Abstract:
A music extracting apparatus has a receiving unit which receives a broadcast signal having a plurality of channels of audio signals, a detecting unit which detects a variation of voice power from the audio signal, a computing unit which computes a difference of amplitude or power between the audio signals of each channel, and a specifying unit which specifies the starting or the ending position of a music section based on the variation detected by the detecting unit and the difference computed by the computing unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in part application of Patent Cooperation Treaty Patent Application No. PCT/JP2009/000556 (filed on Feb. 12, 2009), which claims priority from Japanese patent application JP 2008-032067 (filed on Feb. 13, 2008). All of which are hereby incorporated by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a music extracting apparatus which extracts music portion from broadcasting signals such as radio broadcast or television broadcast, and a music recording apparatus which records the extracted music portion. 
       BACKGROUND ART 
       [0003]    In music program provided on radio or TV broadcasting, most of them are constituted from talk section, such as MC (Master of Ceremony) or DJ (Disc Jockey), and music section. In these programs, talk sections usually exist between music sections. Sometimes the voice of DJ overlaps in the starting or ending portion of the music sections. 
         [0004]    In JP 2005-518560 A1, an apparatus, which extracts music portion from the broadcasting waves, is disclosed. In the apparatus, the starting and the ending position of music section is detected only by stereophonic information. Specifically, it determines that the starting position is detected when the difference value between the audio signals of left and right channels exceeds a first predetermined value, and determines that the ending position is detected when the difference value lowers the second predetermined value (1). 
         [0005]    However, in the conventional method, it sometimes mistakenly determines that the ending position of the music section is detected when the music section has a non stereo-like portion in its midstream. 
       SUMMARY 
       [0006]    A first music extracting apparatus of the present invention comprises a receiving unit which receives a broadcast signal having a plurality of channels of audio signals; a detecting unit which detects a variation of voice power from the audio signal; a computing unit which computes a difference of amplitude or power between the audio signals of each channel, and a specifying unit which specifies the starting or the ending position of a music section based on the variation detected by the detecting unit, and the difference computed by the computing unit. 
         [0007]    A second music extracting apparatus of the present invention comprises a receiving unit which receives a broadcast signal having a left and right channels of audio signals; a detecting unit which detects a transition point where variation of voice power of the audio signal exceeds predetermined value; a computing unit which computes an amplitude difference between the audio signals of each channel, and a specifying unit which specifies the starting or the ending position of a music section based on the amplitude difference in the vicinity of the transition point. 
         [0008]    A music recording apparatus of the present invention comprises a receiving unit which receives a broadcast signal having a plurality of channels of audio signals; a detecting unit which detects a variation of voice power from the audio signal; a computing unit which computes a difference of amplitude or power between the audio signals of each channel; a specifying unit which specifies the starting and the ending position of a music section based on the variation detected by the detecting unit, and the difference computed by the computing unit, and a recording unit which records the music section specified by the specifying unit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a block diagram showing the configuration of music recording and reproducing apparatus. 
           [0010]      FIG. 2  is a flow chart showing a procedure of music recording process. 
           [0011]      FIG. 3  is a flow chart showing a procedure of computation of stereo likelihood in the vicinity of the transition point. 
           [0012]      FIG. 4  is a diagram for explaining a music recording process. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The present invention embodied in a music extracting apparatus or music recording apparatus is specifically described below with the reference to the drawings. 
       [1] Configuration of a Music Recording and Reproducing Apparatus 
       [0014]      FIG. 1  shows the configuration of the music recording and reproducing apparatus. The apparatus has an antenna  1 , a FM (Frequency Modulation) tuner unit  2 , an A/D (Analog to Digital) conversion unit  3 , MP3 codec  4 , a D/A (Digital to Analog) conversion unit  5 , a speaker unit  6 , a HDD-IF (Hard Disk Drive-Interface)  7 , a HDD (Hard Disk Drive)  8 , a DSP (Digital Signal Processor)  9 , a CPU (Central Processing Unit)  10 , a memory  11 , and a controlling unit  12 . 
         [0015]    The FM tuner unit  2  tunes in a broadcast wave chosen by user among the FM broadcast wave inputted from the antenna  1 . Then, the unit  2  demodulates the tuned wave and outputs analog audio signals (i.e. the audio signal of the left channel and the right channel). The A/D conversion unit  3  converts the analog signal acquired by the unit  2  to the digital audio signal. The MP3 codec  4  encodes the digital audio signal to a data compressed by MP3 format. Further, the codec  4  decodes the MP3 compressed data readout from the HDD  8  to a digital audio signal. The HDD-IF  7  interfaces with the HDD  8 . The HDD  8  is a mass storage device for example. 
         [0016]    The DSP  9  detects a transition point from an inputted audio data. The DSP  9  also computes stereo likelihood. Here the transition point is a point where the variation of the power of the audio signal is larger than a predetermined value. The stereo likelihood is expressed by a difference value between the audio data of the left channel and the right channel. The DSP  9  computes the variation of the power of the audio data in order to detect the transition point. 
         [0017]    CPU  10  controls each part of the music recording and reproducing apparatus. The memory  11  operates as a work memory of the CPU  10 . A program for CPU  10  is stored in ROM (not illustrated). In HDD  8 , a data, which is compressed and encoded in MP3 format by the MP3 codec  4 , is recorded. The D/A conversion unit  5  converts a digital audio signal, which is acquired by a decoding function of the codec  4 , to an analog audio signal. The speaker unit  6  outputs the analog audio signal acquired by the D/A conversion unit  5 . 
       [2] Musical Recording Process 
       [0018]      FIG. 2  shows a procedure of music recording process. When recording the music, an audio data from the A/D conversion unit  3  is input to the DSP  9  as well as to the memory  11 . In a first predetermined area of the memory  11 , a first predetermined amount of a new audio data is stored temporarily. This amount corresponds to an audio data for a couple songs (for example, audio data for 15 minutes long). In a second predetermined area of the memory  11 , a second predetermined amount of new audio data is stored temporarily. This amount is corresponds to an audio data for a short time period (for example, 10 seconds). 
         [0019]    Further, during the recording process, the DSP  9  keeps computing the amplitude difference value of the audio data between the left and right channels. Then the computed value is stored in the third predetermined area of the memory  11 . In the third area, the amplitude difference value for the recent 10 seconds is stored, for example. 
         [0020]    The CPU  10  starts the recording process triggered by a user&#39;s instruction. When the process has started, the CPU  10  activates the FM tuner unit  2 , and controls the unit  2  so that the broadcast station selected by the user is tuned. Further, the CPU  10  controls DSP  9  so that the amplitude difference of the left and right channel is computed, and then the computed value is stored in the third area of the memory  11  (step S 1 ). The output of FM tuner unit  2  is transmitted to the A/D conversion unit  3 , and is converted to digital audio data. This audio data is then transmitted to the DSP  9  as well as to the memory  11 . Thereby storing processes of the audio data to the first and the second area of the memory  11  are started. 
         [0021]    Then, when the amount of the data stored to the first area has reached the first predetermined amount, the oldest stored data is deleted from the area while the newest data is stored in turn. Similarly, when the amount of the data stored to the second area has reached the second predetermined amount, the oldest stored data is deleted from the second area while the newest data is stored in turn. 
         [0022]    The DSP  9  starts a computing process of the amplitude difference between the audio data of the left and the right channels inputted to the DSP  9 , and store the result to the third area of the memory  11 . Then, the DSP  9  and CPU  10  perform detecting process of the transition point, and the computing process of the stereo likelihood in vicinity of the transition point (step S 2 ). 
         [0023]      FIG. 3  shows a computing process of the stereo likelihood. First, the DSP  9  read outs a data which was received 5 seconds before the current time as a target audio data from the second area of the memory  11 , wherein the second area stores an audio data which corresponds to 10 seconds long (step S 21 ). Then, the DSP  9  computes the variation of the power of the audio signal and provides to the CPU  10  (step S 22 ). Here, the power corresponds to a squared value of the amplitude of audio signal, for example. 
         [0024]    The CPU  10  determines whether the target audio data regards to the transition point or not based on the variation of the power information of the audio signal inputted from the DSP  9  (step S 23 ). When the variation is larger than a threshold value Th 1 , it is determined that the target audio data regards to the transition point. When determined that it does not regards to the transition point, it goes back to step S 21  and process of the steps S 21  to S 23  are processed again. 
         [0025]    When it is determined that the target audio data regards to the transition point in the step S 23 , the amplitude difference value stored in the third area of the memory  11  is read out. Specifically, the value corresponding to ten second long audio data centered by the transition point is read out. Then the average value of the ten second long data is computed as a stereo likelihood evaluation value. Thereby, computing process of the stereo likelihood is performed. 
         [0026]    Again referring to  FIG. 2 , when the computing process of the step S 2  is completed, then it is determined whether the stereo likelihood evaluation value computed in step S 2  is lower than a threshold value Th 2  or not. When it is equal to or more than Th 2 , it determines that the target audio data regards to the music portion and then goes back to step S 2  again. 
         [0027]    When the evaluation value is less than Th 2  in the step S 3 , it is determined that the target audio data is a talk section such as MC or DJ. In this case, since there is a possibility that the music section may exist afterwards, the time stamp information of the target audio data is memorized as a music starting time Ps (step S 4 ). Then, the process proceeds to step S 5 . In the step S 5 , stereo likelihood in vicinity of the transition point is computed in similar manner as step S 2 . 
         [0028]    When the computation of step S 5  is finished, it is determined that whether the evaluation value computed at step S 5  is less than Th 2  or not (step S 6 ). When evaluation value is equal to or more than Th 2 , the target audio data is determined as a music section. Then, it returns to step S 5 . 
         [0029]    When the evaluation value is less than Th 2  in the step S 6 , the target audio data is determined to be a talk section such as MC or DJ, and is not a music section. Then, it is determined whether the interval between the music starting time Ps and the target audio data is equal to or more than the predetermined time ΔT (step S 7 ). In other word, it is determined whether the interval between a transition point currently determined as a talk section and the transition point previously determined as a talk section is equal to or more than ΔT or not. 
         [0030]    When the interval is less than ΔT, then it determines that the this section is not long enough for the music section and updates the music starting time Ps to the time of the target audio data (step S 8 ). Then it returns to step S 5 . When the interval is determined to be equal to or longer than ΔT, the time of the target audio data is memorized as a music ending time Pe (step S 9 ). Then the audio data existing between the time Ps and Pe is extracted from the audio data stored in the first area of the memory  11  as a music data. The extracted data is then compressed by the MP3 codec  4 , and is recorded on HDD  8  (step S 10 ). Then, Ps is updated to a time memorized as Pe (Step S 11 ), and returns to step S 5 . 
         [0031]    The music recording process is terminated when directed by the user&#39;s operation. Here it is presumed that a music section  100 , a first DJ section  101 , a music section  102 , and a second DJ section  103  appears in this order, as shown in  FIG. 4 . And it is presumed that the recording direction is inputted in the middle of the music section  100 . In such case, an audio data of the section  100  is read out from the second area of the memory  11  as a processing data and then transmitted to the DSP  9 . However, during this period, it may be determined in step S 2  that no transition point is detected. Even if the transition point is detected, it may be determined “no” in the step S 3 , since the stereo likelihood evaluation value is equal to or more than Th 2 . Thus, the process of step S 2  is carried on or the process of steps S 2  and S 3  are iterated. 
         [0032]    Next, when an audio data of the first DJ section  101  is read out from the second area of the memory  11 , a transition point is detected in the step S 2 . Further, since the stereo likelihood evaluation value at the transition point would be less than Th 2 , it is determined “yes” in the step S 3 . Therefore, the time of this transition point is recorded as a music starting time Ps in step S 4 . Then, it proceeds to step S 5 . 
         [0033]    When a transition point is detected in the step S 5 , since it is likely that the evaluation value is less than Th 2 , it proceeds to step S 7 . However, the interval between the time memorized as Ps and the target audio data is less than ΔT, thus it is determined “no” in step S 7  and Ps is updated in step S 8 . Thereby, the processes of step S 6  to S 8  are iterated. 
         [0034]    Next, when an audio data of the music section  102  is read out from the second area of the memory  11 , a transition point may not be detected in the step S 5 . Even if the transition point is detected, since the stereo likelihood evaluation value would be equal to or more than Th 2 , it is determined “no” in the step S 6 . Thus, the process of step S 5  is carried on or the process of steps S 5  and S 6  are iterated. 
         [0035]    Next, when an audio data of the second DJ section  103  is read out from the second area of the memory  11 , a transition point may be detected in the step S 5 . Further, since the stereo likelihood evaluation value at the transition point would be less than Th 2 , it is determined “yes” in the step S 6  and proceeds to step S 7 . Since an interval of time memorized as Ps, and the target audio data is equal to or more than ΔT, it is determined “yes” in step S 7  and proceeds to step S 9 . In the step S 9 , the time corresponding to the target audio data is memorized as Pe. Then, the audio data existing in a period between Ps and Pe is extracted as a music section data from the data memorized in the first area of the memory  11 . Then the extracted data is compressed and recorded to the HDD  8 . 
         [0036]    In order to raise the detection accuracy of the starting or ending position of the music section, it is desirable to set the threshold low so that many transition points can be detected. However, if the threshold is set too low, the numbers of the transition point detected inside the music section tends to increase. In such case, it may mistakenly detect that the ending point has appeared, when there is low stereo likelihood part in the music section. Therefore, it is desirable to detect the starting and ending point of the music section further considering a frequency characteristic in vicinity of a transition point. 
         [0037]    In other words, in the above embodiments, first, it is determined whether the audio data regards to talk section or music section based on the average value of the difference of the left and right channel signals. Then, the starting and the ending positions are specified. However, it may determine further considering frequency characteristics as well. 
         [0038]    An example of frequency characteristics may be MFCC (Mel Frequency Cepstrum Coefficient). Specifically, the likelihood between the MFCC detected in the vicinity of the transition point and the MFCC of the prepared standard data is computed. Then it is determined that the audio data in the vicinity of the transition point is music section when the likelihood is equal to or more than Th 3  and the stereo likelihood evaluation value is equal to or more than Th 2 . 
         [0039]    The present invention is not limited to the foregoing embodiment but can be modified variously by one skilled in the art without departing from the spirit of the invention as set forth in the appended claims.