Directional Audio Parameter Encoding for Low-Bitrate Spatial Metadata
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Solution Overview
Problem
Current methods for encoding directional audio coding parameters, such as DirAC metadata, face challenges in achieving low bit-rates while maintaining high quality, particularly due to the large amount of data required for transmitting 3D audio scenes, and previous solutions have compromised on spatial resolution or limited applications to specific scenarios like teleconferences.
Innovation Solution
The proposed solution involves quantizing and encoding directional audio coding parameters with different resolutions for diffuseness and direction parameters, using a parameter quantizer and encoder to generate an encoded representation, and employing a two-fold weighted averaging process to prioritize time-frequency bins with higher audio signal power, allowing for efficient data reduction while maintaining quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If directional audio coding parameters are transmitted with high spatial resolution, then the quality of spatial audio reproduction is improved, but the data rate increases significantly
Solution Approach 1:
The patent applies different quantization resolutions to different parameter types: diffuseness parameters use coarser quantization (fewer bits) while direction parameters use finer quantization (more bits). This local differentiation of quality matches the perceptual importance of each parameter type, maintaining spatial accuracy where needed while reducing overall data rate.
Solution Approach 2:
The patent changes the representation parameters by using separate quantization schemes for diffuseness and direction parameters. Diffuseness is quantized with fewer bits (e.g., 3-5 bits) while direction parameters use more bits (e.g., 6-8 bits per angle), optimizing the balance between quality and data rate through parameter-specific adaptation.
2Ease of manufacture
If uniform quantization resolution is applied to all directional audio parameters, then the encoding process is simplified, but the quality is compromised for perceptually less important parameters
Solution Approach 1:
The patent implements local quality by applying different quantization resolutions to different parameter types. Diffuseness parameters (which have perceptual redundancy) use coarser quantization, while direction parameters (which require higher accuracy for spatial localization) use finer quantization. This resolves the contradiction by maintaining high quality where needed while accepting lower quality where perceptually tolerable.
Solution Approach 2:
The patent changes the quantization parameters based on parameter type: using fewer quantization levels for diffuseness (e.g., 8 levels) and more levels for direction angles (e.g., 64-256 levels). This parameter adaptation allows the system to optimize overall quality while managing encoding complexity through structured differentiation.
3Measurement precision
If high data rate is used for transmitting DirAC metadata, then the quality of spatial audio coding is maintained, but the efficiency of transmission is reduced
Solution Approach 1:
The patent applies local quality optimization by differentiating quantization precision across parameter types. Diffuseness parameters use coarser quantization (lower bit rate) while direction parameters use finer quantization (higher bit rate), achieving efficient transmission by allocating bits according to perceptual importance rather than uniformly.
Solution Approach 2:
The patent changes the data representation parameters by using variable-length coding and different quantization precisions for different parameter types. This parameter adaptation enables the system to maintain spatial audio quality while significantly improving transmission efficiency through optimized bit allocation.
Data Source
AI summary
An apparatus for encoding directional audio coding parameters having diffuseness parameters and direction parameters, has: a parameter quantizer for quantizing the diffuseness parameters and the direction parameters; a parameter encoder for encoding quantized diffuseness parameters and quantized direction parameters; and an output interface for generating an encoded parameter representation having information on encoded diffuseness parameters and encoded direction parameters.