Harmonic Transposition Filter Bank Sharing for Efficient HFR
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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 allows for the sharing of analysis and synthesis filter bank pairs among multiple harmonic transposers, enabling frequency domain transposition by mapping nonlinearly modified subband signals into selected subbands of a common filter bank.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple filter banks are used for different transposition orders, then the audio quality and bandwidth of the high band signal are improved, but the computational complexity increases significantly
Solution Approach 1:
The patent implements a universal filter bank structure that can perform multiple transposition operations (T=2, T=3, T=4) by configuring the same analysis and synthesis filter banks with different transposition factors. This eliminates the need for separate filter bank pairs for each transposition order, thereby maintaining high audio quality while significantly reducing computational complexity.
Solution Approach 2:
The patent merges multiple separate filter bank operations into a single unified filter bank system. By combining the analysis and synthesis filter banks into shared resources that serve multiple transposition orders, the system achieves the same audio quality improvement without the proportional increase in computational complexity that would result from using separate filter banks for each transposition order.
2Length of stationary object
If several orders of transposition are employed to synthesize the required bandwidth, then the high band signal bandwidth is improved, but the number of filter banks required increases
Solution Approach 1:
The patent creates a universal filter bank system that can generate multiple transposition orders (T=2, T=3, T=4) from a single analysis-synthesis filter bank pair. This allows the system to synthesize the required high band signal bandwidth through multiple transposition operations without requiring a separate filter bank for each order, thereby increasing bandwidth while controlling the number of filter banks.
3Speed
If upsampling of the core signal is added to convert to the sampling rate of the output signal, then the sampling rate compatibility is improved, but the computational complexity increases
Solution Approach 1:
The patent merges the upsampling operation with the existing filter bank structure. By integrating the upsampling function into the synthesis filter bank operations already required for transposition, the system achieves sampling rate conversion without adding separate upsampling hardware or algorithms, thereby maintaining sampling rate compatibility while minimizing additional computational complexity.
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 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 Pis different from the resolution factorF.