VVC Block Decoding Constraints for CTU and Transform Size Control
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Solution Overview
Problem
Existing video coding standards face challenges in efficiently decoding video frames due to the complexity and variability of block structures, particularly in versatile video coding (VVC), which can lead to increased implementation costs and resource utilization.
Innovation Solution
Implementing a method for decoding video frames by constraining and signaling the maximum transform and coding tree unit sizes using fixed-length codewords, allowing for efficient decoding by determining the appropriate block sizes based on decoded constraints from the bitstream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If video coding standards use complex and variable block structures to improve compression performance, then compression efficiency is improved, but device complexity and implementation cost increase
Solution Approach 1:
The patent applies parameter changes by introducing constraint parameters (max_transform_block_size_constraint, max_coding_tree_unit_size_constraint) that limit the range of block sizes used in video coding. By constraining these parameters to specific values or ranges, the implementation complexity is reduced while maintaining acceptable compression efficiency. The encoder and decoder agree on these constraints, allowing for simplified hardware or software implementations.
Solution Approach 2:
The patent segments the video coding process by dividing it into different constraint levels. The general constraint information syntax provides overarching limitations, while specific transform block and coding tree unit constraints provide finer-grained control. This segmentation allows different parts of the system to operate with appropriate levels of complexity.
2Adaptability or versatility
If video coding standards support a wide range of block sizes for versatility, then adaptability is improved, but resource utilization increases
Solution Approach 1:
The patent introduces dynamic constraints that can be adjusted based on the specific video content and application requirements. The constraint parameters can be modified to allow more or fewer block sizes depending on the desired balance between versatility and resource usage. This dynamic approach allows the system to adapt to different scenarios without requiring support for all possible block sizes simultaneously.
Solution Approach 2:
The patent applies partial action by implementing a subset of the full range of block sizes defined in the video coding standard. Rather than supporting all possible block sizes, the system selectively supports only those needed for the target application, reducing resource utilization while maintaining sufficient coding versatility.
3Adaptability or versatility
If variable-length codewords are used for signaling block sizes, then encoding flexibility is improved, but decoding complexity increases
Solution Approach 1:
The patent uses fixed-length codewords for signaling constraint parameters, which are simpler and more efficient than variable-length codewords. While variable-length codewords might provide slightly more encoding flexibility, the fixed-length approach significantly reduces decoding complexity and is sufficient for the constraint signaling requirements. The simplicity of fixed-length coding outweighs the minor loss in flexibility.
Data Source
AI summary
Decoding an image frame from a bitstream, the image frame being divided into a plurality of coding tree units. The method comprises decoding a maximum transform block size constraint and or a maximum coding tree unit (CTU) size constraint from the bitstream; and decoding a maximum enabled transform block size and/or a maximum enabled CTU size from the bitstream. The decoded maximum enabled transform block size is less than or equal to the decoded maximum transform block size constraint. The decoded maximum enabled CTU size is less than or equal to the decoded maximum CTU size constraint. Determining each of the one or more transform blocks for each of the plurality of coding tree units according to the decoded maximum enabled transform block size, maximum enabled CTU and split flags decoded from the bitstream; and decode each of the determined one or more transform blocks from the bitstream.