Overlapping Filter Banks With Approximate Blocks for Low Delay
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Solution Overview
Problem
Existing digital signal processing systems face challenges with significant total delay due to the non-zero delay introduced by transform filters, particularly in unidirectional filter arrangements, which can be inconvenient in various applications.
Innovation Solution
The proposed audio processing system employs a method and device for efficient real-to-imaginary operation in the frequency-domain representation of audio signals, utilizing a synthesis stage and an analysis stage connected by a processor to form a partially complex frequency-domain representation. This involves using FIR filters with output buffers to compute approximate values of time-domain representations, allowing the analysis stage to initiate computations earlier and reduce pass-through time by using approximate values from the synthesis stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transform filters are used for real-to-imaginary conversion in frequency-domain representation, then accurate signal processing is achieved, but total delay becomes considerable
Solution Approach 1:
The synthesis stage computes approximate values of time blocks ahead of their actual output time. Specifically, the output of the synthesis stage at time n is made available to the analysis stage at time n-d1, where d1≥1 represents the number of time blocks ahead. This preliminary computation allows the analysis stage to start processing earlier without waiting for complete synthesis output, thereby reducing total delay while maintaining processing accuracy through subsequent refinement with exact values.
2Measurement precision
If exact values from synthesis stage are waited for before analysis stage computation, then processing accuracy is maintained, but pass-through time increases
Solution Approach 1:
The analysis stage performs partial computation using approximate values from the synthesis stage before the complete exact values are available. Instead of waiting for all synthesis output to be finalized, the analysis stage processes available approximate data immediately and refines the results later when exact values become available. This partial action approach reduces pass-through time while maintaining sufficient processing accuracy for the application.
Data Source
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AI summary
An arrangement of overlapping filter banks comprises a synthesis stage and an analysis stage. The synthesis stage receives a first signal segmented into time blocks and outputs, based thereon, an intermediate signal to be received by the analysis stage forming the basis for the computation of a second signal segmented into time frames. In an embodiment, the synthesis stage is operable to release an approximate value of the intermediate signal in a time block located L - 1 time blocks ahead of its output block, which approximate value is computed on the basis of any available time blocks of the first signal, so that the approximate value contributes, in the analysis stage, to the second signal. The delay is typically reduced by L - 1 blocks. Applications include audio signal processing in general and real -to-complex conversion in particular.