WO2010070770A1 - 音声帯域拡張装置及び音声帯域拡張方法 - Google Patents
音声帯域拡張装置及び音声帯域拡張方法 Download PDFInfo
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L21/00—Processing of the speech or voice signal to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
- G10L21/02—Speech enhancement, e.g. noise reduction or echo cancellation
- G10L21/038—Speech enhancement, e.g. noise reduction or echo cancellation using band spreading techniques
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
- G10L19/04—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis using predictive techniques
- G10L19/06—Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L25/00—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00
- G10L25/03—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00 characterised by the type of extracted parameters
- G10L25/24—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00 characterised by the type of extracted parameters the extracted parameters being the cepstrum
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10L—SPEECH ANALYSIS OR SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING; SPEECH OR AUDIO CODING OR DECODING
- G10L25/00—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00
- G10L25/27—Speech or voice analysis techniques not restricted to a single one of groups G10L15/00 - G10L21/00 characterised by the analysis technique
Definitions
- the present invention relates to a voice band extending apparatus and a voice band extending method for generating a wide band voice signal from a narrow band voice signal.
- the speech signal is separated into a sound source signal and a spectrum envelope by linear prediction analysis, and the high frequency signal is generated by distorting the sound source signal by nonlinear processing such as full-wave rectification and half-wave rectification. It becomes a broadband.
- the spectral envelope is broadened by using a mapping function from a narrow-band spectral envelope learned in advance to a broadband spectral envelope.
- a technique for generating a broadband signal by synthesizing a spectrum envelope and a sound source signal having a wider band is known.
- the speech signal is separated into a sound source signal and a spectrum envelope by linear prediction analysis, the fundamental frequency of the sound source signal is obtained, and the sound source signal is shifted to a high frequency region and a low frequency region by a frequency that is an integral multiple of the basic frequency to widen the bandwidth Technology is known.
- Japanese Patent Application Laid-Open No. 09-101798 JP 09-055578 A Japanese Patent Application Laid-Open No. 09-101798 JP 09-055578 A
- mapping function for generating a wideband signal from a narrowband signal calculated in advance by learning learns an average mapping relationship using a large number of data. Therefore, the average mapping function is different from the optimum value for the applied audio signal, and it is not possible to obtain a wide band signal with high sound quality. Furthermore, since it is necessary to store various audio signals in order to improve the sound quality, the capacity of the database increases.
- the disclosed voice band extending apparatus calculates a mapping function for generating a high-frequency component from a low-frequency component of the spectrum by using frequency conversion means for calculating a spectrum by frequency-converting an input signal and the spectrum.
- a mapping function calculating means and generating a spectrum of a higher frequency than the spectrum band based on the mapping function, and integrating the generated high frequency spectrum and the spectrum calculated by the frequency converting means,
- Broadband spectrum generating means for generating a spectrum wider than the spectrum band calculated by the frequency converting means, and frequency inverse converting means for calculating an output signal by frequency inversely converting the broadband spectrum.
- a mapping function is calculated from a spectrum of a narrowband signal, and a spectrum having a higher frequency than that of the narrowband is generated using the calculated mapping function so as to widen the bandwidth. Can be achieved.
- FIG. It is a block diagram which shows the main function structural example of the audio
- FIG. It is a block diagram which shows the main function structural example of a wideband spectrum production
- 3 is a flowchart illustrating an example of a voice band expansion process according to the first embodiment. It is a block diagram which shows the main function structural example of the audio
- FIG. It is a figure which shows an example of the relationship between an evaluation value and an error. It is a block diagram which shows the main function structural example of a wideband spectrum production
- FIG. 10 is a flowchart illustrating an example of a voice band expansion process according to the second embodiment. It is a block diagram which shows the main function structural example of the audio
- FIG. It is a block diagram which shows the main function structural example of a wideband spectrum production
- 14 is a flowchart illustrating an example of a voice band expansion process according to the third embodiment.
- FIG. 14 is a flowchart illustrating an example of a voice band expansion process according to the fourth embodiment.
- Frequency conversion means 12 32 Mapping function calculation means 13, 22, 33, 42 Broadband spectrum generation means 14 Frequency inverse conversion means 21, 41 Mapping function evaluation means 31 Sound source / envelope separation means 131 High frequency spectrum generation means 132, 222, 332, 422 Integration means 221 Spectrum correction means 331, 421 High frequency separation information generation means 333, 423 Sound source / envelope synthesis means
- FIG. 1 is a block diagram illustrating an example of a main functional configuration of the voice band extending apparatus 1 according to the first embodiment.
- the audio band extending device 1 includes a frequency conversion unit 11, a mapping function calculation unit 12, a wideband spectrum generation unit 13, and a frequency inverse conversion unit 14.
- the frequency conversion means 11 acquires an audio input signal (hereinafter also referred to as a narrowband signal) transmitted via a network or the like, performs time-frequency conversion (hereinafter referred to as frequency conversion), and performs frequency information (hereinafter referred to as spectrum). Calculated).
- the frequency conversion is performed using techniques such as Fourier transform and discrete cosine transform.
- the input signal is described as a narrow-band signal of 300 Hz to 3400 Hz, but is not limited to this band.
- the frequency conversion unit 11 outputs the calculated spectrum to the mapping function calculation unit 12 and the broadband spectrum generation unit 13.
- the mapping function calculation unit 12 calculates a mapping function for generating a high frequency component from a low frequency component for the spectrum acquired from the frequency conversion unit 11.
- Equation (1) represents a model of the spectral mapping function.
- an error between the estimated value of the spectrum and the actual spectrum y (x i ) is calculated by the equation (2).
- the model parameters a and b are calculated from the equations (2), (3), and (4) using the spectrum y (x i ) of the narrowband signal.
- the pitch frequency ⁇ is calculated by the following equation.
- ⁇ freq / a_max (6)
- x Input signal M: Length of interval for calculating correlation coefficient (sample)
- a Start position of signal for calculating correlation coefficient corr (a): Correlation coefficient when the shift position is a a_max: a corresponding to the maximum correlation coefficient
- i Signal index (sample) freq: Sampling frequency (Hz)
- the mapping function calculation unit 12 outputs the calculated mapping function to the broadband spectrum generation unit 13.
- the broadband spectrum generating means 13 acquires the spectrum of the narrowband signal from the frequency converting means 11 and acquires the mapping function from the mapping function calculating means 12. Next, the broadband spectrum generating means 13 generates a spectrum having a wider band than the band of the narrowband signal using the acquired spectrum and the mapping function. Details of the broadband spectrum generating means 13 will be described with reference to FIG.
- the broadband spectrum generation unit 13 outputs the generated broadband spectrum to the frequency inverse conversion unit 14.
- FIG. 2 is a block diagram showing an example of the main functional configuration of the broadband spectrum generating means 13.
- the broadband spectrum generating unit 13 includes a high band spectrum generating unit 131 and an integrating unit 132.
- the high-frequency spectrum generating unit 131 generates a higher-frequency spectrum than the narrow-band spectrum by inputting a frequency higher than the narrow-band to the mapping function acquired from the mapping function calculating unit 12.
- the integration unit 132 integrates the high-frequency spectrum and the narrow-band spectrum generated by the high-frequency spectrum generation unit 131 to generate a wideband spectrum.
- a wideband spectrum For example, an example of widening a narrowband signal will be described.
- the spectrum of a narrowband signal has information on the number of bands of 0 to T, and this is expanded to twice the number of bands of 0 to 2T.
- the spectrum of the narrowband signal is set to the narrowband component of the broadband spectrum.
- a spectrum generated using a mapping function is set to a high-frequency component of a broadband spectrum.
- the Nyquist frequency component is zero.
- S_w [2T] 0 (9)
- S_w [i] Wide spectrum of the i-th frequency band
- S_n [i] Narrow band spectrum of i-th frequency band
- S_f [i] Spectrum of the i-th frequency band generated by applying the mapping function From the above, it is possible to generate a wideband spectrum by doubling the number of narrowband spectra, for example.
- the frequency inverse transform unit 14 acquires a broadband spectrum from the broadband spectrum generation unit 13, performs frequency time conversion (frequency inverse transform) on the acquired broadband spectrum, and outputs the time domain. Calculate the signal.
- FIG. 3 is a conceptual diagram of processing for generating a high-frequency spectrum. As shown in FIG. 3, a process for generating a high-frequency spectrum of 4 to 8 kHz from a narrow-band signal of 0 to 4 kHz will be described.
- a mapping function for generating a high-frequency spectrum (eg, 4-8 kHz) from a narrow-band signal spectrum bandwidth (eg, 0-4 kHz) is calculated.
- a high-frequency (4 to 8 kHz) spectrum is generated by inputting a high-frequency (4 to 8 kHz) frequency to the mapping function.
- the spectrum of the narrow band signal (0 to 4 kHz) and the generated high band (4 to 8 kHz) spectrum can be integrated to generate a wide band (0 to 8 kHz) spectrum.
- FIG. 4 is a diagram illustrating an example of the smoothing process.
- the spectrum of the high frequency part of the narrowband signal is generated with a mapping function (one-dot chain line).
- the boundary (4 kHz) may be smoothly connected by changing the high-frequency spectrum of the original narrowband signal so as to gradually become the generated spectrum (one-dot chain line).
- the weighting coefficient is determined so that the high-frequency spectrum of the narrowband signal gradually becomes a spectrum generated using the mapping function.
- a weighted average of the high-frequency spectrum and the generated spectrum may be taken using this weighting factor.
- FIG. 5 is a flowchart illustrating an example of the voice band expansion process according to the first embodiment.
- the frequency conversion means 11 performs frequency conversion (time frequency conversion) on the time domain input signal to calculate a frequency domain spectrum.
- the mapping function calculation means 12 uses the spectrum calculated by the frequency conversion means 11 to calculate a mapping function for generating a high-frequency component from the low-frequency component of the spectrum. Specifically, as described above, a model serving as a mapping function is given and its parameters are calculated.
- the broadband spectrum generating means 13 generates a spectrum having a wider band than the narrow band by using the spectrum generated by the frequency converting means 11 and the mapping function calculated by the mapping function calculating means 12. .
- the high frequency spectrum generating means 131 inputs a frequency in a frequency higher than the narrow band to the mapping function to generate a high frequency spectrum.
- the integration unit 132 generates a wideband spectrum by integrating the narrowband spectrum and the highband spectrum generated by the highband spectrum generation unit 131.
- the frequency reverse conversion unit 14 performs frequency reverse conversion (frequency time conversion) on the wideband spectrum generated by the wideband spectrum generation unit 13, and calculates an output signal in the time domain.
- a mapping function can be calculated using a spectrum of a narrowband signal, and a high-frequency spectrum can be generated using the calculated mapping function to widen the band. Therefore, it is possible to improve the sound quality of the broadband signal.
- a mapping function suitable for the input signal can be obtained, and a high-frequency spectrum corresponding to the spectral characteristics of the input signal can be generated.
- the smoothing process is performed when the spectra are integrated, the generation of a discontinuous spectrum at the boundary of spectrum integration can be prevented, and a smooth spectrum can be generated even at the boundary.
- FIG. 6 is a block diagram illustrating an example of a main functional configuration of the voice band extending apparatus 2 according to the second embodiment. In the functions shown in FIG. 6, the same functions as those shown in FIG.
- the voice band extension device 2 includes a frequency conversion unit 11, a mapping function calculation unit 12, a mapping function evaluation unit 21, a broadband spectrum generation unit 22, and a frequency inverse conversion 14.
- the mapping function evaluation unit 21 and the broadband spectrum generation unit 22 will be described.
- the mapping function evaluation unit 21 evaluates the performance of the mapping function calculated by the mapping function calculation unit 12. For example, the mapping function is evaluated by calculating the evaluation value as follows.
- the mapping function evaluation means 21 calculates an error V between the spectrum obtained by frequency-converting the input signal and the spectrum generated by applying the mapping function, using Expression (10). Moreover, the mapping function evaluation means 21 calculates
- FIG. 7 is a diagram illustrating an example of the relationship between the evaluation value and the error.
- the evaluation value is a value between 0 and 1
- a function is set in advance so that the evaluation value decreases as the error increases.
- a correspondence table between evaluation values and errors may be set.
- the relationship between the evaluation value and the error shown in FIG. 7 is an example, and it is only necessary to satisfy the relationship that the evaluation value decreases as the error increases. Further, when the error becomes larger than a predetermined value, a condition such as setting the evaluation value to 0 may be added. Further, the reciprocal of the error may be used as the evaluation value.
- the evaluation value calculated using the error is output to the broadband spectrum generating means 22 together with the mapping function.
- the broadband spectrum generating means 22 generates a broadband spectrum using the spectrum of the narrowband signal, the mapping function, and the evaluation value. Details of the broadband spectrum generating means 22 will be described with reference to FIG.
- FIG. 8 is a block diagram showing an example of the main functional configuration of the broadband spectrum generating means 22.
- the broadband spectrum generating unit 22 includes a high band spectrum generating unit 131, a spectrum correcting unit 221, and an integrating unit 222.
- the same functions as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.
- the spectrum correction unit 221 corrects the high-frequency spectrum generated by the high-frequency spectrum generation unit 131 using the evaluation value calculated by the mapping function evaluation unit 21. For example, the correction is performed using Expression (11) that multiplies the high-frequency spectrum by the evaluation value.
- S'w [i] ⁇ ⁇ Sw [i] (11) Sw [i]: High-frequency spectrum generated by applying the mapping function ⁇ : Evaluation value of the mapping function S'w [i]: High-frequency spectrum corrected using the evaluation value
- the evaluation value ⁇ of the mapping function is a function that calculates the evaluation value from the error between the spectrum generated by the mapping function and the narrow-band spectrum as described above. (Or a correspondence table) (see FIG. 7).
- the integration unit 222 is basically the same as the integration unit 132 described with reference to FIG. The difference is that the high-frequency spectrum corrected by the spectrum correcting means 221 is used as the high-frequency spectrum to be integrated. Thereby, it is possible to prevent the high-frequency spectrum generated by using the mapping function having a small evaluation value from affecting the broadband spectrum after integration.
- FIG. 9 is a flowchart illustrating an example of a voice band expansion process according to the second embodiment.
- the same reference numerals are given to the same processes as those shown in FIG.
- step S21 the mapping function evaluation unit 21 evaluates the performance of the mapping function calculated by the mapping function calculation unit 12. As described above, the evaluation of the mapping function is performed by obtaining an error between the narrow-band spectrum and the spectrum generated by using the mapping function and calculating an evaluation value from this error.
- the broadband spectrum generating means 22 first corrects the high-frequency spectrum generated by applying the mapping function using the evaluation value calculated by the mapping function evaluating means 21. . As described above, the correction is performed by multiplying the spectrum by the evaluation value. Next, the broadband spectrum generating means 22 generates a broadband spectrum by integrating the narrow band spectrum and the corrected high band spectrum. At this time, the smoothing process described in the first embodiment may be added.
- the evaluation value of the calculated mapping function can be calculated, and the high-frequency spectrum generated using the mapping function can be corrected based on the evaluation value. That is, the high-frequency spectrum generated using the mapping function with poor performance can be prevented from affecting the broadband spectrum after integration.
- Embodiment 3 differs from the above embodiments in that the spectrum after frequency conversion is separated into a sound source signal and a spectrum envelope.
- FIG. 10 is a block diagram illustrating an example of a main functional configuration of the voice band extending device 3 according to the third embodiment. In the function shown in FIG. 10, the same functions as those shown in FIG.
- the voice band extending device 3 includes a frequency converting unit 11, a sound source / envelope separating unit 31, a mapping function calculating unit 32, a broadband spectrum generating unit 33, and a frequency inverse transform 14.
- the sound source / envelope separating unit 31, the mapping function calculating unit 32, and the broadband spectrum generating unit 33 will be described.
- the sound source / envelope separating means 31 separates the spectrum calculated by the frequency converting means 11 into a sound source signal and a spectrum envelope. This separation processing is performed by a technique such as linear prediction analysis or cepstrum lifter.
- the separated sound source signal and / or spectrum envelope will be referred to as separation information.
- the sound source / envelope separating unit 31 outputs the separated separation information to the mapping function calculating unit 32 and the broadband spectrum generating unit 33.
- the mapping function calculation means 32 calculates a mapping function for generating a high frequency component from a low frequency component for the separation information separated by the sound source / envelope separation means 31.
- separation information for calculating the mapping function there are three patterns of a sound source signal and a spectrum envelope, only a sound source signal, and only a spectrum envelope. Hereinafter, these will be described in order.
- the mapping function calculation unit 32 calculates a mapping function for each of the sound source signal and the spectrum envelope. Since the mapping function of the sound source signal is the same as the calculation method for the spectrum as described in the above embodiment, the description thereof is omitted here. Hereinafter, calculation of the mapping function for the spectral envelope will be described.
- the following model (12) is given as a mapping function of the spectral envelope.
- an error between the power spectrum estimation value of the spectrum envelope and the power spectrum z (x i ) of the actual spectrum envelope is calculated by Expression (13).
- the model parameters c, d, and e are calculated from the equations (13), (14), (15), and (16) using the power spectrum z (x i ) of the spectrum envelope of the narrowband signal.
- the mapping function from the low-frequency component to the high-frequency component for the spectrum envelope can be calculated.
- the model is merely an example and is not limited to the above model.
- the mapping function calculation unit 32 outputs the calculated mapping functions of the sound source signal and the spectrum envelope to the wideband spectrum generation unit 33.
- the mapping function calculation means 32 calculates a mapping function from the low frequency component to the high frequency component for the sound source signal. Since the mapping function of the sound source signal is the same as the calculation method for the spectrum as described in the above embodiment, the description thereof is omitted here. Further, the mapping function calculation unit 32 outputs the calculated mapping function of the sound source signal to the broadband spectrum generation unit 33.
- the mapping function calculation means 32 calculates a mapping function from the low frequency component to the high frequency component for the spectrum envelope.
- the mapping function can be calculated by giving a model as described above and calculating its parameters. Further, the mapping function calculation means 32 outputs the calculated spectral envelope mapping function to the broadband spectrum generation means 33.
- the broadband spectrum generating means 33 uses the separation information separated by the sound source / envelope separating means 31 and the mapping function calculated by the mapping function calculating means 32 to generate wideband separated information rather than the narrow band. Next, the broadband spectrum generating unit 33 generates a broadband spectrum based on the generated broadband separation information.
- the details of the broadband spectrum generating means 33 will be described with reference to FIG.
- FIG. 11 is a block diagram showing an example of the main functional configuration of the broadband spectrum generating means 33.
- the broadband spectrum generating unit 33 includes a high band separation information generating unit 331, an integrating unit 332, and a sound source / envelope synthesizing unit 333.
- the high frequency band separation information generation unit 331 generates high band separation information from the narrow band by using the calculated mapping function and the frequency higher than the narrow band.
- the separation information has three patterns of the sound source signal and the spectrum envelope, only the sound source signal, and only the spectrum envelope, the function of the high frequency separation information generation unit 331 will be described for each case.
- the high frequency band separation information generation unit 331 inputs a frequency higher than the narrow band to the mapping function of the sound source signal and the spectral envelope calculated by the mapping function calculation unit 32 to input the high frequency sound source signal and the spectrum. Generate an envelope. Next, the high frequency band separation information generation unit 331 outputs the generated high frequency sound source signal and spectrum envelope to the integration unit 332.
- the high-frequency separation information generating unit 331 generates a high-frequency sound source signal by inputting a frequency higher than the narrow band to the mapping function of the sound source signal calculated by the mapping function calculating unit 32. Further, since the mapping function of the spectrum envelope is not calculated, the high frequency band separation information generating unit 331 uses a mapping function learned in advance or repeats the low frequency band as in the prior art. Generate a spectral envelope. Next, the high frequency band separation information generation unit 331 outputs the generated high frequency sound source signal and spectrum envelope to the integration unit 332.
- the high frequency band separation information generating unit 331 generates a high frequency spectrum envelope by inputting a frequency higher than the narrow band to the spectral envelope mapping function calculated by the mapping function calculating unit 32. In addition, since the mapping function of the sound source signal is not calculated, the high frequency separation information generating unit 331 uses a mapping function learned in advance or repeats the low frequency, as in the prior art. Generate a sound source signal. Next, the high frequency band separation information generation unit 331 outputs the generated high frequency sound source signal and spectrum envelope to the integration unit 332.
- the integration unit 332 integrates the narrowband sound source signal and the high frequency sound source signal generated by the high frequency separation information generation unit 331.
- the integration unit 332 integrates the narrow band spectrum envelope and the high band spectrum envelope generated by the high band separation information generation unit 331.
- the integration method is as described in the integration unit 132 of the first embodiment.
- the integrated sound source signal and spectrum envelope are output to the sound source / envelope synthesis means 333.
- the sound source / envelope synthesizing unit 333 synthesizes the sound source signal and the spectrum envelope which are integrated and widened to generate a wide band spectrum.
- the spectrum of the wideband signal is calculated by Equation (17) using the spectrum of the wideband sound source signal and the spectrum of the wideband spectrum envelope.
- Sw [i] SRw [i] ⁇ EVw [i] (17)
- SRw [i] Spectrum of the i-th wideband source signal
- EVw [i] spectrum of the i-th wideband spectrum envelope
- the integration unit 332 and the sound source / envelope synthesizing unit 333 are processed in this order.
- the integration unit 332 may perform integration.
- the sound source / envelope synthesizing unit 333 synthesizes a narrow band sound source signal and a spectrum envelope.
- the sound source / envelope separating unit 33 synthesizes the high frequency sound source signal and the spectrum envelope generated by the high frequency separated information generating unit 331.
- the integration unit 332 may integrate the narrowband spectrum and the highband spectrum after synthesis. Further, when the integration is performed by the integration unit 333, the above-described smoothing process may be performed.
- the integration and synthesis processing when the separation information is a sound source signal and a spectrum envelope will be specifically described.
- FIG. 12A is a diagram showing a power spectrum of a narrowband signal.
- FIG. 12B and FIG. 12C show that the power spectrum of the narrowband signal is separated into the sound source signal and the spectrum envelope.
- FIG. 12B is a diagram illustrating an example of widening the sound source signal.
- a mapping function for generating a high frequency component from a low frequency component is calculated using a sound source signal of 0 to 4 kHz, and a sound source signal of 4 to 8 kHz is generated using the calculated mapping function. Is done.
- the generated sound source signal is integrated with a narrow band sound source signal to become a sound source signal A having a wider band.
- FIG. 12C is a diagram illustrating an example of widening the spectrum envelope.
- a mapping function for generating a high frequency component from a low frequency component is calculated using a spectral envelope of 0 to 4 kHz, and a spectral envelope of 4 to 8 kHz is generated using the calculated mapping function. Is done.
- the generated spectral envelope is integrated with the narrow-band spectral envelope to become a broadband spectral envelope B.
- FIG. 13 is a diagram illustrating an example of a synthesis process of a sound source signal and a spectrum envelope.
- a spectrum with a broad band is generated.
- the mapping function can be calculated based on the spectrum of the input signal, and a high-frequency spectrum suitable for the current input signal can be generated.
- FIG. 14 is a flowchart illustrating an example of a voice band expansion process according to the third embodiment.
- the same reference numerals are given to the same processing as the processing shown in FIG. 5, and description thereof is omitted.
- step S31 the sound source / envelope separating means 31 separates the frequency-converted spectrum into a sound source signal and a spectrum envelope.
- the mapping function calculation means 32 calculates a mapping function for generating a high frequency component from the low frequency component using the separation information separated by the sound source / envelope separation means 31. Specifically, as described above, a model serving as a mapping function is given and its parameters are calculated. There are three patterns for calculating a mapping function: a mapping function of a sound source signal and a spectrum envelope, a mapping function of only a sound source signal, and a mapping function of only a spectrum envelope.
- the broadband spectrum generating unit 33 first generates separation information in a higher band than the narrow band by using the mapping function calculated by the mapping function calculating unit 32.
- the mapping function is calculated for the sound source signal and the spectral envelope
- the high frequency sound source signal and the spectral envelope are generated using the respective mapping functions.
- a high frequency sound source signal is generated using the mapping function of the sound source signal.
- a high-frequency spectral envelope is generated using conventional techniques.
- the mapping function is calculated only for the spectral envelope, a high-frequency spectral envelope is generated using the spectral envelope mapping function.
- the sound source signal a high-frequency sound source signal is generated using a conventional technique.
- the broadband spectrum generating means 33 integrates the generated high-frequency sound source signal and spectrum envelope into the narrow-band sound source signal and spectrum envelope, respectively.
- a combined spectrum is generated by synthesizing the integrated sound source signal and spectrum envelope.
- the smoothing process described in the first embodiment may be added.
- the mapping function for separating the spectrum of the narrowband signal into the sound source signal and the spectrum envelope and generating the highband component from the lowband component using the separated separation information can be calculated. it can.
- the mapping function for separating the spectrum of the narrowband signal into the sound source signal and the spectrum envelope and generating the highband component from the lowband component using the separated separation information can be calculated. it can.
- by generating a high-frequency spectrum using the calculated mapping function to widen the band it is possible to improve the sound quality of the wide-band signal.
- a mapping function suitable for the input signal can be obtained, and a high-frequency spectrum corresponding to the spectral characteristics of the input signal can be generated.
- FIG. 15 is a block diagram of a main functional configuration example of the voice band extending apparatus 4 according to the fourth embodiment.
- the same functions as those shown in FIGS. 1 and 10 are denoted by the same reference numerals, and the description thereof is omitted.
- the voice band extending device 4 includes a frequency converting unit 11, a sound source / envelope separating unit 31, a mapping function calculating unit 32, a mapping function evaluating unit 41, a broadband spectrum generating unit 42, and a frequency inverse transform 14. .
- the mapping function evaluation unit 41 and the broadband spectrum generation unit 42 will be described.
- the mapping function evaluation unit 41 evaluates the performance of the mapping function calculated by the mapping function calculation unit 32.
- the evaluation is performed in the same manner as the mapping function evaluation unit 21 of the second embodiment. That is, if the mapping function is calculated only for the sound source signal, the error between the sound source signal generated using the mapping function of the sound source signal and the narrow-band sound source signal is calculated, and the evaluation value is obtained from the error. Thus, the mapping function is evaluated.
- This evaluation is performed in the same manner when the mapping function of only the spectral envelope is calculated and when the mapping functions of the sound source signal and the spectral envelope are calculated.
- the broadband spectrum generating means 42 generates a broadband spectrum using the evaluation value and mapping function acquired from the mapping function evaluating means 41 and the narrow band sound source signal and spectrum envelope acquired from the sound source / envelope separating means 31.
- the details of the broadband spectrum generating means 42 will be described with reference to FIG.
- FIG. 16 is a block diagram showing an example of the main functional configuration of the broadband spectrum generating means 42. As shown in FIG. In the functions shown in FIG. 16, the same functions as those shown in FIG. As shown in FIG. 16, the broadband spectrum generating unit 42 includes a high band separation information generating unit 331, a high band separation information correcting unit 421, an integrating unit 422, and a sound source / envelope synthesizing unit 423.
- the broadband spectrum generating unit 42 includes a high band separation information generating unit 331, a high band separation information correcting unit 421, an integrating unit 422, and a sound source / envelope synthesizing unit 423.
- the high frequency band separation information correction unit 421 corrects the high band separation information generated by the high frequency band separation information generation unit 331 using the evaluation value of the mapping function.
- the separation information since the separation information has three patterns of the sound source signal and the spectrum envelope, only the sound source signal, and only the spectrum envelope, the function of the high frequency separation information correction unit 421 will be described for each case.
- the high frequency band separation information correction unit 421 corrects the high frequency sound source signal and the spectrum envelope generated by the high frequency band separation information generation unit 331 using the evaluation values of the respective mapping functions. First, the correction of the sound source signal will be described.
- the high frequency sound source signal generated by using the mapping function of the sound source signal is corrected by the equation (18) using the evaluation value of the mapping function of the sound source signal.
- SR'w [i] ⁇ ⁇ SRw [i] (18)
- ⁇ Evaluation value of mapping function of sound source signal
- the evaluation value ⁇ of mapping function is the sound source signal calculated by the mapping function and the sound source of the narrowband signal It is obtained by a function (or correspondence table) for calculating an evaluation value from an error from the signal.
- the high frequency spectral envelope generated by applying the spectral envelope mapping function is modified by the formula (19) using the evaluation value of the spectral envelope mapping function.
- SE'w [i] ⁇ ⁇ SEw [i] (19)
- the mapping function evaluation value ⁇ is the spectral envelope generated using the mapping function as described above. And a function (or correspondence table) for calculating an evaluation value from the error between the spectral envelope of the narrowband signal.
- the high frequency band separation information correction unit 331 outputs the corrected high frequency sound source signal and spectrum envelope to the integration unit 422.
- the high frequency band separation information correction unit 421 corrects the sound source signal generated by the high frequency band separation information generation unit 331 using the evaluation value of the mapping function of the sound source signal.
- the method of correction is as described above.
- the high-frequency spectral envelope is not corrected.
- the high frequency band separation information generating unit 331 outputs the corrected high frequency sound source signal and the uncorrected high frequency spectrum envelope to the integrating unit 332.
- the high frequency band separation information correction unit 421 corrects the spectrum envelope generated by the high frequency band separation information generation unit 331 using the evaluation value of the mapping function of the spectrum envelope. The method of correction is as described above. Here, since the mapping function of the sound source signal is not calculated, the high frequency sound source signal is not corrected. Next, the high frequency band separation information generating unit 331 outputs the corrected high frequency spectrum envelope and the uncorrected high frequency sound source signal to the integrating unit 332.
- the integration unit 422 integrates the narrowband sound source signal and the high frequency sound source signal output by the high frequency separation information correction unit 421. Further, the integration unit 332 integrates the narrow band spectrum envelope and the high band spectrum envelope output by the high band separation information correction unit 421.
- the integration method is as described in the integration unit 132 of the first embodiment.
- the integrated sound source signal and spectrum envelope are output to the sound source / envelope synthesizing unit 423.
- the sound source / envelope synthesizing means 423 synthesizes the sound source signal and the spectrum envelope which are integrated and widened to generate a wide band spectrum.
- the synthesis is performed by the sound source / envelope synthesis unit 423 first, and then the integration unit 422 performs integration. May be.
- the sound source / envelope synthesizing unit 423 synthesizes a narrow band sound source signal and a spectrum envelope.
- the sound source / envelope synthesizing unit 423 synthesizes the high frequency sound source signal and the spectral envelope output by the high frequency separation information correcting unit 421.
- the integration unit 422 may integrate the narrowband spectrum and the highband spectrum after synthesis.
- the above-described smoothing process may be performed.
- the mapping function calculated using the separation information it is possible to determine the contribution degree or acceptance of the calculated high frequency spectrum based on the evaluation.
- FIG. 17 is a flowchart illustrating an example of a voice band extension process according to the fourth embodiment.
- the same reference numerals are given to the same processing as the processing shown in FIG. 5 and FIG. 14, and description thereof is omitted.
- step S41 the mapping function evaluation unit 41 evaluates the performance of the mapping function calculated by the mapping function calculation unit 32.
- the evaluation is made by calculating the evaluation value of the mapping function as described above.
- the broadband spectrum generating means 42 first generates separation information of a higher frequency than the narrow band using the mapping function calculated by the mapping function calculating means 32.
- the mapping function is calculated for the sound source signal and the spectrum envelope
- the high frequency sound source signal and the spectrum envelope are generated using the respective mapping functions.
- a high frequency sound source signal is generated using the mapping function of the sound source signal.
- a high-frequency spectral envelope is generated using conventional techniques.
- the mapping function is calculated only for the spectral envelope, a high-frequency spectral envelope is generated using the spectral envelope mapping function.
- the sound source signal a high-frequency sound source signal is generated using a conventional technique.
- the broadband spectrum generating unit 42 modifies the sound source signal and / or the spectrum envelope generated using the mapping function calculated by the mapping function calculating unit 32 using the evaluation value of the mapping function.
- the broadband spectrum generating unit 42 modifies the sound source signal and / or the spectrum envelope generated using the mapping function calculated by the mapping function calculating unit 32 using the evaluation value of the mapping function.
- the broadband spectrum generating means 42 integrates the high frequency sound source signal and the spectrum envelope into the narrow band sound source signal and the spectrum envelope, respectively. Further, the broadband spectrum generating means 42 generates a broadband spectrum by synthesizing the integrated sound source signal and the spectrum envelope. At this time, the smoothing process described in the first embodiment may be added.
- the mapping function calculated based on the separation information can be evaluated. Moreover, the contribution degree and acceptance / rejection of the generated high-frequency spectrum can be determined based on the evaluation.
- A is a matrix in which the spectra of narrowband signals are arranged, and b is a column vector in which spectra having a frequency index q larger than the first row of the matrix A are arranged.
- the linear prediction coefficient p can be calculated by calculating an inverse matrix of A and using Equation (23).
- the inverse matrix of A is obtained by a known method such as a generalized inverse matrix.
- the linear prediction coefficient p is a coefficient for inputting a low-frequency spectrum of a narrow-band signal and predicting a high-frequency spectrum by q.
- Ap b (20)
- p Linear prediction coefficient (m-dimensional column vector)
- b Column vector (o-dimensional column vector) in which spectra with a frequency index q larger than the first row of matrix A are arranged
- s t spectrum with frequency index t
- a spectrum of a higher frequency than the spectrum of the input signal is generated by multiplying the matrix A ′ of Expression (24) by a linear prediction coefficient.
- A'p b '(24)
- p Linear prediction coefficient (m-dimensional column vector)
- the high-frequency spectrum generated using the linear prediction coefficient is as follows.
- the calculation result (b ′) is set for the range (t to t ⁇ o + 2q) that can be calculated by the linear prediction coefficient, and the range (t ⁇ o + 2q to 2T ⁇ 1) that cannot be calculated is set to 0.
- the sound source signal and the linear prediction coefficient of a spectrum envelope can be calculated similarly.
- the contents of the voice band expansion process described in each of the embodiments described above are used as a program for causing a computer to execute the program, and this program is installed from a server or the like and executed by the computer to realize the voice band expansion process described above. It is also possible.
- the recording medium is a recording medium that records information optically, electrically, or magnetically, such as a CD-ROM, flexible disk, magneto-optical disk, etc., and information is electrically recorded, such as a ROM, flash memory, etc.
- Various types of recording media such as a semiconductor memory can be used.
- the disclosed voice band extending device can be applied to devices such as mobile terminals and IP telephones.
Abstract
Description
12,32 写像関数算出手段
13,22,33,42 広帯域スペクトル生成手段
14 周波数逆変換手段
21,41 写像関数評価手段
31 音源・包絡分離手段
131 高域スペクトル生成手段
132,222,332,422 統合手段
221 スペクトル修正手段
331,421 高域分離情報生成手段
333,423 音源・包絡合成手段
<機能構成>
図1は、実施形態1にかかる音声帯域拡張装置1の主要機能構成例を示すブロック図である。図1に示すように、音声帯域拡張装置1は、周波数変換手段11、写像関数算出手段12、広帯域スペクトル生成手段13、周波数逆変換手段14を含む。
ここで、スペクトルの推定値と実際のスペクトルy(xi)との誤差を式(2)により算出する。
モデルのパラメータa,bは、狭帯域信号のスペクトルy(xi)を用いて、式(2)(3)(4)より算出する。ここで、ピッチ周波数θは以下の式で算出する。
θ= freq/a_max (6)
x:入力信号
M:相関係数を算出する区間の長さ(サンプル)
a:相関係数を算出する信号の開始位置
corr(a):ずらし位置がaの場合の相関係数
a_max: 最大相関係数に対応するa
i:信号のインデックス(サンプル)
freq:サンプリング周波数(Hz)
以上、モデルのパラメータa,bを算出することで、入力信号のスペクトルに対して低域成分から高域成分を生成するための写像関数を算出することができる。なお、モデルについては一例を示したにすぎず、上記モデルに限定されるものではない。また、写像関数算出手段12は、算出した写像関数を広帯域スペクトル生成手段13に出力する。
S_w[i] = S_n[i] i= 0,...,T-1 (7)
広帯域のスペクトルの高域成分に、写像関数を用いて生成したスペクトルを設定する。
S_w[i] = S_f[i] i= T,...,2T-1 (8)
ナイキスト周波数の成分は0とする。
S_w[2T] = 0 (9)
S_w[i]:i番目の周波数帯域の広帯域のスペクトル
S_n[i]:i番目の周波数帯域の狭帯域のスペクトル
S_f[i]:写像関数を適用して生成されたi番目の周波数帯域のスペクトル
以上より、狭帯域のスペクトルの帯域数を例えば2倍にして広帯域のスペクトルを生成することができる。
実施形態1にかかる音声帯域拡張装置1の処理について説明する。図5は、実施形態1にかかる音声帯域拡張処理の一例を示すフローチャートである。ステップS11において、周波数変換手段11は、時間領域の入力信号に対して周波数変換(時間周波数変換)を行い、周波数領域のスペクトルを算出する。
次に、実施形態2にかかる音声帯域拡張装置2について説明する。実施形態2では、算出した写像関数を評価することで、算出された高域のスペクトルの寄与度や採否を評価に基づいて決定することができる。
図6は、実施形態2にかかる音声帯域拡張装置2の主要機能構成例を示すブロック図である。図6に示す機能において、図1に示す機能と同様の機能のものは同じ符号を付し、その説明を省略する。
また、写像関数評価手段21は、式(10)を用いて算出した誤差Vから評価値を求める。例えば、図7を用いて誤差から評価値を算出する。図7は、評価値と誤差との関係の一例を示す図である。
S'w[i] = α × Sw[i] (11)
Sw[i]:写像関数を適用して生成した高域のスペクトル
α:写像関数の評価値
S'w[i]:評価値を用いて修正した高域のスペクトル
写像関数の評価値αは、前述した通り写像関数で生成したスペクトルと狭帯域のスペクトルとの誤差から評価値を算出する関数(又は対応テーブル等)により求める(図7参照)。
実施形態2にかかる音声帯域拡張装置2の処理について説明する。図9は、実施形態2にかかる音声帯域拡張処理の一例を示すフローチャートである。図9に示す処理において、図5に示す処理と同様の処理を行うものは同じ符号を付し、その説明を省略する。
次に、実施形態3にかかる音声帯域拡張装置3について説明する。実施形態3では、周波数変換後のスペクトルに対して音源信号、スペクトル包絡に分離するところが上記各実施形態とは異なる。
図10は、実施形態3にかかる音声帯域拡張装置3の主要機能構成例を示すブロック図である。図10に示す機能において、図1に示す機能と同様の機能のものは同じ符号を付し、その説明を省略する。
写像関数算出手段32は、音源信号及びスペクトル包絡それぞれに対して写像関数を算出する。音源信号の写像関数については、上記実施形態で説明したようにスペクトルに対する算出の仕方と同様であるため、ここでは説明を省略する。以下、スペクトル包絡に対する写像関数の算出について説明する。
ここで、スペクトル包絡のパワースペクトル推定値と、実際のスペクトル包絡のパワースペクトルz(xi)との誤差を式(13)により算出する。
モデルのパラメータc,d,eは、狭帯域信号のスペクトル包絡のパワースペクトルz(xi)を用いて、式(13)、(14)、(15)、(16)より算出される。これより、モデルのパラメータc,d,eを算出することで、スペクトル包絡に対しての低域成分から高域成分への写像関数を算出することができる。なお、モデルについては一例を示したにすぎず、上記モデルに限定されるものではない。また、写像関数算出手段32は、算出した音源信号及びスペクトル包絡それぞれの写像関数を広帯域スペクトル生成手段33に出力する。
写像関数算出手段32は、音源信号に対して低域成分から高域成分への写像関数を算出する。音源信号の写像関数については、上記実施形態で説明したようにスペクトルに対する算出の仕方と同様であるため、ここでは説明を省略する。また、写像関数算出手段32は、算出した音源信号の写像関数を広帯域スペクトル生成手段33に出力する。
写像関数算出手段32は、スペクトル包絡に対して低域成分から高域成分への写像関数を算出する。スペクトル包絡の写像関数については、前述した通りモデルを与えて、そのパラメータを算出することで写像関数を算出することができる。また、写像関数算出手段32は、算出したスペクトル包絡の写像関数を広帯域スペクトル生成手段33に出力する。
高域分離情報生成手段331は、写像関数算出手段32により算出された音源信号、スペクトル包絡それぞれの写像関数に対して、狭帯域よりも高域の周波数を入力して高域の音源信号及びスペクトル包絡を生成する。次に、高域分離情報生成手段331は、生成した高域の音源信号及びスペクトル包絡を統合手段332に出力する。
高域分離情報生成手段331は、写像関数算出手段32により算出された音源信号の写像関数に対して、狭帯域よりも高域の周波数を入力して高域の音源信号を生成する。また、高域分離情報生成手段331は、スペクトル包絡の写像関数は算出されていないため、従来技術と同様に、予め学習された写像関数を用いたり低域を繰り返したりするなどして高域のスペクトル包絡を生成する。次に、高域分離情報生成手段331は、生成した高域の音源信号及びスペクトル包絡を統合手段332に出力する。
高域分離情報生成手段331は、写像関数算出手段32により算出されたスペクトル包絡の写像関数に対して、狭帯域よりも高域の周波数を入力して高域のスペクトル包絡を生成する。また、高域分離情報生成手段331は、音源信号の写像関数は算出されていないため、従来技術と同様に、予め学習された写像関数を用いたり低域を繰り返したりするなどして高域の音源信号を生成する。次に、高域分離情報生成手段331は、生成した高域の音源信号及びスペクトル包絡を統合手段332に出力する。
Sw[i] = SRw[i] × EVw[i] (17)
Sw[i]:i番目の広帯域信号のスペクトル
SRw [i]:i番目の広帯域の音源信号のスペクトル
EVw [i]:i番目の広帯域のスペクトル包絡のスペクトル
なお、ここでは統合手段332、音源・包絡合成手段333の順に処理する例について説明したが、先に音源・包絡合成手段333により合成を行い、次に、統合手段332により統合を行うように構成してもよい。この場合、まず、音源・包絡合成手段333は、狭帯域の音源信号及びスペクトル包絡を合成する。また、音源・包絡分離手段33は、高域分離情報生成手段331により生成された高域の音源信号及びスペクトル包絡を合成する。次に、統合手段332は、合成後における狭帯域のスペクトルと高域のスペクトルとを統合すればよい。また、統合手段333により統合を行う際に、前述した平滑化処理を行うようにしてもよい。
実施形態3にかかる音声帯域拡張装置3の処理について説明する。図14は、実施形態3にかかる音声帯域拡張処理の一例を示すフローチャートである。図14に示す処理において、図5に示す処理と同様の処理を行うものは同じ符号を付し、その説明を省略する。
次に、実施形態4にかかる音声帯域拡張装置4について説明する。実施形態4では、分離情報に基づいて算出された写像関数を評価することで、算出された高域のスペクトルの寄与度や採否を評価に基づいて決定することができる。
図15は、実施形態4にかかる音声帯域拡張装置4の主要機能構成例を示すブロック図である。図15に示す機能において、図1及び図10に示す機能と同様の機能のものは同じ符号を付し、その説明を省略する。
高域分離情報修正手段421は、高域分離情報生成手段331により生成された高域の音源信号、スペクトル包絡を、それぞれの写像関数の評価値を用いて修正する。まず、音源信号の修正について説明する。
SR'w[i] = β × SRw[i] (18)
SRw[i]:音源信号の写像関数を適用して生成した高域の音源信号
SR'w[i]:評価値を用いて修正した高域の音源信号
β:音源信号の写像関数の評価値
写像関数の評価値βは、写像関数で算出した音源信号と狭帯域信号の音源信号との誤差から評価値を算出する関数(又は対応テーブル)により求める。
SE'w[i] = γ × SEw[i] (19)
SEw[i]:スペクトル包絡の写像関数を適用して生成した高域のスペクトル包絡
SE'w[i]:評価値を用いて修正した高域のスペクトル包絡
γ:スペクトル包絡の写像関数の評価値
写像関数の評価値γは、前述した通り写像関数を用いて生成されたスペクトル包絡と狭帯域信号のスペクトル包絡との誤差から評価値を算出する関数(又は対応テーブル)により求める。
高域分離情報修正手段421は、高域分離情報生成手段331により生成された音源信号を、音源信号の写像関数の評価値を用いて修正する。修正の仕方は前述した通りである。ここで、スペクトル包絡の写像関数は算出されていないので、高域のスペクトル包絡については修正しない。次に、高域分離情報生成手段331は、修正した高域の音源信号、修正していない高域のスペクトル包絡を統合手段332に出力する。
高域分離情報修正手段421は、高域分離情報生成手段331により生成されたスペクトル包絡を、スペクトル包絡の写像関数の評価値を用いて修正する。修正の仕方は前述した通りである。ここで、音源信号の写像関数は算出されていないので、高域の音源信号については修正しない。次に、高域分離情報生成手段331は、修正した高域のスペクトル包絡、修正していない高域の音源信号を統合手段332に出力する。
実施形態4にかかる音声帯域拡張装置4の処理について説明する。図17は、実施形態4にかかる音声帯域拡張処理の一例を示すフローチャートである。図17に示す処理において、図5及び図14に示す処理と同様の処理を行うものは同じ符号を付し、その説明を省略する。
前述した各実施形態における変形例について説明する。各実施形態では、写像関数に関してモデルを与えてそのパラメータを算出することで写像関数を算出することにしていたが、ここでは、線形予測係数を算出する。以下、線形予測係数の求め方について説明する。
Ap=b (20)
A:m×oの行列(狭帯域信号のスペクトルを並べた行列)
p:線形予測係数(m次元列ベクトル)
b:行列Aの第一行よりも周波数のインデックスがq大きいスペクトルを並べた列ベクトル(o次元列ベクトル)
st:周波数のインデックスがtのスペクトル
次に、算出した線形予測係数を用いて高域のスペクトルを算出する例について説明する。入力信号(狭帯域信号)のスペクトルよりも高域のスペクトルは、式(24)の行列A'に線形予測係数を乗算することで生成される。
A'p=b' (24)
A':m×oの行列(狭帯域信号のスペクトルを並べた行列)
p:線形予測係数(m次元列ベクトル)
b':高域のスペクトル(o次元列ベクトル)
式(24)より、行列A'の第一行よりも周波数のインデックスがq大きいスペクトルが算出される。線形予測係数を用いて生成した高域のスペクトルは次の通りである。
S_f[t-o+1+q+i] = b'[i] i=0,,,,q-1 (25)
S_f[t-o+2q+i] = 0 i=0,,,,2T-1-t+o-2q (26)
S_f[i]:線形予測係数を用いて生成したi番目のスペクトル
t:線形予測係数を適用する狭帯域スペクトルの最大周波数のインデックス
狭帯域信号のスペクトルと、狭帯域よりも高域のスペクトルとの統合は、各実施形態で説明した統合と同様に行えばよい。また、スペクトルの線形予測係数を算出する例について説明したが、音源信号、スペクトル包絡の線形予測係数についても同様にして算出することができる。
Claims (9)
- 入力信号を周波数変換してスペクトルを算出する周波数変換手段と、
前記スペクトルを用いて、前記スペクトルの低域成分から高域成分を生成するための写像関数を算出する写像関数算出手段と、
前記写像関数に基づいて前記スペクトルの帯域よりも高域のスペクトルを生成し、生成した前記高域のスペクトルと前記周波数変換手段により算出されたスペクトルとを統合することにより、前記周波数変換手段により算出されたスペクトルの帯域よりも広帯域のスペクトルを生成する広帯域スペクトル生成手段と、
前記広帯域のスペクトルを周波数逆変換して出力信号を算出する周波数逆変換手段と
を備える音声帯域拡張装置。 - 前記写像関数に基づいて生成されたスペクトルと、前記周波数変換手段により算出されたスペクトルとの誤差を用いて写像関数の評価値を算出する評価手段とを更に備え、
前記広帯域スペクトル生成手段は、
前記評価値を用いて前記高域のスペクトルを修正する請求項1記載の音声帯域拡張装置。 - 前記周波数変換手段により算出されたスペクトルを音源信号とスペクトル包絡とに分離する分離手段とを更に備え、
前記写像関数算出手段は、
前記分離手段により分離された分離情報を用いて、前記分離情報の低域成分から高域成分を生成するための写像関数を算出し、
前記広帯域スペクトル生成手段は、
前記写像関数に基づいて前記スペクトルの帯域よりも高域の分離情報を生成し、生成した前記高域の分離情報と前記分離手段により分離された分離情報とを統合し、統合した分離情報に基づいて前記広帯域のスペクトルを生成する請求項1記載の音声帯域拡張装置。 - 前記写像関数に基づいて生成された分離情報と、前記分離手段により分離された分離情報との誤差を用いて写像関数の評価値を算出する評価値算出手段とを更に備え、
前記広帯域スペクトル生成手段は、
前記評価値を用いて前記高域の分離情報を修正する請求項3記載の音声帯域拡張装置。 - 前記分離情報は、前記音源信号及び/又は前記スペクトル包絡である請求項3記載の音声帯域拡張装置。
- 前記写像関数は、線形予測係数を算出する関数である請求項1乃至5いずれか1項に記載の音声帯域拡張装置。
- 前記広帯域スペクトル生成手段は、
前記写像関数と前記スペクトルの帯域よりも高域の周波数とを用いて、前記スペクトルの帯域よりも高域のスペクトルを生成する高域スペクトル生成手段と、
前記高域のスペクトルと前記周波数変換手段により算出されたスペクトルとを統合する統合手段とを備える請求項1記載の音声帯域拡張装置。 - 前記統合手段は、
前記周波数変換手段により算出されたスペクトルの高域成分が、前記写像関数を用いて生成したスペクトルに徐々になるよう平滑化処理を行う請求項7記載の音声帯域拡張装置。 - 入力信号を周波数変換してスペクトルを算出する周波数変換段階と、
前記スペクトルを用いて前記スペクトルの低域成分から高域成分を生成するための写像関数を算出する写像関数算出段階と、
前記写像関数に基づいて前記スペクトルの帯域よりも高域のスペクトルを生成し、生成した前記高域のスペクトルと前記周波数変換段階により算出されたスペクトルとを統合することにより、前記周波数変換段階により算出されたスペクトルの帯域よりも広帯域のスペクトルを生成する広帯域スペクトル生成段階と、
前記広帯域のスペクトルを周波数逆変換して出力信号を算出する周波数逆変換段階と
を有する音声帯域拡張方法。
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JP2015206958A (ja) * | 2014-04-23 | 2015-11-19 | 山本 裕 | 音声信号処理装置 |
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US10339945B2 (en) | 2014-06-26 | 2019-07-02 | Huawei Technologies Co., Ltd. | Coding/decoding method, apparatus, and system for audio signal |
US9779747B2 (en) | 2014-06-26 | 2017-10-03 | Huawei Technologies Co., Ltd. | Coding/decoding method, apparatus, and system for audio signal |
WO2015196835A1 (zh) * | 2014-06-26 | 2015-12-30 | 华为技术有限公司 | 编解码方法、装置及系统 |
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US20110282655A1 (en) | 2011-11-17 |
US8781823B2 (en) | 2014-07-15 |
EP2360687A1 (en) | 2011-08-24 |
JPWO2010070770A1 (ja) | 2012-05-24 |
JP5423684B2 (ja) | 2014-02-19 |
EP2360687A4 (en) | 2012-07-11 |
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