System and method for processing an audio signal
View Patent ↗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, the method comprising:
filtering an input signal with a complex-valued filter of a filter cascade to produce a first filtered signal, the complex-valued filter being configured to operate on complex-valued inputs;
filtering the first filtered signal with a second complex-valued filter of the filter cascade to produce a second filtered signal;
performing phase alignment on one or more of the filtered signals using a complex multiplier; and
summing the phase-aligned filtered signals to produce a reconstructed output signal.
2. The method of claim 1 wherein the complex-valued filters each contain a single pole.
3. The method of claim 1 further comprising:
subtracting the first filtered signal from the input signal to derive a first sub-band signal;
subtracting the second filtered signal from the first filtered signal to derive a second sub-band signal;
performing phase alignment on one or more of the sub-band signals using a complex multiplier; and
summing the phase-aligned sub-band signals to produce a reconstructed output signal.
4. The method of claim 3 further comprising disposing of an imaginary portion of one or more of the phase aligned sub-band signals.
5. The method of claim 3 further comprising performing amplitude compensation on one or more of the sub-band signals.
6. The method of claim 3 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 modifying one or more of the filtered signals.
8. The method of claim 3 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 3 further comprising modifying one or more of the sub-band signals.
10. The method of claim 3 wherein the sub-band signals are frequency components of the input signal.
11. A system for processing an audio signal, the system comprising:
a memory; and
a processor executing instructions stored in the memory for:
filtering an input signal with a complex-valued filter of a filter cascade to produce a first filtered signal, the complex-valued filter configured to operate on complex-valued inputs;
filtering the first filtered signal with a second complex-valued filter of the filter cascade to produce a second filtered signal;
performing phase alignment on one or more of the filtered signals using a complex multiplier; and
summing the phase-aligned filtered signals to produce a reconstructed output signal.
12. The system of claim 11 wherein the complex-valued filters each contain a single pole.
13. The system of claim 11 wherein the processor further executes instructions for performing:
subtracting the first filtered signal from the input signal to derive a first sub-band signal;
subtracting the second filtered signal from the first filtered signal to derive a second sub-band signal;
performing phase alignment on one or more of the sub-band signals using a complex multiplier; and
summing the phase-aligned sub-band signals to produce a reconstructed output signal.
14. The system of claim 13 wherein the processor further executes instructions for performing amplitude compensation on one or more of the sub-band signals.
15. The system of claim 13 wherein the processor further executes instructions for performing a time delay on one or more of the sub-band signals.
16. The system of claim 13 wherein the processor further executes instructions for modifying one or more of the sub-band signals based on an analysis path from the filter cascade.
17. The system of claim 11 the processor further executes instructions for pre-processing 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, the complex-valued filter being configured to operate on complex-valued inputs;
filtering the first filtered signal with a second complex-valued filter of the filter cascade to produce a second filtered signal;
performing phase alignment on one or more of the filtered signals using a complex multiplier; and
summing the phase-aligned filtered signals to produce a constructed output signal.
19. The machine-readable medium of claim 18 wherein the complex-valued filter and the second complex-valued filter each contain a single pole.
20. The machine-readable medium of claim 18 wherein the method further comprises:
subtracting the first filtered signal from the input signal to derive a first sub-band signal;
subtracting the next filtered signal from the first filtered signal to derive a second sub-band signal;
performing phase alignment on one or more of the sub-band signals using a complex multiplier; and
summing the phase-aligned sub-band signals to produce a reconstructed output signal.
21. The machine-readable medium of claim 20 wherein the method further comprises performing amplitude compensation on one or more of the sub-band signals.
22. The machine-readable medium of claim 20 wherein the method further comprises performing a time delay on one or more the sub-band signals.
23. The machine-readable medium of claim 20 wherein the method further comprises pre-processing the input signal prior to filtering the input signal with the filter cascade.