System and Method for Processing an Audio Signal
Systems and methods for audio signal processing are provided. In exemplary embodiments, a filter cascade of complex-valued filters are used to decompose an input audio signal into a plurality of frequency components or sub-band signals. These sub-band signals may be processed for phase alignment, amplitude compensation, and time delay prior to summation of real portions of the sub-band signals to generate a reconstructed audio signal.
1 . A method for processing audio signals, comprising:
filtering an input signal with a complex-valued filter of a filter cascade to produce a first filtered signal;
subtracting the first filtered signal from the input signal to derive a first sub-band signal;
filtering the first filtered signal with a next complex-valued filter of the filter cascade to produce a next filtered signal; and
subtracting the next filtered signal from the first filtered signal to derive a next sub-band signal.
2 . The method of claim 1 wherein the complex-valued filter and the next complex-valued filter are single pole, complex-valued filters.
3 . The method of claim 1 further comprising performing phase alignment on one or more of the sub-band signals.
4 . The method of claim 3 further comprising disposing of an imaginary portion of the one or more phase aligned sub-band signals.
5 . The method of claim 1 further comprising performing amplitude compensation on one or more of the sub-band signals.
6 . The method of claim 1 further comprising performing a time delay on one or more of the sub-band signals for cross-sub-band alignment.
7 . The method of claim 6 further comprising summing the delayed one or more sub-band signals to generate a reconstructed audio signal.
8 . The method of claim 1 further comprising pre-processing the input signal prior to filtering the input signal with the complex-valued filter of the filter cascade.
9 . The method of claim 1 further comprising modifying one or more of the sub-band signals based on an analysis path from the filter cascade.
10 . The method of claim 1 wherein the sub-band signals are frequency components of the input signal.
11 . A system for processing an audio signal, comprising:
an audio processing engine comprising a filter cascade of complex-valued filters configured to derive a plurality of sub-band signals from an input signal, the set of complex-valued filters arranged in the filter cascade whereby an output of each complex-valued filter is passed to a next complex-valued filter in the filter cascade.
12 . The system of claim 11 wherein the complex-valued filters are single pole, complex-valued filters.
13 . The system of claim 11 wherein the audio processing engine further comprises a reconstruction module configured to perform phase alignment on one or more of the sub-band signals.
14 . The system of claim 11 wherein the audio processing engine further comprises a reconstruction module configured to perform amplitude compensation on one or more of the sub-band signals.
15 . The system of claim 11 wherein the audio processing engine further comprises a reconstruction module configured to perform a time delay on one or more of the sub-band signals.
16 . The system of claim 11 wherein the audio processing engine further comprises a modification module configured to modify one or more of the sub-band signals based on an analysis path from the filter cascade.
17 . The system of claim 11 further comprising a conditioning module configured to pre-process the input signal prior to filtering the input signal with the filter cascade.
18 . A machine-readable medium having embodied thereon a program, the program being executable by a machine to perform a method for processing an audio signal, the method comprising:
filtering an input signal with a complex-valued filter of a filter cascade to produce a first filtered signal;
subtracting the first filtered signal from the input signal to derive a first sub-band signal;
filtering the first filtered signal with a next complex-valued filter of the filter cascade to produce a next filtered signal; and
subtracting the next filtered signal from the first filtered signal to derive a next sub-band signal.
19 . The machine-readable medium of claim 18 wherein the complex-valued filter and the next complex-valued filter are single pole, complex-valued filters.
20 . The machine-readable medium of claim 18 wherein the method further comprises performing phase alignment on one or more of the sub-band signals.
21 . The machine-readable medium of claim 18 wherein the method further comprises performing amplitude compensation on one or more of the sub-band signals.
22 . The machine-readable medium of claim 18 wherein the method further comprises performing a time delay on one or more the sub-band signals.
23 . The machine-readable medium of claim 18 wherein the method further comprises pre-processing the input signal prior to filtering the input signal with the filter cascade.