Adaptive transition frequency between noise fill and bandwidth extension
First Claim
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1. A method for processing an audio signal, comprising:
- dividing spectral coefficients of an initial set of spectral coefficients representing at least a portion of said audio signal into a plurality of frequency bands, each of the plurality of frequency bands comprising a plurality of frequencies between an upper frequency of the frequency band and a lower frequency of the frequency band; and
after dividing spectral coefficients into the plurality of frequency bands, determining a first transition frequency for the initial set of spectral coefficients based on a distribution of spectral holes in the initial set of spectral coefficients, whereinsaid first transition frequency defines a border between a first frequency range intended to be a subject for noise filling of spectral holes and a second frequency range intended to be a subject for bandwidth extension, anddetermining the first transition frequency based on the distribution of spectral holes in the initial set of spectral coefficients comprises choosing the first transition frequency based on the distribution of spectral holes in the initial set of spectral coefficients such that;
1) at least one frequency band that comprises a frequency that is less than said first transition frequency includes at least one quantized coefficient and
2) each of said frequency bands that comprises a frequency that is greater than said first transition frequency does not include any quantized coefficients.
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Abstract
A method for spectrum recovery in spectral decoding of an audio signal, comprises obtaining of an initial set of spectral coefficients representing the audio signal, and determining a transition frequency. The transition frequency is adapted to a spectral content of the audio signal. Spectral holes in the initial set of spectral coefficients below the transition frequency are noise filled and the initial set of spectral coefficients are bandwidth extended above the transition frequency. Decoders and encoders being arranged for performing part of or the entire method are also illustrated.
44 Citations
11 Claims
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1. A method for processing an audio signal, comprising:
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dividing spectral coefficients of an initial set of spectral coefficients representing at least a portion of said audio signal into a plurality of frequency bands, each of the plurality of frequency bands comprising a plurality of frequencies between an upper frequency of the frequency band and a lower frequency of the frequency band; and after dividing spectral coefficients into the plurality of frequency bands, determining a first transition frequency for the initial set of spectral coefficients based on a distribution of spectral holes in the initial set of spectral coefficients, wherein said first transition frequency defines a border between a first frequency range intended to be a subject for noise filling of spectral holes and a second frequency range intended to be a subject for bandwidth extension, and determining the first transition frequency based on the distribution of spectral holes in the initial set of spectral coefficients comprises choosing the first transition frequency based on the distribution of spectral holes in the initial set of spectral coefficients such that;
1) at least one frequency band that comprises a frequency that is less than said first transition frequency includes at least one quantized coefficient and
2) each of said frequency bands that comprises a frequency that is greater than said first transition frequency does not include any quantized coefficients. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus for processing an audio signal, the apparatus being adapted to:
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divide spectral coefficients of an initial set of spectral coefficients representing at least a portion of said audio signal into a plurality of frequency bands, each of the plurality of frequency bands comprising a plurality of frequencies between an upper frequency of the frequency band and a lower frequency of the frequency band; and after dividing spectral coefficients of an initial set of spectral coefficients representing at least a portion of said audio signal into a plurality of frequency bands, determine a first transition frequency for the initial set of spectral coefficients based on a distribution of spectral holes in the initial set of spectral coefficients, wherein said first transition frequency defines a border between a first frequency range intended to be a subject for noise filling of spectral holes and a second frequency range intended to be a subject for bandwidth extension, and the apparatus is configured to determine the first transition frequency based on the distribution of spectral holes in the initial set of spectral coefficients by performing a process comprising choosing the first transition frequency based on the distribution of spectral holes in the initial set of spectral coefficients such that;
1) at least one frequency band that comprises a frequency that is less than said first transition frequency includes at least one quantized coefficient and
2) each of said frequency bands that comprises a frequency that is greater than said first transition frequency does not include any quantized coefficients.
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11. A computer program product comprising a non-transitory computer readable medium storing a computer program, the computer program comprising:
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instructions for dividing spectral coefficients of an initial set of spectral coefficients representing at least a portion of said audio signal into a plurality of frequency bands, each of the plurality of frequency bands comprising a plurality of frequencies between an upper frequency of the frequency band and a lower frequency of the frequency band; and instructions for, after dividing spectral coefficients of an initial set of spectral coefficients representing at least a portion of said audio signal into a plurality of frequency bands, determining a first transition frequency for the initial set of spectral coefficients based on a distribution of spectral holes in the initial set of spectral coefficients, wherein said first transition frequency defines a border between a first frequency range intended to be a subject for noise filling of spectral holes and a second frequency range intended to be a subject for bandwidth extension, and the instructions for determining the first transition frequency based on the distribution of spectral holes in the initial set of spectral coefficients comprises instructions for choosing the first transition frequency based on the distribution of spectral holes in the initial set of spectral coefficients such that;
1) at least one frequency band that comprises a frequency that is less than said first transition frequency includes at least one quantized coefficient and
2) each of said frequency bands that comprises a frequency that is greater than said first transition frequency does not include any quantized coefficients.
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Specification