embodiment described above, even if not an expert having special musical knowledge, individual note information is input to an input music sound signal mixed with a plurality of instrument sounds such as a music CD. The code name can be detected from the overall sound without detection.

  In addition, according to this configuration, even if the constituent sounds are the same chord, even if the performance tempo fluctuates, or conversely, the sound source that is playing intentionally fluctuating the tempo, the code for each measure The name can be detected.

  In particular, in the configuration of this embodiment, processing that requires time resolution of beat detection with the simple configuration (same as the configuration of the tempo detection device) and processing that requires frequency resolution of code detection (configuration of the tempo detection device described above). Based on this, it is possible to simultaneously perform a configuration in which a code name can be detected.

  The tempo detection device, the code name detection device, and the program capable of realizing them according to the present invention are not limited to the above illustrated examples, and various modifications can be made without departing from the scope of the present invention. Of course.

  The tempo detection device, the code name detection device of the present invention, and a program capable of realizing them include a video editing process for synchronizing an event in a video track with a beat time in a music track when creating a music promotion video, etc. Audio editing processing that finds beat positions by beat tracking, cuts and pastes the sound signal waveform of music, controls elements such as lighting color, brightness, direction, special effects, etc. in synchronization with human performance, It can be used in various fields, such as live stage event control that automatically controls clapping and cheering, and computer graphics synchronized with music.

1 is an overall block diagram of a tempo detection device according to the present invention. It is a block diagram of a structure of a scale sound level detection part. 4 is a flowchart showing a flow of processing of a beat detection unit 3. It is a graph which shows the figure of the sum total of the waveform of a part of a certain music, the level of each scale sound, and the level increment value of each scale sound. It is explanatory drawing which shows the concept of autocorrelation calculation. It is explanatory drawing explaining the determination method of the first beat position. It is explanatory drawing which shows the method of determining the position of the subsequent beat after the first beat position determination. It is a graph which shows the distribution state of the coefficient k changed according to the value of s. It is explanatory drawing which shows the determination method of the beat position after 2nd. It is a screen display figure which shows the example of the confirmation screen of a beat detection result. It is a screen display figure which shows the example of the confirmation screen of a bar detection result. It is a whole block diagram of the code | cord | chord detection apparatus of this invention which concerns on Example 2. FIG. It is a graph which shows the level of the scale sound of each flame | frame output from the chord detection scale level detection part 5 of the same part of a music. It is a graph which shows the example of a display of the bass detection result by the bass sound detection part. It is a screen display figure which shows the example of the confirmation screen of a code detection result.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input part 2 Beat detection scale sound level detection part 3 Beat detection part 4 Measure detection part 5 Chord detection scale sound level detection part 6 Bass sound detection part 7 Code name determination part 20 Waveform pre-processing part 21 FFT operation part 22 Level Detector 23, 30, 40, 50, 60, 70 Buffer

Claims (10)

An input means for inputting an acoustic signal;
A scale sound level detection means for performing an FFT operation at a predetermined time interval from an input acoustic signal and obtaining a level of each scale sound for each predetermined time;
The increment value of each scale sound level for each predetermined time is summed for all the scale sounds to obtain a total of level increment values indicating the degree of change in the overall sound for each predetermined time. Beat detection means for detecting the average beat interval and the position of each beat from the sum of the incremental values of the level indicating the degree of change in the overall sound for each,
The average value of the scale level for each beat is calculated, and the increment value of the average level of each scale sound for each beat is added for all the scale sounds to indicate the degree of change in the overall sound for each beat. A tempo detecting device comprising bar detecting means for obtaining a value and detecting a time signature and a bar line position from a value indicating a degree of change of the entire sound for each beat.   In detecting the average beat interval and the position of each beat by the beat detecting means, the average beat interval is obtained from the autocorrelation of the total level increment value of each scale sound, and then the level increment value of each scale sound. The first beat position is calculated by calculating the cross-correlation between the sum of the above and a function having a period at the average beat interval, and the second and subsequent beat intervals also have a period at the average beat interval. 2. The tempo detection apparatus according to claim 1, wherein the tempo detection apparatus is obtained by calculating a cross-correlation with a function it has.   In detecting the average beat interval and the position of each beat by the beat detecting means, the average beat interval is obtained from the autocorrelation of the total level increment value of each scale sound, and then the level increment value of each scale sound. And a function having a period at the average beat interval to obtain a first beat position, and the second and subsequent beat intervals are added to the average beat interval by + α or 2. The tempo detection apparatus according to claim 1, wherein a cross-correlation with a function obtained by adding an interval of-[alpha] is calculated.   In detecting the average beat interval and the position of each beat by the beat detecting means, the average beat interval is obtained from the autocorrelation of the total level increment value of each scale sound, and then the level increment value of each scale sound. The first beat position is calculated by calculating the cross-correlation between the sum of the above and a function having a period at the average beat interval, and the second and subsequent beat intervals are gradually increased from the average beat interval. 2. The tempo detection device according to claim 1, wherein a cross correlation with a function which is or gradually narrows is calculated.   In detecting the average beat interval and the position of each beat by the beat detecting means, the average beat interval is obtained from the autocorrelation of the total level increment value of each scale sound, and then the level increment value of each scale sound. The first beat position is calculated by calculating the cross-correlation between the sum of the above and a function having a period at the average beat interval, and the second and subsequent beat intervals are gradually increased from the average beat interval. 2. The tempo detection device according to claim 1, wherein the cross correlation with the function having an interval that becomes smaller or narrower is calculated by shifting a beat position in the middle thereof.   When obtaining the time signature and bar line position by the above bar detection means, the average value of the level of each scale sound for each beat is calculated, and the increment value of the average level of each scale sound for each beat is calculated for all scale sounds. In total, a value indicating the degree of change in the overall sound for each beat is obtained, the time signature is obtained from the autocorrelation of the value indicating the degree of change in the overall sound for each beat, and further, the change in the overall sound for each beat The tempo detection device according to claim 1, wherein the position having the largest value indicating the degree is set as the bar line position with the first beat as the first beat. An input means for inputting an acoustic signal;
First scale sound level detection means for performing FFT calculation using a parameter suitable for beat detection at predetermined time intervals from the input acoustic signal, and obtaining the level of each scale sound for each predetermined time;
The increment value of each scale sound level for each predetermined time is summed for all the scale sounds to obtain a total of level increment values indicating the degree of change in the overall sound for each predetermined time. Beat detection means for detecting the average beat interval and the position of each beat from the sum of the incremental values of the level indicating the degree of change in the overall sound for each,
The average value of the scale level for each beat is calculated, and the increment value of the average level of each scale sound for each beat is added for all the scale sounds to indicate the degree of change in the overall sound for each beat. A bar detecting means for obtaining a value and detecting a time signature and a bar line position from a value indicating a change degree of the whole sound for each beat;
From the input acoustic signal, an FFT operation is performed using a parameter suitable for chord detection at a predetermined time interval different from that at the time of the previous beat detection, and the level of each scale sound for each predetermined time is calculated. Second scale level detection means to be obtained;
Bass sound detection means for detecting a bass sound from the level of the low-frequency scale sound in each measure out of the detected scale levels,
A chord name detecting device comprising chord name determining means for determining a chord name of each measure from the detected bass sound and the level of each scale sound.   When a plurality of bass sounds are detected in a measure in the bass sound detecting means, the chord name determining means divides the measure into several chord detection ranges according to the bass sound detection result. 8. The chord name detection apparatus according to claim 7, wherein a chord name in the chord detection range is determined from a bass sound and a level of each scale sound in each chord detection range. Computer
An input means for inputting an acoustic signal;
A scale sound level detection means for performing an FFT operation at a predetermined time interval from an input acoustic signal and obtaining a level of each scale sound for each predetermined time;
The increment value of each scale sound level for each predetermined time is summed for all the scale sounds to obtain a total of level increment values indicating the degree of change in the overall sound for each predetermined time. Beat detection means for detecting the average beat interval and the position of each beat from the sum of the incremental values of the level indicating the degree of change in the overall sound for each,
The average value of the scale level for each beat is calculated, and the increment value of the average level of each scale sound for each beat is added for all the scale sounds to indicate the degree of change in the overall sound for each beat. A tempo detection program for obtaining a value and functioning as a measure detecting means for detecting a time signature and a measure line position from a value indicating a degree of change in the overall sound for each beat. Computer
An input means for inputting an acoustic signal;
First scale sound level detection means for performing FFT calculation using a parameter suitable for beat detection at predetermined time intervals from the input acoustic signal, and obtaining the level of each scale sound for each predetermined time;
The increment value of each scale sound level for each predetermined time is summed for all the scale sounds to obtain a total of level increment values indicating the degree of change in the overall sound for each predetermined time. Beat detection means for detecting the average beat interval and the position of each beat from the sum of the incremental values of the level indicating the degree of change in the overall sound for each,
The average value of the scale level for each beat is calculated, and the increment value of the average level of each scale sound for each beat is added for all the scale sounds to indicate the degree of change in the overall sound for each beat. A bar detecting means for obtaining a value and detecting a time signature and a bar line position from a value indicating a change degree of the whole sound for each beat;
From the input acoustic signal, an FFT operation is performed using a parameter suitable for chord detection at a predetermined time interval different from that at the time of the previous beat detection, and the level of each scale sound for each predetermined time is calculated. Second scale level detection means to be obtained;
Bass sound detection means for detecting a bass sound from the level of the low-frequency scale sound in each measure out of the detected scale levels,
A chord name detection program which functions as chord name determination means for determining chord names of each measure from the detected bass sound and the level of each scale sound.

Images