Device and method for bandwidth extension for audio signals
First Claim
1. An audio signal decoding apparatus, comprising:
- a demultiplexer that demultiplexes low-band encoding parameters, index information, and scale factor information from encoded information transmitted from an encoding apparatus that encodes an audio signal;
a low-band decoder that decodes the low-band encoding parameters to obtain a synthesized low frequency spectrum;
a spectrum replicator that replicates a high frequency subband spectrum based on the index information using the synthesized low frequency spectrum;
a spectrum envelope adjuster that adjusts an amplitude of the replicated high frequency subband spectrum using the scale factor information,a harmonic frequency estimator that estimates a frequency of a harmonic component in the synthesized low frequency spectrum;
a harmonic frequency adjuster that adjusts a frequency of a harmonic component in the high frequency subband spectrum using the estimated harmonic frequency spectrum; and
an output that generates an output signal using the synthesized low frequency spectrum and the high frequency subband spectrum.
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Accused Products
Abstract
The purpose of the present invention is to more efficiently extend, using a low bit rate, the bandwidth of input signals having a harmonics structure, in order to obtain better audio quality. The present invention is installed in a device that extends bandwidth for audio signal encoding and decoding. This novel bandwidth extension encoding identifies a low-frequency spectrum component having the highest correlation to a high-frequency bandwidth signal among input signals, duplicates a high-frequency spectrum by energy adjustment of said component, and maintains the harmonic relationship between the low-frequency spectrum and the duplicated high-frequency spectrum by adjusting the spectral peak position of the duplicated high-frequency spectrum, on the basis of a harmonic frequency estimated from a composite low-frequency spectrum.
37 Citations
7 Claims
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1. An audio signal decoding apparatus, comprising:
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a demultiplexer that demultiplexes low-band encoding parameters, index information, and scale factor information from encoded information transmitted from an encoding apparatus that encodes an audio signal; a low-band decoder that decodes the low-band encoding parameters to obtain a synthesized low frequency spectrum; a spectrum replicator that replicates a high frequency subband spectrum based on the index information using the synthesized low frequency spectrum; a spectrum envelope adjuster that adjusts an amplitude of the replicated high frequency subband spectrum using the scale factor information, a harmonic frequency estimator that estimates a frequency of a harmonic component in the synthesized low frequency spectrum; a harmonic frequency adjuster that adjusts a frequency of a harmonic component in the high frequency subband spectrum using the estimated harmonic frequency spectrum; and an output that generates an output signal using the synthesized low frequency spectrum and the high frequency subband spectrum. - View Dependent Claims (2, 3, 4)
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5. An audio signal encoding apparatus, comprising:
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a low-band encoder that encodes a low frequency audio signal and outputs synthesized low frequency spectrum, and generates low-band parameters and outputs the parameters; a subband splitter that transforms a high frequency audio signal to a frequency spectrum and split a high frequency spectrum into a plurality of high frequency subbands, the high frequency spectrum being obtained using time-frequency transformed an input audio signal; a searcher that identifies the most correlated portion from the synthesized low frequency spectrum for each of the high frequency subbands and outputs the identification result as index information; a scale factor estimator that estimates an energy scale factor between each of the high frequency subbands and the most correlated portion identified from the synthesized low frequency spectrum and outputs the scale factor as scale factor information; a harmonic frequency estimator that estimates and outputs a harmonic frequency of the synthesized low frequency spectrum and a harmonic frequency of the transformed input audio signal; and a multiplexer that multiplexes the low-band parameter, the index information, and the scale factor information.
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6. An audio signal decoding method, comprising:
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demultiplexing low-band encoding parameters, index information, and scale factor information from encoded information transmitted from an encoding apparatus that encodes an audio signal; decoding the low-band encoding parameters to obtain a synthesized low frequency spectrum; replicating a high frequency subband spectrum based on the index information using the synthesized low frequency spectrum; 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 spectrum; and generating an output signal using the synthesized low frequency spectrum and the high frequency subband spectrum.
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7. An audio signal encoding method, comprising:
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encoding a low frequency audio signal and outputs synthesized low frequency spectrum, and generates low-band parameters and outputs the parameters; transforming a high frequency audio signal to a frequency spectrum; splitting a high frequency spectrum into a plurality of high frequency subbands, the high frequency spectrum being obtained using time-frequency transformed an input audio signal; identifying the most correlated portion from the synthesized low frequency spectrum for each of the high frequency subbands; outputting the identification result as index information; estimating an energy scale factor between each of the high frequency subbands and the most correlated portion identified from the synthesized low frequency spectrum and outputs the scale factor as scale factor information; estimating a harmonic frequency of the synthesized low frequency spectrum and a harmonic frequency of the transformed input audio signal; and multiplexing the low-band parameter, the index information, and the scale factor information.
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Specification