Chroma Block Intra Prediction Mode Selection

Solution Overview

Problem

Current video coding technologies face inefficiencies in processing small blocks due to the need for a large number of intra prediction directions and increased burdens on hardware and software implementations, particularly in terms of mode decision and processing overhead.

Innovation Solution

A method is introduced where the block size of a chroma block is checked against a threshold, and if it is less than or equal to the threshold, a reduced subset of intra prediction modes is used, specifically including direct copy and Cross Correlation Linear Model (CCLM) modes, to perform intra prediction, thereby reducing the computational load.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a large number of intra prediction modes are used for small chroma blocks, then prediction accuracy is improved, but device complexity and processing overhead increase significantly

Engineering Contradiction:

Improveprediction accuracyVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies different intra prediction mode strategies to different block sizes. For small chroma blocks (4x4, 8x4, 4x8), a reduced set of prediction modes is used, while larger blocks can utilize the full range of prediction modes. This local differentiation optimizes the balance between prediction accuracy and processing complexity based on block size characteristics.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent segments the intra prediction mode selection process by block size threshold. Small blocks are handled with a simplified mode subset, while larger blocks use the complete mode set. This segmentation allows the system to reduce complexity for small blocks without sacrificing prediction accuracy for larger blocks where it matters more.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If a large number of intra prediction modes are used for small chroma blocks, then prediction accuracy is improved, but processing overhead increases significantly

Engineering Contradiction:

Improveprediction accuracyVSAvoidprocessing overhead

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent applies different intra prediction mode strategies to different block sizes. For small chroma blocks (4x4, 8x4, 4x8), a reduced set of prediction modes is used, while larger blocks can utilize the full range of prediction modes. This local differentiation optimizes the balance between prediction accuracy and processing complexity based on block size characteristics.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

For small chroma blocks, the patent applies partial action by using only a subset of the available intra prediction modes rather than all modes. This partial application is sufficient for small blocks where full mode exploration would be excessive and wasteful of processing resources, while still achieving adequate prediction accuracy.

Inventive Principle:

Principle #16Partial or excessive action

3Adaptability or versatility

If all intra prediction modes are applied to small chroma blocks, then coding completeness is improved, but compression efficiency decreases due to increased bit requirements

Engineering Contradiction:

Improvecoding completenessVSAvoidbit requirements

Core Design Contradiction:

Adaptability or versatilityVSLoss of information

Solution Approach 1:

The patent applies different intra prediction mode strategies to different block sizes. For small chroma blocks (4x4, 8x4, 4x8), a reduced set of prediction modes is used, while larger blocks can utilize the full range of prediction modes. This local differentiation optimizes the balance between prediction accuracy and processing complexity based on block size characteristics.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the parameter of intra prediction mode quantity based on block size. For small chroma blocks, the mode quantity parameter is reduced to a subset, while for larger blocks the full parameter set is used. This parameter adaptation improves compression efficiency by reducing the number of bits needed to encode prediction modes for small blocks where the reduction has the greatest impact.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11665359B2Method and apparatus for prediction and transform for small blocks

Publication Date: 2023.05.30 TENCENT AMERICA LLC

AI summary

A method of video decoding for a video decoder includes determining whether a block size of a chroma block is less than or equal to a block size threshold. The method further includes, in response to a determination that the block size of the chroma block is greater than the block size threshold, selecting an intra prediction mode for the chroma block from a plurality of intra prediction modes. The method further includes, in response to a determination that the block size of the chroma block is less than or equal to the block size threshold, selecting the intra prediction mode for the chroma block from a subset of the plurality of intra prediction modes. The method further includes performing intra prediction for the chroma block based on a chroma sample obtained with the selected intra prediction mode to encode the chroma block.