Audio Upmix Distortion Limiter Using Linear Combination
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Solution Overview
Problem
Existing audio processing systems face challenges in providing high-quality upmix signal representations from downmix signal representations and object-related parametric information, often resulting in audible distortions due to user-interactivity and bitrate constraints in multi-channel audio applications.
Innovation Solution
An apparatus and method that utilize a distortion limiter to perform a linear combination of a user-specified rendering matrix and a target rendering matrix, using a parameter extracted from the bitstream representation, to reduce or eliminate audible distortions in upmix signal representations, while maintaining computational efficiency and user control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If user-interactivity is implemented for extreme object rendering, then user control over rendering settings is improved, but audible distortions in upmix signal representations increase
Solution Approach 1:
The patent applies preliminary anti-action by pre-calculating and storing optimal rendering matrices that prevent audible distortions before user interaction occurs. The system maintains a database of pre-computed rendering matrices that can be selectively applied to counteract potential distortions from user-specified extreme rendering settings, thus preventing rather than correcting the harmful effect.
Solution Approach 2:
The patent introduces an intermediary mechanism - a selection module that chooses between user-specified rendering matrices and pre-computed optimal rendering matrices based on distortion criteria. This intermediary layer mediates between user control requirements and distortion prevention, allowing the system to respect user intent while avoiding harmful audible distortions through intelligent matrix selection.
2Loss of energy
If parametric coding techniques are used for bitrate-efficient transmission, then resource consumption is reduced, but audio quality of output audio signals deteriorates under extreme object rendering
Solution Approach 1:
The patent applies preliminary action by pre-computing optimal rendering matrices during an offline preparation phase, storing them for later use during actual audio playback. This preliminary computation avoids the need for complex real-time calculations during decoding, maintaining low resource consumption while ensuring high audio quality through the use of pre-optimized matrices that prevent distortions.
Solution Approach 2:
The patent changes the parameter representation by working with rendering matrix coefficients rather than raw audio signals. By encoding and transmitting compact parametric representations of rendering matrices instead of full audio waveforms, the system achieves bitrate efficiency while the pre-computed nature of these matrices ensures they are optimized for audio quality even under extreme rendering conditions.
3Object-affected harmful factors
If a linear combination of user-specified rendering matrix and target rendering matrix is performed, then audible distortions are reduced, but computational complexity increases
Solution Approach 1:
The patent applies partial action by performing the linear combination operation only when necessary - specifically, only when the user-specified rendering matrix is selected and when distortion reduction is beneficial. The system does not always compute linear combinations, but selectively applies them based on the rendering mode and distortion assessment, thus reducing overall computational complexity while still achieving distortion reduction where needed.
Solution Approach 2:
The patent uses disposable computational approximations by implementing efficient, simplified linear combination operations that trade some computational precision for speed. The linear combination uses pre-computed matrix coefficients and simple weighted averaging operations rather than complex optimization algorithms, providing adequate distortion reduction with minimal computational overhead suitable for real-time playback.
Data Source
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AI summary
An apparatus for providing an upmix signal representation on the basis of a downmix signal representation and an object-related parametric information, which are included in a bitstream representation of an audio content, in independence on a user-specified rendering matrix, the apparatus comprises a distortion limiter configured to obtain a modified rendering matrix using a linear combination of a user-specified rendering matrix in a target rendering matrix in dependence on a linear combination parameter. The apparatus also comprises a signal processor configured to obtain the upmix signal representation on the basis of the downmix signal representation and the object-related parametric information using the modified rendering matrix. The apparatus is also configured to evaluate a bitstream element representing the linear combination parameter in order to obtain the linear combination parameter.