Refined Intra Prediction Angles for Non-Square Video Blocks
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Solution Overview
Problem
Existing video coding technologies face inefficiencies in intra prediction, particularly in handling non-square rectangles and non-standard angles, leading to suboptimal compression and reconstruction of video data.
Innovation Solution
Implement an angle-to-offset mapping lookup table using powers of two derivative values for refined intra prediction angles, allowing for more precise mapping of intra prediction angles, especially for non-square blocks, and incorporating delta angles to extend the range of available angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional intra prediction methods are used for non-square blocks, then device complexity is reduced, but manufacturing precision deteriorates due to suboptimal compression and reconstruction accuracy
Solution Approach 1:
The patent pre-calculates derivative values for various intra prediction angles and stores them in lookup tables before actual video decoding. This preliminary preparation allows the decoder to quickly retrieve pre-computed values instead of performing complex calculations in real-time, thereby improving reconstruction accuracy while maintaining low computational complexity during actual operation.
Solution Approach 2:
The patent replaces complex mathematical calculations (trigonometric functions for angle-based offset computation) with a lookup table system that uses simple array indexing and bit-shifting operations. This substitution of mechanical computation with data retrieval structures significantly reduces computational complexity while preserving or improving reconstruction accuracy through the use of pre-optimized derivative values.
2Manufacturing precision
If more intra prediction angles are provided for non-square blocks, then manufacturing precision improves, but device complexity increases due to larger lookup tables and more computation
Solution Approach 1:
The patent divides the intra prediction angle space into multiple segments or ranges, with different lookup tables or derivative value sets optimized for specific angle ranges and block shape categories. This segmentation allows the system to provide comprehensive angle coverage for high compression accuracy while keeping each individual lookup table compact and manageable in size.
Solution Approach 2:
The patent applies different derivative values and lookup table configurations locally according to specific block characteristics (square vs. non-square, different aspect ratios, different angle ranges). Rather than using a single large lookup table for all cases, the system selects and applies locally-optimized derivative values tailored to each block's specific geometry and prediction angle requirements.
3Productivity
If standard intra prediction angles are used, then ease of operation is maintained, but productivity deteriorates due to suboptimal compression efficiency
Solution Approach 1:
The patent enables the video decoding system to automatically select and apply the appropriate derivative values and lookup tables based on the block characteristics and prediction angle, without requiring manual configuration or complex control logic. The system self-adapts by using simple criteria (block shape, angle index) to retrieve the correct pre-computed values, thereby improving compression efficiency while maintaining ease of operation.
Solution Approach 2:
The patent changes the fundamental parameter representation from raw angle values requiring trigonometric calculations to discrete index values that directly map to pre-computed derivative values in lookup tables. This parameter transformation simplifies the operational complexity while enabling more precise and efficient compression through optimized derivative value selection for different block types.
Data Source
AI summary
Processing circuitry receives, from a coded video bitstream, coded information of a current coding block in a current picture. The coded information is indicative of a directional intra prediction of the current coding block. The processing circuitry determines an index to an entry in an angle-to-offset mapping lookup table according to the coded information of current coding block. The angle-to-offset mapping lookup table stores a set of derivative values that are associated with angles, the set of derivative values includes two or more integers that are powers of two. The processing circuitry accesses the entry to obtain a derivative value, determines, for a pixel in the current coding block, an offset indicative of a reference location in the current picture according to the derivative value and a location of the pixel, and reconstructs the pixel in the current coding block based on the reference location in the current picture.