Frequency band extension apparatus and method, encoding apparatus and method, decoding apparatus and method, and program

A frequency band extension apparatus, comprising:na plurality of band-pass filters that obtain a plurality of lowband subband signals from an input signal;a frequency envelope extracting circuit that extracts a frequency envelope from the plurality of lowband subband signals obtained by the plurality of band-pass filters, wherein the frequency envelope extracting circuit obtains at least one first-order slope of the frequency envelope that is computed in a weighted manner from the plurality of lowband subband signals obtained by the plurality of band-pass filters; anda highband signal generating circuit that generates highband signal components, on the basis of the frequency envelope obtained by the frequency envelope extracting circuit, and the plurality of lowband subband signals obtained by the band-pass filters,wherein a frequency band of the input signal is extended by using the highband signal components generated by the highband signal generating circuit.

A frequency band extension method comprising:nobtaining a plurality of lowband subband signals from an input signal;extracting a frequency envelope from the obtained plurality of lowband subband signals, wherein the frequency envelope extracted comprises at least one first-order slope of the frequency envelope that is computed in a weighted manner from the plurality of lowband subband signals;generating highband signal components on the basis of the extracted frequency envelope, and the obtained plurality of lowband subband signals; andextending a frequency band of the input signal by using the generated highband signal components.

A non-transitory computer-readable medium storing a computer-executable program which, when executed by a processor, performs a method for causing a computer controlling a frequency band extension apparatus to execute a control process, the method comprising:nobtaining a plurality of lowband subband signals from an input signal;extracting a frequency envelope from the obtained plurality of lowband subband signals, wherein the frequency envelope extracted is at least one first-order slope of the frequency envelope that is computed in a weighted manner from the plurality of lowband subband signals;generating highband signal components on the basis of the extracted frequency envelope, and the obtained plurality of lowband subband signals; andextending a frequency band of the input signal by using the generated highband signal components.

An encoding apparatus comprising:na subband division circuit that divides an input signal into a plurality of subbands, and generates lowband subband signals including a plurality of subbands on a lowband side, and highband subband signals including a plurality of subbands on a highband side;a lowband encoding circuit that encodes the lowband subband signals, and generates lowband encoded data;a frequency envelope extracting circuit that extracts a frequency envelope from the lowband subband signals, wherein the frequency envelope extracted is at least one first-order slope of the frequency envelope that is computed in a weighted manner from the lowband subband signals generated by the subband division circuit;a pseudo-highband-signal generating circuit that generates pseudo highband signals, from the frequency envelope obtained by the frequency envelope extracting circuit and the lowband subband signals;a pseudo-highband-signal-correction-information calculating circuit that compares the highband subband signals obtained by the subband division circuit with the pseudo highband signals generated by the pseudo-highband-signal generating circuit, and obtains pseudo-highband-signal correction information;a highband encoding circuit that encodes the pseudo-highband-signal correction information, and generates highband encoded data; anda multiplexing circuit that multiplexes the lowband encoded data generated by the lowband encoding circuit and the highband encoded data generated by the highband encoding circuit to obtain an output code string.

An encoding method comprising:ndividing an input signal into a plurality of subbands, and generating lowband subband signals including a plurality of subbands on a lowband side, and highband subband signals including a plurality of subbands on a highband side;encoding the lowband subband signals, and generating lowband encoded data;extracting a frequency envelope from the lowband subband signals, wherein the frequency envelope extracted is at least one first-order slope of the frequency envelope that is computed in a weighted manner from the lowband subband signals;generating pseudo highband signals from the extracted frequency envelope and the lowband subband signals;comparing the highband subband signals with the generated pseudo highband signals, and obtaining pseudo-highband-signal correction information;encoding the pseudo-highband-signal correction information, and generating highband encoded data; andmultiplexing the generated lowband encoded data and the generated highband encoded data to obtain an output code string.

A non-transitory computer-readable medium storing a computer-executable program which, when executed by a processor, performs a method for causing a computer controlling an encoding apparatus to execute a control process, the method comprising:ndividing an input signal into a plurality of subbands, and generating lowband subband signals including a plurality of subbands on a lowband side, and highband subband signals including a plurality of subbands on a highband side;encoding the lowband subband signals, and generating lowband encoded data;extracting a frequency envelope from the lowband subband signals, wherein the frequency envelope extracted is at least one first-order slope of the frequency envelope that is computed in a weighted manner from the lowband subband signals;generating pseudo highband signals from the extracted frequency envelope and the lowband subband signals;comparing the highband subband signals with the generated pseudo highband signals, and obtaining pseudo-highband-signal correction information;encoding the pseudo-highband-signal correction information, and generating highband encoded data; andmultiplexing the generated lowband encoded data and the generated highband encoded data to obtain an output code string.

A decoding apparatus comprising:na demultiplexing circuit that demultiplexes inputted encoded data, and generates lowband encoded data and highband encoded data;a lowband decoding circuit that decodes the lowband encoded data, and generates lowband subband signals;a frequency envelope extracting circuit that extracts a frequency envelope from a plurality of subband signals of the lowband subband signals, wherein the frequency envelope extracted is at least one first-order slope of the frequency envelope, that is computed in a weighted manner from the plurality of subband signals of the lowband subband signals;a pseudo-highband-signal generating circuit that generates pseudo highband signals, from the frequency envelope obtained by the frequency envelope extracting circuit and the lowband subband signals;a highband decoding circuit that decodes the highband encoded data, and generates pseudo-highband-signal correction information; anda pseudo-highband-signal correcting circuit that corrects the pseudo highband signals by using the pseudo-highband-signal correction information to generate corrected pseudo highband signals.

A decoding method comprising:nobtaining encoded data from an input code string;demultiplexing the obtained encoded data, and generating lowband encoded data and highband encoded data;decoding the lowband encoded data, and generating lowband subband signals;extracting a frequency envelope from a plurality of subband signals of the lowband subband signals, wherein the frequency envelope extracted is at least one first-order slope of the frequency envelope that is computed in a weighted manner from the plurality of subband signals of the lowband subband signals;generating pseudo highband signals from the extracted frequency envelope and the lowband subband signals;decoding the highband encoded data, and generating pseudo-highband-signal correction information; andcorrecting the pseudo highband signals by using the pseudo-highband-signal correction information to generate corrected pseudo highband signals.

A non-transitory computer-readable medium storing a computer-executable program which, when executed by a processor, performs a method for causing a computer controlling a decoding apparatus to execute a control process, the method comprising:ndemultiplexing inputted encoded data, and generating lowband encoded data and highband encoded data;decoding the lowband encoded data, and generating lowband subband signals;extracting a frequency envelope from a plurality of subband signals of the lowband subband signals, wherein the frequency envelope extracted is at least one first-order slope of the frequency envelope that is computed in a weighted manner from the plurality of subband signals of the lowband subband signals;generating pseudo highband signals from the extracted frequency envelope and the lowband subband signals;decoding the highband encoded data, and generating pseudo-highband-signal correction information; andcorrecting the pseudo highband signals by using the pseudo-highband-signal correction information to generate corrected pseudo highband signals.