High-Band Encoding Sub-Band Bit Allocation for Audio Fidelity
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Solution Overview
Problem
The existing audio encoding and decoding methods, such as G.719, face challenges in maintaining sound quality during bandwidth extension, particularly in high frequency bands due to insufficient bit allocation, leading to noise generation and sub-optimal representation of spectral information.
Innovation Solution
A method and apparatus for high band coding and decoding that generate bit allocation information for each sub-band based on a full band envelope, determining necessary updates and generating refinement data to improve the representation of high frequency spectral information, thereby enhancing sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bandwidth extension is applied to generate high frequency signal by folding low frequency signal, then the high band can be reconstructed, but the sound quality deteriorates due to insufficient bit allocation and noise generation
Solution Approach 1:
The high band is divided into multiple sub-bands, and bit allocation information is generated for each sub-band based on the full band envelope. This segmentation allows selective refinement of specific sub-bands that require it, improving overall sound quality while efficiently using available bits.
Solution Approach 2:
The patent applies local quality improvement by determining which specific sub-bands need envelope updates based on bit allocation information, and generating refinement data only for those determined sub-bands. This ensures that spectral information is accurately represented where needed without wasting bits on already adequate sub-bands.
2Productivity
If bits are allocated based on normalized spectrum through energy-based bit allocation, then bitstream can be generated, but important spectral information in high bands is lost due to insufficient bits
Solution Approach 1:
The patent uses the full band envelope as feedback to guide bit allocation in the high band. By comparing the envelope characteristics across different sub-bands, the system determines which sub-bands require refinement and allocates bits accordingly, ensuring important spectral information is preserved.
Solution Approach 2:
The full band envelope is calculated and analyzed before performing high band coding. This preliminary action allows the system to pre-determine which sub-bands will need refinement, enabling more effective bit allocation and preventing information loss in critical frequency regions.
3Reliability
If noise filling method is applied to generate noise codebook based on dequantized low frequency spectrum, then noise can be generated for specific bands, but the fidelity deteriorates due to noise generation
Solution Approach 1:
The patent changes the approach from generating noise to refining the envelope parameters of specific sub-bands. By generating refinement data that updates envelope parameters based on the full band envelope, the system maintains signal fidelity while completing the high band reconstruction without introducing noise artifacts.
Data Source
AI summary
A high-band encoding/decoding method and device for bandwidth extension are provided. A high-band encoding method comprising the steps of: generating sub band-specific bit allocation information on the basis of a low-band envelope; determining, on the basis of the sub band-specific bit allocation information, the sub band requiring an envelope update in a high band; and generating, for the determined sub band, refinement data relating to the envelope update. A high-band decoding method comprising the steps of: generating sub band-specific bit allocation information on the basis of a low-band envelope; determining, on the basis of the sub band-specific bit allocation information, the sub band requiring an envelope update in a high band; and decoding, for the determined sub band, refinement data relating to the envelope update, thereby updating the envelope.