Block Vector Prediction with Default Predictors in Intra-Block Copy Coding
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Solution Overview
Problem
The HEVC standard's intra block copy (BC) prediction mode inefficiently signals block vector (BV) values and fails to effectively handle blocks with predictable displacements, leading to suboptimal coding efficiency.
Innovation Solution
Implementing a default BV predictor with a non-zero value, using skip mode with predicted BV values, and employing merge mode for BV prediction to enhance coding efficiency by reducing bit rate and improving quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If intra BC prediction mode is implemented with standard BV signaling, then prediction functionality is provided, but coding efficiency is suboptimal due to inefficient BV value signaling
Solution Approach 1:
The patent applies preliminary action by establishing default BV predictors (such as vertical, horizontal, or diagonal direction vectors) before actual encoding occurs. These default predictors are pre-defined based on block position and size, allowing the encoder to directly use or modify them without complex calculations, thereby improving coding efficiency while maintaining simple signaling.
Solution Approach 2:
The patent changes parameters by introducing multiple default BV predictor types (vertical, horizontal, diagonal) with different non-zero component configurations. The encoder selects and signals only the necessary predictor type and differential values, transforming the signaling from transmitting complete BV pairs to transmitting compact predictor indices and small differential adjustments, thus improving efficiency.
2Reliability
If BV values are signaled for every block, then accurate prediction is achieved, but bit rate increases due to redundant signaling of predictable displacements
Solution Approach 1:
The patent uses copying by creating default BV predictors that replicate common displacement patterns (vertical, horizontal, diagonal movements) based on block characteristics. Instead of signaling actual BV values for every block, the encoder copies the appropriate default predictor and only signals small differential values when the actual BV deviates from the default, significantly reducing bit rate while maintaining prediction accuracy.
Solution Approach 2:
The patent extracts only the essential deviation information from the actual BV values. By separating the predictable portion (handled by default predictors) from the unpredictable portion (represented by differentials), the system extracts and signals only the necessary differential values, reducing the quantity of signaled data while preserving prediction accuracy.
3Productivity
If default BV predictor with non-zero value is used, then coding efficiency improves for blocks with predictable displacement, but complexity increases in determining and signaling the predictor type
Solution Approach 1:
The patent applies local quality by making the default BV predictor selection dependent on local block characteristics such as position within the picture and block size. Different default predictors (vertical, horizontal, diagonal) are assigned based on the specific local context of each block, allowing the system to adapt to local patterns while using simple, deterministic rules for selection, thus improving efficiency without excessive complexity.
Data Source
AI summary
Innovations in the area of prediction of block vector (“BV”) values improve encoding or decoding of blocks using intra block copy (“BC”) prediction. For example, some of the innovations relate to use of a default BV predictor with a non-zero value. Other innovations relate to use of a selected one of multiple BV predictor candidates for a current block. Still other innovations relate to use of a skip mode in which a current intra-BC-predicted block uses a predicted BV value.