Asymmetric Windows and Truncated Filters for Virtual Bass Latency
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Solution Overview
Problem
Legacy virtual bass systems introduce excessive latency due to symmetric time domain windows in transposer-based audio processing, which is problematic for applications like gaming and telecommunications, where delays above 100 milliseconds become noticeable.
Innovation Solution
Implementing a latency reduction system that uses asymmetric analysis and synthesis windows with a base transposition factor greater than two, combined with truncated Nyquist prototype filters and a time-lagged virtual bass signal to reduce latency in virtual bass processing systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If symmetric time domain windows are used in transposer-based virtual bass systems, then the system structure is simple and easy to implement, but the latency becomes excessive (3200 samples)
Solution Approach 1:
The patent applies asymmetry by using asymmetric analysis windows and asymmetric synthesis windows instead of symmetric windows. The asymmetric analysis window has different tap weights at corresponding positions from the center, and the asymmetric synthesis window similarly has different tap weights. This asymmetry allows the system to reduce latency significantly (from 3200 samples to around 640 samples) while maintaining virtual bass functionality.
2Loss of time
If a base transposition factor greater than two is used, then latency is reduced, but the harmonic structure becomes more complex
Solution Approach 1:
The patent changes the parameter of base transposition factor from the conventional value of 2 to a value greater than 2. This parameter change enables latency reduction while the complexity of harmonic structure is managed through the use of asymmetric windows and energy adjustment processes.
3Loss of time
If truncated Nyquist prototype filters are used, then latency is reduced, but filter design complexity increases
Solution Approach 1:
The patent applies the extraction principle by truncating the Nyquist prototype filters, which removes the tail portions of the filters that contribute most to latency. This truncation reduces latency while the filter design complexity is managed through systematic truncation methods that preserve essential filter characteristics.
4Loss of time
If virtual bass signal is time-lagged, then latency is reduced, but synchronization between bass and audio signal becomes challenging
Solution Approach 1:
The patent applies feedback by using energy adjustment processes that monitor and adjust the virtual bass signal to maintain proper synchronization with the original audio signal. The energy adjustment ensures that even with time-lagging, the virtual bass remains properly synchronized and integrated with the audio content.
Data Source
AI summary
A latency reduction system in a virtual bass processing system performs harmonic transposition on low frequency components of an audio signal to generate transposed data indicative of harmonics of the audio signal. The system uses a base transposition factor greater than two, and generates the harmonics in response to frequency-domain values determined by forward and inverse transform stages that use asymmetric analysis and synthesis windows. The system combines a virtual bass signal with the delayed wide band audio signal through analysis filter banks having filter coefficient truncated Nyquist filters. The virtual bass signal may lag the delayed wide band audio signal when combining with the audio signal to further reduce the latency caused by the harmonic transposition. The virtual bass input signal may be directly routed from a CQMF analysis filter bank of a preceding Hybrid filter bank stage, in order to avoid the delay associated with a Nyquist filter bank.