Coding Mode Signaling for Small Video Blocks
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Solution Overview
Problem
Current video coding technologies face challenges in efficiently encoding and decoding small blocks, particularly in determining the appropriate prediction mode for blocks sized 4×4 luma samples, which affects compression efficiency and bandwidth usage.
Innovation Solution
The method involves determining whether a current block is coded in intra block copy (IBC) mode based on prediction information, and if not, checking its size threshold to decide on intra prediction mode, with specific flags and sequence parameter sets guiding the decoding process to optimize coding mode signaling for small blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If intra prediction mode is used for small blocks (4×4 luma samples), then compression efficiency is improved, but signaling complexity increases
Solution Approach 1:
The patent extracts the IBC mode determination from the general prediction mode decision process by introducing a dedicated IBC flag. This separates the IBC mode signaling path from other intra prediction modes, allowing small blocks to be handled with a simple flag check rather than complex mode selection, thereby reducing signaling complexity while maintaining compression efficiency.
Solution Approach 2:
The patent applies different coding strategies to different block sizes. For small blocks (4×4 luma samples), it uses a simplified approach with IBC flag checking, while for larger blocks it employs full intra prediction mode selection. This localized quality approach optimizes the balance between compression efficiency and signaling complexity for each block size category.
2Measurement precision
If IBC mode is enabled for all blocks, then prediction accuracy is improved, but bandwidth usage increases
Solution Approach 1:
The patent segments the block processing into two categories: small blocks (4×4 luma samples) and larger blocks. For small blocks, it checks the IBC flag to determine mode, while for larger blocks it uses tile type information. This segmentation allows IBC mode to be selectively applied only where beneficial, improving prediction accuracy for small blocks without unnecessarily increasing bandwidth usage for all blocks.
Solution Approach 2:
Instead of enabling IBC mode for all blocks universally, the patent applies IBC mode selectively based on block size and specific conditions (IBC flag for small blocks, tile type for larger blocks). This partial action approach ensures IBC mode is used only when it provides meaningful prediction accuracy improvement, avoiding excessive bandwidth consumption.
3Productivity
If block size threshold is set low, then intra prediction mode selection is improved for small blocks, but decoding complexity increases
Solution Approach 1:
The patent changes the block size threshold parameter to specifically target 4×4 luma samples. This parameter change creates a clear boundary condition that simplifies decoding logic - blocks exactly at this threshold size get special IBC flag handling, while all other blocks follow standard procedures. This resolves the contradiction by making the threshold both low enough to improve small block prediction and simple enough to avoid increasing decoding complexity.
Data Source
AI summary
An apparatus for video encoding includes processing circuitry that determines that a current block is not coded in an intra block copy (IBC) mode. Responsive to the determination that the current block is not coded in the IBC mode, the processing circuitry determines whether a size of the current block is greater than a threshold. The processing circuitry encodes a mode prediction flag into a coded bitstream based on the size of the current block being greater than the threshold. The mode prediction flag indicates whether the current block is coded in an intra prediction mode.