Chroma Transform Block Limits for Efficient Video Encoding

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Solution Overview

Problem

The increasing demand for high-resolution and high-quality images leads to a significant increase in transmission and storage costs due to the rise in the amount of transmitted information, necessitating high-efficient image compression technologies.

Innovation Solution

An image encoding/decoding method and apparatus that limits the maximum size of a chroma transform block to improve encoding/decoding efficiency and facilitates the transmission of a bitstream.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the maximum size of chroma transform block is increased to maintain detail quality, then image quality is improved, but encoding/decoding complexity and processing time increase

Engineering Contradiction:
Improveimage qualityVSAvoidencoding/decoding complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies parameter changes by dynamically adjusting the chroma transform block size based on the chroma component ratio. When the chroma component ratio is 1:2 or 1:4, the maximum chroma transform block size is limited to half or one-quarter of the luma transform block size, respectively. This parameter adjustment optimizes the balance between image quality and encoding complexity for different color sampling scenarios.

Inventive Principle:
Principle #35Parameter changes

2Productivity

If the maximum size of chroma transform block is limited to reduce complexity, then encoding/decoding efficiency is improved, but image quality may deteriorate

Engineering Contradiction:
Improveencoding/decoding efficiencyVSAvoidimage quality
Core Design Contradiction:
ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by differentiating the maximum transform block size constraints based on the specific chroma component ratio. Instead of applying a uniform limitation, the system adapts the constraint level locally: using stricter limitations (half size or one-quarter size) for 1:2 or 1:4 ratios, while allowing larger blocks for 1:1 ratios. This localized adaptation maintains image quality where needed while optimizing efficiency where appropriate.

Inventive Principle:
Principle #3Local quality

3Quantity of substance

If chroma transform block size is reduced to compress data, then transmission cost decreases, but detail loss increases

Engineering Contradiction:
Improvetransmission costVSAvoiddetail loss
Core Design Contradiction:
Quantity of substanceVSLoss of information

Solution Approach 1:

The patent uses parameter changes to optimize the balance between compression efficiency and detail preservation. By adjusting the maximum chroma transform block size parameter based on the chroma component ratio, the system achieves better compression (lower transmission cost) for 1:2 and 1:4 sampling formats while preserving sufficient detail quality, avoiding the need for excessive compression that would cause detail loss.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP3989557B1Method and apparatus for encoding/decoding video using maximum size limitation of chroma transform block, and method for transmitting bitstream
Publication Date: 2026.04.22 LG ELECTRONICS INC
  • EP3989557B1 patent drawingFigure 1
  • EP3989557B1 patent drawingFigure 2
  • EP3989557B1 patent drawingFigure 3

AI summary

An image encoding/decoding method and apparatus are provided. An image decoding method performed by an image decoding apparatus may include determining a prediction mode of a current block, generating a prediction block of the current block based on inter prediction mode information, based on the prediction mode of the current block being an inter prediction mode, generating a residual block of the current block based on a transform block of the current block, and reconstructing the current block based on the prediction block and the residual block of the current bloc.