Aliasing cancellation in audio effects algorithms
AssigneeSTMicroelectronics Asia Pacific Pte Ltd
InventorsMohammed Javed Absar, Sapna George, Antonio Mario Alvarez-Tinoco
Life of this patent
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Abstract
A method for effecting aliasing cancellation in an audio effects algorithm using a delay modulated signal, derived from interpolation of a delay modulator at an instantaneous sampling frequency, including: determining the instantaneous sampling frequency 1/Tisf and band limiting an input signal, to which the audio effects algorithm is to be applied to ½ Tisf prior to interpolation.
Claims10
A method of aliasing cancellation is an audio effects algorithm using a delay modulated signal, derived from interpolation of a delay modulator at an instantaneous sampling frequency, comprising:
- determining the instantaneous sampling frequency 1/Tisf;
- and
- band limiting an input signal, to which the audio effects algorithm is to be applied, to ½ Tisf prior to interpolation.
A method of aliasing cancellation, comprising:
- determining the instantaneous sampling frequency 1/Tisf for an analogue input signal x(t);
- band limiting the analogue input signal x(t) to ½Tisf, and
- deriving a delay modulation signal of a sampled version x[n] of the band limited analogue signal by using the expression
- y[n]=x({n+D/2sin(won)}Ts)
- where n=integer
- D=maximum delay
- wo=oscillating frequency of the delay modulator;
- and
- Ts=1/sampling frequency.
A method of aliasing cancellation, comprising:
- determining the instantaneous sampling frequency 1/Tisf for an analogue input signal x(t);
- band limiting the analogue input signal x(t) to ½Tisf;
- and
- deriving a delay modulation signal of a sampled version x[n] of the band limited analogue signal by using the expression
- y[n]=x(n+D/2sin(won)}Ts)
- interpolating the delay modulation signal by using
- y
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- where n=integer
- D=maximum delay
- wo=oscillating frequency of the delay modulator;
- and
- Ts=1/sampling frequency.
A method of aliasing cancellation, comprising:
- determining the instantaneous sampling frequency 1/Tisf for an analogue input signal x(t);
- band limiting the analogue input signal x(t) to ½Tisf;
- and
- deriving a delay modulation signal of a sampled version x[n] of the band limited analogue signal by using the expression
- y[n]=x({n+D/2sin(won)}Ts),
- wherein the instantaneous sampling frequency, for a generalised modulating function g(n) is derived from
- Tisf=[1+g(n)−g(n−1)]Ts
- where n=integer
- D=maximum delay
- wo=oscillating frequency of the delay modulator;
- and
- Ts=1/sampling frequency.
A method of aliasing cancellation, comprising:
- determining the instantaneous sampling frequency 1/Tisf for an analogue input signal x(t);
- band limiting the analogue input signal x(t) ½Tisf;
- and
- deriving a delay modulation signal of a sampled version x[n] of the band limited analogue signal by using the expression
- y[n]=x({n+D/2sin(won)}Ts)
- interpolating the delay modulation signal by using
- y
-
- [
- n
- ]
- =
-
- ∑
- k
- m
- -
- N
- N
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-
- x
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- wherein the instantaneous sampling frequency, for a generalised modulating function g(n) is derived from
- Tisf=[1+g(n)−g(n−1)Ts
- where n=integer
- D=maximum delay
- wo=oscillating frequency of the delay modulator;
- and
- Ts=1/sampling frequency.
An audio signal device for generating audio effects, comprising:
- a digital signal processor configured to perform the following functions:
- determining the instantaneous sampling frequency 1/Tisf for an analogue input signal x(t);
- band limiting the analogue input signal x(t) to ½ Tisf;
- and
- deriving a delay modulation signal of a sampled version x[n] of the band limited analogue signal by using the expression
- y[n]=x({n+D/2sin(won)}Ts)
- wherein n=integer
- D=maximum delay
- wo=oscillating frequency of the delay modulator;
- and
- Ts=1/sampling frequency.
An audio signal device for generating audio effects, comprising:
- a digital signal processor configured to effect aliasing cancellation in an audio effects algorithm using the following steps:
- determining the instantaneous sampling frequency 1/Tisf for an analogue input signal x(t);
- band limiting the analogue input signal x(t) to ½ Tisf;
- and
- deriving a delay modulation signal of a sampled version x[n] of the band limited analogue signal by using the expression
- y[n]=x({n+D/2sin(won)}Ts)
- interpolating the delay modulation signal by using
- y
-
- [
- n
- ]
- =
-
- ∑
- k
- m
- -
- N
- N
-
-
- x
-
- [
- n
- ′
- -
- k
- ]
-
- [
- sin
-
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- π
-
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- Δ
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- k
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- T
- s
- /
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- n
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- N
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-
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- n
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- 2
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- sin
-
- (
- w
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- n
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- )
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-
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- =
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- [
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- sin
-
- (
- w
- o
-
- n
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- ]
-
- T
- s
- -
- n
- ′
-
- T
- s
- wherein the instantaneous sampling frequency for a generalised modulating function g(n) is derived from
- Tisf=[1+g(n)−g(n−1)]Ts
- where n=integer
- D=maximum delay
- wo=oscillating frequency of the delay modulator;
- and
- Ts=1/sampling frequency.
Dependencies are inferred from the claim text.