High Frequency Decoding via Excitation Class Transformation
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Solution Overview
Problem
The existing audio encoding and decoding schemes, such as G.719, face challenges in reconstructing high frequency signals for bandwidth extension, leading to potential noise generation and reduced audio quality due to insufficient bits in specific frequency bands.
Innovation Solution
A method and apparatus for high frequency decoding that involves decoding an excitation class, modifying the low frequency spectrum based on the excitation class, and generating a high frequency excitation spectrum, thereby improving the quality of the reconstructed audio signal without excessive complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a noise filling method is applied to generate noise for specific bands when bits are insufficient, then the audio signal can be reconstructed in bands with insufficient bits, but noise quality and audio fidelity deteriorate
Solution Approach 1:
The patent introduces an excitation class as an intermediary parameter that mediates between the decoded low frequency spectrum and the generated high frequency excitation spectrum. This excitation class, derived from the low frequency spectrum characteristics, serves as a bridge to generate more accurate high frequency components without direct noise filling, thereby improving audio fidelity while maintaining reconstruction reliability.
2Quantity of substance
If a bandwidth extension scheme is applied to generate high frequency signals by folding low frequency signals, then high frequency signals can be generated with limited bit allocation, but audio quality and spectral accuracy deteriorate
Solution Approach 1:
The patent changes the parameter representation by introducing an excitation class parameter that captures the essential characteristics of the low frequency spectrum. Instead of directly folding the low frequency spectrum to generate high frequency signals, the system transforms the low frequency spectrum into an excitation class parameter, which is then used to generate a high frequency excitation spectrum. This parameter transformation maintains spectral accuracy while achieving efficient bit allocation.
3Ease of manufacture
If existing G.719 decoding schemes are used for bandwidth extension, then the decoding process can be implemented with standard algorithms, but audio quality and high frequency reconstruction accuracy deteriorate
Solution Approach 1:
The patent segments the decoding process into distinct stages: decoding the excitation class from the low frequency spectrum, modifying the low frequency spectrum based on the excitation class, and generating the high frequency excitation spectrum. This segmentation allows the system to maintain implementation simplicity by using standard decoding algorithms for each stage while improving overall audio quality through the specialized excitation class processing.
Data Source
AI summary
Disclosed are a method and an apparatus for high frequency decoding for bandwidth extension. The method for high frequency decoding for bandwidth extension comprises the steps of: decoding an excitation class; transforming a decoded low frequency spectrum on the basis of the excitation class; and generating a high frequency excitation spectrum on the basis of the transformed low frequency spectrum. The method and apparatus for high frequency decoding for bandwidth extension according to an embodiment can transform a restored low frequency spectrum and generate a high frequency excitation spectrum, thereby improving the restored sound quality without an excessive increase in complexity.