Block Vector Clipping for Screen Content Video Coding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In High Efficiency Video Coding (HEVC) systems, the Intra-block copy (IntraBC) mode faces challenges when dealing with unavailable or invalid block vectors, as they can point to unreconstructed areas, leading to inefficient video coding and decoding processes.
Innovation Solution
The method involves clipping the original block vector to create a valid clipped block vector that ensures the reference block is either above or to the left of the current coding unit, or using replacement pixel data to make unavailable reference pixels available for Intra-block copy compensation, thereby preventing invalid block vectors and ensuring valid prediction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If block vector prediction is used for IntraBC mode, then coding efficiency is improved, but invalid block vectors pointing to unreconstructed areas cause decoding failures
Solution Approach 1:
The patent applies preliminary action by checking the validity of block vectors before using them for prediction. The system determines whether a block vector points to a valid reconstructed area prior to performing IntraBC mode decoding, and only proceeds with prediction if the vector is valid, thus preventing decoding failures while maintaining efficiency gains
Solution Approach 2:
The patent introduces an intermediary validation mechanism that acts as a mediator between block vector prediction and the actual prediction process. This intermediary checks the validity of referenced pixels and blocks, allowing the system to maintain high coding efficiency through prediction while ensuring reliability by preventing use of invalid vectors
2Reliability
If block vector clipping is applied to ensure valid reference blocks, then prediction reliability is improved, but processing complexity increases
Solution Approach 1:
The patent applies local quality by implementing block vector clipping that is selectively applied only when necessary. The system determines locally whether a block vector needs clipping based on the specific conditions of each prediction unit, rather than applying a uniform complex processing to all cases, thus maintaining simplicity where possible while ensuring validity where needed
3Productivity
If replacement pixel data is used for unavailable reference pixels, then IntraBC mode can proceed, but coding accuracy may be compromised
Solution Approach 1:
The patent applies beforehand cushioning by preparing replacement pixel data in advance for situations where reference pixels are unavailable. The system pre-establishes alternative pixel values that can be used as substitutes, allowing IntraBC mode to continue processing without interruption while maintaining acceptable prediction accuracy through these pre-prepared replacement values
Data Source
AI summary
A method of video coding using coding modes including IntraBC mode (Intra-block copy mode) for a picture is disclosed. The system determines whether the current reference block is located above a current coding unit (CU) containing the current prediction unit (PU) in a vertical direction and whether the current reference block is located on a left side of the current CU in a horizontal direction based on the original block vector (BV). If both results are not true, the original BV is clipped to a clipped BV so that a relocated reference block corresponding to the clipped BV is above the current CU in the vertical direction or to the left side of the current CU in the horizontal direction. The clipped BV is used as a predictor for encoding or decoding of a current BV or used for IntraBC encoding or decoding of the current PU.