Intra Block Copy Buffer Default Value Refreshing
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Solution Overview
Problem
Current video coding technologies face challenges in achieving improved compression ratios with minimal sacrifice in picture quality, especially when dealing with limited network resources and increasing demands for higher video quality, due to constraints in bitstream conformance and memory usage in intra block copy (IBC) referencing.
Innovation Solution
The implementation of a dedicated buffer for IBC referencing, initialized to a default value, which removes block vector validation bitstream conformance constraints, allowing for robustness in coded bitstreams and avoiding undefined samples, thereby eliminating the need for additional memory and bitstream conformance checks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated buffer for IBC referencing is implemented with default value initialization, then robustness of coded bitstream is improved and undefined samples are avoided, but device complexity increases due to additional buffer management
Solution Approach 1:
The buffer is initialized to default values (e.g., -1) before use, so that when IBC block vectors point to positions before the current CTU row, they automatically reference valid default values rather than undefined memory. This preliminary initialization prevents bitstream conformance errors and eliminates the need for additional validation checks during decoding.
2Reliability
If block vector validation bitstream conformance constraints are removed, then decoding robustness is improved and undefined samples are avoided, but manufacturing precision deteriorates due to relaxed conformance requirements
Solution Approach 1:
Instead of treating out-of-range block vectors as errors requiring validation and correction, the patent converts this potential harm into a benefit by designing the buffer with default values that automatically provide valid reference samples. This eliminates the need for complex validation logic while maintaining or improving decoding robustness.
3Adaptability or versatility
If additional line memory is allocated for IBC prediction, then IBC referencing capability is improved, but memory requirements increase
Solution Approach 1:
The dedicated buffer serves multiple functions: it stores IBC reference samples, provides default values for out-of-range accesses, and eliminates the need for separate validation structures. This multi-functionality achieves robust IBC referencing without requiring additional line memory beyond the buffer itself.
Data Source
AI summary
A method of coding implemented by a decoding device, comprising initializing a dedicated buffer for intra block copy (IBC) referencing, when a current coding tree unit (CTU) to be decoded is a first CTU of a CTU row, determining whether a current block in the current CTU is predicted using IBC mode, obtaining an IBC block vector for the current block when the current block is predicted using IBC mode, and obtaining predicted sample values for the current block, based on reference samples from the dedicated buffer and the IBC block vector for the current block.