Entropy Encoder Context Initialization for Low-Bitrate Video Coding
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Solution Overview
Problem
Existing video coding systems face issues with increased overhead code quantity due to macroblocks containing significant coefficients, leading to image degradation and potential failure to meet bit rate requirements during low bit rate coding.
Innovation Solution
An entropy encoder with a context initializer that adjusts the slice quantization parameter by subtracting a predetermined offset from the input quantization parameter, reducing the overhead code quantity and improving coding efficiency by optimizing the generation probability of symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If quantization parameter is increased to reduce bit rate, then bit rate requirement is met, but image quality degrades
Solution Approach 1:
The patent modifies the quantization parameter by subtracting an offset value to create a slice quantization parameter. This parameter transformation allows the system to meet bit rate requirements while maintaining image quality by optimizing the distribution of quantization strength across different macroblocks.
2Device complexity
If context is initialized with original quantization parameter, then coding process is simple, but overhead code quantity increases
Solution Approach 1:
The patent introduces a modified quantization parameter (slice quantization parameter = quantization parameter - offset) for context initialization. This parameter adjustment reduces the overhead code quantity by optimizing the probability distribution of symbols in macroblocks with significant coefficients, thereby improving coding efficiency without significantly complicating the coding process.
3Productivity
If standard context initialization is used, then coding efficiency is maintained, but overhead code quantity increases in low bit rate conditions
Solution Approach 1:
The patent applies different quantization parameters for context initialization based on local characteristics of macroblocks. By using a reduced offset value for macroblocks containing significant coefficients, the system optimizes the probability distribution locally, reducing overhead code quantity in critical areas while maintaining overall coding efficiency.
Solution Approach 2:
The patent dynamically adjusts the slice quantization parameter by subtracting an offset from the original quantization parameter. This parameter modification adapts the context initialization to the actual content characteristics, reducing overhead code quantity in low bit rate conditions while preserving coding efficiency through optimized probability modeling.
Data Source
AI summary
An entropy encoder, a video coding apparatus, a video coding method and a video coding program can cope with the adverse effects that arise as a result of a local increase of overhead code quantity. The quantization parameter output form the code quantity control unit of a video coding apparatus is input to a third arithmetic unit before being input to the context initializer in an entropy encoder and a quantization parameter offset value is subtracted from it there. The discrepancy relating the generation probability of a symbol where significant coefficients exist can be improved by initializing an arithmetic coding context by using the quantization parameter obtained by subtracting a predetermined value form the quantization parameter defined by a rate control unit.