Adaptive Delay Diversity Filtering for Variable-Delay Echo Cancellation
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Solution Overview
Problem
Existing adaptive filters face challenges in efficiently canceling echo signals due to large variations in time delay between microphone and speaker signals, leading to increased computational load and error, especially when applied to multiple smartphone products with varying signal travel paths.
Innovation Solution
An adaptive delay diversity filter with multiple sub-filters is implemented, where sub-filters cover different time intervals and share calculated values to reduce computational load, and a pruning method is used to gradually decrease the number of active sub-filters, focusing on the acoustic path delay for efficient echo cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the filter length is increased to cope with large time delay variation, then the echo cancellation accuracy is improved, but the convergence time becomes longer and computational load increases
Solution Approach 1:
The patent divides the single long adaptive filter into multiple parallel sub-filters with different filter lengths. Each sub-filter processes a portion of the time delay range, allowing the system to achieve accurate echo cancellation across large delay variations without requiring any single sub-filter to be excessively long, thus reducing individual convergence times while maintaining overall accuracy.
Solution Approach 2:
The patent dynamically selects and switches between multiple sub-filters based on the current time delay conditions. By adapting which sub-filter is active according to the varying delay environment, the system optimizes convergence speed for each specific condition while maintaining accurate echo cancellation, rather than using a fixed long filter that would always converge slowly.
2Measurement precision
If the filter length is increased to cope with large time delay variation, then the echo cancellation accuracy is improved, but the computational load is increased
Solution Approach 1:
The patent segments the computational task across multiple parallel sub-filters, each handling a specific portion of the time delay range. This segmentation allows the system to achieve comprehensive echo cancellation accuracy without any single filter requiring excessive computational resources, distributing the load efficiently across multiple smaller processing units.
Solution Approach 2:
The patent employs multiple sub-filters with filter lengths that are individually shorter than the total required coverage, but collectively sufficient to handle the entire time delay variation range. This partial action approach in each sub-filter reduces individual computational requirements while the combination of multiple sub-filters achieves the necessary overall accuracy.
3Adaptability or versatility
If multiple sub-filters are used to cover different time intervals, then the adaptability to time delay variation is improved, but the device complexity is increased
Solution Approach 1:
The patent segments the time delay coverage into multiple intervals, each handled by a dedicated sub-filter. This segmentation improves adaptability to different delay conditions by having specialized filters for different ranges, while the modular structure makes the complexity manageable through systematic organization and potential hardware optimization.
Solution Approach 2:
The patent designs the multiple sub-filters to work together as a unified echo cancellation system, where each sub-filter is a standard adaptive filter structure that can be implemented using the same hardware or software framework. This multi-functionality approach allows the system to handle various time delay conditions while maintaining consistent implementation complexity across different sub-filters.
Data Source
AI summary
An adaptive filter and an echo cancellation apparatus and method using the same, utilize an adaptive delay diversity filter for coping with the situation in which variation in a time delay between a reference signal and a target signal of an adaptive filter is large. The adaptive delay diversity filter includes multiple sub-filters, each of which generates output through filtering by utilizing a signal, obtained by applying different time delay values to the reference signal, as a reference signal, and selects the best output value among generated output values of the multiple sub-filters, as an output value of the adaptive delay diversity filter. Further, the adaptive delay diversity filter includes a means for reducing a computational load.