Audio Entropy Context Mapping Across Transform Length Switches
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Solution Overview
Problem
Conventional audio coding methods experience a significant loss in coding efficiency when frequent switching occurs between different time or frequency resolutions, as they 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, using interpolation, extrapolation, sub-sampling, or up-sampling to adapt to changing time or frequency resolutions, allowing for more frequent switching without compromising coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If context resetting is used when switching between different time or frequency resolutions, then synchronization between encoder and decoder is maintained, but coding efficiency deteriorates significantly
Solution Approach 1:
The patent introduces a codebook index as an intermediary element that carries context information between encoder and decoder. This index allows the decoder to retrieve the correct codebook page without requiring full context resetting, thus maintaining synchronization while preserving coding efficiency during resolution switching.
Solution Approach 2:
The patent performs preliminary actions by pre-organizing codebooks into multiple pages, where each page contains codebooks for different contexts. This preliminary structuring allows the encoder and decoder to synchronously access the appropriate codebook page based on the transmitted index, avoiding the need for context resetting during resolution changes.
2Adaptability or versatility
If frequent switching between different resolutions is performed to adapt to signal characteristics, then adaptability improves, but coding efficiency deteriorates due to sub-optimal codebook selection
Solution Approach 1:
The patent implements dynamic codebook selection by allowing the system to switch between different codebook pages based on the current signal characteristics and resolution requirements. The codebook index dynamically points to the most appropriate codebook page, enabling frequent resolution switching without losing coding efficiency.
Solution Approach 2:
The patent changes the parameter of codebook selection by using multiple codebook pages with different contexts. When resolution switching occurs, the system changes which codebook page is active based on the transmitted index, allowing adaptive signal processing while maintaining optimal coding efficiency for each resolution state.
3Productivity
If context information is preserved across resolution switches, then coding efficiency is maintained, but complexity of context management increases
Solution Approach 1:
The patent segments the codebook into multiple pages, where each page contains codebooks for specific contexts. This segmentation simplifies context management by organizing codebooks into discrete, manageable units that can be independently selected and transmitted via the codebook index, reducing the complexity of tracking context across resolution switches.
Solution Approach 2:
The patent uses copying by transmitting a compact codebook index that references pre-defined codebook pages at both encoder and decoder sides. Instead of transmitting or managing full context information, the system copies the reference (index) to the appropriate codebook page, significantly reducing context management complexity while preserving coding efficiency.
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.