Voice audio encoding device, voice audio decoding device, voice audio encoding method, and voice audio decoding method

A speech/audio coding apparatus comprising:

• a transformation section that transforms an input signal from a time domain to a frequency domain;
• an estimation section that estimates an energy envelope which represents an energy level for each of a plurality of subbands obtained by splitting a frequency spectrum of the input signal;
• a quantization section that quantizes the energy envelopes;
• a group determining section that groups the quantized energy envelopes into a plurality of groups;
• a first bit allocation section that allocates bits to the plurality of groups;
• a second bit allocation section that allocates the bits allocated to the plurality of groups to subbands on a group-by-group basis;
• and
• a coding section that encodes the frequency spectrum using bits allocated to the subbands,
• wherein the group determining section determines a dominant frequency band which is a subband in which an energy envelope of the frequency spectrum has a local maximum value and subbands on both sides of the dominant frequency band each forming a descending slope of an energy envelope as dominant groups, and determines continuous subbands other than the dominant frequency band as non-dominant groups.

A speech/audio decoding apparatus comprising:

• a de-quantization section that de-quantizes a quantized spectral envelope;
• a group determining section that groups the quantized spectral envelopes into a plurality of groups;
• a first bit allocation section that allocates bits to the plurality of groups;
• a second bit allocation section that allocates the bits allocated to the plurality of groups to subbands on a group-by-group basis;
• a decoding section that decodes a frequency spectrum of a speech/audio signal using the bits allocated to the subbands;
• an envelope shaping section that applies the de-quantized spectral envelope to the decoded frequency spectrum and reproduces a decoded spectrum;
• and
• an inverse transformation section that inversely transforms the decoded spectrum from a frequency domain to a time domain,
• wherein the group determining section determines a dominant frequency band which is a subband in which an energy envelope of the frequency spectrum has a local maximum value and subbands on both sides of the dominant frequency band each forming a descending slope of an energy envelope as dominant groups and determines continuous subbands other than the dominant frequency band as non-dominant groups.

A speech/audio coding method comprising:

• transforming an input signal from a time domain to a frequency domain;
• estimating an energy envelope that represents an energy level for each of a plurality of subbands obtained by splitting a frequency spectrum of the input signal;
• quantizing the energy envelopes;
• grouping the quantized energy envelopes into a plurality of groups;
• allocating bits to the plurality of groups;
• allocating the bits allocated to the plurality of groups to subbands on a group-by-group basis;
• and
• encoding the frequency spectrum using bits allocated to the subbands,
• wherein, in the grouping, determining a dominant frequency band which is a subband in which an energy envelope of the frequency spectrum has a local maximum value and subbands on both sides of the dominant frequency band each forming a descending slope of an energy envelope as dominant groups, and determining continuous subbands other than the dominant frequency band as non-dominant groups.

A speech/audio decoding method comprising:

• de-quantizing a quantized spectral envelope;
• grouping the quantized spectral envelope into a plurality of groups;
• allocating bits to the plurality of groups;
• allocating the bits allocated to the plurality of groups to subbands on a group-by-group basis;
• decoding a frequency spectrum of a speech/audio signal using the bits allocated to the subbands;
• applying the de-quantized spectral envelope to the decoded frequency spectrum and reproducing a decoded spectrum;
• and
• inversely transforming the decoded spectrum from a frequency domain to a time domain,
• wherein, in the grouping, determining a dominant frequency band which is a subband in which an energy envelope of the frequency spectrum has a local maximum value and subbands on both sides of the dominant frequency band each forming a descending slope of an energy envelope as dominant groups, and determining continuous subbands other than the dominant frequency band as non-dominant groups.