Partially Complex Modulated Filter Bank for Alias-Controlled Subbands
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Solution Overview
Problem
Existing audio signal processing technologies face challenges in achieving high-quality spectral envelope adjustment and frequency selectivity while minimizing aliasing, especially when using cosine-modulated filter banks, which can result in narrow sound impressions and incorrect sound source placement due to computational complexity constraints.
Innovation Solution
A partially complex modulated filter bank is introduced, which processes real-valued subband signals to generate complex-valued signals with minimal aliasing and increased computational efficiency, allowing for better quality manipulation by using a multiband filter and calculator to combine real-valued signals into complex-valued signals, and vice versa, maintaining the advantages of complex filter banks with reduced complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a complex exponential modulated filter bank is used for spectral envelope adjustment, then the quality of signal processing is improved, but the computational complexity increases
Solution Approach 1:
The filter bank is divided into two separate banks: a cosine modulated filter bank for high frequencies and a complex exponential modulated filter bank for low frequencies. This segmentation allows each bank to operate in its optimal frequency range, maintaining high signal processing quality while reducing overall computational complexity by applying complex processing only where necessary.
Solution Approach 2:
Different filter bank types are applied to different frequency regions based on their specific requirements. The complex exponential modulated filter bank is used locally in the low frequency range where high quality is critical, while the computationally simpler cosine modulated filter bank is used in the high frequency range, optimizing the trade-off between quality and complexity locally.
2Device complexity
If a cosine modulated filter bank is used to reduce computational complexity, then the computational complexity is reduced, but aliasing increases causing narrow sound impressions and incorrect sound source placement
Solution Approach 1:
The frequency spectrum is segmented into low and high frequency bands, each handled by an appropriate filter bank type. The complex exponential modulated filter bank processes low frequencies where aliasing control is critical for accurate sound source placement, while the cosine modulated filter bank handles high frequencies where computational efficiency is more important.
Solution Approach 2:
A frequency-dependent switching mechanism acts as an intermediary, directing different frequency components to appropriate filter banks. This mediator ensures that signals are processed by the optimal filter type for their frequency range, preventing aliasing in critical low frequency regions while maintaining computational efficiency in high frequency regions.
Data Source
AI summary
An apparatus for processing a plurality of real-valued subband signals using a first real-valued subband signal and a second real-valued subband signal to provide at least a complex-valued subband signal comprises a multiband filter for providing an intermediate real-valued subband signal and a calculator for providing the complex-valued subband signal by combining a real-valued subband signal from the plurality of real-valued subband signals and the intermediate subband signal.