Equalization for audio mixing
First Claim
1. A method for mixing an N-channel input audio signal to generate an M-channel output audio signal, where N and Mare positive integers, the method comprising the steps of:
- (a) transforming the N-channel input audio signal from a time domain into a frequency domain;
(b) generating a first spectral loudness measure for the N-channel input audio signal;
(c) mixing N frequency-domain input channel signals corresponding to the N-channel input audio signal to generate M frequency-domain mixed channel signals;
(d) generating a second spectral loudness measure for the M frequency-domain mixed channel signals;
(e) equalizing the M frequency-domain mixed channel signals using a frequency-dependent gain factor that is based on the first and second spectral loudness measures to generate M equalized mixed channel signals; and
(f) transforming the M equalized mixed channel signals from the frequency domain into the time domain to generate the M-channel output audio signal.
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Accused Products
Abstract
During mixing of an N-channel input signal to generate an M-channel output signal, the mixed channel signals are equalized (e.g., amplified) to maintain the overall energy/loudness level of the output signal substantially equal to the overall energy/loudness level of the input signal. In one embodiment, the N input channel signals are converted to the frequency domain on a frame-by-frame basis, and the overall spectral loudness of the N-channel input signal is estimated. After mixing the spectral components for the N input channel signals (e.g., using weighted summation), the overall spectral loudness of the resulting M mixed channel signals is also estimated. A frequency-dependent gain factor, which is based on the two loudness estimates, is applied to the spectral components of the M mixed channel signals to generate M equalized mixed channel signals. The M-channel output signal is generated by converting the M equalized mixed channel signals to the time domain.
37 Citations
23 Claims
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1. A method for mixing an N-channel input audio signal to generate an M-channel output audio signal, where N and Mare positive integers, the method comprising the steps of:
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(a) transforming the N-channel input audio signal from a time domain into a frequency domain; (b) generating a first spectral loudness measure for the N-channel input audio signal; (c) mixing N frequency-domain input channel signals corresponding to the N-channel input audio signal to generate M frequency-domain mixed channel signals; (d) generating a second spectral loudness measure for the M frequency-domain mixed channel signals; (e) equalizing the M frequency-domain mixed channel signals using a frequency-dependent gain factor that is based on the first and second spectral loudness measures to generate M equalized mixed channel signals; and (f) transforming the M equalized mixed channel signals from the frequency domain into the time domain to generate the M-channel output audio signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 15)
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9. An M-channel output audio signal generated by:
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(a) transforming the N-channel input audio signal from a time domain into a frequency domain; (b) generating a first spectral loudness measure for the N-channel input audio signal; (c) mixing N frequency-domain input channel signals corresponding to the N-channel input audio signal to generate M frequency-domain mixed channel signals, where N and M are positive integers; (d) generating a second spectral loudness measure for the M frequency-domain mixed channel signals; (e) equalizing the M frequency-domain mixed channel signals using a frequency-dependent gain factor that is based on the first and second spectral loudness measures to generate M equalized mixed channel signals; and (f) transforming the M equalized mixed channel signals from the frequency domain into the time domain to generate the M-channel output audio signal. - View Dependent Claims (10, 11, 16)
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12. An apparatus for mixing an N-channel input audio signal to generate an M-channel output audio signal, where N and M are positive integers, the apparatus comprising:
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a set of one or more transform blocks configured to transform the N-channel input audio signal from a time domain into a frequency domain; a mixer configured to mix N frequency-domain input channel signals corresponding to the N-channel input audio signal to generate M frequency-domain mixed channel signals; one or more loudness estimators configured to generate a first spectral loudness measure for the N-channel input audio signal and a second spectral loudness measure for the M frequency-domain mixed channel signals; an equalizer configured to equalize the M frequency-domain mixed channel signals using a frequency-dependent gain factor that is based on the first and second spectral loudness measures to generate M equalized mixed channel signals; and a set of one or more inverse transform blocks configured to transform the M equalized mixed channel signals from the frequency domain into the time domain to generate the M-channel output audio signal. - View Dependent Claims (13, 14, 17, 18, 19, 20)
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21. A method for mixing an N-channel input audio signal to generate an M-channel output audio signal, where N and M are positive integers, the method comprising the steps of:
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(a) generating a first loudness measure for the N-channel input audio signal; (b) mixing N input channel signals corresponding to the N-channel input audio signal to generate M mixed channel signals; (c) generating a second loudness measure for the M mixed channel signals; and (d) equalizing the M mixed channel signals using a frequency-dependent gain factor that is based on the first and second loudness measures to generate the M-channel output audio signal, wherein the frequency-dependent gain factor gk(ω
) is given by;
where; Γ
k(ω
) is the first loudness measure;Λ
k(ω
) is the second loudness measure;ε
is a positive constant; andβ
is a constant larger than 1.
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22. An M-channel output audio signal generated by:
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(a) generating a first loudness measure for an N-channel input audio signal; (b) mixing N input channel signals corresponding to the N-channel input audio signal to generate M mixed channel signals, where N and M are positive integers; (c) generating a second loudness measure for the M mixed channel signals; and (d) equalizing the M mixed channel signals using a frequency-dependent gain factor that is based on the first and second loudness measures to generate the M-channel output audio signal, wherein the frequency-dependent gain factor gk(ω
) is given by;
where; Γ
k(ω
) is the first loudness measure;Λ
k(ω
) is the second loudness measure;ε
is a positive constant; andβ
is a constant larger than 1.
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23. An apparatus for mixing an N-channel input audio signal to generate an M-channel output audio signal, where N and M are positive integers, the apparatus comprising:
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(a) a mixer configured to mix N input channel signals corresponding to the N-channel input audio signal to generate M mixed channel signals; (b) one or more loudness estimators configured to generate a first loudness measure for the N-channel input audio signal and a second loudness measure for the M mixed channel signals; and (c) an equalizer configured to equalize the M mixed channel signals using a frequency-dependent gain factor that is based on the first and second loudness measures to generate the M-channel output audio signal, wherein the frequency-dependent gain factor gk(ω
) is given by;
where; Γ
k(ω
) is the first loudness measure;Λ
k(ω
) is the second loudness measure;ε
is a positive constant; andβ
is a constant larger than 1.
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Specification