Intra Block Copy Buffer Validation for Video Coding Efficiency
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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 encoder/decoder processing, 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 methods to validate block vectors and adjust reference areas, including normalization and clipping to ensure valid references within the buffer bounds, and dynamic buffer updates for efficient prediction and reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a regular buffer is used to store reference samples for intra block copy mode, then the complexity of encoder/decoder processing is reduced and coding efficiency is improved, but the buffer management and block vector validation become more complex
Solution Approach 1:
The patent divides the reference buffer into separate components: a regular buffer for storing reference samples and separate validation logic for block vectors. This segmentation allows the buffer to be used efficiently for coding while the complexity of validation is isolated to specific functions, reducing overall processing complexity.
Solution Approach 2:
The patent introduces an intermediary validation mechanism that checks whether reference locations fall within buffer bounds before accessing reference samples. This intermediary layer simplifies buffer management by handling boundary conditions separately from the main coding process.
2Reliability
If block vector validation is performed to ensure valid references, then coding accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent performs block vector validation as a preliminary action before using reference samples in the intra block copy mode. By validating block vectors in advance and storing validation results, the system ensures coding accuracy while reducing the complexity of repeated validation during processing.
Solution Approach 2:
The validation mechanism uses the block vector components and buffer dimensions to self-determine validity without requiring complex external checks. The system serves itself by using readily available parameters (block vector components, buffer bounds) to perform validation.
3Measurement precision
If reference locations are computed using block vector and sample location, then prediction accuracy is improved, but the risk of out-of-bounds access increases
Solution Approach 1:
The patent applies preliminary anti-action by computing reference locations and then immediately checking whether they fall within buffer bounds before accessing reference samples. This preventive approach maintains prediction accuracy while avoiding harmful out-of-bounds access through early validation.
Solution Approach 2:
The patent converts the potential harm of out-of-bounds access into a benefit by using the boundary check information to improve validation logic. When reference locations fall outside bounds, the system uses this information to invalidate block vectors appropriately, turning a potential error into a useful validation mechanism.
4Manufacturing precision
If normalization and clipping are applied to block vector components, then valid references are ensured, but processing steps increase
Solution Approach 1:
The patent applies parameter changes by normalizing and clipping block vector components to ensure they fall within valid ranges. These parameter transformations maintain reference location accuracy while using simple, standardized operations that can be efficiently implemented.
Data Source
AI summary
A method of visual media processing includes determining, for a conversion between a current video block of visual media data and a bitstream representation of the current video block, a buffer that stores reference samples for prediction in an intra block copy mode; for a sample spatially located at location of the current video block relative to an upper-left position of a coding tree unit including the current video block and having a block vector, computing a corresponding reference in the buffer at a reference location, wherein the reference location is determined using the block vector and the location; and upon determining that the reference location lies outside the buffer, re-computing the reference location based at least in part on a location of the current video block relative to the coding tree unit including the current video block.