Frequency Domain Audio Post-Processing for Perceptual Quality
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Solution Overview
Problem
Existing audio signal compression techniques, despite exploiting perceptual masking effects, still face challenges in maintaining high sound quality at low bit rates due to limitations in accurate perceptual modeling and decoder-side post-processing, particularly in frequency domain processing.
Innovation Solution
The implementation of adaptive frequency domain post-processing that applies modification gain factors to each frequency coefficient, based on Local Masking Magnitude, Local Masked Magnitude, and Average Magnitude, to enhance the perceptual quality of audio signals, using weighted sums and normalization to maintain energy balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If speech/audio compression is used to reduce bit rate, then bandwidth requirement is reduced, but sound quality deteriorates
Solution Approach 1:
The patent applies perceptual weighting filtering to distribute quantization error non-uniformly across the spectrum, concentrating error energy in spectral valley areas where it is less perceptible and preserving error energy in spectral peak areas where it is more perceptible. This local differentiation of error distribution maintains sound quality in critical frequency regions while allowing higher compression.
2Manufacturing precision
If perceptual weighting filter is applied in encoder, then perceptual quality is improved, but device complexity increases
Solution Approach 1:
The patent introduces a perceptual weighting filter as an intermediary component that shapes the quantization error spectrum. This filter acts as a mediator between the quantizer and the reconstruction process, transforming the error distribution to align with human perceptual characteristics without requiring complex alternative coding schemes.
3Manufacturing precision
If frequency domain post-processing is applied, then perceptual quality is enhanced, but computational complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the perceptual weighting filter uses the reconstructed signal itself to estimate quantization error and adjust filtering parameters. This self-service approach allows the system to adapt to the actual reconstruction quality without requiring external control signals or complex pre-computation, reducing overall system complexity while maintaining enhanced perceptual quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the perceptual quality of audio signals by selectively amplifying significant frequencies and reducing energy in less significant areas, effectively enhancing sound quality without requiring additional bits, especially in scenarios where time domain post-processing is insufficient or unavailable.
Implementation Method 1
Post-processing block 120 further improves the perceptual quality of the quantized signal by reducing the energy of low quality and perceptually less significant frequency components
Data Source
AI summary
In an embodiment, a method of frequency domain post-processing is disclosed. The method includes applying adaptive modification gain factor to each frequency coefficient, and determining gain factors based on Local Masking Magnitude and Local Masked Magnitude.