Method and apparatus for loudspeaker equalization
A method, apparatus and system are disclosed herein for loudspeaker equalization. In one embodiment, the system comprises an input for receiving samples of an input signal, a pre-compensator to produce a pre-compensated output in response to the samples of an input signal, parameters of a loudspeaker model, and previously predistorted samples of the input signal, and a loudspeaker, corresponding to the loudspeaker model, to produce an audio output in response to the pre-compensated output.
1 . An audio system comprising:
an input for receiving samples of an input signal;
a pre-compensator to produce a pre-compensated output in response to the samples of an input signal, parameters of a loudspeaker model, and previously predistorted samples of the input signal;
a loudspeaker, corresponding to the loudspeaker model, to produce an audio output in response to the pre-compensated output.
2 . The audio system defined in claim 1 wherein the pre-compensator uses non-linear compensation to modify the samples of the input signal in a manner opposite to distortion that is to occur from the loudspeaker.
3 . The audio system defined in claim 1 wherein the pre-compensator comprises an inverse module to compute the inverse of the loudspeaker model.
4 . The audio system defined in claim 3 wherein the inverse module computes the inverse of the loudspeaker model using the samples of an input signal, parameters of a loudspeaker model, and previously distorted samples of the input signal.
5 . The audio system defined in claim 3 wherein the inverse module comprises:
a polynomial coefficient calculator to compute coefficients of a polynomial; and
a polynomial root solver to generate a root of the polynomial in response to the coefficients.
6 . The audio system defined in claim 5 wherein the polynomial coefficient calculator computes the coefficients using the samples of an input signal, parameters of the loudspeaker model, and previously predistorted samples of the input signal.
7 . The audio system defined in claim 5 wherein the inverse is given by a second order polynomial.
8 . The audio system defined in claim 5 wherein the root is a real root.
9 . The audio system defined in claim 5 wherein the polynomial root solver comprises a quadratic equation solver.
10 . The audio system defined in claim 5 wherein the polynomial root solver computes roots of the polynomial and selects a real root from the roots.
11 . The audio system defined in claim 5 further comprising a digital multiplier to scale output of the inverse module.
12 . The audio system defined in claim 11 further comprising a gain unit to scale output of the inverse module to drive the loudspeaker.
13 . The audio system defined in claim 3 further comprising a memory to store the parameters of the loudspeaker model.
14 . The audio system defined in claim 3 further comprising a buffer memory to store the states of the inverse module.
15 . The audio system defined in claim 1 further comprising a digital gain amplifier to control signal levels of samples being input into the pre-compensator.
16 . The audio system defined in claim 1 further comprising an analog gain amplifier responsive to the pre-compensated output to control signal levels of signals corresponding to the pre-compensated output that are to drive the loudspeaker.
17 . The audio system defined in claim 1 further comprising a digital multiplier to scale the output of the exact inverse module.
18 . A method comprising:
receiving samples of an input signal;
generating a pre-compensated output in response to the samples of an input signal, parameters of a loudspeaker model, and previously predistorted samples of the input signal; and
producing an audio output with a loudspeaker, corresponding to the loudspeaker model, in response to the pre-compensated output.
19 . The method defined in claim 18 further comprising using non-linear compensation to modify the samples of the input signal in a manner opposite to distortion that is to occur from the loudspeaker.
20 . The method defined in claim 18 wherein generating a pre-compensated output comprises computing the inverse of the loudspeaker model using the samples of an input signal, parameters of the loudspeaker model, and previously distorted samples of the input signal.
21 . The method defined in claim 18 wherein generating a pre-compensated output comprising:
calculating coefficients of a polynomial in response to an input signal, parameters of a model of the loudspeaker, and state information regarding past filter outputs; and
determining roots of a polynomial corresponding to the coefficients.
22 . The method defined in claim 21 wherein the inverse is given by a second order polynomial.
23 . The method defined in claim 21 further comprising selecting a real root from the roots.
24 . The method defined in claim 18 further comprising scaling the pre-compensated output.
25 . The method defined in claim 18 further comprising controlling signal levels of samples of the input signal prior to generating the pre-compensated output.
26 . The method defined in claim 18 further controlling signal levels of signals corresponding to the pre-compensated output that are to drive the loudspeaker, in response to the pre-compensated output.
27 . An article of manufacture having one or more recordable media storing instructions which, when executed by a system, cause the system to perform a method comprising:
receiving samples of an input signal;
generating a pre-compensated output in response to the samples of an input signal, parameters of a loudspeaker model, and previously predistorted samples of the input signal; and
producing an audio output with a loudspeaker, corresponding to the loudspeaker model, in response to the pre-compensated output.
28 . The article of manufacture defined in claim 27 wherein generating a pre-compensated output comprising:
calculating coefficients of a polynomial in response to an input signal, parameters of a model of the loudspeaker, and state information regarding past filter outputs; and
determining roots of a polynomial corresponding to the coefficients.