Audio Filterbank Reconstruction for Low Latency and Bass Resolution
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Solution Overview
Problem
Existing filter banks face high latency due to the need to match the latency of low-frequency filters with higher frequency filters, constraining the overall latency and impacting the impulse response.
Innovation Solution
A method to generate modified impulse responses by applying fade and time-reverse operations on ideal impulse responses to create low-latency filter banks, ensuring perfect reconstruction and reduced latency while preserving frequency resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the latency of low frequency filters is reduced, then the overall latency of the filter bank is reduced, but the impulse response accuracy deteriorates
Solution Approach 1:
The patent applies dynamics by making the filter bank latency adaptive rather than fixed. Different frequency bands are allowed to have different latencies based on their requirements, with the system dynamically managing the recombination process to accommodate varying latency needs across frequency bands while maintaining overall system functionality
Solution Approach 2:
The patent segments the filter bank into independent frequency bands with different latency characteristics. Instead of forcing a uniform latency across all bands, each band can be processed independently with its own optimal latency, and the results are recombined without requiring synchronization to a common high latency value
2Manufacturing precision
If the number of samples used for low frequency filters is increased to accurately represent the impulse response, then the impulse response accuracy is improved, but the latency increases
Solution Approach 1:
The patent applies local quality by allowing different parts of the frequency spectrum to have different latency and sample length characteristics. Low frequency filters can use longer impulse responses where needed, while high frequency filters use shorter responses, with each frequency band optimized locally rather than constrained by a global parameter
3Ease of operation
If high frequency filters are delayed to match the latency of low frequency filters, then the filter bank reconstruction is simplified, but the overall latency increases
Solution Approach 1:
The patent inverts the conventional approach by not delaying high frequency filters to match low frequency filters, but instead allowing low frequency filters to have longer latency and recombining results without requiring all bands to be synchronized to a common delay value. This reverses the traditional synchronization paradigm
Data Source
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AI summary
A filterbank, suitable for modifying audio signals with dynamic gains in each band, is constructed so that the perceived latency is small, while a larger group delay is applied at low frequencies to enable higher frequency resolution in the lower frequency bands. The higher group delay at low frequencies is achieved by inserting an all-pass filter into the reconstructed filter response.