JP4507822B2 - Music providing system, music providing method, and music providing program - Google Patents

Description

  The present invention relates to a music providing system that provides music to a mobile phone via a wireless base station.

  In recent years, with the widespread use of mobile phones, a technique for improving sound quality during calls on the mobile phones has been implemented. The codecs for each major mobile phone system are shown below. The method is shown in the order of codec type, transmission band kbit / sec, and voice band kbit / sec.

PHS: ADPCM, 32, 32
PDC Full rate: VSELP, 11.2, 6.7
PDC Half rate: PSI-CELP, 5.6, 3.45
GSM Full rate: RPE-LTP, 22.8, 13
cdmaOne: EVRC, 9.6, 8
WCDMA (FOMA): AMR, 38.6, 12/23
Landline (reference): PCM, 64, 64
Note that the transmission band refers to the band of the entire wireless section, and the voice band refers to the band of the part through which the voice signal flows.

  For example, the encoding process by the EVRC codec used in the cdma network is performed according to the procedure shown in FIG. First, for the audio analog input (step S101), the audio analog input signal is normalized (step S102). Subsequently, band filtering processing (removal of low frequency components and high frequency components) with analog signals (step S103) and analog / digital conversion processing (quantization: from analog to linear PCM) (step S104) are performed. Thereafter, the small amplitude portion is deleted from the speech waveform (step S105), and it is identified whether or not it is a human voice, and noise removal processing is performed (step S106). Then, the audio signal is encoded (step S107) and converted into a transmission code (redundant configuration, error correction code added) (step S108).

  By encoding the voice according to the above procedure, in the small amplitude compression process of step S105, in the case of a silence interval or a noise interval, only the signal of noise is transmitted to lower the transmission rate, and the power required for transmission and the portable power are reduced. The power consumption of the telephone can be reduced. Further, the background noise is removed by the process of step S106 to improve the sound quality (clarification) of the call voice.

On the other hand, in recent years, cases of listening to music with a mobile phone are increasing. In particular, there are the following services as music flows on a mobile phone network. (1) Auditioning music: Call a music auditioning company and specify the song you want to listen to to audition the music. (2) Outgoing melody service: When A calls and calls B, A listens to the music specified by B instead of the ring back tone (Ring Back Tone service). .) (3) Self-sending melody service: A ringing (Ring
A listens to music specified by A instead of Back Tone).

  Then, when listening to music on a mobile phone using the service described above, the sound source file provided by the music supplier was transmitted as it was to the mobile phone of the person who listened to the music via the mobile phone network. . Then, when the person A who listens to music is a narrow-band mobile phone (PDC, GSM, cdmaOne), the sound quality deteriorates due to the voice codec characteristics of the mobile phone network during transmission from the mobile phone to the radio base station. There was a problem that. Here, with reference to FIG. 9, the above-described transmission melody service will be briefly described, and the flow of the sound source file and the state of sound quality deterioration in the case of the cdmaOne network will be described.

  As shown in FIG. 9, first, when a call is made from the caller mobile phone U101 to the called mobile phone U102 subscribed to the caller service, the radio base stations constituting the mobile phone network 110 that receives the call request 101, 104, MSC (Mobile Switching Center) 102, 103, GS (Gateway Switch: relay base station) 105, etc., the status of the called mobile phone U102 as a subscriber is confirmed ( Arrows L1, L2, L3, L4, L5). At this time, the MSC 102 on the calling side mobile phone U101 side accesses the subscriber service management server 106 via the GS 105, and refers to the subscriber database 107 whether or not the called side mobile phone U102 is subscribed to the calling melo service. (Arrow L6). When the called mobile phone U102 is subscribed to the service, the MSC 102 makes an activation request to the melody playback control server 108, and sends the sound source file designated by the subscriber to the calling mobile phone U101. Request to transmit instead (arrow L7).

  Then, the melody playback control server 108 reads the WAV format sound source file F3 from the sound source database 109 (arrow M1), converts it into PCM 64 kbit / sec, and transmits it to the radio base station 101 via the GS 105 and the MSC 102. (Arrows M2, M3, M4). For this reason, deterioration of sound quality does not occur during transmission from the melody reproduction control server 108 to the wireless base station 101. Then, the radio base station 101 performs encoding corresponding to the codec of the caller mobile phone U101. For example, encoding for an EVRC codec of 8 kbit / sec is performed. Therefore, a situation occurs in which the sound quality of music is greatly deteriorated in this section (arrow M5). That is, the radio base station 101 performs the EVRC codec, which is an audio encoding process using the same algorithm as the process shown in FIG. 8 described above, and the sound quality of the sound source file deteriorates.

  Here, the above-described deterioration of music will be described in detail. This deterioration is due to the process of clarifying the voice, which is a feature of the EVRC codec described above. Specifically, in the process of step S105, the small amplitude portion is deleted after the analog signal normalization and the band filter process. That is, for a sound source file, when the dynamic range is large and the sound volume is large, the portion and the small portion change continuously. For example, the sound source file (waveform) shown in FIG. Since the small volume portion of the section is deleted (see FIG. 10B), there is a problem that the music is partially interrupted and the sound quality is deteriorated.

The processing in step S106 is a function specific to a voice codec that removes background noise and increases the clarity of voice. This function has a reference value that distinguishes speech and noise internally, and compares this reference value with the predicted gain of the input signal (Prediction Gain) to identify speech and noise (from the reference value). Voice with high prediction gain). And the audio codec is 20msec (160
Sample) is encoded as one frame, but when the correlation between signal frames is small, the prediction gain: Prediction Gain is small. At this time, when the speech is viewed in units of 20 msec, the inter-frame correlation is large and the prediction gain is large, but in the case of noise, the prediction gain is small because of a random signal. When the sound changes suddenly in orchestra, rock music, etc., the correlation between frames is small, the prediction gain is small, and the possibility of being regarded as noise increases. In the case of orchestra and rock music, when viewed in a frequency space, it is distributed over a wide frequency band and may have frequency characteristics close to noise. Therefore, in such a song, the sound quality is severely deteriorated. When it is regarded as noise, only a signal that is not encoded and is not transmitted is transmitted, and in the frame (every 20 ms) in which the noise identification signal is received, low-level pseudo noise (white noise) is received at the receiving terminal side. ) Is not reproduced as the original music, and the sound quality deteriorates.

  In summary, the causes of sound quality degradation are as follows. The sound source file F3 is transmitted from the melody reproduction control server 108 at 64 kbit / sec μ LawPCM. Since the GS 105 and the MSC 102 transmit as they are at 64 kbit / sec, there is no deterioration in sound quality. On the other hand, in the radio base station 101, it is converted into a radio section signal by a voice codec peculiar to the mobile phone system. At this time, since the band between the radio base station 101 and the mobile phone U101 is narrow, encoding specialized for speech is performed. For this reason, normal music tends to be regarded as noise, so the sound quality deteriorates.

  In addition, if the above functions are removed from the existing codec provided in mobile phones and wireless base stations, the sound quality of music can be prevented, but the noise removal function will not work and the quality of normal voice calls will deteriorate. The codec specification itself cannot be changed. Also, even if the noise removal function is removed, building a codec device with such an algorithm takes a lot of work, and it is also possible to replace it with what is already provided in a mobile phone or wireless base station. There also arises a problem that a great deal of cost is required.

  A technique for suppressing deterioration in sound quality is disclosed in Patent Document 1. In this patent document 1, in a voice call between mobile phones, when the mobile phones use the same codec in the same mobile phone network, the base phone is not converted into PCM in the mobile phone network. A codec through system is disclosed in which an encoded signal used between a station and a mobile phone is directly exchanged between the mobile phones. As a result, the number of times of encoding by the codec is reduced to prevent deterioration of voice quality. However, the technique described in Patent Document 1 is a codec-through technique related to audio data during a call, and cannot improve the sound quality of music data. That is, as described above, even if a sound source file is transmitted using codec through, the sound quality deteriorates at the initial audio encoding process.

JP-A-11-55716

  As described above, the conventional music providing system has a problem that the sound quality of the music cannot be maintained because the codec specialized for voice is used because the band between the radio base station and the mobile phone is narrow. .

  When a music playback request was made, the prepared sound source file was connected to the mobile phone network in voice mode (64kbit / sec PCM) and heard. Since there is one sound source file for one content, the same sound source file is connected to all reproduction requesting subscribers for the same content. Therefore, particularly in a narrow-band mobile phone, sound quality deterioration due to codec characteristics in the wireless section occurs, and music with good sound quality cannot be provided.

  The degree of sound quality degradation varies greatly depending on the codec type of the mobile phone. When listening to music with W-CDMA and PHS, it is possible to listen with almost the same sound quality as when listening to landline telephones. In the case of cdma, GSM, and PDC, the sound quality is greatly degraded depending on the music due to the encoding characteristics of each codec. In other words, in cdma, GSM, and PDC, when a song with a large number of frequency components is heard, the audio codec cannot follow, causing interruptions and stuttering and greatly degrading sound quality. On the other hand, in the case of a song with a small number of frequency components, there is little deterioration in sound quality.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a music providing system and the like that can provide music with little deterioration in sound quality, particularly to a mobile phone that employs a narrowband codec.

The music providing system according to the present invention provides music to a mobile phone via a radio base station, and includes a sound source file storage means, a codec type detection means, and a sound source file transmission means. The sound source file storage means stores a plurality of sound source files corresponding to codec characteristics with different numbers of chords, which is the number of frequencies transmitted simultaneously, for the music. The codec type detection means detects the codec type of the mobile phone. The sound source file transmitting means obtains a sound source file having the maximum number of chords less than or equal to the number of chords that can be transmitted to the codec type detected by the codec type detecting means from the sound source file storing means, and the sound source file is obtained from the radio base station. To the mobile phone.

  When a song with a large number of simultaneous transmission frequencies (hereinafter referred to as the number of chords) is played in a narrow-band codec, the song is severely deteriorated in sound quality with interruptions and stuttering. Therefore, in the present invention, a song having a small number of simultaneous transmission frequencies (hereinafter referred to as chords) is created in advance, and this sound source file is connected according to the codec characteristics when a reproduction is requested. Since the number of chords that can be transmitted differs for each codec, a sound source file having the maximum number of chords that is less than or equal to the number of chords that can be transmitted is selected and connected from among a plurality of sound source files. The more chords, the deeper the music. On the other hand, music with a small number of chords becomes simple music with a small depth at the center of the main melody, but the sound quality does not deteriorate much even when played with a narrowband codec.

  Further, the codec type detection means may detect the codec type of the mobile phone based on a network type included in an input activation signal or based on negotiation with the radio base station side. The sound source file transmitting means may transmit the sound source file instead of the ringback tone of the mobile phone.

The music providing method according to the present invention is a method for providing music to a mobile phone via a wireless base station. That is, a plurality of sound source files having different numbers of chords that are simultaneously transmitted frequencies are stored in advance for the music, and the codec type of the mobile phone is detected and transmitted to the detected codec type. A sound source file having the maximum number of chords less than or equal to the number of chords is acquired from the stored sound source files, and the acquired sound source file is transmitted from the radio base station to the mobile phone. A music providing program according to the present invention is for realizing the above-described means in a music providing computer that provides music to a mobile phone via a wireless base station.

  In other words, an object of the present invention is to provide a function for listening to music with little deterioration in sound quality by reproducing a sound source processed for a narrowband codec. That is, the present invention automatically creates a sound source file for a narrow band from a basic sound source file, and selects and connects a sound source file with the best sound quality according to the mobile phone type at the time of playback request. Sound quality deterioration can be prevented.

According to the present invention, in a service for listening to music on a mobile phone, a plurality of sound source files corresponding to the codec characteristics of the mobile phone ( a plurality of sound source files having different numbers of chords, which is the number of frequencies transmitted simultaneously) are created in advance. Accumulate and listen to music of the best sound quality by selecting and listening to the optimal sound source file ( sound source file with the maximum number of chords less than the number of chords that can be sent) according to the codec type at the time of playback request be able to. In other words, since a sound source file optimal for a narrow-band codec is selected and connected, it is possible to listen to a song with little deterioration in sound quality.

  The sound source file transmitted through the mobile phone network includes a sound source file that is played instead of the ringing tone, and is provided from the music providing device to the mobile phone through the mobile phone network. In the following embodiment, a case where the above-described calling melo service is provided in the cdma network will be described. However, the sound source file transmitted through the cellular phone network is not limited to the sound source file that is played instead of the ringing sound by the calling melo service.

  FIG. 1 is a diagram showing an overview of the overall system configuration in the first embodiment. Hereinafter, description will be given based on this drawing.

  A system for realizing the calling-mello service includes a calling-side mobile phone U1, a receiving-side mobile phone U2, a mobile phone network 50, radio base stations 51 and 52 installed in the mobile phone network 50, GS53, MSC 54 and 55, and the like. In addition to the basic configuration that enables communication with mobile phones, the melody playback control server 1 (music providing device) that provides music connected to the MSC 54 and GS 53 and the user who subscribes to the melody service are registered. And a subscriber service management server 3 that manages them. The melody reproduction control server 1 includes a sound source database 2 that stores sound source files to be provided, and the subscriber service management server 3 includes a subscriber database 4.

  In addition, since the specific configuration of the calling melo service is as described in the background art above, its detailed description is omitted. Here, in FIG. 1, the calling-side mobile phone is denoted by reference symbol U <b> 1, and the called-side mobile phone is denoted by reference symbol U <b> 2. Further, the installation status of the radio base stations 51 and 52, the MSCs 54 and 55, and the GS 53 is not limited to the status shown in this figure. For example, the melody reproduction control server 1 may be activated from the MSC 55 located on the receiving side mobile phone U2 side.

  In the present invention, since the melody reproduction control server 1 has a feature, the configuration and operation of the melody reproduction control server 1 will be mainly described in detail. That is, what happens after the melody reproduction control server 1 is activated in the MSC 54 when a call is made from the calling side mobile phone U1 to the called side mobile phone U2 subscribed to the calling melo service. explain.

FIG. 2 is a functional block diagram showing the configuration of the melody reproduction control server in FIG. Hereinafter, a description will be given based on FIG. 1 and FIG.

  The melody reproduction control server 1 is constituted by a general server computer, and the following processing unit is constructed in the CPU 10 by incorporating a predetermined program.

  First, the melody reproduction control server 1 includes a melody reproduction instruction reception unit 11 that receives an activation instruction from the MSC 54 via the GS 53, and a codec type detection unit 12 (codec type detection means) that detects the codec type of the originating mobile phone U1. And a sound source file transmitting unit 13 (sound source file transmitting means) for transmitting a sound source file corresponding to the codec type of the calling side mobile phone U1 from the radio base station 51 to the calling side mobile phone U1.

  The sound source database 2 that is the storage device is formed with a sound source file storage unit 20 (sound source file storage means) for storing a sound source file to be provided to the calling-side mobile phone U1, and for each provided music Multiple sound source files according to the codec characteristics. Hereafter, each said structure is explained in full detail.

  A sound source file corresponding to each codec type is created in advance from a basic sound source and stored in the sound source file storage unit 20. The sound source file storage unit 20 includes a plurality of files for the same song. Therefore, the file number is managed as file-id + codec-ID.

  The melody reproduction instruction receiving unit 11 notifies the codec type detection unit 12 when receiving an instruction to distribute the sound source file from the MSC 54 to the calling-side mobile phone U1.

  When there is a music playback request, the codec type detection unit 12 determines the codec type of the calling side mobile phone U1 based on the network type and calling company code in the activation signal (IAM: arrow L7), The sound source file transmission unit 13 is notified of the codec type.

  The sound source file transmission unit 13 reads the best sound source file corresponding to the codec notified from the codec type detection unit 12 from the sound source file storage unit 20 and transmits the sound source file via the GS 53, the MSC 54, and the radio base station 51. To the mobile phone U1.

  Next, the connection operation at the time of sound quality improvement in the sound source supply system of FIG. 1 will be described.

  When there is a music reproduction request, the melody reproduction control server 1 listens to music having the optimum sound quality within a reproducible range by the codec type of the caller mobile phone U1. The procedure for selecting the optimum sound source for the calling-side mobile phone U1 is as follows.

1) The melody reproduction control server 1 is activated by the activation signal (IAM) from the MSC 54.
2) The caller code and the network type are extracted from the IAM, and the codec type of the caller mobile phone U1 is determined.
3) The number of transmittable chords b corresponding to the codec type is determined.
4) Each sound source file has constituent chord numbers a1, a2, a3,.
5) Select a sound source file having the maximum number of constituent chords a below b.
6) Transmit the selected sound source in the audio mode (PCM 64 kbit / sec).
7) In the case of an incoming call from a fixed telephone, since there is no limit on the number of chords that can be transmitted, a sound source having the maximum number of frequency components is selected.

  For example, as shown in FIG. 2, there are three types of sound source files F1, F2, and F3 for the same song, and the number of constituent chords is a1 = 3, a2 = 8, and a3 = 40, respectively. The maximum number of chords that can be transmitted is PDC Half rate: 3, PDC Full rate: 6, cdma: 10, PHS: 40, fixed telephone: no limit. At this time, when transmitting to cdma, a song having the maximum number of chords of 10 or less is selected. In this case, since it is 8, the sound source file F2 (a2 = 8) is selected.

  FIG. 3 is a flowchart showing a method of creating each sound source file from the basic sound source. Hereinafter, description will be given based on this drawing.

First, a basic sound source is input (step S11). The basic sound source is divided into frames every 20 msec (step S12). Each frame is converted into a frequency space (step S13). M pitch frequencies (formant frequencies) are extracted (step S14). The harmonic component of the pitch frequency is added to the fundamental frequency component (step S15). Smoothing is performed (step S16). Smoothing is a mechanism that prevents sudden changes in the fundamental frequency by adding the frequency components of the previous frame, since the sound quality deteriorates when the fundamental frequency changes greatly every 20 msec frame. By smoothing, the continuity of music can be maintained and the change in sound quality can be reduced. For example, if the frequency component before smoothing of the Kth frame is F (K, ω), the frequency component after smoothing is G (K, ω), and the frequency is ω,
G (K, ω) = F (K, ω) * ((1−α) + αG (K−1, ω))
Ask for. Subsequently, N fundamental frequency components are extracted (step S17). The comb filter compresses components other than the harmonic components of the N fundamental frequency components (step S18). By inverse Fourier transform, the time space is restored (step S19), and a sound source file for a narrow band is created (step S20).

  FIG. 4 is a flowchart showing the operation of the melody reproduction control apparatus. FIG. 5 is a sequence diagram showing an operation in the entire music supply system. The overall operation of the music supply system will be described below with reference to FIGS. In addition, referring to FIG. 1, the flow of a sound source file is also shown.

  First, when the calling side mobile phone U1 makes a call to the receiving side mobile phone U2 (step S31 in FIG. 5), the MSC 54 determines whether or not the receiving side mobile phone U2 has subscribed to the calling melo service. And get a response (not shown). If the user is subscribed, the MSC 54 issues an activation instruction to the melody reproduction control server 1 via the GS 53 in order to play the sound source file instead of the ringback tone (step S32 in FIG. 5).

  Subsequently, the melody reproduction control server 1 that has received the activation instruction (step S21 in FIG. 4) detects the codec type of the originating mobile phone U1 based on the activation signal (IAM) (step S22 in FIG. 4, FIG. 5). Step S33). Then, the sound source file encoded corresponding to the codec type is searched and read from the sound source database 2 (step S23 in FIG. 4 and steps S34 and S35 in FIG. 5).

  Thereafter, the sound source file is transmitted to the calling-side mobile phone U1 (step S24 in FIG. 4 and step S36 in FIG. 5). As a result, the sound source file is transmitted to the calling-side mobile phone U1 (arrows M1 to M5 in FIG. 1). Therefore, since the sound source file with little deterioration is transmitted to the calling-side mobile phone U1, the user can listen to the high-quality music while waiting for the call by reproducing the sound source file (step S37 in FIG. 5). ).

  Thereafter, when the incoming side mobile phone U2 responds (affirmative determination in step S25 of FIG. 4, step S38 of FIG. 5), that is, when the incoming side user answers the telephone, the melody reproduction control server 1 is instructed to disconnect in GS53 (Step S39 in FIG. 5), the melody reproduction control server 1 stops the transmission of the sound source file (Step S26 in FIG. 4). Then, a call can be made between the calling-side mobile phone U1 and the receiving-side mobile phone U2 (steps S40 and S41 in FIG. 5).

  Although the case of the cdma network has been described here, the present invention can also create a sound source file corresponding to each codec type in the same manner for other codec types. Therefore, by storing a sound source file suitable for each codec type in the sound source database 2 in advance, music without deterioration in sound quality can be provided to all users.

  Further, the melody reproduction control server 1 determines the codec type of the caller mobile phone U1 based on the network type included in the activation signal (IAM), and selects the sound source file having the best sound quality according to the codec type. In this way, in the music supply system of this embodiment, since the sound source file dedicated to the narrowband codec is selected and heard, the music with the best sound quality within the range that can be played back by the codec of the mobile phone is heard. Can.

  FIG. 6 is a flowchart showing the operation of the melody reproduction control server in the second embodiment. FIG. 7 is a sequence diagram showing the operation of the entire system in the second embodiment. Hereinafter, description will be made based on FIGS. 1, 6, and 7. However, the description of the same part as the first embodiment is omitted.

  In this embodiment, the configuration is basically the same as that of the first embodiment, and the determination of the codec type of the mobile phone is further devised. That is, the melody reproduction control server 1 obtains the codec type of the calling-side mobile phone U1 by negotiation. Then, by selecting and reproducing the best sound source file corresponding to the codec type obtained by the negotiation, it is possible to hear music with little deterioration in sound quality.

  6 and 7, only different parts from the first embodiment will be described. The melody reproduction control server 1 that has received the activation instruction (step S21 in FIG. 6), then inquires the codec type of the caller mobile phone U1 to the caller MSC 54 via GS53 (step S22 ′ in FIG. 6, FIG. 6). 7 step S331). A response is obtained (step S332 in FIG. 7), and the codec type is known.

  Thus, in this embodiment, since the melody reproduction control server 1 spontaneously determines the codec type, the mobile phone is activated not only when the reproduction is requested but also from the melody reproduction control server 1 side. The effect that it is applicable also to a case is acquired.

  The present invention can be widely used for all services for listening to music on a mobile phone. For example, the present invention provides an outgoing melody service that sends music to a mobile phone instead of a ringing tone (ringback tone), or a service that listens to music by calling a music listening agent and specifying a song that the user wants to listen to. Therefore, it is possible to provide music with no deterioration in sound quality, which has industrial applicability.

It is a figure which shows the outline | summary of the whole system configuration | structure in 1st embodiment. It is a functional block diagram which shows the structure of the melody reproduction | regeneration control server in 1st embodiment. It is a flowchart which shows the method of producing each sound source file from the basic sound source in 1st embodiment. It is a flowchart which shows operation | movement of the melody reproduction | regeneration control server in 1st embodiment. It is a sequence diagram which shows the operation | movement in the whole system in 1st embodiment. It is a flowchart which shows operation | movement of the melody reproduction | regeneration control server in 2nd embodiment. It is a sequence diagram which shows the operation | movement in the whole system in 2nd embodiment. It is a flowchart which shows the flow of the encoding process for audio | voices. It is the schematic which shows the structure of the whole system which implement | achieves the transmission melody service in a prior art example. It is explanatory drawing which shows the mode of the signal in the process which removes a part of audio | voice coding process in a prior art example, ie, a small amplitude part.

Explanation of symbols

1 Melody playback control server (music provider)
2 Sound source database (sound source file storage means)
3 Subscriber Service Management Server 4 Subscriber Database 11 Melody Playback Instruction Accepting Unit 12 Codec Type Detection Unit (Codec Type Detection Unit)
13 Sound source file transmission unit (sound source file transmission means)
20 Sound source file storage (sound source file storage means)
50 Mobile phone network 51, 52 Wireless base station 53 Relay exchange (GS)
54,55 Mobile phone exchange (MSC)
U1 Calling mobile phone U2 Calling mobile phone

Claims (6)

In a music providing system that provides music to a mobile phone via a wireless base station,
Sound source file storage means for storing a plurality of sound source files having different numbers of chords, which is the number of frequencies to be transmitted simultaneously, with respect to the music;
Codec type detection means for detecting the codec type of the mobile phone;
The sound source file having the maximum number of chords that can be transmitted to the codec type detected by the codec type detection means is acquired from the sound source file storage means, and the sound source file is transmitted from the radio base station to the mobile phone. Sound source file transmission means to perform,
A music providing system characterized by comprising: The codec type detection means detects the codec type of the mobile phone based on a network type included in the input activation signal;
The music providing system according to claim 1. The codec type detection means detects the codec type of the mobile phone based on the negotiation with the radio base station side;
The music providing system according to claim 1. The sound source file transmitting means transmits the sound source file instead of the ringback tone of the mobile phone;
The music providing system according to any one of claims 1 to 3. In a method for providing music to a mobile phone via a wireless base station,
A plurality of sound source files having different numbers of chords, which are the number of frequencies transmitted simultaneously, are stored in advance for the music,
Detecting the codec type of the mobile phone;
The sound source file having the maximum number of chords that can be transmitted to the detected codec type is acquired from the accumulated sound source files,
The acquired sound source file is transmitted from the wireless base station to the mobile phone.
A method for providing music. A computer that provides music to mobile phones via wireless base stations
Sound source file storage means for storing a plurality of sound source files having different numbers of chords, which is the number of frequencies to be transmitted simultaneously, with respect to the music;
Codec type detection means for detecting the codec type of the mobile phone;
The sound source file having the maximum number of chords that can be transmitted to the codec type detected by the codec type detection means is acquired from the sound source file storage means, and the sound source file is transmitted from the radio base station to the mobile phone. Sound source file transmission means to perform,
A program for providing music to achieve this.

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