DirAC Spatial Audio Coding With Tiered Ambisonics Synthesis
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Solution Overview
Problem
Existing spatial audio coding technologies face challenges in efficiently synthesizing higher-order Ambisonics signals while maintaining audio quality, particularly in low-bitrate transmission scenarios, due to quantization errors and energy fluctuations in directional components.
Innovation Solution
The method employs a three-tiered approach for generating sound field descriptions, including low-order, mid-order, and high-order components, with energy compensation for low-order and mid-order components, and limited diffuse component synthesis up to a certain order, using Directional Audio Coding (DirAC) parameters and a down-mix signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If higher-order Ambisonics signals are synthesized using traditional methods, then spatial audio quality is improved, but computational complexity and quantization errors increase
Solution Approach 1:
The patent segments the Ambisonics signal synthesis into three distinct components: low-order components (directly from input signal), mid-order components (synthesized with both direct and diffuse portions), and high-order components (synthesized with direct portion only). This segmentation allows each component to be processed with appropriate complexity, reducing overall computational burden while maintaining spatial audio quality.
Solution Approach 2:
The patent applies different synthesis quality levels to different order components. Low-order components receive full processing with energy compensation, mid-order components receive synthesized direct and diffuse portions, while high-order components receive simplified processing with direct portion only. This local quality approach optimizes computational resources while preserving critical spatial information.
2Measurement precision
If higher-order Ambisonics signals are synthesized with full diffuse component synthesis, then spatial resolution is improved, but energy fluctuations and quantization errors increase
Solution Approach 1:
The patent segments diffuse component synthesis to only mid-order components, excluding high-order components from diffuse synthesis. This selective approach maintains spatial resolution where it matters most (mid-orders) while avoiding energy fluctuations and quantization errors that would arise from synthesizing diffuse components across all orders.
Solution Approach 2:
The patent applies partial diffuse component synthesis rather than complete synthesis across all orders. By limiting diffuse synthesis to mid-order components only, the patent achieves sufficient spatial resolution without the excessive action of synthesizing diffuse components for high-order components, thereby maintaining energy stability.
3Manufacturing precision
If low-order components are generated with energy compensation, then audio quality is maintained, but processing time increases
Solution Approach 1:
The patent segments energy compensation processing to apply only to low-order components, excluding mid and high-order components. This targeted approach maintains audio quality for the most critical low-order components while avoiding the time cost of applying energy compensation to all components, thus resolving the contradiction between quality and processing time.
Data Source
AI summary
An apparatus for generating a sound field description using an input signal having a mono-signal or a multi-channel signal includes: an input signal analyzer for analyzing the input signal to derive direction data and diffuseness data; a low-order components generator for generating a low-order sound field description from the input signal up to a predetermined order and mode; a mid-order components generator for generating a mid-order sound field description above the predetermined order or at the predetermined order and above the predetermined mode and below or at a high order, wherein the mid-order sound field description comprises a direct contribution and a diffuse contribution; and a high-order components generator for generating a high-order sound field description comprising a sound field component above the high order using a synthesis of at least one direct portion, wherein the high-order sound field description comprises a direct contribution only.