Hierarchical Audio Decoding for HOA Compatibility
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Solution Overview
Problem
Current methods for compressing Higher-Order Ambisonics (HOA) content are not compatible with existing surround sound formats, limiting their deployment and compatibility with existing decoders.
Innovation Solution
A hierarchical decoding method that includes a base layer for surround sound and an enhancement layer for HOA, allowing backward compatibility with conventional surround sound decoders while enabling full 3D audio decoding with an enhanced decoder, utilizing prediction and residual coding to minimize bit rate requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If HOA content is compressed using existing monolithic architecture, then high-quality spatial audio encoding is achieved, but compatibility with existing surround sound formats and decoders is lost
Solution Approach 1:
The HOA compression is divided into two independent stages: a dimensionality reduction stage that processes HOA coefficients, and a second stage that encodes the reduced signals. This segmentation allows the first stage to optimize for HOA quality while the second stage can produce outputs compatible with conventional surround sound formats, thus resolving the contradiction between high-quality spatial audio encoding and format compatibility
Solution Approach 2:
The patent embeds HOA-specific processing within a broader compatible framework. The dimensionality reduction stage processes HOA content specifically, while the output is structured to be compatible with conventional surround sound decoders. This nesting allows HOA functionality to be contained within a compatible container format, enabling both high-quality spatial audio and broad decoder compatibility
2Loss of information
If dimensionality reduction is applied to HOA content, then information loss is minimized and irrelevancy is reduced, but the complexity of signal processing increases
Solution Approach 1:
The dimensionality reduction stage performs preliminary processing on HOA content by identifying and retaining only the dominant sound components before the main encoding stage. This preliminary action reduces the amount of data that needs to be processed in subsequent stages, minimizing information loss while actually reducing the overall computational complexity of the system by eliminating redundant processing of insignificant components
3Productivity
If parallel perceptual encoders are used for dominant sound components, then encoding efficiency is improved, but the overall system complexity and bit rate requirements increase
Solution Approach 1:
The dimensionality reduction stage extracts only the dominant sound components from the full HOA content, separating them from less significant components. This extraction allows the parallel perceptual encoders to process only the essential audio information, improving encoding efficiency while reducing the total bit rate requirements by not encoding redundant or less perceptible audio data
Data Source
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AI summary
The invention introduces a new concept for hierarchical coding of HOA content. A method for encoding a hierarchical audio bitstream comprises rendering a HOA input signal to surround sound, encoding the surround sound for a base layer output signal, decoding the encoded surround sound to obtain a reconstructed surround sound signal, performing dimensionality reduction on the received HOA input signal, calculating a residual between the dimensionality-reduced HOA signal and the reconstructed surround sound signal, encoding the residual signal, and multiplexing structural information about the HOA input signal, the encoded residuals and the encoded surround sound into a bitstream to obtain a hierarchical audio bitstream.