Audio Signal Reconstruction via Group Delay Alignment
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Solution Overview
Problem
Current audio signal reconstruction methods using filter banks introduce latency due to cascaded sub-components with successive lags, which is unacceptable in real-time applications like telecommunications, where standards require low latency.
Innovation Solution
The method involves grouping decomposed audio frequency sub-band signals with successively shifted group delays and applying a delay function, based on a psychoacoustic model and delay table, to realign and combine them, reducing latency while preserving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If filter banks are used to decompose audio signals into sub-components, then signal processing capability is improved, but latency increases due to successive lags in cascaded sub-components
Solution Approach 1:
The patent segments the frequency spectrum into multiple bands and processes each band independently through separate filter paths. By dividing the signal decomposition into discrete frequency segments that can be processed in parallel, the system reduces the cumulative latency that would otherwise result from cascaded filter processing while maintaining comprehensive signal analysis capability.
Solution Approach 2:
The patent introduces a time-domain dimension to the frequency-domain processing by applying delays tailored to each frequency band's specific lag characteristics. This dimensional approach allows the system to compensate for filter bank latency by introducing opposite-phase delays, thereby realigning signal components without sacrificing the frequency-selective processing benefits.
2Manufacturing precision
If delays are applied to realign sub-components for reconstruction, then signal alignment is improved, but latency between modified signal and original signal increases
Solution Approach 1:
The patent applies different delay values to different frequency bands based on their specific group delay characteristics. Instead of using a uniform delay for all components, the system tailors the delay compensation locally to each frequency band's actual lag, achieving precise realignment while minimizing overall latency by applying only the necessary compensation.
Solution Approach 2:
The patent dynamically adjusts delay parameters for each frequency band based on measured or pre-calculated group delay characteristics. By changing the delay parameter to match the specific lag of each band, the system achieves optimal signal alignment. The delay function is defined using a delay table that maps frequency bands to their corresponding compensation delays.
3Loss of time
If latency is reduced for real-time applications, then real-time performance is improved, but signal processing performance deteriorates
Solution Approach 1:
The patent performs delay compensation in advance by pre-calculating the required delay values for each frequency band based on their inherent lag characteristics. This preliminary action allows the system to compensate for filter bank delays before signal processing occurs, enabling real-time operation without sacrificing processing accuracy. The delay function is prepared in advance and applied consistently throughout signal processing.
Data Source
AI summary
Systems and methods for reconstructing decomposed audio signals are presented. In exemplary embodiments, a decomposed audio signal is received. The decomposed audio signal may include a plurality of frequency sub-band signals having successively shifted group delays as a function of frequency from a filter bank. The plurality of frequency sub-band signals may then be grouped into two or more groups. A delay function may be applied to at least one of the two or more groups. Subsequently, the groups may be combined to reconstruct the audio signal, which may be outputted accordingly.