Immersive Audio Coding Through Downmix Energy Compaction
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Solution Overview
Problem
Existing technologies face challenges in efficiently transmitting and storing immersive audio signals, such as ambisonics signals, with high perceptual quality while maintaining a bandwidth-efficient manner.
Innovation Solution
The proposed solution involves encoding a multi-channel input signal to determine a plurality of downmix channel signals, performing energy compaction on these signals to generate compacted channel signals, and determining joint coding metadata that allows upmixing to reconstruct the original multi-channel signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of audio channels and directivity patterns is increased to improve soundfield description precision, then the perceptual quality is improved, but the bit-rate requirement and bandwidth consumption increase
Solution Approach 1:
The patent segments the multi-channel audio signal into a reduced set of downmix channels by projecting the original channels onto a lower-dimensional subspace. This segmentation allows the signal to be represented with fewer channels while preserving the essential spatial information, thereby reducing the bit-rate requirement while maintaining perceptual quality.
Solution Approach 2:
The patent extracts only the most significant spatial components from the full multi-channel signal by using energy compaction techniques. The extraction process identifies and retains the essential directional information while discarding redundant components, achieving high precision soundfield description with reduced bandwidth consumption.
2Loss of energy
If energy compaction is performed on downmix channel signals to reduce the number of channels, then the bit-rate efficiency is improved, but the complexity of signal processing increases
Solution Approach 1:
The patent applies preliminary action by pre-computing the downmix matrix that projects the original multi-channel signal onto the reduced subspace. This pre-computed matrix can be efficiently applied to the signal during encoding, reducing the real-time processing complexity while maintaining the bit-rate efficiency benefits of energy compaction.
Solution Approach 2:
The patent changes the parameter space by transforming the signal from the original channel domain to a compressed domain with fewer channels. This parameter transformation achieves dimensionality reduction while the encoding/decoding operations remain computationally manageable through efficient matrix operations and energy compaction techniques.
3Productivity
If downmix channel signals are encoded with reduced channels to improve bandwidth efficiency, then the transmission efficiency is improved, but the reconstruction accuracy of the original multi-channel signal may deteriorate
Solution Approach 1:
The patent implements feedback through the joint coding of metadata that describes the downmix matrix and energy compaction parameters. This metadata feedback allows the decoder to accurately reconstruct the original multi-channel signal from the compressed downmix channels, ensuring that transmission efficiency does not come at the cost of reconstruction accuracy.
Solution Approach 2:
The patent achieves universality by creating a coding system that can represent audio signals across different channel configurations and spatial resolutions. The downmix approach with joint coding metadata provides a universal representation that can be accurately reconstructed regardless of the original signal's complexity, maintaining both transmission efficiency and reconstruction accuracy.
Data Source
AI summary
The present document describes a method (700) for encoding a multi-channel input signal (201). The method (700) comprises determining (701) a plurality of downmix channel signals (203) from the multi-channel input signal (201) and performing (702) energy compaction of the plurality of downmix channel signals (203) to provide a plurality of compacted channel signals (404). Furthermore, the method (700) comprises determining (703) joint coding metadata (205) based on the plurality of compacted channel signals (404) and based on the multi-channel input signal (201), wherein the joint coding metadata (205) is such that it allows upmixing of the plurality of compacted channel signals (404) to an approximation of the multi-channel input signal (201). In addition, the method (700) comprises encoding (704) the plurality of compacted channel signals (404) and the joint coding metadata (205).