Intra-frame Prediction Coding Mode Selection
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Solution Overview
Problem
The High Efficiency Video Coding (HEVC) standard's rate distortion optimization (RDO) process is computationally intensive due to the large number of coding modes, leading to inefficient calculations, particularly in the fine selection stage of intra-frame prediction coding, where many calculated modes are not used as the optimal mode, reducing coding efficiency.
Innovation Solution
An intra-frame prediction coding method that determines candidate modes for a current coding block and neighboring blocks, saving them in lists to adaptively skip unnecessary RDO calculations, thereby reducing computational load and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rate distortion optimization (RDO) is performed for every possible coding mode, then coding accuracy is improved, but calculation amount increases exponentially
Solution Approach 1:
The patent divides the coding modes into two separate stages: coarse selection stage and fine selection stage. In the coarse selection stage, a simplified SATD algorithm is used to quickly identify the most probable optimal mode. In the fine selection stage, a fine RDO algorithm is applied only to the selected modes. This segmentation reduces the calculation amount while maintaining coding accuracy.
Solution Approach 2:
The patent performs preliminary action by using the simplified SATD algorithm in the coarse selection stage to pre-identify the most probable optimal mode before applying the computationally intensive fine RDO algorithm. This preliminary filtering ensures that RDO calculations are only performed on the most promising modes, reducing overall calculation amount while maintaining accuracy.
2Productivity
If fine RDO algorithm is applied to all candidate modes, then compression efficiency is maintained, but coding time increases
Solution Approach 1:
The patent applies partial action by using the fine RDO algorithm only on the most probable optimal mode identified in the coarse selection stage, rather than applying it to all candidate modes. This selective application maintains compression efficiency for the most important modes while significantly reducing coding time.
Solution Approach 2:
The patent implements skipping by allowing the coarse selection stage to quickly identify the most probable optimal mode using the simplified SATD algorithm, then rushing through the fine selection stage by applying fine RDO only to this selected mode. Modes at the end of the candidate list are skipped, as their probability of being the optimal mode is rather low.
Data Source
AI summary
An intra-frame prediction coding method includes determining N candidate intra-frame prediction modes for a current coding block, and saving the N candidate intra-frame prediction modes to a candidate mode list, N being a positive integer. The method also includes obtaining, by processing circuitry of a coder, optimal coding modes respectively corresponding to spatially neighboring coding blocks and an upper-layer coding block of the current coding block, and saving the optimal coding modes respectively corresponding to the spatially neighboring coding blocks and the upper-layer coding block to a neighboring mode list. The method further includes determining an optimal coding mode for the current coding block based on the candidate mode list and the neighboring mode list.