Motion Vector Entropy Coding Adaptation for Video Compression
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Solution Overview
Problem
Current video coding systems face inefficiencies in encoding and decoding motion vector information, particularly in scalable and multiview video coding, where the set of valid motion vector component values may be empty or smaller than usual, leading to challenges in entropy coding and motion vector prediction.
Innovation Solution
The proposed solution involves selecting a current block for encoding, determining a reference type or picture index, and encoding motion vector information based on the determined reference type or index, which allows for specialized entropy coding and motion vector derivation processes, including bypassing certain decoding steps and using context-adaptive binary arithmetic coding (CABAC) contexts tailored to the reference picture type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If specialized entropy coding is used for motion vectors based on reference picture type, then coding efficiency is improved, but device complexity increases
Solution Approach 1:
The patent applies different entropy coding strategies to different motion vector types based on their reference picture characteristics. For motion vectors referencing pictures with special motion vector fields, a simplified coding approach is used, while other motion vectors use standard CABAC contexts. This local differentiation improves overall coding efficiency without uniformly increasing complexity across all motion vectors.
Solution Approach 2:
The patent changes the parameters of the entropy coding process based on the reference picture type. When a reference picture is identified as having a special motion vector field, the coding parameters are adjusted to bypass certain decoding steps and use derived motion vectors, thereby improving efficiency while managing complexity through conditional parameter selection.
2Device complexity
If motion vector prediction is bypassed for certain reference pictures, then decoding complexity is reduced, but measurement precision of motion vectors may be affected
Solution Approach 1:
The patent performs preliminary identification of reference pictures with special motion vector fields before the motion vector decoding process. By pre-classifying reference pictures and preparing derived motion vector values in advance, the system can bypass complex prediction steps during actual decoding, reducing complexity while maintaining precision through pre-computed accurate values.
Solution Approach 2:
The patent introduces an intermediary mechanism where motion vectors for pictures with special fields are derived through a specific process rather than direct prediction. This intermediary derivation process acts as a bridge, allowing the system to bypass standard prediction while still obtaining accurate motion vector values, thus balancing complexity reduction with precision maintenance.
3Productivity
If the set of valid motion vector values is restricted for certain reference pictures, then coding efficiency is improved, but adaptability of motion vector encoding is reduced
Solution Approach 1:
The patent implements dynamic adaptability by allowing the motion vector coding strategy to change based on the reference picture type. For standard reference pictures, the full range of motion vector values and coding methods is available, providing high adaptability. For pictures with special motion vector fields, the system dynamically switches to a restricted but more efficient coding mode, thus achieving both efficiency improvement and adaptability preservation through conditional behavior.
Data Source
AI summary
Methods, apparatus and computer program products are provided in which a set of valid motion vector values for encoding and decoding may depend on a reference picture used. A current block of a frame is selected for encoding, and a reference block for the current block is selected. On the basis of the selected reference block a reference type is determined. On the basis of the reference type and the reference block a motion vector for the current block is determined. Motion vector information is encoded and decoded on the basis of the determined motion vector.