Entropy Decoding Context Pre-fetch and Miss Handling
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Solution Overview
Problem
Conventional video decoding performance is bottlenecked by entropy decoding due to data dependency issues, particularly exacerbated by large and complex context tables.
Innovation Solution
An entropy decoding apparatus with a context pre-fetch and miss handling mechanism, featuring a pre-fetch circuit and context pre-load buffer that pre-fetches candidate contexts and buffers them, re-fetching target contexts as needed to support efficient entropy decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large and complex context table is used for entropy decoding, then decoding accuracy is improved, but decoding speed deteriorates due to data dependency issues
Solution Approach 1:
The patent implements a context pre-fetch mechanism that proactively loads context data from the context table into a buffer before it is actually needed by the entropy decoding circuit. This preliminary action breaks the data dependency chain, allowing the decoding circuit to operate at full speed without waiting for context data, thus resolving the contradiction between using a large context table for accuracy and maintaining decoding speed.
2Quantity of substance
If context data is fetched on-demand during entropy decoding, then memory usage is reduced, but decoding latency increases
Solution Approach 1:
The patent pre-loads context data into a dedicated buffer before decoding operations begin, rather than fetching data on-demand during decoding. This approach trades some additional memory usage for significantly reduced decoding latency, as the context data is already available when needed without causing stalls in the decoding pipeline.
3Reliability
If the entropy decoding circuit waits for context data before processing, then data accuracy is ensured, but processing throughput decreases
Solution Approach 1:
The patent implements a context pre-fetch buffer that stores context data in advance, allowing the entropy decoding circuit to process data continuously without waiting for context information. This eliminates processing stalls while maintaining data accuracy, as the pre-fetched context data is guaranteed to be the correct version needed for accurate decoding.
Solution Approach 2:
The patent introduces a context buffer as an intermediary between the context table and the entropy decoding circuit. This buffer acts as a mediator that decouples the decoding circuit from direct dependency on the context table, allowing the circuit to operate at full throughput while the buffer manages context data retrieval and validity tracking.
Data Source
AI summary
An entropy decoding apparatus includes an entropy decoding circuit, a pre-fetch circuit, and a context pre-load buffer. The pre-fetch circuit pre-fetches at least one candidate context for entropy decoding of a part of an encoded bitstream of a frame before the entropy decoding circuit starts entropy decoding of the part of the encoded bitstream of the frame. The context pre-load buffer buffers the at least one candidate context. When a target context actually needed by entropy decoding of the part of the encoded bitstream of the frame is not available in the context pre-load buffer, the context pre-load buffer instructs the pre-fetch circuit to re-fetch the target context, and the entropy decoding circuit stalls entropy decoding of the part of the encoded bitstream of the frame.