Asymmetric Audio Windowing for Low-Delay Subband Reconstruction
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Solution Overview
Problem
Modern 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 in these parameters.
Innovation Solution
The use of asymmetric window functions in analysis and synthesis filterbanks, where the first portion of window coefficients has higher energy values than the second portion, allows for reduced delay or improved quality without increasing delay, by strategically applying these coefficients to earlier or later time-domain samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If symmetric window functions are used in conventional audio encoding, then reconstruction quality is maintained, but delay increases
Solution Approach 1:
The patent applies asymmetry by using asymmetric window functions where the first portion has higher energy coefficients than the second portion. This asymmetric distribution allows the encoding process to prioritize earlier time-domain samples with higher energy coefficients, thereby reducing the overall delay while maintaining reconstruction quality through the strategic energy distribution across the window function portions.
Solution Approach 2:
The patent implements local quality by differentiating the energy distribution within different portions of the window function. The first portion is assigned higher energy coefficients to process earlier samples with greater weight, while the second portion has lower energy coefficients. This local differentiation optimizes the balance between delay reduction and quality maintenance by applying different processing priorities to different temporal regions.
2Manufacturing precision
If higher bit rates are used, then audio quality improves, but transmission bandwidth increases
Solution Approach 1:
The patent changes the parameter distribution within the window function by assigning different energy values to different portions. This parameter change allows more efficient representation of the audio signal in the transformed domain, improving quality while reducing the overall bit rate requirement by optimizing how energy is distributed across the processing window rather than uniformly across all coefficients.
3Measurement precision
If complex-valued audio subband values are generated, then spectral representation accuracy improves, but computational complexity increases
Solution Approach 1:
The patent segments the window function into distinct portions with different energy characteristics. This segmentation allows the computational process to focus more resources on processing the high-energy first portion that contributes most to spectral accuracy, while using fewer resources for the lower-energy second portion, thereby optimizing the trade-off between spectral representation accuracy and computational complexity.
Data Source
AI summary
An embodiment of an apparatus for generating audio subband values in audio subband channels has an analysis windower for windowing a frame of time-domain audio input samples being in a time sequence extending from an early sample to a later sample using an analysis window function having a sequence of window coefficients to obtain windowed samples. The analysis window function has a first group of window coefficients and a second group of window coefficients. The first group of window coefficients is used for windowing later time-domain samples and the second group of window coefficients is used for windowing an earlier time-domain samples. The apparatus further has a calculator for calculating the audio subband values using the windowed samples.