Cross Product Harmonic Transposition for Audio Artifact Reduction
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Solution Overview
Problem
Existing harmonic transposition methods in audio coding systems suffer from artifacts such as 'ghost' pitches and metallic sounds, especially for signals with prominent periodic structures, and computational complexity when addressing these issues.
Innovation Solution
A method and system that utilize a nonlinear combination of multiple analysis subbands in a frequency domain, employing phase modification and magnitude adjustment, to generate a high frequency component by mapping subband signals through cross-product enhancement, incorporating a multiple-input-single-output unit for improved harmonic series completion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional harmonic transposition methods are used to reconstruct high frequency components, then coding efficiency is improved and bit-rate is reduced, but artifacts such as 'ghost' pitches and metallic sounds occur especially for signals with prominent periodic structures
Solution Approach 1:
The patent introduces cross-product terms as intermediary elements that mediate between the low frequency components and the reconstructed high frequency components. These cross-product terms (products of pairs of frequency components) serve as intermediate representations that capture harmonic relationships more accurately, thereby reducing artifacts in the final reconstructed signal while maintaining low bit-rate coding efficiency
2Manufacturing precision
If multiple transposition orders are used to improve harmonic series completion, then audio quality is enhanced, but computational complexity increases
Solution Approach 1:
The patent applies partial action by focusing computational resources on generating only the necessary cross-product terms that contribute to harmonic series completion, rather than computing all possible transposition orders. This selective approach achieves sufficient harmonic accuracy while significantly reducing the computational burden compared to exhaustive multiple transposition order methods
3Manufacturing precision
If cross-product enhancement with multiple analysis subbands is implemented, then harmonic series completion is improved and artifacts are reduced, but processing complexity increases
Solution Approach 1:
The patent segments the frequency spectrum into multiple analysis subbands, processing each subband separately to generate cross-product terms. This segmentation allows for more precise harmonic series completion by capturing local spectral characteristics in each subband, while the modular structure of processing individual subbands independently helps manage and distribute the computational complexity across multiple smaller processing stages
Data Source
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AI summary
The present invention relates to audio coding systems which make use of a harmonic transposition method for high frequency reconstruction (HFR). A system and a method for generating a high frequency component of a signal from a low frequency component of the signal is described. The system comprises an analysis filter bank providing a plurality of analysis subband signals of the low frequency component of the signal. It also comprises a non-linear processing unit to generate a synthesis subband signal with a synthesis frequency by modifying the phase of a first and a second of the plurality of analysis subband signals and by combining the phase-modified analysis subband signals. Finally, it comprises a synthesis filter bank for generating the high frequency component of the signal from the synthesis subband signal.