Virtual Prediction Buffer for Intra Block Copy Video Coding
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Solution Overview
Problem
Current video coding technologies face challenges in efficiently managing buffers and block vectors for intra block copy mode, leading to complex encoding and decoding processes, invalid block vectors, inefficient coding, and handling of CTU sizes smaller than 128x128, particularly in determining valid block vectors for chroma blocks due to dual tree partition structures.
Innovation Solution
The implementation of a regular buffer for intra block copy (IBC) mode to store reference samples, with defined block vectors and bitstream conformance constraints, ensures valid block vectors and efficient coding by maintaining a virtual buffer to track reference samples and using predefined bit-depths for pixel storage, allowing for adaptive reference area selection based on current block locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a virtual buffer is used to track reference samples for intra block copy mode, then coding efficiency is improved and complexity is reduced, but buffer management complexity increases
Solution Approach 1:
The patent introduces a virtual buffer as an intermediary data structure that tracks reference sample availability without requiring physical buffer allocation. This virtual buffer acts as a mediator between the block vector validation process and the actual reference sample storage, simplifying the encoding/decoding logic while maintaining coding efficiency through proper reference sample management
Solution Approach 2:
The patent uses a virtual copy of the buffer state (virtual buffer) to track reference sample availability. Instead of managing complex physical buffer allocations, the system creates a virtual representation that mirrors the buffer state, allowing efficient validation of block vectors without the overhead of actual buffer management operations
2Ease of manufacture
If block vector validity is made independent of sample block location and reconstruction status, then encoding simplicity is improved, but reference sample availability accuracy may be compromised
Solution Approach 1:
The patent segments the block vector validation process into two independent parts: (1) geometric validity checking based on block vector components alone, and (2) reference sample availability checking using the virtual buffer. This segmentation allows the encoding logic to be simplified by checking only geometric constraints initially, while the virtual buffer independently tracks actual sample availability, ensuring both simplicity and accuracy
Solution Approach 2:
The patent performs preliminary tracking of reference sample availability in the virtual buffer before actual block vector validation. By pre-establishing the virtual buffer state that reflects which reference samples are available, the encoding process can simply check block vectors against this pre-computed state without complex conditional logic during the validation phase
3Quantity of substance
If a regular buffer stores reference samples with predefined bit-depths, then memory efficiency is improved, but flexibility in handling various CTU sizes is reduced
Solution Approach 1:
The patent uses parameter changes by allowing the virtual buffer to dynamically adapt its tracking scope based on CTU size parameters. The actual buffer storage maintains fixed bit-depth definitions for memory efficiency, while the virtual buffer adjusts which regions it tracks based on the current CTU configuration, achieving both memory efficiency and adaptability through parameter-driven behavior changes
Data Source
AI summary
A method of visual media processing method includes performing a conversion between a current video block of a current picture of a visual media data and a bitstream representation of the visual media data. The conversion is based on a reference region from the current picture comprising reference samples used for deriving a prediction block of the current video block. A virtual buffer of a defined size is used for tracking availability of the reference samples for deriving the prediction block.