Broadband frequency translation for high frequency regeneration
First Claim
1. A method for processing an audio signal that comprises:
- obtaining a frequency-domain representation of a baseband signal having some but not all spectral components of the audio signal;
obtaining an estimated spectral envelope of a residual signal having spectral components of the audio signal that are not in the baseband signal;
deriving a noise-blending parameter from a measure of noise content of the residual signal; and
assembling data representing the frequency-domain representation of the baseband signal, the estimated spectral envelope and the noise-blending parameter into an output signal suitable for transmission or storage.
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Accused Products
Abstract
An audio signal is conveyed more efficiently by transmitting or recording a baseband of the signal with an estimated spectral envelope and a noise-blending parameter derived from a measure of the signal'"'"'s noise-like quality. The signal is reconstructed by translating spectral components of the baseband signal to frequencies outside the baseband, adjusting phase of the regenerated components to maintain phase coherency, adjusting spectral shape according to the estimated spectral envelope, and adding noise according to the noise-blending parameter. Preferably, the transmitted or recorded signal also includes an estimated temporal envelope that is used to adjust the temporal shape of the reconstructed signal.
234 Citations
33 Claims
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1. A method for processing an audio signal that comprises:
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obtaining a frequency-domain representation of a baseband signal having some but not all spectral components of the audio signal;
obtaining an estimated spectral envelope of a residual signal having spectral components of the audio signal that are not in the baseband signal;
deriving a noise-blending parameter from a measure of noise content of the residual signal; and
assembling data representing the frequency-domain representation of the baseband signal, the estimated spectral envelope and the noise-blending parameter into an output signal suitable for transmission or storage. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for processing an audio signal that comprises:
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obtaining a plurality of subband signals that represent the audio signal;
obtaining a frequency-domain representation of a baseband signal by applying a first analysis filterbank to a first group of one or more subband signals that includes some but not all of the plurality of subband signals;
obtaining a temporally flattened representation of a second group of one or more subband signals that are not included in the first group of subband signals by modifying the second group of subband signals according to an inverse of an estimated temporal envelope of the second group of subband signals;
obtaining an estimated spectral envelope of the temporally flattened representation of the second group of subband signals;
deriving a noise-blending parameter from a measure of noise content of the temporally flattened representation of the second group of subband signals; and
assembling data representing the frequency-domain representation of the baseband signal, the estimated spectral envelope and the noise-blending parameter into an output signal suitable for transmission or storage.
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9. A method for generating a reconstructed audio signal that comprises:
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receiving a signal containing data representing a baseband signal derived from the audio signal, an estimated spectral envelope, and a noise-blending parameter derived from a measure of noise content of the audio signal;
obtaining from the data a frequency-domain representation of the baseband signal;
obtaining a regenerated signal comprising regenerated spectral components by translating spectral components of the baseband in frequency;
adjusting phase of the regenerated spectral components to maintain phase coherency within the regenerated signal;
obtaining an adjusted regenerated signal by obtaining a noise signal in response to the noise-blending parameter, modifying the regenerated signal by adjusting amplitudes of the regenerated spectral components according to the estimated spectral envelope and the noise-blending parameter, and combining the modified regenerated signal with the noise signal; and
obtaining a time-domain representation of the reconstructed signal corresponding to a combination of the spectral components in the adjusted regenerated signal with spectral components in the frequency-domain representation of the baseband signal. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for generating a reconstructed audio signal that comprises:
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receiving a signal containing data representing a baseband signal derived from the audio signal, an estimated spectral envelope, an estimated temporal envelope, and a noise-blending parameter;
obtaining from the data a frequency-domain representation of the baseband signal;
obtaining a regenerated signal comprising regenerated spectral components by translating spectral components of the baseband in frequency;
adjusting phase of the regenerated spectral components to maintain phase coherency within the regenerated signal;
obtaining a noise signal in response to the noise-blending parameter;
obtaining an adjusted regenerated signal by adjusting amplitudes of the regenerated spectral components according to the estimated spectral envelope and combining them with the noise signal;
obtaining a time-domain representation of the baseband signal by applying a first synthesis filterbank to the frequency-domain representation of the baseband signal;
obtaining a time-domain representation of the adjusted regenerated signal by applying a second synthesis filterbank to the adjusted regenerated signal and applying modulation according to the estimated temporal envelope; and
obtaining a time-domain representation of the reconstructed signal such that it represents a combination of the time-domain representation of the baseband signal and the modified time-domain representation of the adjusted regenerated signal.
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19. A medium readable by a device and conveying one or more programs of instructions for execution by the device to perform a method for processing an audio signal, wherein the method comprises:
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obtaining a frequency-domain representation of a baseband signal having some but not all spectral components of the audio signal;
obtaining an estimated spectral envelope of a residual signal having spectral components of the audio signal that are not in the baseband signal;
deriving a noise-blending parameter from a measure of noise content of the residual signal; and
assembling data representing the frequency-domain representation of the baseband signal, the estimated spectral envelope and the noise-blending parameter into an output signal suitable for transmission or storage. - View Dependent Claims (20, 21, 22, 23)
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24. A medium readable by a device and conveying one or more programs of instructions for execution by the device to perform a method for processing an audio signal, wherein the method comprises:
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obtaining a plurality of subband signals that represent the audio signal;
obtaining a frequency-domain representation of a baseband signal by applying a first analysis filterbank to a first group of one or more subband signals that includes some but not all of the plurality of subband signals;
obtaining a temporally flattened representation of a second group of one or more subband signals that are not included in the first group of subband signals by modifying the second group of subband signals according to an inverse of an estimated temporal envelope of the second group of subband signals;
obtaining an estimated spectral envelope of the temporally flattened representation of the second group of subband signals;
deriving a noise-blending parameter from a measure of noise content of the temporally flattened representation of the second group of subband signals; and
assembling data representing the frequency-domain representation of the baseband signal, the estimated spectral envelope and the noise-blending parameter into an output signal suitable for transmission or storage.
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25. A medium readable by a device and conveying one or more programs of instructions for execution by the device to perform a method for generating a reconstructed audio signal, wherein the method comprises:
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receiving a signal containing data representing a baseband signal derived from the audio signal, an estimated spectral envelope, and a noise-blending parameter derived from a measure of noise content of the audio signal;
obtaining from the data a frequency-domain representation of the baseband signal;
obtaining a regenerated signal comprising regenerated spectral components by translating spectral components of the baseband in frequency;
adjusting phase of the regenerated spectral components to maintain phase coherency within the regenerated signal;
obtaining an adjusted regenerated signal by obtaining a noise signal in response to the noise-blending parameter, modifying the regenerated signal by adjusting amplitudes of the regenerated spectral components according to the estimated spectral envelope and the noise-blending parameter, and combining the modified regenerated signal with the noise signal; and
obtaining a time-domain representation of the reconstructed signal corresponding to a combination of the spectral components in the adjusted regenerated signal with spectral components in the frequency-domain representation of the baseband signal. - View Dependent Claims (26, 27, 28, 29, 30)
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31. A medium readable by a device and conveying one or more programs of instructions for execution by the device to perform a method for generating a reconstructed audio signal, wherein the method comprises:
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receiving a signal containing data representing a baseband signal derived from the audio signal, an estimated spectral envelope, an estimated temporal envelope, and a noise-blending parameter;
obtaining from the data a frequency-domain representation of the baseband signal;
obtaining a regenerated signal comprising regenerated spectral components by translating spectral components of the baseband in frequency;
adjusting phase of the regenerated spectral components to maintain phase coherency within the regenerated signal;
obtaining a noise signal in response to the noise-blending parameter;
obtaining an adjusted regenerated signal by adjusting amplitudes of the regenerated spectral components according to the estimated spectral envelope and combining them with the noise signal;
obtaining a time-domain representation of the baseband signal by applying a first synthesis filterbank to the frequency-domain representation of the baseband signal;
obtaining a time-domain representation of the adjusted regenerated signal by applying a second synthesis filterbank to the adjusted regenerated signal and applying modulation according to the estimated temporal envelope; and
obtaining a time-domain representation of the reconstructed signal such that it represents a combination of the time-domain representation of the baseband signal and the modified time-domain representation of the adjusted regenerated signal.
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32. A medium conveying an output signal generated by a method for processing an audio signal, wherein the method comprises:
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obtaining a frequency-domain representation of a baseband signal having some but not all spectral components of the audio signal;
obtaining an estimated spectral envelope of a residual signal having spectral components of the audio signal that are not in the baseband signal;
deriving a noise-blending parameter from a measure of noise content of the residual signal; and
assembling data representing the frequency-domain representation of the baseband signal, the estimated spectral envelope and the noise-blending parameter into the output signal conveyed by the medium. - View Dependent Claims (33)
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Specification