Encoding device, decoding device, encoding method and decoding method

摘要

An encoding device is provided for improving decoded signal quality. A local search unit conducts a local search on a plurality of sub-bands generated by dividing spectrum data, and calculates lattice vectors for the spectra in the plurality of sub-bands. A multi-rate indexing unit uses the lattice vectors to perform multi-rate indexing on each of the sub-bands, and generates indexing information showing the results thereof. A band selection unit determines certain sub-bands from amongst the plurality of sub-bands in a plurality of encoding layers as perceptually important sub-band groups, where these are: within a selection range of sub-bands wherein the total number of encoding bits allocated to each of the plurality of sub-bands in the indexing information is equal to or less than an already set value, and within a sub-band selection range with the highest total energy of each of the plurality of sub-bands.

主权项

1. A speech coding apparatus that includes 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 coding apparatus comprising:
a receiver that receives 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; a searching processor that divides the difference spectrum data inputted to the at least one higher layer to generate a plurality of subbands, and performs a neighborhood search for the plurality of subbands to calculate lattice vectors for the spectra of the plurality of subbands; an encoder that performs 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; a selector that determines 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; an adjustor that rearranges 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; anda transmitter that transmits the coded information, the rearranged index information, and band information indicating the specific subband group as an encoded speech 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.