Minimum-Phase Adaptive Filtering for Low-Delay Signal Processing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing signal processing techniques in audio devices introduce significant group delay, leading to issues like perceivable echo, reduced perceptual coherence, and decreased sound quality, which are critical in applications such as audio devices and telecommunication systems where strict compliance with group delay specifications is mandatory.
Innovation Solution
The method involves passing an input signal through an adaptive time domain filter, transforming it into a transform domain, analyzing the transformed signal to determine desired gains, synthesizing a minimum phase time domain filter characteristic, and updating the adaptive filter with this characteristic to minimize group delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If block processing with FFT analysis and IFFT overlap-add synthesis is used to improve signal processing capability, then frequency domain processing is achieved, but significant group delay is introduced
Solution Approach 1:
The patent segments the signal processing into separate analysis and processing paths. The input signal is divided into multiple sub-bands using a filter bank, allowing independent processing of each sub-band with reduced delay. This segmentation enables frequency domain processing capabilities while minimizing the overall group delay by processing smaller sub-bands rather than the entire signal block at once.
Solution Approach 2:
The patent introduces an intermediary all-pass filter between the analysis filter bank and the processing stage. This all-pass filter compensates for the phase distortion introduced by the analysis filters, allowing for more accurate signal reconstruction with reduced group delay. The intermediary element enables the system to achieve both frequency domain processing and low delay performance.
2Stability of the object's composition
If buffering is applied to prepare input signal for block operations, then processing stability is improved, but minimum group delay increases
Solution Approach 1:
The patent applies different buffering strategies to different parts of the signal processing system. Rather than uniformly buffering the entire signal path, it buffers only the necessary portions in the analysis path while maintaining minimal buffering in the synthesis path. This local differentiation of buffering quality allows processing stability where needed while minimizing delay in the critical output path.
3Manufacturing precision
If multi-band processing techniques are used to improve performance, then signal processing quality is enhanced, but resource requirements for echo or feedback cancellation increase
Solution Approach 1:
The patent employs dynamic adaptation of the filter bank parameters and processing characteristics based on the input signal conditions. The system can dynamically adjust the number of sub-bands, filter characteristics, and processing intensity to match the actual signal requirements. This dynamic behavior enables high processing quality when needed while reducing resource consumption during simpler signal conditions, thereby lowering overall device complexity requirements.
Data Source
AI summary
Adaptive processing of an input signal is achieved by offline analysis, with inline processing comprising an adaptive filter. The method comprises passing the input signal through an adaptive time domain filter to produce an output signal. The input signal and/or output signal is used as an offline analysis signal. The analysis signal is transformed into a transform domain (eg frequency domain) to produce a transformed analysis signal. The transformed analysis signal is analysed, for example by ADRO, to produce a plurality of desired gains each corresponding to a respective transform domain sub-band. A time domain filter characteristic is synthesised to at least approach the desired gains. The adaptive filter is updated with the synthesised filter characteristic. Minimum phase adaptive filter techniques are found to possess particular benefits in this scheme.