Complex Modulated Filterbank for Shorter Audio Subband Filtering
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Solution Overview
Problem
Current filtering methods for audio signals, particularly in HRTF-related applications, face inefficiencies due to long impulse responses and computational complexity, and existing Fourier transforms struggle with maintaining quality in signal manipulation.
Innovation Solution
A filter apparatus and method that utilize a complex modulated filter bank with shorter impulse responses, allowing for parallel processing of subband signals, transforming time domain inputs into the subband domain for efficient filtering with improved computational efficiency and quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If direct filtering in time domain is used, then filtering quality is maintained, but computational complexity increases due to long impulse responses
Solution Approach 1:
The patent divides the time domain signal into multiple frequency subbands using a complex modulated filter bank. Each subband is processed independently with shorter impulse response filters, thereby segmenting the original complex filtering task into simpler parallel subtasks that reduce overall computational complexity while maintaining filtering quality.
Solution Approach 2:
The patent transforms the filtering operation from the time domain to the frequency domain by using a complex modulated filter bank. This dimensional change allows filtering to be performed in the frequency domain where shorter impulse responses suffice, reducing computational complexity while preserving the filtering effect.
2Productivity
If Fourier transform methods are used, then frequency domain processing is enabled, but quality degradation occurs in signal manipulation
Solution Approach 1:
The patent applies different filtering characteristics to different frequency subbands rather than applying a uniform filter across the entire spectrum. Each subband receives tailored filtering appropriate to its frequency characteristics, preserving signal quality while enabling efficient frequency domain processing.
Solution Approach 2:
The patent uses complex modulation parameters to transform the filter bank characteristics, enabling efficient frequency domain processing while maintaining signal fidelity. By adjusting modulation parameters, the system achieves both computational efficiency and quality preservation.
3Productivity
If subband domain filtering is used, then computational efficiency improves, but filtering precision may be reduced
Solution Approach 1:
The patent performs preliminary frequency domain decomposition using a complex modulated filter bank before applying subband filtering. This preliminary action organizes the signal into frequency subbands, enabling subsequent efficient subband filtering while preserving the precision needed for high-quality audio processing.
Solution Approach 2:
The complex modulated filter bank acts as an intermediary between the time domain signal and the subband filtering operation. It transforms the signal into a form that enables efficient subband processing while maintaining the fidelity required for high-precision filtering.
Data Source
Figure 1a~1c
Figure 1d~1e
Figure 2~4
AI summary
A filter apparatus for filtering a time domain input signal to obtain a time domain output signal, which is a representation of the time domain input signal filtered using a filter characteristic having an non-uniform amplitude/frequency characteristic, comprises a complex analysis filter bank (101) for generating a plurality of complex subband signals from the time domain input signals, a plurality of intermediate filters, wherein at least one of the intermediate filters (102) of the plurality of the intermediate filters has a non-uniform amplitude/frequency characteristic, wherein the plurality of intermediate filters have a shorter impulse response compared to an impulse response of a filter having the filter characteristic, and wherein the non-uniform amplitude/frequency characteristics of the plurality of intermediate filters together represent the non-uniform filter characteristic, and a complex synthesis filter bank (103) for synthesizing the output of the intermediate filters to obtain the time domain output signal.