Flexible CTU Edge Partitioning for Boundary-Aligned Video Coding
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Solution Overview
Problem
Modern video coding standards like H.264/AVC, HEVC, VVC, and AV1 face inefficiencies in picture partitioning, particularly when object boundaries are not aligned with fixed partitioning, requiring more bits to signal boundaries and motion, leading to increased data usage.
Innovation Solution
The method involves partitioning a coded picture into coding tree units (CTUs) where CTUs adjacent to the picture boundaries have smaller dimensions than those not adjacent, allowing for adaptive signaling and restricting splitting types based on predetermined size thresholds to optimize bit usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If fixed-size CTU partitioning is used for all pictures, then decoding simplicity is maintained, but bit usage increases when object boundaries are misaligned with partitioning grid
Solution Approach 1:
The patent implements dynamic CTU row height adjustment by introducing syntax elements (ctu_row_height_minus1, first_ctu_row_height, last_ctu_row_height) that allow the encoder to signal varying row heights in the CTU partitioning structure. This enables the partitioning grid to adapt to object boundaries, reducing the need for additional bits to signal misaligned boundaries while maintaining a structured decoding process.
Solution Approach 2:
The patent applies different CTU row heights to different regions of the picture based on local content requirements. Specifically, rows adjacent to object boundaries can have reduced heights to align with the boundary, while other rows maintain standard heights. This localized adaptation optimizes bit usage without requiring complete restructuring of the partitioning system.
2Loss of information
If CTU rows adjacent to boundaries have smaller dimensions, then bit usage is reduced for signaling boundaries, but decoding complexity increases due to variable size handling
Solution Approach 1:
The patent performs preliminary signaling of CTU row height configuration through syntax elements in the bitstream before actual decoding occurs. The encoder signals ctu_row_height_minus1 and related parameters that define the vertical sizes of CTU rows, allowing the decoder to pre-compute the partitioning structure and handle variable sizes systematically, reducing the operational complexity during the actual decoding process.
Solution Approach 2:
The patent modifies the CTU partitioning parameters by introducing variable row heights through syntax elements. Instead of using a fixed CTU size throughout the picture, the system allows the height parameter to change for specific rows, particularly those adjacent to boundaries. This parameter flexibility enables more efficient boundary representation while maintaining a standardized decoding framework.
3Productivity
If uniform CTU size is used throughout the picture, then encoding simplicity is maintained, but efficiency decreases when object boundaries require non-uniform partitioning
Solution Approach 1:
The patent segments the picture into CTU rows with different heights based on boundary requirements. By dividing the picture structure into variable-height rows rather than uniform blocks, the system can better align partitioning with object boundaries. This segmentation approach improves encoding efficiency by reducing the number of bits needed to signal boundary positions while introducing a more complex partitioning structure that requires additional syntax elements.
Data Source
AI summary
Systems and methods may provide flexible picture partitioning, a method includes receiving a coded picture that is partitioned into a plurality of coding tree units (CTUs), wherein at least one row or column of CTUs, among the plurality of CTUs of the coded picture, that is adjacent to a boundary of the coded picture has a size dimension that is smaller than a corresponding size dimension of each CTU among the plurality of CTUs that is not adjacent to any boundary of the coded picture; and decoding the coded picture based on the plurality of CTUs, wherein the at least one row or column of CTUs includes a first CTU row or a first CTU column of the coded picture that is adjacent to a top boundary or left boundary of the coded picture, respectively.