Audio Upmixer Phase-Shift Path for Accurate Channel Correlation
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Solution Overview
Problem
Existing parametric multi-channel audio coding techniques face challenges in accurately controlling inter-channel correlation during the upmixing process, often resulting in incorrect output correlations due to phase shifting of decorrelated signals.
Innovation Solution
An upmixer that applies phase shifts only to the downmix audio signal while keeping the decorrelated signal unmodified, allowing precise control over inter-channel correlation by combining phase-shifted and unmodified signals to produce upmixed audio channels with maintained decorrelation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase shift is applied to the decorrelated signal to restore inter-channel phase relation, then spatial accuracy is improved, but inter-channel correlation control deteriorates
Solution Approach 1:
The upmixing process is segmented into two independent paths: one processing the downmix signal with phase shift to achieve spatial accuracy, and another processing the decorrelated signal without phase shift to maintain correlation control. These segmented paths are then combined to achieve both objectives simultaneously.
Solution Approach 2:
Different quality requirements are applied locally to different signal components: the downmix signal path receives phase shifting treatment for spatial accuracy, while the decorrelated signal path maintains original phase characteristics for correlation control. This local differentiation resolves the contradiction by allowing each component to optimize for its specific requirement.
2Measurement precision
If phase shift is applied to downmix signal to restore original phase relation, then spatial hearing accuracy is improved, but decorrelation is lost
Solution Approach 1:
The signal processing is divided into two segments: the downmix signal is phase-shifted to restore spatial hearing accuracy, while the decorrelated signal is kept unmodified to preserve decorrelation stability. This segmentation allows both contradictory requirements to be satisfied in their respective domains.
Solution Approach 2:
The decorrelated signal acts as an intermediary that carries the decorrelation property without phase shift, while the phase-shifted downmix signal provides spatial accuracy. The combination of these two intermediaries produces the final upmixed signal that possesses both spatial hearing accuracy and decorrelation stability.
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
An upmixer for upmixing a downmix audio signal into an upmixed audio signal describing one or more upmixed audio channels comprises a parameter applier configured to apply upmixing parameters to upmix the downmix audio signal in order to obtain the upmixed audio signal. The parameter applier is configured to apply a phase shift to the downmix audio signal to obtain a phase-shifted version of the downmix audio signal, while leaving a decorrelated signal unmodified by the phase shift. The parameter applier is further configured to combine the phase-shifted version of the downmix audio signal with the decorrelated signal to obtain the upmixed audio signal.