Ambisonics 2D Rendering with Virtual Loudspeakers for Uniform Loudness
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Solution Overview
Problem
Existing 2D loudspeaker setups attenuate sound sources from directions where no loudspeakers are placed, leading to uneven loudness and localization issues, especially for off-center listening positions.
Innovation Solution
Add virtual loudspeakers at positions where no real loudspeakers are available, such as the top and bottom, and use a modified decode matrix to distribute coefficients from these virtual positions to real loudspeakers, ensuring energy preservation and improved localization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional 2D loudspeaker setup is used, then the device complexity is low, but sound sources from directions without loudspeakers are attenuated leading to uneven loudness
Solution Approach 1:
The patent introduces virtual loudspeakers as intermediary elements that do not physically exist but are mathematically represented in the decode matrix. These virtual loudspeakers fill the gaps in the 2D setup by providing directional coverage for positions where no physical loudspeaker is located, thereby achieving uniform loudness distribution without adding physical hardware complexity
Solution Approach 2:
The patent extends the conventional 2D loudspeaker setup by adding virtual loudspeakers in the vertical dimension (top and bottom directions). This transforms the effective coverage from a flat 2D plane to a 3D spherical soundfield representation, allowing accurate rendering of sound sources from all directions including those above and below the horizontal plane
2Measurement precision
If virtual loudspeakers are added to improve coverage, then sound localization is improved, but the decode matrix complexity increases
Solution Approach 1:
The patent segments the decode matrix into distinct components: real loudspeaker channels and virtual loudspeaker channels. The virtual loudspeaker coefficients are extracted and redistributed to real loudspeakers through a systematic process, allowing the complex 3D soundfield to be decomposed into manageable parts that can be processed and rendered accurately
Solution Approach 2:
The patent modifies the decode matrix parameters by introducing weighting factors and normalization constants that account for the virtual loudspeaker positions. These parameter adjustments ensure that the energy distribution remains consistent across all directions while maintaining the mathematical integrity of the Ambisonics decomposition
3Measurement precision
If energy-preserving rendering is implemented, then localization accuracy is improved, but computational requirements increase
Solution Approach 1:
The patent performs preliminary calculations by pre-computing the decode matrix for the virtual 3D loudspeaker setup and storing it in a normalized form. This preliminary action allows the complex energy-preserving rendering to be efficiently executed during actual audio playback without requiring heavy real-time computational power, as the matrix operations can be performed with standard audio processing hardware
Data Source
AI summary
Improved methods and/or apparatus for decoding an encoded audio signal in soundfield format for L loudspeakers. The method and/or apparatus can render an Ambisonics format audio signal to 2D loudspeaker setup(s) based on a rendering matrix. The rendering matrix has elements based on loudspeaker positions and wherein the rendering matrix is determined based on weighting at least an element of a first matrix with a weighting factor g=1/â{square root over (L)}. The first matrix is determined based on positions of the L loudspeakers and at least a virtual position of at least a virtual loudspeaker that is added to the positions of the L loudspeakers.