Spatial Audio Direction Encoding With Adaptive Quantization Levels
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Solution Overview
Problem
Existing audio encoders face challenges in efficiently encoding directional metadata for spatial audio, particularly at lower bitrates, where only the most important metadata can be conveyed.
Innovation Solution
The proposed solution involves an apparatus and method that use a codebook with multiple quantization levels to encode direction parameter values. This codebook is arranged such that each quantization level includes a set of quantization values, allowing for iterative re-encoding based on the number of bits required for entropy encoding, until the bit requirement matches an allocated number of bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a codebook with multiple quantization levels is used to encode direction parameter values, then the bitrate required for encoding directional metadata is reduced, but the manufacturing precision of the encoding process increases due to iterative re-encoding operations
Solution Approach 1:
The codebook structure is made dynamic through multiple quantization levels (e.g., 2-bit, 3-bit, 4-bit codebooks) that can be selectively applied. The encoder iteratively re-encodes direction parameter values using different quantization levels until the bit requirement matches the allocated bits, allowing adaptive precision control based on available bitrate
Solution Approach 2:
The quantization precision parameter is changed iteratively through different codebook levels. The encoder starts with a higher precision codebook and progressively reduces precision by switching to lower-bit codebooks until the encoding fits the allocated bitrate, thereby optimizing the trade-off between precision and bitrate
2Adaptability or versatility
If iterative re-encoding based on bit requirements is performed, then the adaptability to different bitrates is improved, but the productivity of the encoding process decreases
Solution Approach 1:
Multiple codebooks with different quantization levels are pre-prepared and stored in the encoder. This preliminary preparation allows the encoder to quickly switch between codebooks based on allocated bitrate without performing complex computations during the actual encoding process, thus maintaining high encoding speed while achieving bitrate adaptability
Solution Approach 2:
The encoding process is made dynamic by selecting appropriate quantization levels based on allocated bits. The encoder can quickly adapt to different bitrate requirements by choosing from pre-defined codebook levels, enabling versatile operation across different bitrate scenarios without significant productivity loss
3Ease of operation
If quantization levels are arranged to include preceding quantization level values, then the ease of operation is improved through simplified codebook structure, but the loss of information increases due to quantization
Solution Approach 1:
The codebooks are structured in a nested manner where each higher-bit codebook contains the quantization values of lower-bit codebooks. For example, a 4-bit codebook includes all 2-bit and 3-bit quantization values. This nested structure simplifies the encoding operation by allowing progressive refinement from coarser to finer quantization, while managing information loss through controlled approximation at each level
Data Source
AI summary
An apparatus comprising means configured to obtain direction parameter values (108) associated with at least two time-frequency parts (202) of at least one audio signal (102); and encode the obtained direction parameter values based on a codebook (206), wherein the codebook comprises two or more quantization levels arranged such that a first quantization level comprises a first set of quantization values, and a second or succeeding quantization level comprises a second or further set of quantization values and preceding quantization level quantization values.