Patent Publication Number: US-2010126331-A1

Title: Method of evaluating vocal performance of singer and karaoke apparatus using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 10-2008-116291, filed on Nov. 21, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field of the Invention 
     The present general inventive concept relates to a method of evaluating a vocal performance of a singer and a karaoke apparatus to perform the method, and more particularly, to a method of evaluating the vocal performance of the singer by comparing a total voice energy of the singer and an energy corresponding to a reference pitch, and a karaoke apparatus to perform the method. 
     2. Description of the Related Art 
     Various karaoke apparatuses used to evaluate the vocal performance of a singer have been developed. A method used in a conventional karaoke apparatus is to rate a singer&#39;s skill according to whether the singer releases an appropriate level of voice energy at a specific time. This method is advantageous in that it can be simply realized but has a problem in that the accuracy of a pitch is not considered. 
     In order to solve the above problem, a method using an accompaniment melody has been used. The method using an accompaniment melody rates a singer&#39;s skill according to whether the singer&#39;s pitch harmonizes with the accompaniment melody. However, this method requires massive computation and has a problem in that an octave error cannot be accurately extracted. Also, the accompaniment melody may not be considered as always harmonizing with the singer&#39;s melody. 
     Accordingly, there is a demand for a method of evaluating the vocal performance of a singer more accurately and also requiring less computation. 
     SUMMARY 
     Example embodiments of the present general inventive concept provide a method of evaluating the vocal performance of a singer more accurately and a karaoke apparatus to perform the method. 
     Additional features and utilities of the present general inventive concept will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the general inventive concept. 
     The foregoing and/or other features and utilities of the present general inventive concept may be achieved by providing a method of evaluating a vocal performance of a singer using a karaoke apparatus, the method including extracting a voice energy of a singer, extracting a reference pitch using musical instrument digital interface (MIDI) data, and comparing the voice energy and an energy of the reference pitch and evaluating the vocal performance of the singer. 
     The extracting the reference pitch may include extracting the reference pitch using a frequency of a note included in the MIDI data. 
     The extracting the reference pitch may include extracting the energy of the reference pitch using the Goertzel algorithm. 
     The energy of the reference pitch may be extracted using the following equation: 
         P   B =2 cos(2 πf) s   i−1   s   i−2   +s   i−1   s   i−1   +s   i−2   s   i−2    
     wherein s i =x i +2 cos(2 πf)s i−1 −s i−2 , P B  denotes the energy of the reference pitch, f denotes the frequency of the note, and x i  denotes an input sample. 
     The extracting the voice energy may include converting a voice of the singer into a digital signal, dividing the digital signal into a plurality of frames, and extracting the voice energy of each of the frames. 
     The voice energy may be extracted using the following equation: 
     
       
         
           
             
               P 
               A 
             
             = 
             
               
                 ∑ 
                 
                   i 
                   = 
                   1 
                 
                 N 
               
                
               
                 X 
                 i 
                 2 
               
             
           
         
       
     
     wherein P A  denotes the voice energy, X i  denotes an input sample, and N denotes the size of a frame. 
     The foregoing and/or other features and utilities of the present general inventive concept may also be achieved by providing a karaoke apparatus including a voice energy extraction unit to extract a voice energy of a singer, a reference pitch extraction unit to extract a reference pitch using MIDI data, and a control unit to evaluate vocal performance of the singer using the voice energy and an energy of the reference pitch. 
     The reference pitch energy extraction unit may extract the reference pitch using a frequency of a note included in the MIDI data. 
     The reference pitch energy extraction unit may use the following equation by applying the Goertzel algorithm, which is constituted depending on the reference pitch: 
         P   B =2 cos(2 πf) s   i−1   s   i−2   +s   i−1   s   i−1   +s   i−2   s   i−2    
     wherein s i =x i +2 cos(2 πf)s i−1 −s i−2 , P B  denotes the energy of the reference pitch, f denotes the frequency of the note, and x i  denotes an input sample. 
     The karaoke apparatus may further include a conversion unit to convert a voice of the singer into a digital signal, and the voice energy extraction unit may divide the digital signal into a plurality of frames and extract the voice energy of each of the frames. 
     The voice energy extraction unit may extract the voice energy using the following equation: 
     
       
         
           
             
               P 
               A 
             
             = 
             
               
                 ∑ 
                 
                   i 
                   = 
                   1 
                 
                 N 
               
                
               
                 X 
                 i 
                 2 
               
             
           
         
       
     
     wherein P A  denotes the voice energy, X i  denotes an input sample, and N denotes the size of a frame. 
     The foregoing and/or other features and utilities of the present general inventive concept may also be achieved by providing a recording medium having recorded thereon a program to cause a computer to perform a method of evaluating a vocal performance of a singer using a karaoke apparatus, the method including extracting a voice energy of a singer, extracting a reference pitch using musical instrument digital interface (MIDI) data, and comparing the voice energy and an energy of the reference pitch and evaluating the vocal performance of the singer. 
     The foregoing and/or other features and utilities of the present general inventive concept may also be achieved by providing a method of evaluating a vocal performance, the method including determining a voice energy of a voice input to an evaluation device, determining a reference pitch energy from a recorded signal, and comparing the voice energy and reference pitch energy to evaluate the vocal performance. 
     The reference pitch energy may be estimated according to a frequency of one or more notes in the recorded signal. 
     The results of the evaluation of the vocal performance may be displayed during the vocal performance. 
     The foregoing and/or other features and utilities of the present general inventive concept may also be achieved by providing a method of evaluating a vocal performance, the method including comparing a voice energy of a voice to a reference pitch energy of a recorded signal, and determining accuracy of the vocal performance according to a difference between the voice energy and the reference pitch energy. 
     The voice energy may be compared to the reference pitch energy during the vocal performance. 
     The results of the determined accuracy may be displayed during the vocal performance. 
     The foregoing and/or other features and utilities of the present general inventive concept may also be achieved by providing a method of evaluating a vocal performance, the method including determining a reference pitch energy of a recorded note and one or more octaves above and/or below the recorded note, and comparing a voice to the reference pitch energy to determined accuracy of the vocal performance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other features and advantages of the present general inventive concept will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a block diagram illustrating a karaoke apparatus according to an exemplary embodiment of the present general inventive concept; 
         FIG. 2  is a view illustrating a spectrum of the Goertzel filter according to the Goertzel algorithm; 
         FIG. 3  is a flowchart illustrating a method of evaluating a vocal performance of a singer according to an exemplary embodiment of the present general inventive concept; 
         FIG. 4  is a block diagram illustrating a karaoke apparatus according to another exemplary embodiment of the present general inventive concept; and 
         FIG. 5  is a flowchart illustrating a method of evaluating vocal performance of a singer according to another exemplary embodiment of the present general inventive concept. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to various exemplary embodiments of the present general inventive concept, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below in order to explain the present general inventive concept by referring to the figures. 
       FIG. 1  is a block diagram illustrating a karaoke apparatus according to an exemplary embodiment of the present general inventive concept. The karaoke apparatus according to an exemplary embodiment of the present general inventive concept evaluates a vocal performance of a singer by comparing voice energy and energy corresponding to a reference pitch. 
     As shown in  FIG. 1 , the karaoke apparatus  100  according to an exemplary embodiment of the present general inventive concept may include a voice input unit  110 , a conversion unit  120 , an energy extraction unit  130 , a comparison unit  140 , a control unit  150 , a file loader unit  160 , and a musical instrument digital interface (MIDI) data extraction unit  170 . 
     The voice input unit  110  may receive a voice signal from a singer from an outer source, such as through a microphone. The voice input unit  110  may transmit the input voice signal to the conversion unit  120 . 
     The conversion unit  120  may convert the voice signal into a digital signal. The conversion unit  120  may transmit the digital signal to the energy extraction unit  130 . 
     The energy extraction unit  130  may include a voice energy extractor  131  and a reference pitch energy extractor  135 . The voice energy extractor  131  may extract an energy of the voice of a singer and the reference pitch energy extractor  135  may extract an energy corresponding to a reference pitch to evaluate the vocal performance of the singer. 
     The voice energy extractor  131  may extract the voice energy of the singer in a unit of frame using the following equation: 
     
       
         
           
             
               
                 
                   
                     P 
                     A 
                   
                   = 
                   
                     
                       ∑ 
                       
                         i 
                         = 
                         1 
                       
                       N 
                     
                      
                     
                       X 
                       i 
                       2 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                      
                     
                         
                     
                      
                     1 
                   
                   ] 
                 
               
             
           
         
       
     
     wherein P A  denotes voice energy, X i  denotes an input sample, and N denotes the size of the frame. 
     Meanwhile, the reference pitch energy extractor  135  may generate a reference pitch used to evaluate the vocal performance of a singer from a MIDI file and may extract the energy of the reference pitch using the Goertzel algorithm. 
     The Goertzel algorithm is as follows: 
         P   B =2 cos(2 πf) s   i−1   s   i−2   +s   i−1   s   i−1   +s   i−2   s   i−2    
     wherein s i =x i +2 cos(2 πf)s i−1 −s i−2 , P B  denotes the reference pitch energy, f denotes a frequency of a note, and x i  denotes an input sample. 
     Using the above Goertzel algorithm, the reference pitch energy extractor  135  may estimate an energy having a pitch corresponding to the frequency (f). A different method other than the Goertzel algorithm may be used to estimate energy having a specific pitch. However, the Goertzel algorithm is advantageous in that it requires less computation to estimate the energy of a specific pitch. 
     A reference frequency may be set to be identical to the frequency of a current note (f), and the frequency width of a bin depends on the number of input samples (x i ). Since the frequency width of the bin increases by geometric progression as the pitch increases, the frequency width becomes narrower as the number of input samples increases. 
     The correlation between the bins in the Goertzel algorithm will be described with reference to  FIG. 2 .  FIG. 2  illustrates a spectrum of the Goertzel filter according to the Goertzle algorithm, wherein N denotes the number of a current note. 
     As shown in  FIG. 2 , there are 3 bins, wherein N−12 and N+12 indicate that there are 12 notes and 12 half-notes per one octave. W N , W N−12 , W N+12  denote widths of the bins. 
     Referring to  FIG. 2 , there is a difference of a multiple of 2 between a previous octave and a next octave. This is because the higher the note is, the wider the frequency range, and the frequency range increases by geometric progression. Accordingly, the width of the next octave is two times larger that that of the previous octave. 
     The weight values given to the bins may not be the values of A N , A N−12 , and A N+12  illustrated in  FIG. 2 . One important consideration in the present general inventive concept is the value of a first harmonic. Accordingly, the bin of the first harmonic may ideally have the largest weight value. The weight value of another bin would therefore decrease as the number of harmonics increases. This method may result in a more accurate evaluation of the vocal performance of a singer compared to a method in which the same weight value is applied. 
     In  FIG. 2 , only the 3 described octaves are illustrated for the convenience of explanation, but the number of octaves is not limited thereto. The present general inventive concept is also applicable to the case in which different quantities of octaves are presented. 
     The Goertzel filter can cover various octaves neighboring the octave of a current note because of at least the following reasons: 
     First, a singer may sing a note several octaves higher or lower than the current note. Such a singing method is typical and concerns the style preferred by a singer. Therefore, it may be unreasonable to give a penalty to the singer who sings in this manner. 
     Second, a singer may change the harmonic component of a multiple frequency as well as a note frequency when singing a song. The Goertzel filter is useful in estimating the harmonic component. 
     Referring back to  FIG. 1 , the comparison unit  140  may compare the voice energy extracted by the voice energy extractor  131  and the reference pitch energy extracted by the reference pitch energy extractor  135  to calculate a difference therebetween. Actually, the section of the note may be larger than one frame. Accordingly, the comparison unit  140  compares the voice energy extracted from all of the frames included in the note and the reference pitch energy. 
     The result of the comparison may be stored to an internal buffer (which may be a well-known type of buffer, and therefore is not shown). The result of the comparison may be thusly stored to provide a temporary result regarding the singer&#39;s vocal performance. That is, the singer can learn a temporary result of evaluating his/her vocal performance while singing a song. 
     Also, the result of comparison stored in the internal buffer (not shown) may be used to calculate a final score. 
     The file loader unit  160  may read out a song file from any of various sources, such as, for example, a compact disk or a semiconductor memory. The file loader unit  160  may divide the song file into MIDI data and accompaniment data and may transmit the MIDI data to the MIDI data extraction unit  170 . 
     The file loader unit  160  may transmit the accompaniment data to a reproducing means (which may be a well-known type of reproducing means, and therefore is not shown) to reproduce the accompaniment regarding the song. 
     The MIDI data extraction unit  170  may extract the MIDI data at the same time as the singer starts singing a song. The MIDI data extraction unit  170  may extract song information such as a note number, a note starting time, a note duration, etc. 
     The MIDI data extraction unit  170  may obtain information regarding the lyrics of a song at a current note. The information regarding the lyrics of a song may include information regarding a location of a vowel in one or more words included in the lyrics. Since a pitch generally occurs at the vowel and does not occur at the consonant, it may be beneficial to analyze a time during which the vowel is sung to evaluate the vocal performance of a singer. 
     The control unit  150  the operations of the karaoke apparatus  100 . More particularly, the control unit  150  may control a staring point of a song, synchronize the MIDI, the lyrics, and an audio stream, and control other operations of the karaoke apparatus  100  such as displaying the lyrics of a song, the score of a singer, etc. 
     Accordingly, the vocal performance of a singer can be evaluated more accurately than with the conventional methods and devices. 
       FIG. 3  is a flowchart illustrating a method of evaluating vocal performance of a singer according to an exemplary embodiment of the present general inventive concept. 
     The conversion unit  120  may convert a voice signal input through the voice input unit  110  into a digital signal in operation S 310 . 
     The voice energy extractor  131  may divide the digital signal into a plurality of frames in operation S 320  and extract a voice energy per each of the frames in operation S 330 . 
     The reference pitch energy extractor  135  may extract the frequency of a current note from MIDI data in operation S 340 , and may extract a reference pitch energy using the Goertzel algorithm in operation S 350 . 
     The comparison unit  140  may compare the voice energy and the reference pitch energy in operation S 360  and the control unit  150  may calculate a score according the result of comparison in operation S 370 . 
     Accordingly, the vocal performance of a singer can be evaluated more accurately than with the conventional methods and devices. 
       FIG. 4  is a block diagram illustrating a karaoke apparatus according to another exemplary embodiment of the present general inventive concept. The karaoke apparatus according to this embodiment may include a voice energy extractor  410 , a reference pitch energy extractor  430 , and a control unit  450 . 
     The voice energy extractor  410  may extract a voice energy of a singer, and the reference pitch energy extractor  430  may extract a reference pitch using MIDI data and extract an energy corresponding to the pitch from the whole voice signal. 
     The control unit  450  may evaluate the vocal performance of a singer using the voice energy and the reference pitch energy. 
       FIG. 5  is a flowchart illustrating a method of evaluating a vocal performance of a singer according to another exemplary embodiment of the present general inventive concept. In order to evaluate the vocal performance of a singer, voice energy of the singer is extracted in operation S 510 . 
     A reference pitch may be extracted using MIDI data in operation S 520 . 
     The vocal performance of the singer may be evaluated by comparing the voice energy and the reference pitch in operation S 530 . 
     Accordingly, the vocal performance of a singer can be evaluated more accurately and with a less amount of computation than that required in a conventional method and apparatus. 
     The present general inventive concept can also be embodied as computer-readable codes on a computer-readable medium. The computer-readable medium can include a computer-readable recording medium and a computer-readable transmission medium. The computer-readable recording medium is any data storage device that can store data as a program which can be thereafter read by a computer system. Examples of the computer-readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, DVDs, magnetic tapes, floppy disks, and optical data storage devices. The computer-readable recording medium can also be distributed over network coupled computer systems so that the computer-readable code is stored and executed in a distributed fashion. The computer-readable transmission medium can be transmitted through carrier waves or signals (e.g., wired or wireless data transmission through the Internet). Also, functional programs, codes, and code segments to accomplish the present general inventive concept can be easily construed by programmers skilled in the art to which the present general inventive concept pertains. 
     Although various example embodiments of the present general inventive concept have been illustrated and described, it will be appreciated by those skilled in the art that changes may be made in these example embodiments without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.