Motion Vector Difference Entropy Coding With Unified Contexts
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Solution Overview
Problem
Current video codecs face inefficiencies in entropy coding of motion vector differences due to high context numbers, which can lead to ineffective probability adaptation and increased coding complexity, while low context numbers fail to accurately encode bins with varying symbol statistics.
Innovation Solution
Reducing the cutoff value for truncated unary coding of motion vector differences to two bin positions, using a single context for both horizontal and vertical components, and employing advanced motion vector prediction methods to reduce the number of motion vector differences transmitted, along with merging blocks to cluster motion vector differences for transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high number of contexts is provided for entropy coding of motion vector differences, then coding precision is improved, but device complexity increases and probability adaptation becomes ineffective
Solution Approach 1:
The patent merges the context selection for horizontal and vertical motion vector difference components by using a single unified context for both components. This eliminates the need for separate context selections and inspections, thereby reducing device complexity while maintaining coding precision through effective probability adaptation.
Solution Approach 2:
The patent applies a universal context model that serves both horizontal and vertical motion vector difference components. This single context performs multiple functions by adapting probability estimates that are applicable to both components, reducing the overall number of contexts needed while maintaining effective coding precision.
2Measurement precision
If a high number of contexts is provided for entropy coding of motion vector differences, then coding precision is improved, but probability adaptation fails to perform effectively
Solution Approach 1:
By merging the context selection process for horizontal and vertical components into a single unified context, the patent ensures that probability adaptation operates effectively on sufficient data. This prevents the adaptation failure that occurs when contexts are visited too rarely, while maintaining coding precision through the unified probability estimates.
3Measurement precision
If multiple contexts are provided for bin positions, then coding precision is improved, but ease of operation deteriorates due to necessary inspection of neighboring bins
Solution Approach 1:
The patent merges the context selection for both horizontal and vertical motion vector difference components into a single context. This eliminates the need to inspect neighboring bins or syntax element values for context selection, thereby simplifying the decoding process execution while maintaining coding precision through the unified context model.
4Device complexity
If the cutoff value for truncated unary code is reduced to two, then device complexity is reduced, but coding precision may deteriorate
Solution Approach 1:
By reducing the cutoff value to two and merging the context selection for both components into a single context, the patent achieves lower device complexity while preventing coding precision deterioration. The unified context ensures effective probability adaptation that compensates for the reduced binarization range, maintaining overall coding precision.
Solution Approach 2:
The patent changes the cutoff parameter of the truncated unary code from nine to two, and simultaneously changes the context parameter from multiple contexts to a single unified context. This parameter change reduces device complexity while the adaptive probability estimation in the unified context maintains coding precision.
Data Source
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AI summary
A decoder for decoding a video from a data stream into which horizontal and vertical components of motion vector differences are coded using binarizations of the horizontal and vertical components is described, the binarizations equaling a truncated unary code of the horizontal and vertical components, respectively, within a first interval of the domain of the horizontal and vertical components below a cutoff value, and a combination of a prefix in form of the truncated unary code for the cutoff value and a suffix in form of a Exp-Golomb code of the horizontal and vertical components, respectively, within a second interval of the domain of the horizontal and vertical components inclusive and above the cutoff value, wherein the cutoff value is two and the Exp-Golomb code has order one. An entropy decoder is configured to, for the horizontal and vertical components of the motion vector differences, derive the truncated unary code from the data stream using context-adaptive binary entropy decoding with exactly one context per bin position of the truncated unary code, which is common for the horizontal and vertical components of the motion vector differences, and the Exp-Golomb code using a constant equi-probability bypass mode to obtain the binarizations of the motion vector differences. A desymbolizer is configured to debinarize the binarizations of the motion vector difference syntax elements to obtain integer values of the horizontal and vertical components of the motion vector differences; A reconstructor is configured to reconstruct the video based on the integer values of the horizontal and vertical components of the motion vector differences.