Image Coding with NSST for Sparse Transform Coefficients

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Solution Overview

Problem

The increasing demand for high-resolution and high-quality images leads to a significant increase in the amount of information to be transmitted and stored, resulting in higher transmission and storage costs.

Innovation Solution

An image coding method and apparatus utilizing a non-separable secondary transform (NSST) to enhance transform efficiency by decoding and encoding a transform index before transform coefficients, concentrating non-zero coefficients on low frequency components in the frequency domain.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If high-resolution and high-quality images are transmitted or stored, then image quality is improved, but transmission cost and storage cost increase

Engineering Contradiction:

Improveimage qualityVSAvoidamount of data

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent applies a non-separable secondary transform (NSST) to transform coefficient blocks, changing the mathematical transformation parameters from conventional separable transforms. This parameter change concentrates non-zero coefficients more efficiently into fewer transform coefficients, reducing the amount of data that needs to be transmitted or stored while maintaining high image quality

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the conventional separable transform mechanism with a non-separable secondary transform mechanism. This substitution creates a more efficient transformation system that achieves better energy compaction and sparsity, thereby reducing the data quantity required to represent high-quality images

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If conventional transform methods are used, then coding process is simple, but transform efficiency is insufficient

Engineering Contradiction:

Improvetransform efficiencyVSAvoidcoding complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent performs a preliminary non-separable secondary transform on transform coefficient blocks after the initial transform. This preliminary action on the coefficients further concentrates energy and improves sparsity, enhancing transform efficiency without requiring a complete redesign of the coding system

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies the non-separable secondary transform selectively to specific transform coefficient blocks based on predetermined conditions (such as block size, transform type, or content characteristics). This segmentation approach allows the more complex NSST to be applied only where beneficial, balancing improved transform efficiency with controlled coding complexity

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS20260075221A1Image coding method on basis of secondary transform and device therefor

Publication Date: 2026.03.12 LG ELECTRONICS INC

AI summary

An image information decoding method performed by means of a decoding device according to the present invention comprises the steps of: decoding a non-separable secondary transform (NSST) index from a bitstream if NSST is applied to a target block; decoding information relating to transform coefficients with respect to the target block from the bitstream on the basis of the decoded NSST index; and deriving the transform coefficients with respect to the target block on the basis of the decoded information relating to the transform coefficients, wherein the NSST index is decoded prior to the information relating to the transform coefficients with respect to the target block.