A method of enhancing speech quality includes: generating a high-frequency signal by using a low-frequency signal in a time domain; combining the low-frequency signal with the high-frequency signal; transforming the combined signal into a spectrum in a frequency domain; determining a class of a decoded speech signal; predicting an envelope from a low-frequency spectrum obtained in the transforming; and generating a final high-frequency spectrum by applying the predicted envelope to a high-frequency spectrum obtained in the transforming.

A waveform correction processor corrects the waveform of a first digital audio signal (a CD signal, for example) having a first sampling frequency. A bit depth and sampling frequency converter converts the first digital audio signal with the waveform corrected by the first waveform correction processor to a second digital audio signal (a high-resolution digital audio signal, for example) having a second sampling frequency, which is higher than the first sampling frequency. The waveform correction processor corrects the waveform of the second digital audio signal.

A waveform correction processor corrects the waveform of a first digital audio signal (a CD signal, for example) having a first sampling frequency. A bit depth and sampling frequency converter converts the first digital audio signal with the waveform corrected by the first waveform correction processor to a second digital audio signal (a high-resolution digital audio signal, for example) having a second sampling frequency, which is higher than the first sampling frequency. The waveform correction processor corrects the waveform of the second digital audio signal.

A device includes an encoder and a transmitter. The encoder is configured to generate a first high-band portion of a first signal based on a left signal and a right signal. The encoder is also configured to generate a set of adjustment gain parameters based on a high-band non-reference signal. The high-band non-reference signal corresponds to one of a left high-band portion of the left signal or a right high-band portion of the right signal as a high-band non-reference signal. The transmitter is configured to transmit information corresponding to the first high-band portion of the first signal. The transmitter is also configured to transmit the set of adjustment gain parameters corresponding to the high-band non-reference signal.

A decoding apparatus includes: a bandwidth extending part 25 obtaining a decoded extended frequency spectrum sequence by arranging samples based on K samples included in a frequency-domain sample sequence obtained by decoding, on a higher side than the frequency-domain sample sequence; and a fricative sound adjustment releasing part 23 obtaining, if inputted information indicating whether a hissing sound or not indicates being a hissing sound, what is obtained by exchanging all or a part of a low-side frequency sample sequence existing on a lower side than a predetermined frequency in the decoded extended frequency spectrum sequence for all or a part of a high-side frequency sample sequence existing on a higher side than the predetermined frequency in the decoded extended frequency spectrum sequence as an adjusted frequency spectrum sequence, the number of all or the part of the high-side frequency spectrum sequence being the same as the number of all or the part of the low-side frequency spectrum sequence.

A decoding apparatus includes: a bandwidth extending part 25 obtaining a decoded extended frequency spectrum sequence by arranging samples based on K samples included in a frequency-domain sample sequence obtained by decoding, on a higher side than the frequency-domain sample sequence; and a fricative sound adjustment releasing part 23 obtaining, if inputted information indicating whether a hissing sound or not indicates being a hissing sound, what is obtained by exchanging all or a part of a low-side frequency sample sequence existing on a lower side than a predetermined frequency in the decoded extended frequency spectrum sequence for all or a part of a high-side frequency sample sequence existing on a higher side than the predetermined frequency in the decoded extended frequency spectrum sequence as an adjusted frequency spectrum sequence, the number of all or the part of the high-side frequency spectrum sequence being the same as the number of all or the part of the low-side frequency spectrum sequence.

An apparatus for decoding an encoded audio signal, includes a spectral domain audio decoder for generating a first decoded representation of a first set of first spectral portions, the decoded representation having a first spectral resolution; a parametric decoder for generating a second decoded representation of a second set of second spectral portions having a second spectral resolution being lower than the first spectral resolution; a frequency regenerator for regenerating every constructed second spectral portion having the first spectral resolution using a first spectral portion and spectral envelope information for the second spectral portion; and a spectrum time converter for converting the first decoded representation and the reconstructed second spectral portion into a time representation.

An apparatus for decoding an encoded audio signal, includes a spectral domain audio decoder for generating a first decoded representation of a first set of first spectral portions, the decoded representation having a first spectral resolution; a parametric decoder for generating a second decoded representation of a second set of second spectral portions having a second spectral resolution being lower than the first spectral resolution; a frequency regenerator for regenerating every constructed second spectral portion having the first spectral resolution using a first spectral portion and spectral envelope information for the second spectral portion; and a spectrum time converter for converting the first decoded representation and the reconstructed second spectral portion into a time representation.

An apparatus for decoding an encoded audio signal having an encoded representation of a first set of first spectral portions and an encoded representation of parametric data indicating spectral energies for a second set of second spectral portions, has: an audio decoder for decoding the encoded representation of the first set of the first spectral portions to obtain a first set of first spectral portions and for decoding the encoded representation of the parametric data to obtain a decoded parametric data for the second set of second spectral portions indicating, for individual reconstruction bands, individual energies; a frequency regenerator for reconstructing spectral values in a reconstruction band having a second spectral portion using a first spectral portion of the first set of the first spectral portions and an individual energy for the reconstruction band, the reconstruction band having a first spectral portion and the second spectral portion.

An apparatus for decoding an encoded audio signal having an encoded representation of a first set of first spectral portions and an encoded representation of parametric data indicating spectral energies for a second set of second spectral portions, has: an audio decoder for decoding the encoded representation of the first set of the first spectral portions to obtain a first set of first spectral portions and for decoding the encoded representation of the parametric data to obtain a decoded parametric data for the second set of second spectral portions indicating, for individual reconstruction bands, individual energies; a frequency regenerator for reconstructing spectral values in a reconstruction band having a second spectral portion using a first spectral portion of the first set of the first spectral portions and an individual energy for the reconstruction band, the reconstruction band having a first spectral portion and the second spectral portion.