Device and method for bandwidth extension for audio signals

1. An audio signal decoding apparatus, comprising:

a receiver that receives an encoded information;

a memory; and

a processor that

demultiplexes encoding parameters, index information that identifies a most correlated portion from a low frequency spectrum for one or more high frequency subbands, and scale factor information from the encoded information;

replicates a high frequency subband spectrum based on the index information using a synthesized low frequency spectrum, the synthesized low frequency spectrum being obtained by decoding the encoding parameters;

adjusts an amplitude of the replicated high frequency subband spectrum using the scale factor information,

estimates a frequency of a harmonic component in the synthesized low frequency spectrum;

adjusts a frequency of a harmonic component in the high frequency subband spectrum using the estimated harmonic frequency; and

generates an output signal using the synthesized low frequency spectrum and the high frequency subband spectrum;

wherein, within the harmonic frequency estimation, the processor

splits a preselected portion of the synthesized low frequency spectrum into plural blocks;

identifies a frequency of a spectral peak having a maximum amplitude in each of the plural blocks;

calculates spacing between each of the identified spectral peak frequencies; and

calculates the harmonic frequency using the spacing between the identified spectral peak frequencies.

2. An audio signal decoding apparatus, comprising:

a receiver that receives an encoded information;

a memory; and

a processor that

demultiplexes encoding parameters, index information that identifies a most correlated portion from a low frequency spectrum for one or more high frequency subbands, and scale factor information from the encoded information;

replicates a high frequency subband spectrum based on the index information using a synthesized low frequency spectrum, the synthesized low frequency spectrum being obtained by decoding the encoding parameters;

adjusts an amplitude of the replicated high frequency subband spectrum using the scale factor information,

estimates a frequency of a harmonic component in the synthesized low frequency spectrum;

adjusts a frequency of a harmonic component in the high frequency subband spectrum using the estimated harmonic frequency; and

generates an output signal using the synthesized low frequency spectrum and the high frequency subband spectrum;

wherein, within the harmonic frequency adjustment, the processor further

adjusts the plurality of spectral peak frequencies so that the spacing between the spectral peak frequencies after the adjustment is equal to the estimated harmonic frequency, using, as a reference, the highest frequency of the spectral peaks in the synthesized low frequency spectrum.

3. An audio signal decoding method, comprising:

receiving encoded information;

demultiplexing encoding parameters, index information that identifies a most correlated portion from a low frequency spectrum for one or more high frequency subbands, and scale factor information from the encoded information;

replicating a high frequency subband spectrum based on the index information using the synthesized low frequency spectrum, the synthesized low frequency spectrum being obtained by decoding the encoding parameters;

adjusting an amplitude of the replicated high frequency subband spectrum using the scale factor information,

estimating a frequency of a harmonic component in the synthesized low frequency spectrum;

adjusting a frequency of a harmonic component in the high frequency subband spectrum using the estimated harmonic frequency; and

generating an output signal using the synthesized low frequency spectrum and the high frequency subband spectrum;

wherein, within an harmonic frequency estimation

splitting a preselected portion of the synthesized low frequency spectrum into plural blocks;

identifying a frequency of a spectral peak having a maximum amplitude in each of the plural blocks;

calculating spacing between each of the identified spectral peak frequencies; and

calculating the harmonic frequency using the spacing between the identified spectral peak frequencies.

4. An audio signal decoding method, comprising:

receiving an encoded information;

demultiplexing encoding parameters, index information that identifies a most correlated portion from a low frequency spectrum for one or more high frequency subbands, and scale factor information from the encoded information;

replicating a high frequency subband spectrum based on the index information using the synthesized low frequency spectrum, the synthesized low frequency spectrum being obtained by decoding the encoding parameters;

adjusting an amplitude of the replicated high frequency subband spectrum using the scale factor information,

estimating a frequency of a harmonic component in the synthesized low frequency spectrum;

adjusting a frequency of a harmonic component in the high frequency subband spectrum using the estimated harmonic; and

generating an output signal using the synthesized low frequency spectrum and the high frequency subband spectrum;

wherein, within the harmonic frequency adjustment, adjusting the plurality of spectral peak frequencies so that the spacing between the spectral peak frequencies after the adjustment is equal to the estimated harmonic frequency, using, as a reference, the highest frequency of the spectral peaks in the synthesized low frequency spectrum.

5. The audio signal decoding apparatus according to claim 1 ,

wherein the processor calculates the harmonic frequency using an average value of the spacing between the identified spectral peak frequencies.

6. The audio signal decoding method according to claim 3 ,

wherein calculating the harmonic frequency uses an average value of the spacing between the identified spectral peak frequencies.