Harmonic Transposition Filter Banks for Multi-Order HFR
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Solution Overview
Problem
Existing audio coding systems face high computational complexity when implementing multiple orders of harmonic transposition for high frequency reconstruction, requiring multiple filter banks and increasing complexity with each additional order, which affects audio quality and efficiency.
Innovation Solution
The use of advanced nonlinear processing allows for the generation of high frequency components using a single common analysis and synthesis filter bank, reducing computational complexity by modifying phase and amplitude across subbands to achieve multiple transposition orders without the need for multiple filter banks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple filter banks are used for each transposition order, then the high frequency reconstruction quality is improved, but the computational complexity increases significantly
Solution Approach 1:
A single analysis filter bank and a single synthesis filter bank are designed to handle multiple transposition orders (T=2, 3, 4) simultaneously. The filter banks are configured with specific subband mappings that enable them to perform different transposition operations through nonlinear processing, eliminating the need for separate filter banks for each transposition order while maintaining reconstruction quality.
2Device complexity
If a single common filter bank is used for multiple transposition orders, then the computational complexity is reduced, but the ability to achieve accurate high frequency synthesis may be compromised
Solution Approach 1:
The single analysis filter bank and synthesis filter bank are designed with differentiated subband processing capabilities. Each filter bank is configured to handle specific subband mappings corresponding to different transposition orders, allowing local optimization for each transposition scenario while using a unified overall structure. This enables the system to maintain high synthesis accuracy across multiple transposition orders without requiring separate filter banks.
Data Source
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AI summary
The present document relates to audio coding systems which make use of a harmonic transposition method for high frequency reconstruction (HFR), and to digital effect processors, e.g. so-called exciters, where generation of harmonic distortion adds brightness to the processed signal. In particular; a system configured to generate a high frequency component of a signal from a low frequency component of the signal is described, The system may comprise an analysis filter bank (501) configured to provide a set of analysis subband signals from the low frequency component of the signal; wherein the set of analysis subband signals comprises at least two analysis subband signals; wherein the analysis filter bank (501) has a frequency resolution of ?f, The system further comprises a nonlinear processing unit (502) configured to determine a set of synthesis subband signals from the set of analysis subband signals using a transposition order P; wherein the set of synthesis subband signals comprises a portion of the set of analysis subband signals phase shifted by an amount derived from the transposition order P; and a synthesis filter bank (504) configured to generate the high frequency component of the signal from the set of synthesis subband signals; wherein the synthesis filter bank (504) has a frequency resolution of F?f; with F being a resolution factor, with F =1; wherein the transposition order P is different from the resolution factor F.