Audio Coding Context Mapping Across Transform Length Switching
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Solution Overview
Problem
Conventional audio coding methods experience a significant loss in coding efficiency when frequently switching between different time/frequency resolutions, as they reset the context, leading to sub-optimal codebook selection and reduced adaptation to signal characteristics.
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 context information, allowing for more frequent switching without compromising coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If context is reset when switching between different transform lengths, then switching between resolutions can be performed, but coding efficiency deteriorates significantly
Solution Approach 1:
The patent applies preliminary action by pre-adapting the context to the new transform length before actual coding operations begin. When switching between short and long transform blocks, the context is proactively resampled and adapted in advance, ensuring that optimal codebooks are available from the start of each new block type, thereby preventing coding efficiency loss.
Solution Approach 2:
The patent changes the parameters of the context by resampling it to match the new transform length. The context parameters (transform length, sampling rate) are dynamically adjusted when switching between different block types, allowing the coding system to maintain optimal performance across different transform lengths without resetting the context entirely.
2Productivity
If context is not reset when switching between transform lengths, then coding efficiency is maintained, but context inconsistency arises between different resolutions
Solution Approach 1:
The patent applies parameter changes by dynamically resampling the context to match the current transform length. Instead of maintaining a fixed context or resetting it, the context parameters are continuously adjusted to be consistent with the current resolution, ensuring both coding efficiency and context consistency simultaneously.
Solution Approach 2:
The patent introduces dynamics by making the context adaptable and flexible rather than static. The context dynamically changes its resolution and characteristics based on the current transform block type, allowing it to remain consistent across different resolutions while maintaining optimal coding performance.
3Adaptability or versatility
If frequent switching between transform lengths is performed, then adaptation to signal characteristics improves, but coding efficiency deteriorates due to context reset
Solution Approach 1:
The patent applies preliminary action by pre-adapting the context to the new transform length before actual coding operations begin. When switching between short and long transform blocks, the context is proactively resampled and adapted in advance, ensuring that optimal codebooks are available from the start of each new block type, thereby preventing coding efficiency loss.
Solution Approach 2:
The patent changes the parameters of the context by resampling it to match the new transform length. The context parameters (transform length, sampling rate) are dynamically adjusted when switching between different block types, allowing the coding system to maintain optimal performance across different transform lengths without resetting the context entirely.
Data Source
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AI summary
An audio encoder (100) for encoding segments of coefficients, the segments of coefficients representing different time or frequency resolutions of a sampled audio signal, the audio encoder (100) comprising a processor (110) 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 (100) further comprises an entropy encoder (120) for entropy encoding the current coefficient based on the coding context to obtain an encoded audio stream.