Video Deblocking Filter Edge Decision Logic
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Solution Overview
Problem
Current deblocking decision processes in video coding, such as those in the VVC Draft Specification, can lead to over-filtering of natural structures on lines 1 and 2 due to checks only on line 0 and 3, resulting in unnecessary modification of samples across a 4-sample boundary segment.
Innovation Solution
Proposed method involves checking all lines of a 4-sample boundary segment before applying a deblocking filter that can modify more than three samples, ensuring that the long deblocking decision process requires all decision variables from different lines to be equal, thereby avoiding over-filtering on lines 1 and 2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If deblocking filter checks only line 0 and line 3 for a 4-sample boundary segment, then the complexity of the deblocking decision process is reduced, but natural structures on lines 1 and 2 may be incorrectly removed causing over-filtering
Solution Approach 1:
The patent divides the 4-sample boundary segment into four separate lines (line 0, line 1, line 2, line 3) and performs independent gradient calculations for each line. This segmentation allows the system to check each line individually for natural structures, preventing over-filtering while maintaining manageable computational complexity through structured processing.
Solution Approach 2:
The patent performs gradient calculations and edge decisions for all four lines (0, 1, 2, 3) before applying the deblocking filter. By conducting these preliminary checks on all lines including 1 and 2, the system identifies natural structures in advance and prevents incorrect filtering, ensuring accurate deblocking decisions are made before the actual filtering operation.
2Strength
If deblocking filter applies strong filtering based on limited line checks, then the filtering strength increases, but natural structures on lines 1 and 2 are removed causing visual artifacts
Solution Approach 1:
The patent uses gradient calculations to provide feedback about the presence of natural structures on each line. The gradient values indicate whether edges or important structures exist, and this feedback controls whether strong filtering should be applied. By checking all four lines and using their gradient feedback, the system avoids applying strong filtering when natural structures are present on any line, preventing visual artifacts while maintaining filtering strength where appropriate.
Data Source
AI summary
A method (400) for filtering luma block edges. The method includes assigning a value to a first decision variable by performing a block edge decision process using a first set of input samples; assigning a value to a second decision variable by performing the block edge decision process using a second set of input samples; assigning a value to a third decision variable by performing the block edge decision process using a third set of input samples; and assigning a value to a fourth decision variable by performing the block edge decision process using a fourth set of input samples. The method also includes determining that a long filter condition is satisfied. The method also includes, as a result of determining that the long filter condition is satisfied, performing a filtering process for the first set of input samples, the second set of input samples, the third set of input samples and the fourth set of input samples, using a long filter to produce a first set of output samples, a second set of output samples, a third set of output samples and a fourth set of output samples. The long filter condition is satisfied if and only if: the value of the first decision variable is equal to a first value, the value of the second decision variable is equal to the first value, the value of the third decision variable is equal to the first value, and the value of the fourth decision variable is equal to the first value.