Audio Entropy Coding Across Mixed Spectral Resolutions
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Solution Overview
Problem
Conventional audio coding techniques experience a significant loss in coding efficiency when frequent switching occurs between different time or frequency resolutions, as the context is often reset, leading to sub-optimal codebook selection.
Innovation Solution
Implementing a context mapping mechanism that derives new contexts for coefficients with changing resolutions by using interpolation, extrapolation, sub-sampling, or down-sampling of previous coefficients, allowing for more frequent switching between time or frequency resolutions without compromising coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If context is reset when switching between different time or frequency resolutions, then device complexity is reduced, but coding efficiency deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-defining multiple codebooks corresponding to different time and frequency resolutions before encoding begins. When resolution switching occurs, the system can immediately select the appropriate pre-prepared codebook without needing to reset or rebuild context, thereby maintaining coding efficiency while simplifying context management.
2Adaptability or versatility
If frequent switching between different time or frequency resolutions is enabled, then adaptability to signal characteristics is improved, but coding efficiency deteriorates due to context reset
Solution Approach 1:
The patent implements dynamics by enabling frequent switching between different time and frequency resolutions to adapt to varying signal characteristics. The key innovation is that multiple codebooks are prepared in advance for different resolutions, allowing the system to dynamically switch between them based on signal properties without losing coding efficiency, thus resolving the contradiction between adaptability and efficiency.
3Measurement precision
If codebook index transmission is made mandatory, then decoding accuracy is improved, but data rate increases
Solution Approach 1:
The patent applies self-service by organizing codebooks into a hierarchical structure where higher-level codebooks provide general information and lower-level codebooks provide specific details. The decoder can autonomously navigate this hierarchy and select only the necessary codebook level for each situation, achieving accurate decoding without always transmitting full codebook indexes, thus reducing data rate while maintaining precision.
Data Source
AI summary
An audio encoder for encoding segments of coefficients, the segments of coefficients representing different time or frequency resolutions of a sampled audio signal, the audio encoder including a processor for deriving a coding context for a currently encoded coefficient of a current segment based on a previously encoded coefficient of a previous segment, the previously encoded coefficient representing a different time or frequency resolution than the currently encoded coefficient. The audio encoder further includes an entropy encoder for entropy encoding the current coefficient based on the coding context to obtain an encoded audio stream.