Affine Motion Model Restrictions for Video Coding Efficiency
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Solution Overview
Problem
Current video coding technologies face challenges in achieving efficient compression and decompression of video data, particularly in limited bandwidth scenarios and storage devices, with a need for improved compression ratios without compromising picture quality.
Innovation Solution
The method involves determining control point motion vectors for affine inter-prediction in video encoding and decoding, using pixel-based motion vector fields under specific conditions to perform motion compensation, and applying Enhanced bi-linear Interpolation Filter (EIF) for improved coding efficiency, especially in hardware implementations with limited buffers and sequential memory access requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel-based motion vector field is used for affine inter-prediction, then coding efficiency is improved, but number of fetched reference lines increases
Solution Approach 1:
The current block is divided into multiple sub-blocks, and motion compensation is performed separately for each sub-block using its own motion vector. This segmentation allows the system to process smaller regions independently, reducing the number of reference lines that need to be fetched at once while maintaining coding efficiency through localized motion compensation.
Solution Approach 2:
Different motion vectors are applied to different sub-blocks within the current block, allowing each sub-block to have optimized motion compensation parameters. This local quality approach improves overall coding efficiency by adapting to local motion characteristics while limiting the reference line fetch requirements for each sub-block processing.
2Productivity
If Enhanced bi-linear Interpolation Filter (EIF) is applied, then motion compensation is simplified and coding efficiency improves, but hardware implementation complexity increases
Solution Approach 1:
The patent replaces complex 8/4-tap DCT-based interpolation filters with a simpler Enhanced bi-linear Interpolation Filter (EIF). This substitution maintains acceptable motion compensation quality while significantly reducing computational complexity and hardware implementation requirements, thereby improving coding efficiency in practical hardware systems.
3Speed
If sequential fetching of reference lines is implemented, then memory access efficiency improves, but buffer size requirements increase
Solution Approach 1:
By dividing the current block into sub-blocks and processing them sequentially, the system can fetch reference lines in a sequential manner for each sub-block. This segmentation approach allows memory access to be optimized for sequential patterns while keeping the buffer size manageable, as each sub-block processing only requires a limited portion of the reference picture.
Data Source
AI summary
A method for coding a video implemented in an encoder or a decoder, comprising: determining control point motion vectors, CPMVs, for a block according to affine inter-prediction, according to a preselected affine motion model, the block being an affine block; performing motion compensation for the block using a pixel-based motion vector field according to values of the CPMVs, upon fulfilling at least one of the following conditions: A) for a predefined size of a sub-block of M×M, during processing of one line, respectively, of the sub-block the number of lines of the reference picture is less than N, where N is an integer and N is larger than 2.