Synthesis Windowing for Low-Delay Audio Filterbank Reconstruction
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Solution Overview
Problem
Digital audio processing systems face challenges in balancing bit rate, computational complexity, memory requirements, quality, and delay, particularly in real-time applications, where compromises often need to be made among these parameters to achieve optimal performance.
Innovation Solution
The implementation of complex modulated low-delay filterbanks with asymmetric window functions that distribute energy across window coefficients, allowing for reduced delay or improved quality without increasing computational complexity, by using a synthesis window function with a sequence of coefficients divided into two portions where the first portion has higher energy values and fewer coefficients than the second portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional symmetric window functions are used in filter banks, then reconstruction quality can be maintained, but delay increases
Solution Approach 1:
The patent applies asymmetry by using asymmetric window functions instead of conventional symmetric window functions in the filter bank. The asymmetric window function has different characteristics in the beginning and end portions, allowing optimization of delay properties while maintaining reconstruction quality through controlled energy distribution across the asymmetric coefficients.
2Manufacturing precision
If filter bank length is increased to improve reconstruction quality, then quality improves, but delay increases
Solution Approach 1:
The patent applies local quality by distributing energy non-uniformly across the window coefficients, with specific portions having higher energy values than others. This localized energy distribution allows different parts of the filter bank to contribute differently to reconstruction quality, enabling quality improvement without proportionally increasing delay.
3Manufacturing precision
If bit rate is increased to improve audio quality, then quality improves, but transmission bandwidth increases
Solution Approach 1:
The patent applies parameter changes by modifying the window function characteristics (asymmetry and energy distribution) to improve audio reconstruction quality. This approach improves quality through signal processing optimization rather than increasing bit rate, thereby avoiding the need for higher transmission bandwidth.
4Manufacturing precision
If computational complexity is increased to improve reconstruction quality, then quality improves, but processing efficiency decreases
Solution Approach 1:
The patent applies segmentation by dividing the window function into portions with different energy characteristics. This segmented approach with distinct high-energy and low-energy portions enables efficient computational processing while maintaining reconstruction quality, as the structure allows for optimized calculation without requiring excessive computational resources.
Data Source
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AI summary
An apparatus for generating time-domain audio samples or synthesis filterbank (300) comprises a calculator (310) for calculating a frame (330) comprising a sequence of intermediate time-domain samples from audio subband values of block (320). The calculator (310) is coupled to a synthesis windower (360) to which the frame (330) of intermediate time-domain samples is provided. The synthesis windower (360) is adapted to windowing the sequence of intermediate time-domain samples using a synthesis window function (370) and provides a frame (380) of windowed intermediate time-domain samples. The synthesis windower (360) is coupled to an overlap-adder output stage (400) that obtains a block (410) of time-domain samples. The block (410) of the time-domain (output) samples can then for instance be provided to further components for further processing, storing or transforming into audible audio signals.