Spatial Audio Parameter Quantization for Bitrate-Quality Tradeoffs
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Solution Overview
Problem
Current audio encoding technologies face challenges in efficiently quantizing directional components like azimuth and elevation for spatial audio metadata, particularly in multi-channel systems, which affects bitrate and quality of spatial audio representation.
Innovation Solution
The proposed solution involves a method for determining distortion measures using different quantization schemes for azimuth and elevation, allowing for either joint or vector quantization based on bit allocation, which adapts to the variance of direction parameter components within time-frequency blocks, optimizing bit distribution across frequency subbands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If joint quantization scheme is used for azimuth and elevation, then encoding simplicity is improved, but quantization accuracy deteriorates
Solution Approach 1:
The system dynamically selects between joint quantization scheme and separate quantization scheme based on the variance of direction parameter components. When variance is high, separate quantization is chosen to improve accuracy; when variance is low, joint quantization is chosen for simplicity. This dynamic adaptation resolves the contradiction by making the encoding process flexible rather than fixed.
Solution Approach 2:
The invention changes the quantization parameter (from fixed joint quantization to variable selection between joint and separate quantization) based on the statistical properties of the input signal. By monitoring the variance of azimuth and elevation components, the system adjusts the quantization strategy to optimize the trade-off between encoding simplicity and quantization accuracy.
2Measurement precision
If separate quantization scheme is used for azimuth and elevation, then quantization accuracy is improved, but device complexity increases
Solution Approach 1:
The invention segments the quantization process into two distinct paths: joint quantization path and separate quantization path. Each path is optimized for specific scenarios. The segmentation allows the system to apply the appropriate level of complexity based on the input characteristics, reducing overall system complexity while maintaining accuracy when needed.
Solution Approach 2:
The system dynamically switches between joint and separate quantization schemes based on variance thresholds. This dynamic behavior prevents the system from always using the more complex separate quantization, thereby reducing average device complexity while still achieving high accuracy when the input signal characteristics warrant it.
3Productivity
If fixed bit allocation is used for quantization, then encoding speed is improved, but spatial audio quality deteriorates
Solution Approach 1:
The invention changes the bit allocation parameter dynamically based on the variance of direction parameters. When variance is high, more bits are allocated to maintain quality; when variance is low, fewer bits are used to maintain speed. This parameter adaptation resolves the contradiction between encoding speed and spatial audio quality.
Solution Approach 2:
The system applies different quantization precision (local quality) to different time-frequency blocks based on their individual variance characteristics. High-variance blocks receive higher precision treatment while low-variance blocks use coarser quantization, optimizing both overall quality and encoding efficiency.
4Reliability
If adaptive bit allocation is used for quantization, then spatial audio quality is improved, but encoding complexity increases
Solution Approach 1:
The invention changes the bit allocation parameter based on simple variance calculations of the direction parameters. By using variance as the sole criterion for adaptive allocation, the system achieves quality improvement without excessive complexity. The variance calculation is computationally efficient compared to more sophisticated adaptive algorithms.
Data Source
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AI summary
There is disclosed inter alia an apparatus for spatial audio signal encoding comprising means for receiving for each time frequency block of a sub band of an audio frame a spatial audio parameter comprising an azimuth and an elevation; determining a first distortion measure for the audio frame by determining a first distance measure for each time frequency block and summing the first distance measure for each time frequency block;determining a second distortion measure for the audio frame by determining a second distance measure for each time frequency block and summing the second distance measure for each time frequency block, and selecting either the first quantization scheme or the second quantization scheme for quantising the elevation and the azimuth for all time frequency blocks of the sub band of the audio frame, wherein the selecting is dependent on the first and second distortion measures.