Abstract: The present invention pertains to a speech decoding device that is capable of preventing degradation in sound quality associated with an adjustment of the slope of a spectrum of an output signal (a decoding signal), making it less likely that a loss of bandwidth sensitivity due to the attenuation of a higher band region is perceived. For each frame of the bandwidth extension layer decoding signal, a filter assessment unit (304) determines whether or not to apply a low-pass filter to the bandwidth extension layer decoding signal on the basis of a change in energy in the bandwidth extension layer decoding signal. A low-pass filtering unit (306) filters the bandwidth extension layer decoding signal of the frames to which the low-pass filter is to be applied, as determined by the filter assessment unit (304), using the low-pass filter.

Abstract: An encoding device is provided for increasing the quality of an encoded signal, even when encoding music signals. In the encoding device, a Code-Excited Linear Prediction (CELP) encoder generates first encoded data by encoding an input signal, and a CELP decoder generates a decoded signal by decoding the first encoded data input from the CELP encoder. Additionally, a characteristic parameter encoder calculates a parameter that expresses the degree of fluctuation in the ratio of the peak components and the floor components between the spectra of the decoded signal and the input signal.

Abstract: Provided is an encoding apparatus. A threshold value calculating unit (32) calculates a threshold value from a statistical amount of conversion factors of an extended band. A representative conversion factor extracting unit (33) uses the calculated threshold value to extract conversion factors having large amplitudes. If the number of extracted conversion factors does not reach a specified number, the threshold value calculating unit (32) determines, in accordance with a lacking number of conversion factors, an amount by which the threshold value should be lowered, and modifies the threshold value accordingly. The representative conversion factor extracting unit (33) uses the threshold value, which has been modified, to extract conversion factors.

Abstract: An audio encoding apparatus capable of reducing the bit rate even if a codebook having a larger codebook number is selected in a split multi-rate lattice vector quantization is provided. Sub-vector determining unit (121) determines, in the spectrum of an input signal having been divided into a predetermined number of sub-vectors, a sub-vector using the largest number of bits. Positional information encoding unit (122) encodes the positional information of the determined sub-vector. Codebook indication value estimating unit (124) estimates a number of used bits for a codebook indication value of the largest number of used bits by use of the (N?1) other codebook indication values, and generates a number-of-used-bits estimation value. Difference calculating unit (125) calculates a difference by subtracting the number-of-used-bits estimation value from the actual value of the codebook indication value of the largest number of used bits. Difference encoding unit (126) encodes the difference information.

Abstract: An encoding device is disclosed in which frequency domain converters (701, 702) acquire a conversion coefficient in which a frequency band is divided between low end and high end, a sub-band energy calculator (703) divides either the low end or the high end frequency band of the conversion coefficient into a plurality of sub-bands, an importance assessment unit (704) sets a degree of importance for each sub-band, a sparse processor (705), according to the set importance, sets the amplitude value of a specific number of conversion coefficients, from among the plurality of conversion coefficients included in each sub-band, at zero, and a correlation analysis unit (706) calculates the correlation between the corrected conversion coefficient of one frequency band and the conversion coefficient of the other frequency band.

Abstract: By copying to a high-frequency band portion (extension band) a low-frequency band portion in which peaking has been set to a sufficiently low state, this encoding device is capable of preventing generation of a spectrum with overly high peaking in the high-frequency band portion, and of generating a high-quality extension band spectrum. This device comprises: a maximum value search unit which searches, in each of multiple sub-bands obtained by dividing the low-frequency band portion of an audio signal and/or music signal below a prescribed frequency, for the maximum value of the amplitude of a first spectrum obtained by decoding first encoded data, which is encoded data in the low-frequency band portion; and an amplitude normalization unit which obtains a normalized spectrum by normalizing, at the maximum values of the amplitude of each sub-band, the first spectrum contained in each sub-band.

Abstract: An encoding device enables the amount of processing operations to be significantly reduced while minimizing deterioration in the quality of an output signal. This encoding device (101) encodes an input signal by determining the correlation between a first signal generated by using the input signal and a second signal generated by a predetermined method. An importance assessment unit (202) sets the importance of each of a plurality of processing units obtained by dividing the frames of the input signal. A CELP coder (203) performs sparse processing in which the amplitude value of a predetermined number of samples among multiple samples constituted by the first signal and/or the second signal in each processing unit is set to zero according to the importance that was set for each processing unit, and calculates the correlation between the first signal and the second signal, either of which was subjected to sparse processing.

Abstract: A coding apparatus capable of coding a spectrum at a low bit rate and with high quality without producing any disturbance in a harmonic structure of the spectrum. In this apparatus, internal state setting section sets an internal state of a filtering section using a first spectrum S1(k). A pitch coefficient setting section outputs a pitch coefficient T by gradually changing it. The filtering section calculates an estimated value S?2(k) of a second spectrum S2(k) based on a pitch coefficient T. A search section calculates the degree of similarity between S2(k) and S?2(k). At this time, pitch coefficient T? corresponding to the maximum calculated degree of similarity is given to a filter coefficient calculation section. The filter coefficient calculation section determines a filter coefficient ?i using this pitch coefficient T?.

Abstract: Disclosed is a spectral smoothing device with a structure whereby smoothing is performed after a nonlinear conversion has been performed for a spectrum calculated from an audio signal, and with which the amount of processing calculation is significantly reduced while maintaining excellent audio quality. With this spectral smoothing device, a sub band division unit (102) divides an input spectrum into multiple sub bands; a representative value calculation unit (103) calculates a representative value for each sub band using an arithmetic mean and a geometric mean; with respect to each representative value, a nonlinear conversion unit (104) performs a nonlinear conversion the characteristic of which is further emphasized as the value increases; and a smoothing unit (105) that smoothes the representative value which has undergone the nonlinear conversion for each sub band, at the frequency domain.

Abstract: Provided is an encoding device which can obtain a sound quality preferable for auditory sense even if the number of information bits is small. The encoding device includes a shape quantization unit (111) having: a section search unit (121) which searches for a pulse for each of bands into which a predetermined search section is divided; and a whole search unit (122) which performs search for a pulse over the entire search section. The shape of an input spectrum is quantized by a small number of pulse positions and polarities. A gain quantization unit (112) calculates a gain of the pulse searched by the shape quantization unit (111) and quantizes the gain for each of the bands.

Abstract: A voice coding device capable of preventing overall quality degradation even when the bit rate for coding is lowered. The voice coding device codes a wide band signal in a first layer, and codes an extended band signal whose frequency band is located in higher frequency than the wide band signal in an extended band layer. An adaptive band selection unit (301) selects a frequency band to be excluded from a coding object in the extended band layer or a frequency band whose energy is to be attenuated in the extended band layer. A band-limited signal generation unit (302) excludes, within the frequency band of an input signal, the frequency band selected by the adaptive band selection unit (301) from the coding object, or attenuates the energy of the frequency band selected by the adaptive band selection unit (301).

Abstract: In this invention, the design of the Huffman table can be done offline with a large input sequence database. The range of the quantization indices (or differential indices) for Huffman coding is identified. For each value of range, all the input signal which have the same range will be gathered and the probability distribution of each value of the quantization indices (or differential indices) within the range is calculated. For each value of range, one Huffman table is designed according to the probability. And in order to improve the bits efficiency of the Huffman coding, apparatus and methods to reduce the range of the quantization indices (or differential indices) are also introduced.

Abstract: There is disclosed an encoding device capable of improving similarity between the high frequency band spectrum of the original signal and a new spectrum to be generated while realizing a low bit rate when encoding a wide-band signal spectrum. The encoding device has sub-band amplitude calculation units for calculating the amplitude of the respective sub-bands for the high frequency band spectrum obtained from the wide-band signal. A search unit and a gain codebook select some sub-bands from a plurality of sub-bands and only the gain of the selected sub-bands is subjected to encoding. An interpolation unit expresses the gain of the sub-band not selected, by mutually interpolating the selected gains.

Abstract: A decoding device reduces abrupt changes in the number of channels in a decoded signal when transmission errors occur as a result of lost frames in an encoding/decoding system for multichannel signals. In the device, a demultiplexer receives an encoded monaural signal and an encoded differential signal and detects change over time in the received encoded differential signal. An M signal decoder decodes the encoded monaural signal and obtains a decoded monaural signal. An S signal decoder decodes the encoded differential signal and obtains a decoded differential signal. A smoothing unit performs smoothing on the decoded differential signal by means of a computation involving the decoded differential signal and coefficients corresponding to the change over time detected by the demultiplexer. An L/R signal computation unit computes a decoded stereo signal from the decoded monaural signal and the smoothed decoded differential signal.

Abstract: Disclosed is an encoding device which can accurately specify a band having a large error among all the bands by using a small calculation amount. A first position identifier uses a first layer error conversion coefficient indicating an error of a decoding signal for an input signal so as to search for a band having a large error in a relatively wide bandwidth in all the bands of the input signal and generates first position information indicating the identified band. A second position identifier searches for a target frequency band having a large error in a relatively narrow bandwidth in the band identified by the first position identifier and generates second position information indicating the identified target frequency band. An encoder encodes a first layer decoding error conversion coefficient contained in the target frequency band.

Abstract: Provided is a speech/audio encoding apparatus with which it is possible to code a significant frequency domain region with high precision, and to enable high audio quality. A speech/audio encoding apparatus codes a linear prediction coefficient. A significant frequency domain region detection unit identifies a frequency domain region which is aurally significant from the linear prediction coefficient. A frequency domain region repositioning unit repositions the significant frequency domain region which is identified by the significant frequency domain region detection unit. A bit allocation computation unit determines a coding bit allocation on the basis of the significant frequency domain region which is repositioned by the frequency domain region repositioning unit.

Abstract: An encoding apparatus includes a first layer encoder that encodes an input signal, a first layer decoder that decodes the first layer encoded data, a weighting filter that filters a first layer error signal to acquire a weighted first layer error signal, a first layer error transform coefficient calculator that transforms the weighted first layer error signal into a frequency domain, and a second layer encoder that encodes the first layer error transform coefficient. The second layer encoder includes a first shape vector encoder that refers the first layer error transform coefficient to generate a first shape vector and first shape encoded information. A target gain calculator calculates a target gain using the first layer error transform coefficient and the first shape vector, a gain vector generator generates a gain vector, and a gain vector encoder encodes the gain vector to acquire gain encoded information.

Abstract: Disclosed is an encoding device which can accurately specify a band having a large error among all the bands by using a small calculation amount. A first position identifier uses a first layer error conversion coefficient indicating an error of a decoding signal for an input signal so as to search for a band having a large error in a relatively wide bandwidth in all the bands of the input signal and generates first position information indicating the identified band. A second position identifier searches for a target frequency band having a large error in a relatively narrow bandwidth in the band identified by the first position identifier and generates second position information indicating the identified target frequency band. An encoder encodes a first layer decoding error conversion coefficient contained in the target frequency band.

Abstract: An encoding apparatus includes a first layer encoder that encodes a signal, a first layer decoder that decodes first layer encoded data, a first layer error transform coefficient calculator that transforms a first layer error signal into a frequency domain and a second layer encoder that encodes the first layer error transform coefficient to acquire second layer encoded data. The second layer encoder includes a band determiner that determines a band to be encoded by the second layer encoder, and a first shape vector encoder that refers the first layer error transform coefficient included in the band to generate a first shape vector and first shape encoded information, a target gain calculator calculates target gain per subband, a gain vector generator generates a gain vector using a plurality of target gains, and a gain vector encoder encodes the gain vector to acquire gain encoded information.

Abstract: Provided is a decoding device which suppresses generation of an abnormal sound caused by a layer switch.