Methods and apparatus for echo cancellation using an adaptive lattice based non-linear processor
A non-linear processor for managing a speech signal is disclosed. The non-linear processor includes an adaptive lattice filter that generates a prediction error from a residual echo of the speech signal, a signum non-linearity unit that generates an excitation component from the prediction error, an excitation signal mixer that generates an excitation signal from the excitation component and a noise component, an inverse lattice filter that generates a modified residual echo from the excitation signal, and a gain adjuster that adjusts a power of the modified residual echo.
1 . A method for managing a speech signal, comprising:
generating an excitation component for the speech signal;
spectrally shaping a noise component for the speech signal; and
mixing the excitation component with the noise component.
2 . The method of claim 1 , further comprising generating a prediction error signal from the speech signal.
3 . The method of claim 2 , wherein generating the prediction error signal comprises passing the speech signal through an adaptive lattice filter.
4 . The method of claim 3 , wherein passing the speech signal through the adaptive lattice filter comprises employing a gradient adaptive lattice algorithm.
5 . The method of claim 1 , further comprising adjusting a power of the speech signal.
6 . The method of claim 5 , wherein the power of the speech signal is adjusted according to a background noise power measurement of the speech signal.
7 . The method of claim 1 , wherein spectrally shaping the noise component comprises shaping the noise component so that a spectral envelope of the noise component tracks a background noise signal.
8 . The method of claim 1 , wherein the noise component is a white noise source.
9 . The method of claim 1 , wherein mixing the excitation component with the noise component further comprises mixing the excitation component with the noise component at proportions based on an echo return loss enhancement measurement.
10 . The method of claim 1 , wherein mixing the excitation component with the noise component further comprises mixing the excitation component with the noise component at proportions based on double-talk detection.
11 . The method of claim 1 , wherein mixing the excitation component with the noise component further comprises mixing the excitation component with the noise component at proportions based on voice-activity detection.
12 . An apparatus for managing a speech signal, comprising:
a double-talk detector that detects double-talk on the speech signal;
a non-linear processor that center-clips a residual echo from the speech signal in response to a presence of double-talk on the speech signal;
an inverse filter that filters a noise source whose spectral envelope tracks that of a background noise signal to make filtered noise; and
a noise injector that injects the filtered noise onto the speech signal.
13 . The method of claim 12 , wherein the inverse filter is an inverse lattice filter.
14 . The apparatus of claim 12 , further comprising a gain adjuster that adjusts a power of the speech signal.
15 . The apparatus of claim 14 , wherein the gain adjuster adjusts the power of the speech signal according to a background noise power measurement of the speech signal.
16 . The apparatus of claim 12 , wherein the noise source is stationary noise source.
17 . The apparatus of claim 12 , wherein the noise source is white noise.
18 . A computer-readable medium having stored thereon sequences of instructions, the sequences of instructions including instructions which, when executed by a processor, causes the processor to perform:
detecting presence of double-talk on a speech signal;
center-clipping a residual echo from the speech signal;
filtering a noise source whose spectral envelope tracks that of a background noise signal to make filtered noise; and
injecting the filtered noise onto the speech signal.
19 . The computer-readable medium of claim 18 , further comprising adjusting a power of the speech signal.
20 . The computer-readable medium of claim 19 , wherein the power is adjusted according to a background noise power measurement of the speech signal.