Spectrum modeling
First Claim
1. A method of modeling (2,22) a target spectrum (S) by determining filter parameters (pi,qi) of a filter (41) which has a frequency response (S′
- ) approximating the target spectrum (S), characterized in that the method comprises the steps of;
splitting (22) the target spectrum in at least a first part and a second part;
using (22) a first modeling operation on the first part of the target spectrum (S) to obtain auto-regressive parameters (pi);
using (22) a second modeling operation on the second part of the target spectrum to obtain moving-average parameters (qi); and
combining (22) the auto-regressive parameters (pi) and the moving-average parameters (qi) to obtain the filter parameters (pi,qi).
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Abstract
Modeling a target spectrum (S) is provided by determining (21) filter parameters (pi,qi) of a filter which has a frequency response approximating the target spectrum (S), wherein the target spectrum is split in at least a first part and a second part, a first modeling operation is used on the first part of the target spectrum to obtain auto-regressive parameters, a second modeling operation is used on the second part of the target spectrum to obtain moving-average parameters, and the auto-regressive parameters and the moving-average parameters are combined to obtain the filter parameters. The invention is preferably applied in audio coding, wherein a spectrum of a noise component (S) in the signal (A) is modeled.
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Citations
18 Claims
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1. A method of modeling (2,22) a target spectrum (S) by determining filter parameters (pi,qi) of a filter (41) which has a frequency response (S′
- ) approximating the target spectrum (S),
characterized in that the method comprises the steps of;
splitting (22) the target spectrum in at least a first part and a second part;
using (22) a first modeling operation on the first part of the target spectrum (S) to obtain auto-regressive parameters (pi);
using (22) a second modeling operation on the second part of the target spectrum to obtain moving-average parameters (qi); and
combining (22) the auto-regressive parameters (pi) and the moving-average parameters (qi) to obtain the filter parameters (pi,qi). - View Dependent Claims (2, 3, 4, 5, 6, 7)
- ) approximating the target spectrum (S),
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8. A device (2), comprising:
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means (22) for determining filter parameters (pi,qi) of a filter (41) which has a frequency response (S′
) approximating a target spectrum,characterized in that the device further comprises;
means (22) for splitting the target spectrum (S) in at least a first part and a second part;
means (22) for using a first modeling operation on the first part of the target spectrum (S) to obtain auto-regressive parameters (pi);
means (22) for using a second modeling operation on the second part of the target spectrum (S) to obtain moving-average parameters (qi); and
means (22) for combining the auto-regressive parameters (pi) and the moving-average parameters (qi) to obtain the filter parameters (pi,qi).
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9. A method of suppressing noise (6) in an audio signal (A), the method comprising:
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modeling (60) a spectrum of the noise by determining filter parameters (pi,qi) of a filter (61) which has a frequency response approximating the spectrum of the noise;
obtaining (61) reconstructed noise by filtering (61) a white noise (y) with a filter (61), which properties are determined by the filter parameters (pi,qi); and
subtracting (62) the reconstructed noise from the audio signal (A) to obtain a noise-filtered audio signal ({A});
the step of modeling (60) comprising;
splitting (60) the spectrum in at least a first part and a second part;
using (60) a first modeling operation on the first part of the spectrum to obtain auto-regressive parameters (pi);
using (60) a second modeling operation on the second part of the noise spectrum to obtain moving-average parameters (qi); and
combining (60) the auto-regressive parameters (pi) and the moving-average parameters (qi) to obtain the filter parameters (pi,qi);
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10. A device (6) for suppressing noise in an audio signal (A), the device comprising:
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means (60) for modeling a spectrum of the noise by determining filter parameters (pi,qi) of a filter (61) which has a frequency response approximating the spectrum of the noise;
means (61) for obtaining reconstructed noise by filtering (61) a white noise (y) with a filter (61), which properties are determined by the filter parameters (pi,qi); and
means (62) for subtracting the reconstructed noise from the audio signal (A) to obtain a noise-filtered audio signal ({A});
the means for modeling (60) comprising;
means (60) for splitting the spectrum in at least a first part and a second part;
means (60) for using a first modeling operation on the first part of the spectrum to obtain auto-regressive parameters (pi);
means (60) for using a second modeling operation on the second part of the noise spectrum to obtain moving-average parameters (qi); and
means (60) for combining the auto-regressive parameters (pi) and the moving-average parameters (qi) to obtain the filter parameters (pi,qi);
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11. A method of encoding (2,21) an audio signal (A), comprising the steps of:
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determining (200) basic waveforms in the audio signal (A);
obtaining (21) a noise component (S) from the audio signal (A) by subtracting the basic waveforms from the audio signal (A);
modeling (22) a spectrum of the noise component (S) by determining filter parameters (pi,qi) of a filter (41) which has a frequency response (S′
) approximating the spectrum of the noise component (S); and
including (23) the filter parameters (pi,qi) and waveform parameters (Ci) representing the basic waveforms in an encoded audio signal (A′
);
the step of modeling comprising;
splitting (22) the spectrum (S) in at least a first part and a second part;
using (22) a first modeling operation on the first part of the spectrum (S) to obtain auto-regressive parameters (pi);
using (22) a second modeling operation on the second part of the noise spectrum (S) to obtain moving-average parameters (qi); and
combining (22) the auto-regressive parameters (pi) and the moving-average parameters (qi) to obtain the filter parameters (pi,qi). - View Dependent Claims (12, 14, 16, 17, 18)
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13. An audio encoder (2) comprising:
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means (200) for determining basic waveforms in the audio signal (A);
means (21) for obtaining a noise component (S) from the audio signal (A) by subtracting (21) the basic waveforms from the audio signal (A);
means (22) for modeling a spectrum of the noise component (S) by determining filter parameters (pi,qi) of a filter (41) which has a frequency response (S′
) approximating the spectrum of the noise component (S); and
means (23) for including the filter parameters (pi,qi) and waveform parameters (Ci) representing the basic waveforms in an encoded audio signal (A′
);
the means (22) for modeling comprising;
means (22) for splitting the spectrum (S) in at least a first part and a second part;
means (22) for using a first modeling operation on the first part of the spectrum (S) to obtain auto-regressive parameters (pi);
means (22) for using a second modeling operation on the second part of the noise spectrum (S) to obtain moving-average parameters (qi); and
means (22) for combining the auto-regressive parameters (pi) and the moving-average parameters (qi) to obtain the filter parameters (pi,qi). - View Dependent Claims (15)
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Specification