Subblock IBC Prediction Switching for Video Decoding Accuracy
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Solution Overview
Problem
Existing encoding methods for coding units with an intra block copy (IBC) mode suffer from high search costs and reduced prediction accuracy due to uniform intra prediction modes across subblocks, leading to inefficient compression performance.
Innovation Solution
The method extends the block vector (BV) function to allow nesting of another intra prediction mode, such as vertical, angle, or DC prediction, into the IBC mode, determining its use based on subblock characteristics, reducing search costs and improving prediction accuracy without increasing bit rate or search area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a same intra prediction mode is used for all subblocks in the coding unit, then the device complexity is reduced, but the prediction accuracy deteriorates
Solution Approach 1:
The coding unit is divided into multiple subblocks, and each subblock is allowed to use different intra prediction modes independently. This segmentation enables tailored prediction for different texture directions and content characteristics within each subblock, improving overall prediction accuracy without requiring complex global optimization
Solution Approach 2:
Different intra prediction modes are assigned to different subblocks based on their local content characteristics, such as texture directions. This local optimization ensures that each subblock uses the most appropriate prediction mode for its specific features, enhancing prediction accuracy while maintaining manageable device complexity
2Measurement precision
If the search area is increased for IBC prediction, then the prediction accuracy is improved, but the loss of time increases
Solution Approach 1:
The coding unit is segmented into multiple subblocks, each independently processed with IBC prediction. This allows the search to be performed on smaller subblock regions rather than the entire coding unit, reducing the overall search time while maintaining prediction accuracy through fine-grained processing
Solution Approach 2:
IBC prediction is applied selectively to subblocks that benefit from it, rather than uniformly to the entire coding unit. This partial application reduces the total search area and time required, while still achieving improved prediction accuracy where needed
3Measurement precision
If different intra prediction modes are used for different subblocks, then the prediction accuracy is improved, but the device complexity increases
Solution Approach 1:
The coding unit is divided into multiple subblocks that can independently use different intra prediction modes. This segmentation simplifies the overall system architecture by allowing independent, simple decision-making for each subblock rather than requiring complex global optimization across the entire coding unit
Solution Approach 2:
Different intra prediction modes are applied only to subblocks where they provide benefit, rather than forcing uniform complexity across all subblocks. This selective application reduces the overall device complexity while maintaining high prediction accuracy where needed
Data Source
AI summary
A decoding method includes receiving a bitstream; parsing a block vector (BV) of a current subblock from the bitstream, where a prediction mode of a coding unit (CU) of the current subblock is an intra block copy (IBC) mode; determining, for the current subblock based on the BV, whether to use a first intra prediction mode to replace the IBC mode; performing an intra prediction on the current subblock to obtain a predicted value of the current subblock when the first intra prediction mode is to be used to replace the IBC mode; performing an IBC prediction on the current subblock based on the BV to obtain the predicted value when the first intra prediction mode is not to be used to replace the IBC mode; and reconstructing the current subblock based on the predicted value to obtain a reconstructed block of the current subblock.