Arithmetic Audio Coding Context Transfer Across Resolution Changes
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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 they often resort to sub-optimal codebook selection due to context resetting, which is inefficient for adaptive signal processing.
Innovation Solution
Implementing a context mapping mechanism that derives new coding contexts from previous coefficients with different resolutions using interpolation, extrapolation, sub-sampling, or up-sampling techniques, 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 resetting is used when switching between different time or frequency resolutions, then device complexity is reduced, but coding efficiency deteriorates significantly
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing context mapping relationships between different resolutions before actual switching occurs. The encoder pre-establishes mapping tables that define how context states at one resolution correspond to context states at another resolution, so that when switching is needed, the mapping is already prepared and can be applied immediately without resetting the context, thereby maintaining coding efficiency while managing complexity
Solution Approach 2:
The patent introduces an intermediary context mapping mechanism that acts as a bridge between different resolution contexts. Instead of directly resetting context when switching resolutions, the mapping mechanism translates context states from one resolution to another, allowing seamless transitions while preserving the statistical properties needed for efficient entropy coding. This intermediary layer resolves the contradiction by enabling resolution switching without context loss
2Adaptability or versatility
If frequent switching between different time or frequency resolutions is performed, then adaptability to signal characteristics is improved, but coding efficiency deteriorates due to sub-optimal codebook selection
Solution Approach 1:
The patent applies dynamics by making the context state adaptable and changeable according to the current resolution and signal characteristics. The context mapping mechanism dynamically adjusts context parameters based on the current operating resolution and signal properties, allowing the system to frequently switch between resolutions while maintaining optimal codebook selection for each condition. This dynamic adaptation resolves the contradiction by enabling both frequent switching and efficient coding
Solution Approach 2:
The patent changes parameters by adjusting context state parameters according to the current resolution and signal characteristics. The context mapping mechanism modifies probability distribution parameters, codebook selection parameters, and other contextual parameters based on the current operating conditions, allowing frequent resolution switching while maintaining optimal coding efficiency for each specific condition through parameter adaptation
3Ease of operation
If context is reset during resolution switching, then synchronization between encoder and decoder is simplified, but data compression efficiency is reduced
Solution Approach 1:
The patent applies feedback by having the encoder signal resolution switch events to the decoder, allowing the decoder to apply the same context mapping transformations. This feedback mechanism ensures that both encoder and decoder maintain synchronized context states without resetting, preserving compression efficiency while keeping synchronization simple through explicit signaling of context state changes rather than implicit resetting
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.