Encoding device, decoding device, encoding method and decoding method

A speech decoding apparatus that decodes a signal from a speech coding apparatus including at least one lower coding layer and at least one higher coding layer for performing coding processes together, the at least one higher coding layer including a first layer that is higher than the at least one lower coding layer, and a second layer that is higher than the first layer, the speech decoding apparatus comprising:

• a receiver that receives an encoded speech signal over a transmission channel, including coded information generated by the at least one lower coding layer, index information, and band information which are generated in the speech coding apparatus, the index information indicating a result of multi-rate indexing for each of a plurality of subbands generated by dividing spectrum data inputted to the at least one higher layer, using a lattice vector acquired by a neighborhood search for the plurality of subbands, band information indicating a specific subband group which is a selection range of subbands and being determined among the plurality of subbands using coding bits assigned to each of the plurality of subbands and a subband energy which is an energy of each of the plurality of subbands, the selection range of subbands being one of entries in which a total number of coding bits assigned to each of the plurality of subbands in the multi-rate indexing is equal to or less than a number of the coding bits assigned to the first layer and the selection range of subbands being an entry in which a total of subband energies which are the energies of the plurality of subbands is the highest among the entries, each of the entries being a set of continuous subbands in a case where subbands are arranged in ascending or descending order of frequency, and the index information being rearranged at the speech coding apparatus such that a part corresponding to the specific subband group in the index information is located at the top of the index information, and the subbands other than the specific subband group follow the specific subband group while maintaining the ascending or the descending order of frequency;
• an adjustor that performs a rearrangement process which is reversal of a rearrangement process in the speech coding apparatus on the index information when the decoding process is performed in the at least one higher coding layer and that does not perform the rearrangement process on the index information when the decoding process is performed in only a part of at least one higher coding layer;
• a decoder that decodes only a part corresponding to the specific subband group indicated by the band information, in the index information, to generate a decoded signal when a decoding process is performed in only part of the at least one higher coding layer;
• and
• at least one lower coding layer decoder that decodes the coded information of the at least one lower coding layer to generated a lower decoding layer signal to be added to the decoded signal,
• wherein at least one of the receiver and the decoder is configured as a circuit or as a processor, and
• wherein the speech decoding apparatus uses at least one higher coding layer to decode the incoming speech signal using a specific coded parameter that reflects a degree of perceptual importance to improve decoded speech signal quality using part of bit rates, and
• wherein the selection range of subbands includes a subband having the highest subband energy.

A speech coding method in a coding apparatus including at least one lower coding layer and at least one higher coding layer for performing coding processes together, the at least one higher coding layer including a first layer that is higher than the at least one lower coding layer, and a second layer that is higher layer than the first layer, the speech coding method comprising:

• receiving, by a receiver, an incoming speech signal, the incoming speech signal being inputted to the at least one lower coding layer and used to generate (i) coded information generated by the at least one lower coding layer, and (ii) difference spectrum data based on the incoming speech signal and the decoded signals of the coded information of the at least one lower coding layer;
• dividing, by a processor, the difference spectrum data inputted to the at least one higher coding layer to generate a plurality of subbands, and performing a neighborhood search for the plurality of subbands to calculate lattice vectors for the spectra of the plurality of subbands;
• performing, by an encoder, multi-rate indexing for each of the plurality of subbands using a corresponding one of the lattice vectors, to generate index information indicating a result of the multi-rate indexing for each of the plurality of subbands;
• determining, by a selector, a selection range of subbands as a specific subband group in the at least one higher coding layer among the plurality of subbands using the number of coding bits assigned to each of the plurality of subbands in the index information and a subband energy which is an energy of each of the plurality of subbands, the selection range of subbands being one of entries in which a total number of the coding bits is equal to or less than a number of the coding bits assigned to the first layer and the selection range of subbands being an entry in which a total of the subband energies is the highest among the entries, each of the entries being a set of continuous subbands in a case where subbands are arranged in ascending or descending order of frequency;
• rearranging, by an adjustor, the index information such that a part corresponding to the specific subband group in the index information is located at the top of the index information, and the subbands other than the specific subband group follow the specific subband group while maintaining the ascending or the descending order of frequency;
• and
• transmitting, by a transmitter, the coded information, the rearranged index information, and band information indicating the specific subband group as an encoded signal over a transmission channel to a decoding apparatus,
• wherein the speech coding apparatus uses the at least one higher coding layer to encode the incoming speech signal using a specific coded parameter that reflects a degree of perceptual importance to improve encoded speech signal quality using part of bit rates, and
• wherein the selection range of subbands includes a subband having the highest subband energy.

A speech decoding method in a speech decoding apparatus that decodes a signal from a speech coding apparatus including at least one lower coding layer and at least one higher coding layer for performing coding processes together, the at least one higher coding layer including a first layer that is higher than the at least one lower coding layer, and a second layer that is higher layer than the first layer, the speech decoding method comprising:

• receiving, by a receiver, an encoded speech signal over a transmission channel, including coded information generated by the at least one lower coding layer, index information, and band information which are generated in the coding apparatus, the index information indicating a result of multi-rate indexing for each of a plurality of subbands generated by dividing spectrum data inputted to the at least one higher coding layer, using a lattice vector acquired by a neighborhood search for the plurality of subbands, band information indicating a specific subband group which is a selection range of subbands and being determined among the plurality of subbands using coding bits assigned to each of the plurality of subbands and a subband energy which is an energy of each of the plurality of subbands, the selection range of subbands being one of entries in which a total number of coding bits assigned to each of the plurality of subbands in the multi-rate indexing is equal to or less than a number of the coding bits assigned to the first layer and the selection range of subbands being an entry in which a total of subband energies which are energies of the plurality of subbands is the highest among the entries, each of the entries being a set of continuous subbands in a case where subbands are arranged in ascending or descending order of frequency, and the index information being rearranged at the speech coding apparatus such that a part corresponding to the specific subband group in the index information is located at the top of the index information, and the subbands other than the specific subband group follow the specific subband group while maintaining the ascending or the descending order of frequency;
• performing, by an adjustor, a rearrangement process which is reversal of a rearrangement process in the speech coding apparatus on the index information when the decoding process is performed in the at least one higher coding layer and that does not perform the rearrangement process on the index information when the decoding process is performed in only a part of the at least one higher coding layer;
• decoding, by a decoder, only part corresponding to the specific subband group indicated by the band information, in the index information, to generate a decoded signal when a decoding process is performed in only part of the at least one higher coding layer;
• at least one lower coding layer decoder that decodes the coded information of the at least one lower coded layer to generate a lower coding layer decoded signal to be added to the decoded signal,
• wherein the speech decoding method uses the at least one higher coding layer to decode the incoming speech signal using a specific coded parameter that reflects a degree of perceptual importance to improve decoded speech signal quality using part of bit rates, and
• wherein the selection range of subbands includes a subband having the highest subband energy.