Directional Audio Parameter Coding With Multi-Resolution Quantization
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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 teleconference scenarios.
Innovation Solution
The proposed solution involves quantizing and encoding diffuseness and direction parameters with different resolutions, grouping them over frequency and time, and using weighted averaging to reduce data complexity, allowing for efficient encoding and decoding of directional audio coding parameters, thereby achieving a balance between quality and bit-rate reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If directional audio coding parameters are transmitted with high spatial resolution, then audio quality is improved, but data transmission rate increases
Solution Approach 1:
The patent segments the audio spectrum into multiple frequency bands and processes directional parameters separately for each band. This allows selective transmission of high-resolution parameters only for frequency ranges where spatial accuracy is most critical, while using coarser resolution for less critical bands, thereby reducing overall data rate while maintaining perceived audio quality.
Solution Approach 2:
The patent applies different quantization precision levels to different directional parameters based on their perceptual importance. Specifically, azimuth parameters receive higher precision allocation than elevation parameters, and parameters in critical frequency bands receive higher precision than those in less critical bands. This local quality differentiation maintains spatial resolution where needed while minimizing data transmission.
2Measurement precision
If directional parameters are encoded with high precision, then audio quality is improved, but encoding complexity increases
Solution Approach 1:
The patent performs preliminary grouping and averaging of directional parameters across frequency bands before final encoding. By pre-processing the parameters to identify redundant information and establish relationships between bands, the subsequent encoding stage requires fewer computational operations, reducing overall encoding complexity while preserving essential spatial information.
Solution Approach 2:
The patent implements differential encoding where only the differences between parameters in adjacent frequency bands are encoded, rather than encoding absolute values for all parameters. This partial action approach significantly reduces the number of operations required while maintaining reconstruction accuracy, as most directional parameters exhibit smooth variations across frequency.
3Productivity
If data transmission rate is reduced, then bandwidth efficiency is improved, but audio quality deteriorates
Solution Approach 1:
The patent transforms the encoding problem from the time domain to the frequency domain by applying filter bank decomposition. This dimensional change allows the system to exploit frequency-domain redundancies and apply compression techniques that maintain spatial accuracy in critical bands while achieving overall bit rate reduction, thus improving bandwidth efficiency without sacrificing perceived audio quality.
Solution Approach 2:
The patent dynamically adjusts quantization step sizes and precision levels based on the estimated perceptual importance of different frequency bands and spatial parameters. By changing parameters such as quantization resolution and prediction order adaptively, the system allocates bits efficiently to preserve audio quality in critical regions while achieving compression in less critical regions, thereby improving bandwidth efficiency without quality deterioration.
Data Source
AI summary
An apparatus for encoding directional audio coding parameters comprising diffuseness parameters and direction parameters having a parameter calculator (100) for calculating the diffuseness parameters with a first time or frequency resolution and for calculating the direction parameters with a second time or frequency resolution; and a quantizer and encoder processor (200) for generating a quantized and encoded representation of the diffuseness parameters and the direction parameters.