Low-Complexity Transform Adjustments For Video Coding

TL;DR

This paper presents a new method for designing low-complexity approximations of asymmetric trigonometric transforms in video coding, reducing computational costs while maintaining coding efficiency.

Contribution

It introduces a technique that uses DCT-2 computations and orthogonal adjustments to approximate complex transforms efficiently.

Findings

Significant reduction in computational complexity.

Practically identical coding efficiency to original transforms.

Effective for large 32-point transforms in VVC.

Abstract

Recent video codecs with multiple separable transforms can achieve significant coding gains using asymmetric trigonometric transforms (DCTs and DSTs), because they can exploit diverse statistics of residual block signals. However, they add excessive computational and memory complexity on large transforms (32-point and larger), since their practical software and hardware implementations are not as efficient as of the DCT-2. This article introduces a novel technique to design low-complexity approximations of trigonometric transforms. The proposed method uses DCT-2 computations, and applies orthogonal adjustments to approximate the most important basis vectors of the desired transform. Experimental results on the Versatile Video Coding (VVC) reference software show that the proposed approach significantly reduces the computational complexity, while providing practically identical coding efficiency.