Motion Vector Resolution Control in Video Coding
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Solution Overview
Problem
The existing High Efficiency Video Coding (HEVC) system faces issues with adaptive motion vector resolution, particularly in the Intra-block copy (IntraBC) mode and inter prediction mode, leading to resolution mismatches and challenges in Decoded Picture Buffer (DPB) management when blocks in a slice are coded.
Innovation Solution
The proposed solution involves signaling a resolution indicator for integer or fractional-pel resolution for motion vectors and block vectors, converting vectors to appropriate resolutions for storage and prediction, and managing DPB by ensuring the current picture is treated as the only reference picture or using a unified resolution for both vectors within a slice.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If adaptive motion vector resolution is used to allow both integer and fractional-pel resolution, then coding efficiency is improved, but resolution mismatches occur between motion vectors and block vectors
Solution Approach 1:
The patent applies local quality by allowing different resolution types (integer and fractional-pel) to coexist in different regions or contexts within the video coding process. Motion vectors can be at fractional-pel resolution for high precision while block vectors remain at integer resolution, with the system adapting locally to each vector type's requirements rather than enforcing a single global resolution standard.
Solution Approach 2:
The patent changes the resolution parameter of motion vectors adaptively, allowing them to switch between integer and fractional-pel resolutions based on coding conditions. This parameter change enables the system to optimize coding efficiency by using higher precision fractional-pel resolution when beneficial, while maintaining compatibility through integer resolution when appropriate.
2Device complexity
If the current picture is treated as the only reference picture in DPB management, then memory management is simplified, but flexibility in reference picture selection is reduced
Solution Approach 1:
The patent segments the reference picture management into distinct cases: when the current picture is the only reference picture available versus when multiple reference pictures are available. This segmentation allows the system to apply simplified management rules in the first case and more flexible rules in the second case, resolving the contradiction between simplicity and adaptability.
Solution Approach 2:
The patent introduces dynamic behavior in DPB management by allowing the system to adapt its reference picture selection strategy based on availability. When only the current picture is available, the system dynamically simplifies to using only that reference. When multiple references are available, it dynamically enables broader selection, thus achieving both simplicity when needed and flexibility when possible.
3Ease of manufacture
If block vectors are always at integer resolution while motion vectors can be at fractional-pel resolution, then IntraBC mode is simpler to implement, but resolution mismatches arise during prediction
Solution Approach 1:
The patent introduces an intermediary conversion process that mediates between block vectors at integer resolution and motion vectors at fractional-pel resolution. When block vectors need to be used in contexts requiring fractional precision, the system applies interpolation or scaling as an intermediary step to convert them, thus maintaining both the simplicity of integer-based block vectors and the precision requirements of fractional-pel prediction.
Data Source
AI summary
A method of video coding using coding modes including IntraBC mode (Intra-block copy mode) and inter prediction mode is disclosed. In one embodiment, when adaptive motion vector resolution is selected to allow adaptive use of integer resolution or fractional-pel resolution, a resolution indicator having a value corresponding to using integer resolution for all motion vectors and all block vectors is signaled in the current. In another embodiment, if a coded block is coded in the inter prediction mode or the IntraBC mode, the coded MV or BV is converted to a converted MV or BV having fractional-pel resolution if a resolution indicator for the coded block specifies integer resolution. The system then stores the converted MV or BV for encoding or decoding of subsequent blocks.