Asymmetric Windowed Audio Subband Generation for Low-Delay Coding
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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 among these parameters to achieve optimal performance.
Innovation Solution
The implementation of complex-valued low-delay filterbanks with asymmetric window functions that distribute energy differently across window coefficients, allowing for reduced delay and improved quality by extending the filter impulse response without introducing additional delay, and enabling perfect reconstruction in audio coding systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If longer filter impulse response is used to improve reconstruction quality, then manufacturing precision is improved, but loss of time increases
Solution Approach 1:
The patent applies asymmetry by using asymmetric window functions where the first half and second half have different energy distributions. The first half concentrates more energy in fewer coefficients, enabling faster convergence and reduced delay, while the second half provides the necessary extension for high reconstruction quality. This asymmetric energy distribution resolves the contradiction between speed and precision.
Solution Approach 2:
The patent implements local quality by differentiating the energy distribution characteristics between the first half and second half of the window function. The first half is optimized for rapid processing with concentrated energy, while the second half is optimized for reconstruction accuracy with extended energy distribution. This localized optimization allows simultaneous achievement of low delay and high quality.
2Manufacturing precision
If higher bit rate is used to improve quality, then manufacturing precision is improved, but loss of substance increases
Solution Approach 1:
The patent changes the parameter of window function energy distribution from symmetric to asymmetric, with the first half having higher energy concentration than the second half. This parameter change enables the system to achieve high reconstruction quality while maintaining efficient bit rate utilization, as the asymmetric structure allows for more effective use of available data samples.
3Manufacturing precision
If complex-valued filterbanks are used to improve quality, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the window function into two distinct halves with different energy distribution characteristics. The first half is designed for rapid processing with concentrated energy, reducing computational requirements for initial processing stages. The second half handles reconstruction with extended energy distribution. This segmentation allows complex-valued filterbanks to achieve high quality while managing computational complexity through divided processing tasks.
Data Source
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AI summary
An embodiment of an apparatus (100) for generating audio subband values in audio subband channels comprises an analysis windower (110) for windowing a frame (120) 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 (190) comprising a sequence of window coefficients to obtain windowed samples. The analysis window function (190) comprises a first group (200) of window coefficients and a second group (210) of window coefficients. The first group (200) of window coefficients is used for windowing later time-domain samples and the second group (210) of window coefficients is used for windowing an earlier time-domain samples. The apparatus (100) further comprises a calculator (170) for calculating the audio subband values using the windowed samples.