Motion-Compensated Bi-Prediction With Local Illumination Compensation
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Solution Overview
Problem
Existing video coding systems struggle to effectively address local illumination changes among temporal neighboring pictures, which can degrade video quality.
Innovation Solution
Implementing local illumination compensation (LIC) parameters based on bi-predicted reference template samples to adjust samples for current coding units, using a least mean square error approach to minimize differences and apply these parameters during overlapped block motion compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional motion compensation is used, then video compression is achieved, but local illumination changes between temporal neighboring pictures cause quality degradation
Solution Approach 1:
The patent introduces local illumination compensation (LIC) parameters including a scaling factor and an offset value that are dynamically calculated and applied to reference template samples. These parameters transform the reference samples to compensate for local illumination changes between temporal neighboring pictures, thereby maintaining video quality while addressing the harmful effect of illumination variations.
Solution Approach 2:
The patent applies local illumination compensation at the block or sub-block level rather than globally. By calculating LIC parameters for specific local regions and applying them selectively to corresponding reference template samples in those regions, the method addresses local illumination changes without affecting the entire picture, thus preserving video quality in affected areas while maintaining compression efficiency elsewhere.
2Measurement precision
If LIC parameters are calculated using bi-predicted reference template samples, then illumination compensation accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent performs bi-prediction of reference template samples before calculating the LIC parameters. By pre-computing the bi-predicted reference samples and storing them in a buffer, the system prepares the necessary data in advance, which simplifies the subsequent parameter calculation process and reduces the overall computational burden during video decoding.
Solution Approach 2:
The patent introduces bi-predicted reference template samples as an intermediary step between the original reference samples and the final LIC parameter calculation. These intermediate samples serve as a bridge that enables more accurate illumination compensation by combining information from multiple temporal references, while the buffering mechanism manages the computational complexity by organizing data processing in manageable stages.
Data Source
AI summary
Systems, methods, and instrumentalities are described herein for calculating local illumination compensation (LIC) parameters for bi-predicted coding unit (CU). The LIC parameters may be used to generate adjusted samples for the current CU and to address local illumination changes that may exist among temporal neighboring pictures. LIC parameters may be calculated based on bi-predicted reference template samples and template samples for a current CU. Bi-predicted reference template samples may be generated based on reference template samples neighboring temporal reference CUs. For example, the bi-predicted reference template samples may be generated based on averaging the reference template samples. The reference template samples may correspond to template samples for the current CU. A CU may be or may include a coding block and/or a sub-block that may be derived by dividing the coding block.