JP2008250018A - Tempo calculating method and music reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a music reproducing device applicable to an on-vehicle device having limited resources etc., by obtaining the tempo of a music through a light processing. <P>SOLUTION: A tempo acquisition device 7 executes a step of acquiring beats of the music from PCM data of the music and a step of calculating the tempo of the music from intervals between obtained beats, wherein the step of calculating the tempo is characterized in that average values and variance values of beat intervals are obtained at preset time intervals and the obtained variance values are compared to calculate the tempo based upon the average value of a beat interval where the smallest variance is obtained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for calculating the tempo of music. Here, “tempo” means BMP (Beats Per Minute) and means a beat in one minute.

  In recent years, it has been devised to calculate the tempo of music and perform control in accordance with the calculated tempo, for example, displaying it with a graphic equalizer.

  As a method of calculating the tempo, when beats are detected continuously and the number of past beat times close to the current beat time is N or more in the past M beat times, A method of calculating an average beat time with a near past beat time and obtaining a tempo is known (see, for example, Patent Document 1).

As another tempo calculation method, when the time interval of the sound is obtained from the time when the difference value of the envelope value of the reproduced audio signal is larger than the previous difference value and the previous time, and this is used as a reference It is known that the number of integer multiples (the optimal number) is calculated and the tempo is calculated from the time interval when the optimal number is the maximum (see, for example, Patent Document 2).
JP 2000-267654 A JP-A-11-212553

However, in the technique described in Patent Literature 1, when determining the beat, a threshold is set for determining whether the level of the input beat sound exceeds a certain amount. There is also a possibility that an input signal exceeding 1 is not input, and it is not known whether the tempo can be obtained for all the songs.
Further, when the above-described problem is avoided by making it possible to change the threshold value, there is a risk that the processing increases and the operation load increases accordingly.

  In the technique described in Patent Document 2, beat detection and tempo estimation are performed after extracting a specific component of an acoustic signal using a bandpass filter as preprocessing for analyzing the input acoustic signal. Using a band-pass filter means that an increase in computational load according to the number of taps (in the case of FIR filter) or an increase in load processing due to recursive processing (in the case of IIR filter) occurs, and a lightweight operation cannot be realized. there is a possibility.

  As described above, in the calculation of the tempo, if complicated processing or recursive processing is entered, the flow of data is delayed, and the amount of memory temporarily held increases and the processing load fluctuates. In an environment with limited resources such as an in-vehicle device, if the tempo calculation is performed simultaneously with playback and recording, there is a possibility that the playback sound will be adversely affected or the recording process may be adversely affected.

  The present invention has been made paying attention to the above-mentioned conventional problems, and by making it possible to obtain the tempo of music with a lightweight process, it can be applied to in-vehicle devices with limited resources. It is an object of the present invention to provide a tempo calculation method and a music playback device.

  In order to achieve the above object, the invention described in claim 1 is a procedure for acquiring a beat that is a beat of a song from the acoustic information of the song, and a procedure for calculating the tempo of the song from the interval between the acquired beats and beats The tempo calculation method for executing the tempo calculation, wherein in the procedure for calculating the tempo, an average value and a variance value of beat intervals are obtained for each preset time width, and the obtained variance values are compared, A tempo calculation method is characterized in that a tempo is calculated based on an average value of beat intervals at which small variance values are obtained.

  According to a second aspect of the present invention, in the tempo calculation method according to the first aspect, the procedure for acquiring the beat and the procedure for calculating the tempo are executed over the entire music. The calculation method was used.

  The invention described in claim 3 is the tempo calculation method according to claim 1 or 2, wherein in the beat acquisition procedure, the amplitude of the acoustic information is squared and added to determine the beat. A tempo calculation method is characterized in that a beat is acquired based on a signal value.

  According to a fourth aspect of the present invention, in the tempo calculation method according to the third aspect, the rate of change of the beat determination signal value for each set time in which a plurality of beats cannot exist within the range of the time width is calculated. A tempo characterized by obtaining a plurality of beats by obtaining a beat when the rate of change is equal to or greater than a preset threshold value and is an extreme value, thereby obtaining a plurality of beats. The calculation method was used.

  According to a fifth aspect of the present invention, in the tempo calculation method according to any one of the first to fourth aspects, when comparing the variance values in the tempo calculation procedure, the variance value obtained this time and the previous time are compared. The tempo calculation method is characterized in that the average value obtained together with the smaller variance value is stored as a tempo calculation value by comparing with the minimum value of the obtained variance values.

  The invention described in claim 6 is a tempo acquisition device that executes the tempo calculation method according to any one of claims 1 to 5, a playback device that plays back music information recorded on a storage medium, A music storage device capable of storing the music information recorded in the storage medium as data reproducible by the playback device, a tempo acquisition device, a playback device, a control device for controlling the operation of the music storage device, and a user's An operation device for inputting an operation, wherein the control device stores the storage when the user instructs the reproduction of the music recorded on the storage medium and the storage of the music. In parallel with the reproduction process for reproducing the music recorded on the medium, the recording process for storing the music information recorded on the storage medium in the music storage device, and the tempo for calculating the tempo by the tempo acquisition device. And calculation processing, and the music reproducing device, characterized by the execution.

According to the first aspect of the present invention, in calculating the tempo, an average value and a variance value of beat intervals are obtained for each preset time width, and the obtained variance values are compared to obtain the smallest variance value. The tempo was calculated based on the average beat interval.
When the variance value of the beat interval is the smallest, it means the same as when the variation of the beat interval is the smallest, and it can be said that it is the time when the most probable tempo in the song can be calculated.
In addition, every time after obtaining the variance value of the beat interval, the comparison is made with the minimum variance value until the previous time, and the variance value and average value of the beat interval are updated. Since no recursive processing is required, the operation load can be suppressed.
And by suppressing the operation load in this way, it can be applied to in-vehicle devices with limited resources.

  In the second aspect of the present invention, the beat is calculated over the entire music, and the tempo is calculated from the beat interval obtained thereby, so that the beat is based on the acoustic information of only a part of the music. The accuracy of the obtained tempo is high compared to the above calculation.

  In the invention of claim 3, the beat is obtained from the signal value for beat determination obtained by squaring and adding the amplitude of the acoustic information, and the beat is obtained without using recursive processing by the filter. did. For this reason, an operation load is suppressed and a lightweight process is attained.

  In the invention according to claim 4, since the threshold value is set for the rate of change of the signal value for beat determination, it is affected by the difference in the level of the acoustic information depending on the music as compared to setting the threshold value for the acoustic information itself. In addition, erroneous detection due to noise can be prevented. Further, by determining the extreme value of the rate of change as a beat, it is possible to perform a beat determination with a small operation load.

  In the invention according to claim 5, the variance value obtained this time is compared with the minimum value of the variance values obtained until the previous time, and the average value obtained together with the smaller variance value is stored as a value for tempo calculation. As a result, when comparing the beat intervals of the entire music, the data is stored over the entire music, and compared with comparing the data, less data is required and the operation load is further reduced. be able to.

  According to the sixth aspect of the present invention, in the music playback device, the playback of the music on the storage medium, the storage of the music in the music storage device, and the calculation of the tempo are executed simultaneously. Here, since the tempo calculation is a means that requires less operation load, it is possible to suppress skipping during reproduction and an increase in time required for recording.

In the following, an embodiment of a music reproducing apparatus that implements the tempo calculation method of the present invention will be described.
The music playback device of this embodiment includes a tempo acquisition device (7) for executing the tempo calculation method of the present invention, a playback device (5) for playing back music information recorded on the storage medium (1a), and the storage. A music storage device (3) capable of storing music information recorded on the medium (1a) as data reproducible by the playback device (5), the tempo acquisition device (7), the playback device (5), and a music A music playback device comprising a control device (11) for controlling the operation of the storage device (3) and an operation device (9) for inputting a user operation, wherein the control device (11) is operated by a user. When the reproduction of the music recorded on the storage medium (1a) and the storage of the music are instructed, the storage medium is reproduced in parallel with the reproduction process of reproducing the music recorded on the storage medium (1a). Before the music information recorded in (1a) A recording process of storing the music storage device (3), and a music reproduction apparatus characterized by performing a tempo calculation processing of calculating the tempo by the tempo acquisition device (7).

  Based on FIGS. 1-4, the music reproducing apparatus A of Example 1 is demonstrated as the best form of this invention.

First, the configuration of the music playback device A according to the first embodiment will be described.
The music reproducing apparatus A according to the first embodiment is mounted on a vehicle. As shown in FIG. 1, the media driving apparatus 1, the compression processing apparatus 2, the internal music storing apparatus 3, the music searching information storing apparatus 4, and the reproducing apparatus. 5, a list information storage device 6, a tempo acquisition device 7, a user interface device 8, a display device 9, a speaker device 10, and an overall control device 11.

  The media drive device 1 drives at least one of a storage medium 1a (CD (abbreviation of compact disc), MD (abbreviation of mini disc), DVD (digital versatile disc)) brought in from outside the vehicle, The sound information stored in the storage medium 1a is converted into information that can be reproduced. Here, it is assumed that PCM data (Pulese-Code Modulation) is used as acoustic information.

  The compression processing device 2 is a device that compresses the acoustic information of the music taken in by the media driving device 1 using an existing method such as MP3, WMA, or ATRAC3. In addition, when there are various kinds of information added to each song (for example, a tag having a title name, artist name, genre, etc.), these pieces of information are used for song search as attribute information. The information is stored in the information storage device 4.

The internal music storage device 3 is composed of a rewritable magnetic storage medium such as a hard disk drive (Hard disk drive), a flash memory, or the like. It is possible to compress and save.
The acoustic information stored in the internal music storage device 3 can be reproduced by the reproduction device 5 based on the control by the overall control device 11.

  The music search information storage device 4 follows the instructions of the overall control device 11, the music information stored in the internal music storage device 3, the attribute information such as the album name and artist name added to each music, and the tempo acquisition device 7 is associated and stored. Then, when specific search condition information is given, information corresponding to the search information, or information corresponding to a list of music (a list of music information and its storage destination) can be output. .

  The playback device 5 acquires the acoustic information stored in the storage medium 1a of the media driving device 1 or the acoustic information stored in the internal music storage device 3 according to the instruction of the overall control device 11, and plays back the acoustic information. When the acoustic information is compressed, it has a function of releasing (decoding) the compression and outputting as PCM data by a method based on each compression method.

  The list information storage device 6 is created internally by the music playback device A of the first embodiment based on the information stored in the music search information storage device 4 according to the user's instruction or the music playback list created by the user. It has a function to save the list information of the playback song.

  The tempo acquisition device 7 is a device that analyzes PCM data of a song and calculates the tempo of the song. The tempo is calculated when the music is stored in the internal music storage device 3, and at the same time, the data of the music is analyzed for each music, and the obtained tempo information is stored in each music in the music search information storage device 4. Saved in association. Details of the tempo calculation will be described later.

  The user interface device 8 has a role of performing an interface with the user. In the first embodiment, the user interface device 8 uses the touch panel function of the display device 9 to present visual information to the user and input the user's operation. Is what you do. For example, when presenting a reproduction list of music, a button corresponding to the list is displayed, and when the button is selected and operated, the general control device 11 is notified that the corresponding list has been selected. To do.

  The overall control device 11 has a function of controlling the operation of each of the above devices and at the same time realizing a user operation via the user interface device 8.

  Next, the flow of processing for calculating the tempo of the music by the tempo acquisition device 7 will be described with reference to the flowcharts of FIGS.

  FIG. 2 shows the flow of the tempo calculation process. This tempo calculation process is started when a storage medium 1 a such as a CD is inserted into the media driving apparatus 1. In the following description, an example in which an instruction to record (save) acoustic information (PCM data) previously recorded in the storage medium 1a to the internal music storage device 3 will be described.

When the storage medium 1a is set in the media driving device 1, ripping of the acoustic information of the storage medium 1a is started (step S1).
When the acoustic information (PCM data) is recognized (step S2), the reproduction process (step S3), the recording process (step S4), and the beat tempo acquisition process after step S5 are executed in parallel.

  In the recording process, after compression processing such as MP3, WMA, and ATRAC3 is performed in the compression processing device 2, it is sequentially stored in the internal music storage device 3.

In the beat tempo acquisition process, first, the beat acquisition process (step S5) is executed, and when the beat acquisition process result is accumulated for the first set time t1 (step S6), the tempo acquisition process is performed based on the obtained beat interval. (Step S7). This is repeated over the entire music, and the first set time t1 is set to a time (for example, 0.5 to 2 or 3 seconds) such that at least one beat exists. Example 1 second is used.
Details of the beat acquisition process in step S5 and details of the tempo acquisition process in step S7 will be described later.

  When recording of one song is completed (step S8), the overall control device 11 instructs the compression processing device 2 to end the processing, and stores the song as a file in the internal song storage device 3. At the same time, the end of the music is notified to the tempo acquisition device 7 to finish the calculation of the tempo information, determine the tempo information, and the music search information storage device 4 has attributes such as the album name and title name of the music. The tempo information acquired from the tempo acquisition device 7 is stored in association with the information (step S9). Note that the music search information storage device 4 can store general information such as recording time, number of reproductions, user evaluation value, and the like in addition to attribute information and tempo information.

  Next, it is determined whether or not there is a music that can be continuously played back in the media driving device 1 (step S10). If there is a next music, the process from step S2 is continued, and there is no music. The above processing is terminated.

Next, the details of the beat acquisition process of step S5 will be described based on the flowchart of FIG.
In this beat acquisition process, first, the PCM data of the storage medium 1a is sampled (step S101), and the amplitude of the PCM data is squared and added to the beat determination signal value (step S102). When this is finished for the second set time t2 (step S103), this is determined as the current beat determination signal value, and the value added so far is cleared to zero (step S104). Note that the second set time t2 is shorter than the first set time t1, and is a time during which a beat cannot necessarily exist (for example, several to several tens of msec). In the first embodiment, 10 msec is used.

  Next, the difference value of the beat determination signal value determined this time with respect to the previously acquired beat determination signal value is calculated as the current change rate (step S105).

Next, it is determined whether the change rate satisfies the three conditions of the preset threshold value or more, the inflection point, and the preset mask time tm from the previous beat time (step S106). If it is established, it is determined that a beat has occurred, and the current signal time is determined as the beat time (step S107).
In order to determine the inflection point, it may be obtained by differential twice, or the current rate of change is smaller than the previous rate of change, and the previous rate of change is larger than the previous rate of change. You may judge by.
The mask time tm is a time that cannot be assumed due to the nature of the music that the next beat comes from the previous beat time. For example, the mask time tm is set to about several hundred msec.

  The beat determination result determined in this way is added to the beat determination result array (step S108). The beat determination result array is data in which the beat determination result is secured for a certain time t3 from the present, and when one new data (data for the second set time t2) is added, the most past data is discarded. Based on this, tempo calculation described later is performed. Specifically, in the first embodiment, the past 3000 pieces of data are secured as the beat determination result array (t3 = t2 × 3).

  Finally, as the beat determination end process, the currently determined beat determination signal value and the currently calculated change rate are stored for use in the next beat determination process (step S109).

Next, the tempo acquisition process of step S7 will be described with reference to the flowchart of FIG.
This process is started when the first set time t1 has elapsed and the beat determination result array data is updated. First, one piece of data is acquired from the head of the beat determination result array (step S201). Then, it is determined whether or not this is determined to be a beat in the beat determination process (step S202). If this is the beat position, the beat interval is calculated from the difference from the previous beat position (step S203), and the current beat position is stored (step S204).

When the above processing is executed for all the data secured in the beat determination result array (step S205), the average value and variance value of the obtained beat intervals are calculated (step S206).
When the variance value obtained this time is smaller than the minimum value of the variance values obtained until the previous time (step S207), the average value and variance value of the beat interval obtained this time are stored as temporary tempo information. (Step S208).

Then, the tempo is calculated and stored based on the temporary tempo information. The tempo is obtained by dividing 60 by the average beat interval.
In other words, the beat interval average value obtained when the beat interval variation obtained within a certain time is the smallest is adopted as the beat interval representing the music, and the tempo is calculated based on this beat interval.

  This tempo calculation is continued until the recording of one song is completed, as described in the flowchart of FIG. 2, and the tempo stored at the end of the recording becomes the tempo information representing this song and the song The information is output to the search information storage device 4.

  In the music playback device A of the first embodiment, the tempo of all the music recorded in the device A is calculated, and the tempo data is stored in the music search information storage device 4 in association with the attribute information of the music. .

Next, a music selection method using this tempo data will be described.
In this case, on the touch panel display of the display device 9, for example, a plurality of types of buttons representing a difference in speed such as “fast”, “normal”, and “slow” are displayed.

  The user selects one of these buttons to search for a song included in this speed, and a playlist that can be randomly played from the songs hit in the search is stored in the list information storage device 6. Create and start playback in that song order.

  For example, when the music is associated with the button, when it is classified into three types of “fast”, “normal”, and “slow”, two threshold values for distinguishing these areas are set, and these threshold values and tempo data are set. Search based on comparison with.

  As described above, in the first embodiment, the tempo acquisition device 7 calculates the beat determination signal value by adding the square value of the amplitude of the PCM data, and determines the beat from the rate of change of the beat determination signal value. The beat is obtained without using recursive processing by a filter. For this reason, an operation load is suppressed and a lightweight process is attained.

Furthermore, even when calculating the tempo, the beat interval at which the smallest variance value is obtained by calculating the average value and variance value of the beat interval every set fixed time t3 minutes and comparing the obtained variance values. The tempo was calculated based on the average value.
Thus, since the tempo is calculated based on the beat interval when the variation in the beat interval is the smallest, the accuracy of the obtained tempo is high. Moreover, since there is no recursive process in this process, it is possible to reduce the operation load.
And by suppressing the operation load in this way, it can be applied to in-vehicle devices with limited resources.

  Furthermore, in the first embodiment, the beat is acquired at every first set time t1 over the entire music, and the tempo is acquired based on this beat. Therefore, the tempo is based on the PCM data of only a part of the music. The tempo can be obtained with higher accuracy than the above. Moreover, since beat calculation and tempo calculation are performed at each first set time t1, it is possible to save the amount of data compared to the calculation based on storing beats over all songs, and more. The operation load can be reduced.

  In addition, in the first embodiment, since the threshold is set for the rate of change of the signal value for beat determination when obtaining the beat, the output level of the PCM data depends on the music compared to setting the threshold for the PCM data value. Misdetection due to noise can be prevented without being affected by different things. In addition, since the mask time tm is set as the beat determination condition, erroneous detection can be further prevented.

  Further, in the first embodiment, when acquiring the tempo, the average value and variance value of the latest beat determination result array are acquired, and this is compared with the stored average value and variance value, so that the entire tune is obtained. Since the average value of the beat determination result array with the smallest variance value is obtained, data is saved over the entire music, and compared to comparing these, less data is saved and the operation load is light. Can be further improved.

  As described above, in the first embodiment, since the operation load of the tempo acquisition device 7 is small, the music reproducing device A reproduces the music in the storage medium 1a, stores the music in the music storage device, and the tempo. When the calculation and the calculation are simultaneously performed, it is possible to suppress skipping during reproduction and an increase in time required for recording.

Furthermore, in the first embodiment, the tempo data of the obtained music is stored in the music search information storage device 4 in association with the music, and the music is recorded according to the tempo speed of “fast”, “normal”, and “slow”. Search and auto play.
As described above, in the first embodiment, it is possible to analyze a song using the tempo of the song and create a reproduction list.

  As described above, the first embodiment of the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the first embodiment, and the design is not deviated from the gist of the present invention. Modifications are included in the present invention.

  That is, in Example 1, although the example applied to the on-vehicle music reproducing apparatus was shown as a music reproducing apparatus, it is applicable not only to an on-vehicle apparatus but to a portable type.

  Further, in the first embodiment, an example in which a hard disk drive is used as the internal music storage device 3 is shown, but other storage media can be used.

  Further, in the first embodiment, as a procedure for acquiring a beat, the procedure for obtaining the change rate of the value obtained by squaring the amplitude of the PCM data is shown. However, the tempo is calculated from the average value and the variance value of the beat intervals. If so, the beat acquisition procedure is not limited to this.

It is a block diagram which shows the structure of the music reproduction apparatus A of Example 1 of embodiment of this invention. 6 is a flowchart showing an overall processing flow of a tempo calculation procedure by the music reproducing device A according to the first embodiment. It is a flowchart which shows the flow of the beat acquisition process of step S5 in the calculation procedure of the tempo by the music reproduction apparatus A of Example 1. FIG. It is a flowchart which shows the flow of the tempo acquisition process of step S7 in the calculation procedure of the tempo by the music reproduction apparatus A of Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Media drive device 1a Storage medium 2 Compression processing device 3 Internal music storage device 4 Music search information storage device 5 Playback device 6 List information storage device 7 Tempo acquisition device 8 User interface device 9 Display device (operation device)
10 Speaker device 11 Overall control device A Music playback device

Claims (6)

The procedure to obtain the beat that is the beat of the song from the acoustic information of the song,
The procedure to calculate the tempo of the song from the interval between the acquired beats,
A tempo calculation method for executing
In the procedure for calculating the tempo, an average value and a variance value of beat intervals are obtained for each preset time width, and the average values of beat intervals at which the smallest variance value is obtained by comparing the obtained variance values. A tempo calculation method characterized by calculating a tempo based on the above.   2. The tempo calculation method according to claim 1, wherein the step of acquiring the beat and the step of calculating the tempo are executed over the entire music.   3. The tempo calculation according to claim 1, wherein, in the beat acquisition procedure, a beat is acquired based on a beat determination signal value obtained by squaring and adding the amplitude of acoustic information. Method.   Within the range of the time width, the rate of change of the signal value for beat determination is determined for each set time in which a plurality of beats cannot exist, the rate of change is equal to or greater than a preset threshold value, and is an extreme value. 4. The tempo calculation method according to claim 3, wherein a plurality of beats are acquired by repeating the determination of a beat at a certain time, and the beat interval is obtained.   In comparing the variance value in the tempo calculation procedure, the variance value obtained this time is compared with the minimum value of the variance values obtained up to the previous time, and the average value obtained together with the smaller variance value is used for tempo calculation. 5. The tempo calculation method according to claim 1, wherein the tempo calculation method is stored as a value. A tempo acquisition device that executes the tempo calculation method according to any one of claims 1 to 5,
A playback device for playing back music information recorded on a storage medium;
A music storage device capable of storing music information recorded in the storage medium as data reproducible by the playback device;
A control device for controlling the operation of the tempo acquisition device, the playback device, and the music storage device;
An operation device for inputting a user operation;
A music playback device comprising:
When the user instructs the reproduction of the music recorded on the storage medium and the storage of the music, the control device performs the storage in parallel with the reproduction process of reproducing the music recorded on the storage medium. A music playback apparatus, comprising: a recording process for storing music information recorded on a medium in the music storage apparatus; and a tempo calculation process for calculating a tempo by the tempo acquisition apparatus.

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