JP5338962B2 - Bandwidth expansion device, method and program, and telephone terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To generate band extension signals automatically regulated according to hearing circumferential conditions or the like. <P>SOLUTION: The invention relates to a band extension device extending a frequency band of input voice signals according to parameters. The band extension device comprises: feature determination means for collecting circumferential sounds outputting to pronounce voice signals extended in a band, determining features of the circumferential sounds and estimating a feature quantity of the features; and adjustment quantity estimation means for comparing the feature quantity of the features with the parameters and estimating an adjustment quantity of the parameters. <P>COPYRIGHT: (C)2013,JPO&amp;INPIT

Description

  The present invention relates to a band extending apparatus, method and program, and a telephone terminal, and can be applied to, for example, a case where a band exceeding a band upper limit is generated and added to a band-limited voice signal to expand the band. Is.

  For example, in a telephone communication system for sending and receiving voice signals, the frequency band of the transmitted voice signal is 0.3 kHz to 3.4 kHz, which is essentially much narrower than the frequency band of voice emitted by humans. Yes. For this reason, the voice sent through the phone has a poor quality such as being muffled.

  In order to solve such a problem, for example, as in the technique described in Patent Document 1, there is a technique of improving the quality by extending the frequency band of the audio signal to the high frequency side on the reception side.

  In the technology described in Patent Document 1, a higher frequency audio signal (high frequency signal) is generated from the received audio signal (low frequency signal), and the high frequency signal is added to the low frequency signal. Is getting a voice signal. Here, the technique described in Patent Document 1 is characterized in that the addition ratio of the high frequency signal to the low frequency signal can be varied by an external operation.

JP 2000-134162 A

  However, in the technique described in Patent Document 1, the amount of work for manually operating the addition ratio is excessive, and skillful techniques are required, which makes it difficult for general users to operate. .

  In addition, among other band expansion devices, there are devices that allow users, telephone terminal installers, and the like to adjust the characteristics of the high-frequency signal to be generated. However, it is difficult for the operator to appropriately perform the adjustment operation.

  Therefore, there is a demand for a bandwidth expansion device, method and program, and a telephone terminal that can generate a bandwidth expansion signal that is automatically adjusted according to listening ambient conditions and the like.

  According to a first aspect of the present invention, in a band expansion device that expands a frequency band of an input audio signal according to a parameter, (1) collecting ambient sounds that sound and output the band-extended audio signal; And (2) an adjustment amount estimating means for estimating the adjustment amount of the parameter by comparing the feature amount of the feature with the parameter. It is characterized by having.

  According to a second aspect of the present invention, in a band expansion device that expands a frequency band of an input audio signal according to a parameter, (1) a surrounding sound that generates and outputs a band-extended audio signal is collected, and the ambient sound First feature quantity estimating means for judging a feature quantity of the feature, and (2) converting the ambient sound into a signal having characteristics equivalent to a band-extended voice signal, and the parameter And (3) a feature quantity of the second feature quantity estimation means is a feature of the first feature quantity estimation means. And adjusting amount estimating means for estimating the parameter approaching the amount and estimating the adjustment amount of the parameter.

  According to a third aspect of the present invention, there is provided a band extending method for extending a frequency band of an input voice signal according to a parameter. (1) The feature determination unit collects ambient sounds that sound and output the band extended voice signal. Then, the feature of the ambient sound is determined, and the feature amount of the feature is estimated. (2) The adjustment amount estimation unit compares the feature amount of the feature with the parameter, and estimates the adjustment amount of the parameter. It is characterized by doing.

  According to a fourth aspect of the present invention, there is provided a band extending method for extending a frequency band of an input audio signal according to a parameter. (1) The first feature amount estimating means Collecting sounds, determining the characteristics of the ambient sound, and estimating the feature amount of the feature; (2) the second feature amount estimating means is configured to generate the ambient sound equivalent to a band-extended audio signal; A characteristic signal of the converted ambient sound using the parameter, and (3) an adjustment amount estimating unit, wherein the feature amount of the second feature amount estimating unit is the first characteristic amount. The parameter that approaches the feature amount of one feature amount estimation means is estimated, and the adjustment amount of the parameter is estimated.

  According to a fifth aspect of the present invention, there is provided a band expansion program for expanding a frequency band of an input audio signal according to a parameter, and (1) collecting ambient sounds for sound output of the band-extended audio signal. And a feature determination unit that determines the feature of the ambient sound and estimates the feature amount of the feature, and (2) an adjustment that compares the feature amount of the feature with the parameter and estimates the adjustment amount of the parameter It functions as a quantity estimating means.

  According to a sixth aspect of the present invention, there is provided a band expansion program for expanding a frequency band of an input audio signal according to a parameter, and (1) collecting ambient sounds for sound output of the band-extended audio signal. First feature amount estimating means for determining the feature of the ambient sound and estimating the feature amount of the feature; and (2) converting the ambient sound into a signal having characteristics equivalent to the band-extended speech signal. And second feature quantity estimating means for estimating the converted feature quantity of the ambient sound using the parameter, and (3) the feature quantity of the second feature quantity estimating means is the first feature. The parameter that approaches the feature amount of the amount estimation unit is estimated, and the parameter is adjusted to function as an adjustment amount estimation unit that estimates the adjustment amount of the parameter.

  According to a seventh aspect of the present invention, there is provided a telephone terminal including the band extending apparatus according to the first or second aspect of the present invention.

  According to the present invention, it is possible to generate a band extension signal that is automatically adjusted according to the listening ambient condition or the like.

It is a block diagram which shows the structure of the band expansion apparatus which concerns on 1st Embodiment. It is a block diagram which shows the detailed structural example of the extended characteristic adjustment part in 1st Embodiment. It is explanatory drawing of the storage method of the parameter information in the parameter operation device in 1st Embodiment. It is a block diagram which shows the structure of the band expansion apparatus which concerns on 2nd Embodiment. It is a block diagram which shows the detailed structural example of the extended characteristic adjustment part in 2nd Embodiment. It is a block diagram which shows the structure of the deformation | transformation embodiment with respect to 2nd Embodiment.

(A) First Embodiment A band extending apparatus, method and program according to the present invention, and a first embodiment of a telephone terminal will be described below with reference to the drawings.

  In the first embodiment, a noise component of a signal input from a receiving side that receives a band extension signal is extracted, and the magnitude of a signal component output at the time of band extension is changed according to the magnitude of the noise component. As a result, the sound is easy to hear when listening.

(A-1) Configuration of First Embodiment FIG. 1 is a block diagram showing a configuration of a band extending apparatus according to the first embodiment. For example, even if the device (telephone terminal) on which the bandwidth expansion device of the first embodiment is mounted is a soft phone and the bandwidth expansion device is realized by a CPU and a program executed by the CPU, the function Specifically, it can be represented by the functional block diagram of FIG.

  In FIG. 1, the bandwidth expansion apparatus 100 according to the first embodiment includes a bandwidth expansion processing unit 101, an expansion characteristic adjustment unit 102, a transmission acquisition unit 103, an operation unit 104, and a reception sound generation unit 105.

  The band extension processing unit 101 applies the parameter information PA when the operation information AI indicates the extension operation, and forms the band extension signal ES from the received signal TS. The operation information AI performs the extension operation. When not instructed, the received signal TS is passed as it is.

  As a bandwidth extension method applied by the bandwidth extension processing unit 101, for example, a method using a wideband codebook, LPC synthesis, and a high-frequency suppression filter as described in Patent Document 1 is applied. In this case, parameter information that can be changed, which will be described later, is a filter shape (frequency characteristic curve) in the high-frequency suppression filter. A plurality of wideband codebooks having different excitation vector powers may be prepared, and the type of the wideband codebook may be applied as the parameter information. Further, a variable circuit for changing the filter coefficient may be provided at the input stage of the filter coefficient (α) of the LPC synthesis filter, and the filter coefficient of the LPC synthesis filter may be applied as parameter information.

  However, the bandwidth extension method applied by the bandwidth extension processing unit 101 is not limited to the method described in Patent Document 1. For example, a method that does not use LPC synthesis or a method that analytically generates a pseudo high-frequency signal instead of the wideband codebook may be used. However, it is necessary to be a band expansion method in which the characteristics of the high frequency signal change by changing the parameter. The parameter information may be determined according to the band expansion method to be applied.

  The received sound generation unit 105 corresponds to a speaker, a headphone, an earphone, or the like, and outputs a band expansion signal ES or a reception signal TS given from the band expansion processing unit 101.

  The transmission acquisition unit 103 corresponds to a microphone incorporated in a telephone terminal, a microphone attached to a headset, or the like, and captures the voice of a near-end speaker and obtains a transmission signal RS. Here, the transmission signal RS may be a narrow band signal similar to the reception signal TS before the band expansion, or may be a broadband signal similar to the band expansion signal ES.

  The operation unit 104 is used by a user of a telephone terminal equipped with the bandwidth extension device 100 of the first embodiment to instruct whether to enable or disable the bandwidth extension, and represents whether the bandwidth extension is enabled or disabled. The operation instruction information DI is output. For example, an on / off switch or a dip switch may be applied, the function may be assigned to any key of the key input unit, and an icon can be applied in the case of a soft phone. In the case of the first embodiment, the user can instruct only valid / invalid with respect to band expansion, and cannot perform a variable operation on the characteristics of the high frequency signal.

  Operation characteristic information DI, reception signal TS, and transmission signal RS are input to the expansion characteristic adjustment unit 102. Based on these information, the expansion characteristic adjustment unit 102 indicates whether or not to perform a band expansion operation. Information AI and parameter information PA that defines the characteristics of the high frequency signal when the band expansion operation is executed are formed and given to the band expansion processing unit 101.

  FIG. 2 is a block diagram illustrating a detailed configuration example of such an extended characteristic adjustment unit 102. In FIG. 2, the extended characteristic adjustment unit 102 includes a component determination unit 111, a noise level acquisition unit 112, an update necessity determination unit 113, a parameter adjustment unit 114, a parameter operation unit 115, and a received signal determination unit 116.

  The component determination unit 111 determines whether or not the input transmission signal RS is a noise signal that does not include a voice signal. The component determination unit 111 outputs the input transmission signal RS as the determination target signal JS when determined as a noise signal, and does not output the determination target signal JS when determined as not a noise signal, or A meaningless determination target signal JS (for example, all 0) is output. To determine whether or not the input signal is a noise signal, a known noise determination method may be applied. For example, a delay time that maximizes the autocorrelation function that is a correlation function between the transmission signal RS and a signal obtained by delaying the transmission signal RS is periodically estimated (for example, every 10 ms). It is possible to apply a method for determining a noise signal when the time is outside the range of 1.4 ms (range represented by an audio signal).

  The noise level acquisition unit 112 calculates the level of the input determination target signal (noise signal) JS. The noise level acquirer 112 obtains, for example, the sum of squares of the input determination target signal (here, digital signal) JS for a predetermined period (for example, 10 ms) as the noise level information NL. However, the method of forming the noise level information NL is not limited to this. For example, the determination target signal JS may be subjected to frequency analysis, and the maximum level of the analysis result and the frequency at that time may be obtained as the noise level information NL.

  The level acquisition of the noise level acquisition unit 112 and the received signal determination unit 116 described later may be performed at predetermined intervals, or may be acquired only once in one call.

  The update necessity determination unit 113 acquires the noise level information NL and compares it with a preset threshold value. When the noise level information NL exceeds the threshold, the update necessity determination unit 113 updates the filter shape (parameter information) of the high-frequency suppression filter in the band extension processing unit 101 to one with a small suppression degree. Judging to do. When the update necessity determination unit 113 changes from a state in which the threshold is exceeded to a state in which the threshold is not exceeded, the degree of suppression of the filter shape (parameter information) of the high-frequency suppression filter in the band extension processing unit 101 is large. Judge that it will be updated to something. A plurality of threshold values may be prepared. If there are two thresholds, when the smaller threshold is exceeded, the suppression degree is reduced by one step, and when the larger threshold is exceeded, the suppression degree is updated by two steps. It is determined that the parameter to be applied is applied. Moreover, you may make it have the threshold value for raising a suppression degree, and the threshold value for reducing a suppression degree separately. When the update necessity determination unit 113 determines that the parameter information needs to be updated, the identification information indicating the updated filter shape (parameter information) indicated in the determination, and the noise level used for the determination Information NL is output as necessity determination information JI. The update necessity determination unit 113 is provided with identification information (for example, a pointer to be described later) that defines the currently applied filter shape (parameter information), whereby the updated filter shape (parameter information) is obtained. Representing identification information can be obtained.

  The reception signal determination unit 116 receives the reception signal TS and outputs the noise level of the reception signal TS as reception signal characteristic information SL. For example, the reception signal determination unit 116 obtains a signal of a period that does not include speech in the same manner as the component determination unit 111 and then calculates the same calculation method as the noise signal level calculation method applied by the noise level acquisition unit 112. To obtain the noise level of the received signal TS.

  The parameter adjuster 114 performs the following parameter information adjustment operation when the necessity determination information JI is given. The parameter adjuster 114 compares the received signal characteristic information SL with the noise level information NL included in the necessity determination information JI, and the noise level information NL is a predetermined multiple (for example, 1.3 times) of the received signal characteristic information SL. If the noise level information NL is not more than a predetermined multiple of the received signal characteristic information SL, the parameter information included in the necessity determination information JI (here, after the update) is not updated. (Filter shape) identification information is output as update instruction information EP.

  However, the method for determining whether or not to prohibit the execution of the update when the necessity determination information JI is given is not limited to the method described above. For example, the lower limit of the noise level information NL that prohibits execution of update may be set, and the lower limit that prohibits execution of update for both the noise level of the received signal TS and the received signal characteristic information SL. May be set. Further, the determination method for determining whether or not to prohibit execution may be changed according to the determination index used in the update necessity determination unit 113.

  When the operation instruction information DI that does not instruct the extended operation is given, the parameter operator 115 outputs the operation information AI that does not instruct the extended operation, and does not output the parameter information PA at this time (note that the parameter information PA is not changed). It may be output, but the band extension processing unit 101 may ignore it). The parameter operating unit 115 operates as follows when the operation instruction information DI for instructing the extended operation is given. The parameter operator 115 updates the parameter information PA output at the timing when the update instruction information EP is input, and outputs the operation information AI and the parameter information PA instructing the extension operation to the bandwidth extension processing unit 101. For example, as shown in FIG. 3, the parameter operator 115 stores a plurality of parameter information in order of the degree of suppression represented by the filter shape of the high-frequency suppression filter in the band extension processing unit 101, and the pointer POI is It points to the parameter information to be output. The parameter information PA to be output is updated by changing the value of the pointer POI.

(A-2) Operation of the First Embodiment Next, the operation of the bandwidth extension apparatus 100 according to the first embodiment will be described.

  First, an operation when bandwidth extension is not instructed by a user operation on the operation unit 104 will be described.

  At this time, operation instruction information DI not instructing band expansion is output from the operation unit 104, and the operation information AI not instructing band expansion is also transmitted from the expansion characteristic adjustment unit 102 to which the operation instruction information DI is given. The data is output to the processing unit 101. As a result, the reception signal TS passes through the band expansion processing unit 101 as it is, is given to the reception sound generation unit 105, and is output as a sound.

  Inside the extended characteristic adjusting unit 102, the parameter operating unit 115 to which the operation instruction information DI that does not instruct the expansion operation is given outputs the operation information AI that does not instruct the expansion operation. The component determiner 111 to the parameter adjuster 114 and the reception signal determiner 116 may or may not be operating. Even in the case of operation, the parameter operation unit 115 operates so that the parameter information PA to be output is not updated. Also, the operation instruction information DI or operation information AI not instructing the band extension is distributed to the component determination unit 111 to the parameter adjustment unit 114 and the reception signal determination unit 116, and the component determination unit 111 to the parameter adjustment unit 114 and the reception unit. The operation of the signal determiner 116 is stopped.

  Next, an operation when band extension is instructed by a user operation on the operation unit 104 will be described.

  At this time, operation instruction information DI instructing band expansion is output from the operation unit 104, and operation information AI instructing band expansion and parameter information are provided from the expansion characteristic adjustment unit 102 to which the operation instruction information DI is given. The PA is output to the band extension processing unit 101. In the band extension processing unit 101, the internal high-frequency suppression filter is set to suppress high-frequency signals according to the parameter information PA.

  When the reception signal TS is given to the band extension processing unit 101, a band extension signal ES including a high-frequency signal is formed by band extension, and is given to the reception sound generation unit 105 for sound output. When forming the band extension signal ES, the degree of suppression of the high frequency signal is in accordance with the parameter information PA.

  At the time of band expansion, the following operation is performed inside the expansion characteristic adjustment unit 102.

  In the component determination unit 111, it is determined whether or not the input transmission signal RS is a noise signal. If it is a noise signal, it is output to the noise level acquisition unit 112 as a determination target signal JS, and the noise level acquisition unit 112 Thus, the noise level is acquired, and the noise level information NL is given to the update necessity determination unit 113. The update necessity determination unit 113 determines whether or not the parameter information PA needs to be updated by comparing the noise level information NL with a threshold value. If the parameter information PA needs to be updated, the information indicating the updated parameter information PA and the noise level information NL used for the determination are output to the parameter adjuster 114 as the necessity determination information JI.

  In received signal determination unit 116, the noise level of received signal TS is acquired and output to parameter adjuster 114 as received signal characteristic information SL.

  In the parameter adjuster 114, when the noise level information NL included in the necessity determination information JI is larger than a predetermined multiple of the reception signal characteristic information SL, it is determined not to update the parameter. The information defining the updated parameter information included in the necessity determination information JI is output to the parameter operator 115 as the update instruction information EP.

  When the update instruction information EP is given, the parameter information PA given from the parameter operation unit 115 to the bandwidth extension processing unit 101 is updated. When the operation instruction information DI for instructing band extension is given to the parameter operator 115, the operation information AI for instructing band extension is output from the parameter operator 115.

(A-3) Effect of First Embodiment According to the first embodiment, a transmission signal is used as a signal representing an environment for listening to a received signal, and a band extension signal is automatically used according to the environment for listening to the received signal. Can be adjusted. As a result, it is possible to improve the voice quality when the band extension signal is generated without depending on the operation of the user or the like.

(B) Second Embodiment Next, a second embodiment of the bandwidth extending apparatus, method and program, and telephone terminal according to the present invention will be described with reference to the drawings.

  In the second embodiment, the characteristics of the band extension signal are simply estimated from the narrowband signal of the transmission signal, and the extension characteristics are corrected as compared with the broadband signal of the transmission signal acquired separately.

(B-1) Configuration of Second Embodiment FIG. 4 is a block diagram showing a configuration of a bandwidth extension apparatus according to the second embodiment, and is the same as or corresponding to FIG. 1 according to the first embodiment. Are indicated by the same reference numerals.

  In FIG. 4, the bandwidth expansion device 100A according to the second embodiment includes a bandwidth expansion processing unit 101, an expansion characteristic adjustment unit 102A, a transmission acquisition unit 103, an operation unit 104, a received sound generation unit 105, and a sound collection unit 106. .

  The transmission acquisition unit 103, the operation unit 104, and the reception sound generation unit 105 are the same as those in the first embodiment, and a description thereof will be omitted.

  The bandwidth extension processing unit 101 is the same as that of the first embodiment. Hereinafter, the band extension processing unit 101 includes a wideband codebook, an LPC synthesis circuit, and a high-frequency suppression filter as described in Patent Document 1, and the parameter information PA includes a filter coefficient at the time of LPC synthesis, and The description will be made assuming that the codebook is a wideband codebook.

  The sound collection unit 106 corresponds to, for example, a microphone that is different from the microphone constituting the transmission acquisition unit 103, captures the ambient sound of the telephone terminal equipped with the bandwidth expansion device 100A of the second embodiment, and The signal QS is output to the extended characteristic adjuster 102A. The sound collection unit 106 has a larger frequency range in which sound collection is possible than the transmission acquisition unit 103. In other words, the sound collection unit 106 outputs a wideband signal (terminal ambient signal QS), and the transmission acquisition unit 103 outputs a narrowband signal (transmission signal RS). For example, if the upper limit of the frequency at which the transmission acquisition unit 103 can collect sound is 4 kHz, the upper limit of the frequency at which the sound collection unit 106 can collect sound is set to 8 kHz. However, it is desirable that the upper frequency limit of the sound collection unit 106 is equal to or higher than the upper frequency limit generated by the band extension processing unit 101 and output from the received sound generation unit 105.

  Operation instruction information DI, received signal TS, transmission signal RS, and terminal ambient signal QS are input to the extended characteristic adjusting unit 102A of the second embodiment, and the extended characteristic adjusting unit 102A determines the bandwidth based on these information. The operation information AI indicating whether or not to perform the extension operation and the parameter information PA that defines the characteristics of the high frequency signal when the band extension operation is executed are formed and given to the band extension processing unit 101.

  FIG. 5 is a block diagram illustrating a detailed configuration example of the extended characteristic adjustment unit 102A according to the second embodiment. The same reference numerals are given to the same or corresponding parts as those in FIG. 2 according to the first embodiment. ing.

  In FIG. 5, the extended characteristic adjustment unit 102 </ b> A includes a narrowband signal characteristic estimator 121, a wideband signal characteristic estimator 122, a wideband characteristic estimator 123, a received signal determination unit 124, a parameter adjuster 125, and a parameter operation unit 115. The parameter operator 115 is the same as that of the first embodiment, and the description thereof is omitted.

  The narrowband signal characteristic estimator 121 estimates the signal characteristic of the transmission signal RS and outputs it as transmission signal characteristic information RL. As the narrowband signal characteristic estimator 121, for example, a known LPC analyzer may be applied. Here, the LPC coefficient CR0 of the transmission signal RS is generated using the transmission signal RS and the filter coefficient at the time of LPC synthesis in the parameter information PA, and among the transmission signal RS and the parameter information PA, A wideband-corresponding LPC coefficient CR1 is generated using a filter coefficient at the time of LPC synthesis and a wideband codebook. The narrowband signal characteristic estimator 121 calculates a signal power RP of the transmission signal RS obtained by averaging the square sum of the transmission signal RS over time, and outputs the calculation result as one element of the transmission signal characteristic information RL. To do.

  The broadband signal characteristic estimator 122 estimates the signal characteristic of the terminal surrounding signal QS and outputs it as terminal surrounding characteristic information QL. If the narrowband signal characteristic estimator 121 performs LPC analysis, the wideband signal characteristic estimator 122 performs LPC analysis in the same manner as the narrowband signal characteristic estimator 121, but at this time, the wideband codebook is not used. Perform an analysis. However, the LPC coefficients CR0 and CR1 included in the transmission signal characteristic information RL obtained from the narrowband signal characteristic estimator 121 and the orders of the LPC coefficients CQ included in the terminal surrounding characteristic information QL obtained from the wideband signal characteristic estimator 122. Are of the same order. For example, the 10th order can be applied, but is not limited thereto.

  In the above description, the signal characteristics estimated by the narrowband signal characteristic estimator 121 and the wideband signal characteristic estimator 122 are LPC coefficients, but other characteristics are used in accordance with the parameters used in the band extension processing unit 101. Anyway. For example, the signal characteristic to be estimated can be made the frequency characteristic by obtaining a specific frequency component using a known FFT method or the like.

  The broadband characteristic estimator 123 estimates the characteristics at the time of band expansion from the transmission signal characteristic information RL and the parameter information PA, and compares the estimation result with the signal characteristics based on the terminal surrounding characteristic information QL. That is, the broadband characteristic estimator 123 compares the LPC coefficients obtained from the transmission signal characteristic information RL and the terminal surrounding characteristic information QL, and stores the difference correction value as necessity determination information JI. Here, the difference correction value is a value for correcting a difference between signal characteristics based on the estimation result and the terminal surrounding characteristic information QL. In the second embodiment, the minimum value of the differences between the orders of both LPC coefficients is set. However, the present invention is not limited to this, and the designer can arbitrarily determine so that the characteristic value of the signal characteristic can be appropriately acquired. For example, the difference value of each order of the LPC coefficient, the difference average of each order of the LPC coefficient, or a value obtained by multiplying these values by an arbitrary conversion coefficient may be used. Further, not the difference relationship between the LPC coefficients, but the difference in the high frequency codebook such that the LPC coefficient CR1 obtained from the narrowband signal characteristic estimator 121 becomes the LPC coefficient CQ obtained from the wideband signal characteristic estimator 122 is used as the difference information. May be handled.

  The received signal determination unit 124 calculates the signal power TP of the received signal TS and outputs it as received signal characteristic information SL.

  The parameter adjuster 125 calculates the adjustment coefficient as will be described later, multiplies the difference correction value of the LPC coefficient, and outputs it as update instruction information EP to update the parameter of the LPC coefficient. The above adjustment coefficient is represented by a ratio TP / RP between the signal power RP included in the necessity determination information JI and the signal power TP included in the reception signal characteristic information SL.

  The parameter operator 115 updates the LPC coefficient in the parameter information PA based on the update instruction information EP from the parameter adjuster 125. The parameter operating device 115 of the second embodiment does not store much parameter information, but stores parameter information that is updated each time.

(B-2) Operation of Second Embodiment Next, the operation at the time of bandwidth expansion of the bandwidth expansion device 100A according to the second embodiment will be described.

  Also in the second embodiment, when the reception signal TS is given to the band extension processing unit 101, a band extension signal ES including a high frequency signal is formed by the band extension, is given to the reception sound generation unit 105, and is output as a sound. The When forming the band extension signal ES, band extension is performed according to the parameter information PA given from the extension characteristic adjustment unit 102A.

  The ambient sound of the telephone terminal is captured by the sound collection unit 106, and the terminal ambient signal QS, which is a signal wider than the transmission signal RS output from the transmission acquisition unit 103, is obtained and provided to the extended characteristic adjustment unit 102A. . A transmission signal RS and a reception signal TS are also given to the extended characteristic adjustment unit 102A.

  The extension characteristic adjusting unit 102A creates a band extension signal of the transmission signal RS using the parameter information PA, and the signal characteristics of the band extension signal and the terminal ambient signal QS (in the second embodiment, the LPC coefficient). ), The difference correction value is adjusted according to the ratio of the power of the transmission signal RS and the reception signal TS, and the parameter information PA is corrected according to the adjusted difference correction value. The expansion characteristic adjuster 102A operates as follows.

  The signal characteristic of the transmission signal RS is estimated by the narrowband signal characteristic estimator 121 and output as transmission signal characteristic information RL. At this time, the power RP of the transmission signal RS is also calculated. Further, the signal characteristics of the terminal ambient signal QS are estimated by the wideband signal characteristic estimator 122 and output as the terminal ambient characteristic information QL.

  The broadband characteristic estimator 123 estimates the characteristics of the transmission signal RS at the time of band expansion from the transmission signal characteristic information RL and the parameter information PA, and compares the estimation result with the signal characteristics based on the terminal surrounding characteristic information QL. . As a result of the comparison, a difference correction value is calculated, and the difference correction value is stored as necessity determination information JI. Further, the necessity determination information JI includes the power RP of the transmission signal RS. However, the necessity determination information JI may be adjusted as “No”. In this case, for example, when the LPC coefficients CR1 and CQ (or CR1 and CQ) are converted into known LSP coefficients, the difference in frequency of the lower order (for example, 1 to 5 if the overall order is 10th order) The case where the frequency exceeds a predetermined frequency (for example, 100 Hz) may be determined as “No” and the adjustment may not be performed. In this case, as in the necessity determination information JI, a meaningless determination target signal JS (for example, all 0) may be output as in the first embodiment. Similarly, in the case of a high-frequency codebook difference, the necessity determination information JI may also indicate “no” for adjustment.

  The signal power TP of the reception signal TS is calculated by the reception signal determination unit 124 and given to the parameter adjuster 125.

  In the parameter adjuster 125, the ratio between the transmission signal power RP and the reception signal power TP is adjusted by the difference correction value between the estimation characteristic at the time of band expansion of the transmission signal RS and the signal characteristic by the terminal surrounding characteristic information QL. And the parameter information PA is updated according to the multiplication result. In the second embodiment, the adjustment coefficient is always calculated and the parameter information PA is updated. However, the parameter information PA may be updated at a certain interval (for example, every 10 seconds), or a fixed number of times ( For example, it may be updated only once at the start of a call.

(B-3) Effect of Second Embodiment According to the second embodiment, the wideband characteristic of the band extension signal is estimated using the transmission signal, the estimation result, and the same position as the transmission signal The characteristics of the band extension signal can be automatically corrected according to the difference correction value from the broadband signal obtained from the above. As a result, it is possible to improve the voice quality when the band extension signal is generated without depending on the operation of the user or the like.

(C) Other Embodiments In the description of each of the above embodiments, various modified embodiments have been referred to. However, modified embodiments as exemplified below can be cited.

  FIG. 6 is a block diagram showing a configuration of a modified embodiment relative to the second embodiment. In the band extension device 100B of the modified embodiment, the transmission acquisition unit 103 is omitted, and the transmission conversion unit 107 filters the high frequency from the wideband terminal ambient signal QS output from the sound collection unit 106, thereby transmitting the transmission. A signal RS is formed. Others are the same as in the second embodiment.

  In the first embodiment, the adjustment of the degree of suppression of the high frequency signal based on the noise level has been described. However, it is also possible to set the frequency range to be expanded from the noise level information.

  The frequency range f [Hz] to be expanded is included in the reference frequency f1 [Hz], the noise level Ln [dBov] included in the noise level information NL, and the noise level information included in the reception signal characteristic information SL. It is expressed by equation (1) using the noise level Ls [dBov].

f = (Ln−Ls) × fa + f1 (1)
Here, fa is a coefficient for converting a level difference into a frequency, and for example, 12.5 can be applied. Further, for example, 6800 Hz can be applied as the reference frequency f1. The value of (Ln−Ls) is between −40 and 40. When the value of (Ln−Ls) exceeds 40, the value of (Ln−Ls) is less than −40. Replace with -40. However, these values may be designed arbitrarily by the designer according to the environment, and are not limited to these values.

  In the description of each of the above embodiments, the band extension processing unit 101 has been described as having a wideband codebook, an LPC synthesis circuit, and a high-frequency suppression filter. However, the band extension processing unit 101 is not limited to this method, and LPC synthesis. It is also possible to use a method that does not use or a method that analytically generates a pseudo high-frequency signal instead of the wideband codebook. In this case, the parameter is not limited to the filter shape of the high-frequency suppression filter and the filter coefficient at the time of LPC synthesis, and may be either one, or another index may be applied.

  Further, the band extending device is intended to convert the sampling rate in accordance with the band expansion (for example, converting from an 8 kHz sampling signal to a 16 kHz sampling signal), but the sampling frequency is not limited. Further, it may be a band expansion process that enlarges only the range of frequency components included in the signal without changing the sampling frequency.

  DESCRIPTION OF SYMBOLS 100, 100A, 100B ... Band expansion apparatus, 101 ... Band expansion processing part, 102, 102A ... Expansion characteristic adjustment part, 103 ... Transmission transmission part, 104 ... Operation part, 105 ... Received sound generation part, 106 ... Sound collection part, DESCRIPTION OF SYMBOLS 107 ... Transmission conversion part, 111 ... Component determination device, 112 ... Noise level acquisition device, 113 ... Update necessity determination device, 114 ... Parameter adjustment device, 115 ... Parameter operation device, 116 ... Received signal determination device, 121 ... Narrow A band signal characteristic estimator 122, a wideband signal characteristic estimator 123, a wideband characteristic estimator 124, a received signal determiner 125, a parameter adjuster.

Claims (7)

In the band extension device that extends the frequency band of the input audio signal according to the parameters,
A feature determination unit that collects ambient sounds that sound and output a band-extended audio signal, determines features of the ambient sounds, and estimates feature amounts of the features;
A bandwidth expansion apparatus comprising: an adjustment amount estimating unit that compares the feature amount of the feature and the parameter and estimates the adjustment amount of the parameter. In the band extension device that extends the frequency band of the input audio signal according to the parameters,
A first feature quantity estimating means for collecting ambient sounds for sound output of the band-extended audio signal, determining characteristics of the ambient sounds, and estimating the feature quantities of the features;
A second feature amount estimating means for converting the ambient sound into a signal having a characteristic equivalent to a band-extended audio signal and estimating the feature amount of the converted ambient sound using the parameter;
Adjustment amount estimation means for estimating the parameter such that the feature quantity of the second feature quantity estimation means approaches the feature quantity of the first feature quantity estimation means, and estimating the adjustment amount of the parameter. A bandwidth extension device. In the band expansion method for expanding the frequency band of the input audio signal according to the parameters,
The feature determination means collects ambient sounds that sound and output a band-extended audio signal, determines the features of the ambient sounds, estimates the feature amount of the features,
An adjustment amount estimation means compares the feature amount of the feature with the parameter, and estimates the adjustment amount of the parameter. In the band expansion method for expanding the frequency band of the input audio signal according to the parameters,
The first feature quantity estimation means collects ambient sounds that sound and output a band-expanded audio signal, determines features of the ambient sounds, estimates the feature quantities of the features,
The second feature amount estimating means converts the ambient sound into a signal having a characteristic equivalent to a band-extended speech signal, and estimates the feature amount of the converted ambient sound using the parameter.
The adjustment amount estimation means estimates the parameter such that the feature quantity of the second feature quantity estimation means approaches the feature quantity of the first feature quantity estimation means, and estimates the adjustment amount of the parameter. Bandwidth expansion method. A band extension program for extending the frequency band of an input audio signal according to a parameter,
Computer
A feature determination unit that collects ambient sounds that sound and output a band-extended audio signal, determines features of the ambient sounds, and estimates feature amounts of the features;
A bandwidth extension program that functions as an adjustment amount estimating unit that compares the feature amount of the feature with the parameter and estimates the adjustment amount of the parameter. A band extension program for extending the frequency band of an input audio signal according to a parameter,
Computer
A first feature quantity estimating means for collecting ambient sounds for sound output of the band-extended audio signal, determining characteristics of the ambient sounds, and estimating the feature quantities of the features;
A second feature amount estimating means for converting the ambient sound into a signal having a characteristic equivalent to a band-extended audio signal and estimating the feature amount of the converted ambient sound using the parameter;
Estimating the parameters such that the feature quantity of the second feature quantity estimation means approaches the feature quantity of the first feature quantity estimation means, and function as an adjustment quantity estimation means for estimating the adjustment amount of the parameters. A bandwidth extension program characterized by that.   A telephone terminal comprising the band extending apparatus according to claim 1.

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