Video Block Decoding with CTU and Transform Size Constraints
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Solution Overview
Problem
The existing video compression standards, such as HEVC, face challenges in efficiently encoding and decoding video data with varying chroma formats and resolutions, leading to inefficiencies in resource utilization and implementation costs, particularly in high-resolution and high-frame-rate video applications.
Innovation Solution
The VVC standard introduces a method for decoding image frames by constraining and determining transform and coding tree units based on fixed-length codewords, allowing for flexible subprofiling and reducing implementation complexity through early signaling of tool usage and block structure constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If video data is encoded using high-resolution and high-frame-rate formats, then video quality and detail are improved, but resource utilization efficiency deteriorates and implementation costs increase
Solution Approach 1:
The video data is divided into multiple blocks, with different chroma formats (4:2:0, 4:2:2, 4:4:4) applied to different blocks based on their importance. This segmentation allows critical blocks to maintain high quality while less critical blocks use more compressed formats, improving overall resource utilization efficiency while preserving video quality.
Solution Approach 2:
Different chroma sampling formats are applied locally to different blocks within the same video frame. Important blocks (e.g., containing facial features or motion) use 4:2:2 or 4:4:4 formats for high quality, while less important blocks use 4:2:0 format for better compression efficiency, achieving local optimization of both quality and resource usage.
2Adaptability or versatility
If multiple chroma formats are supported for different video blocks, then adaptability and versatility are improved, but device complexity increases
Solution Approach 1:
The encoder pre-processes each block to determine its importance and selects the appropriate chroma format before encoding. This preliminary classification and signaling of format selection simplifies the decoder's task, as it only needs to follow the pre-determined format assignments rather than making complex decisions, thereby reducing device complexity while maintaining versatility.
Solution Approach 2:
The system dynamically selects chroma formats based on block characteristics and content importance, allowing flexible adaptation to different video scenarios. This dynamic selection is controlled through efficient signaling mechanisms that adapt the chroma format per block without requiring complex reconfiguration of the entire decoding system, balancing adaptability with manageable device complexity.
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.