Harmonic Transposition Filter Bank Sharing
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Solution Overview
Problem
Existing harmonic high frequency reconstruction (HFR) methods require multiple filter banks for different transposition orders, leading to increased computational complexity.
Innovation Solution
The method involves sharing an analysis and synthesis filter bank pair among multiple harmonic transposers, using nonlinear processing to map nonlinearly modified subband signals from the analysis filter bank into selected subbands of the synthesis filter bank.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple filter banks are used for different transposition orders, then high frequency reconstruction quality is improved, but computational complexity increases
Solution Approach 1:
The patent implements a single analysis filter bank and a single synthesis filter bank that serve multiple transposition orders simultaneously. The analysis filter bank decomposes the input signal into subbands, and the synthesis filter bank reconstructs the signal from these subbands after nonlinear processing. This universal filter bank pair replaces what would traditionally require multiple separate filter bank pairs, thereby reducing computational complexity while maintaining the ability to perform harmonic transposition at different orders for high frequency reconstruction
Solution Approach 2:
The patent merges the functionality of multiple filter banks into a single shared analysis filter bank and a single shared synthesis filter bank. By combining these resources, the system avoids the redundant computation that would occur if separate filter banks were used for each transposition order, thus reducing overall computational complexity while still enabling multiple transposition operations
Data Source
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 Δf. 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 FΔf; with F being a resolution factor, with F≥1; wherein the transposition order P is different from the resolution factor F.