Entropy-Coded Bit Packing for Fixed-Rate Error-Resilient Streams
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Solution Overview
Problem
Existing methods for lossy coding of signals, particularly audio and video, face challenges in efficiently packing variable-length entropy-coded data into a fixed-rate stream while maintaining error resilience and minimizing delay, as they often result in wastage and increased sensitivity to bit errors due to variable data rates and the need for block-based coding which is not suitable for all applications.
Innovation Solution
A method involving a conveyor system that moves bits from earlier slots to later slots, allowing for the distribution of coarse and touchup codewords to efficiently pack variable-length data, with coarse codewords taking priority and touchup bits providing resolution enhancement, while also incorporating a LIFO stack and delay unit for decoding to maintain error resilience and adapt to varying signal characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If variable-length entropy coded data is packed contiguously into a fixed-rate stream, then coding efficiency is improved, but error resilience deteriorates because a single bit error can propagate and corrupt multiple samples
Solution Approach 1:
The patent divides the contiguous bit stream into fixed-size blocks, where each block contains a predetermined number of bits. This segmentation prevents error propagation beyond block boundaries, as each block is independently decoded. The encoder packs entropy-coded samples into these fixed blocks, and the decoder processes them independently, thereby containing bit errors within single blocks rather than allowing cascading corruption across multiple samples.
2Reliability
If block-based coding is used to improve error resilience, then error propagation is limited, but delay increases and adaptability to varying signal characteristics deteriorates
Solution Approach 1:
The patent employs adaptive entropy coding within the fixed-block framework, allowing the coding parameters to dynamically adjust to varying signal characteristics. The entropy coder adapts its probability models and coding strategies based on the statistical properties of the current block's data, maintaining high coding efficiency despite the fixed-block structure. This dynamic adaptation occurs within each block independently, avoiding the delays associated with larger fixed blocks while preserving error containment benefits.
3Productivity
If entropy coding is used to improve coding efficiency, then bit rate is reduced, but the data rate becomes variable which is inconvenient for fixed-rate transmission
Solution Approach 1:
The patent introduces a temporal dimension by distributing entropy-coded bits across multiple fixed-size blocks over time. Instead of requiring all bits to be transmitted contiguously at variable rates, the encoder packs bits into successive fixed blocks, and the decoder accumulates and processes them in sequence. This transforms the variable-rate problem into a fixed-rate stream where blocks are transmitted at constant rates, while the entropy coding efficiency is preserved within each block's bit allocation.
Data Source
AI summary
A method is described for packing variable-length entropy coded data into a fixed rate data stream along with resolution enhancement data, the method providing tightly constrained propagation of transmission channel errors and graceful degradation of signal resolution as entropy-coded data rate increases. An application to a multiband ADPCM audio codec is also described.