Shared Filter Banks for Multi-Order Harmonic Transposition
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Solution Overview
Problem
Existing harmonic transposition methods in audio coding systems require multiple filter banks for different transposition orders, leading to increased computational complexity and inefficiency, especially when upsampling is needed to match the sampling rate of the output signal.
Innovation Solution
The method involves sharing a common analysis and synthesis filter bank pair among multiple harmonic transposers, utilizing nonlinear processing to map modified subband signals across different transposition orders, allowing for efficient frequency domain transposition and reducing the need for multiple filter banks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple filter banks are used for different transposition orders, then the accuracy of high frequency reconstruction is improved, but the computational complexity increases significantly
Solution Approach 1:
The patent implements a universal filter bank structure that serves multiple transposition orders simultaneously. The same filter bank is reused across different transposition operations, allowing one filter bank to perform the function of multiple specialized filter banks. This multi-functional approach maintains reconstruction accuracy for various transposition orders while significantly reducing the total number of filter banks required, thereby lowering computational complexity.
Solution Approach 2:
The patent combines multiple filter bank operations into a single shared filter bank structure. By merging the functionality of separate filter banks for different transposition orders into one unified structure, the system achieves the same high frequency reconstruction accuracy without the computational overhead of multiple independent filter banks. The shared structure processes signals for multiple transposition orders through a common filtering mechanism.
2Adaptability or versatility
If multiple filter banks are implemented for different transposition orders, then the bandwidth extension capability is improved, but the system efficiency deteriorates
Solution Approach 1:
The universal filter bank structure enables the system to handle multiple transposition orders and bandwidth extension scenarios through a single efficient mechanism. This multi-functional design maintains the adaptability to extend bandwidth across different frequency ranges while improving system efficiency by eliminating redundant filtering operations that would occur with separate filter banks for each transposition order.
3Device complexity
If a common filter bank pair is shared among multiple harmonic transposers, then the computational complexity is reduced, but the ability to handle different transposition orders simultaneously may be compromised
Solution Approach 1:
The patent designs the common filter bank pair with universal characteristics that enable it to effectively handle multiple transposition orders simultaneously. The filter bank structure is configured to process signals for different transposition factors through shared filtering operations, maintaining the adaptability to handle various transposition scenarios while reducing computational complexity. The universal design ensures that no transposition order is compromised despite using a single filter bank pair.
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.