HLC: A High-Quality Lightweight Mezzanine Codec Featuring High-Throughput Palette

TL;DR

HLC is a new lightweight mezzanine image codec that uses a novel palette and optimization techniques to achieve high throughput and quality with reduced hardware resources.

Contribution

The paper introduces a practical, high-throughput palette and a co-designed rate-distortion optimization for mezzanine coding, improving quality and efficiency over existing codecs.

Findings

HLC achieves the same throughput as JPEG-XS at 4K@120fps.

HLC uses half the LUT resources compared to JPEG-XS.

HLC improves BD-PSNR by over 3dB on various content datasets.

Abstract

Existing mezzanine image codecs lack specialized screen content coding tools and therefore struggle to maintain high image quality under bandwidth constraints, especially in areas with dense text. Although distribution codecs offer advanced screen content compression techniques, their high computational complexity makes them impractical for mezzanine coding. To address this shortfall, we introduce the High-quality Lightweight Codec (HLC), a solution centered on enabling practical, high-throughput palette for mezzanine coding. The core innovation is a novel data-dependency-free palette that eliminates the throughput bottlenecks. To ensure its effectiveness across all content, a co-designed rate-distortion optimization module arbitrates between the palette and traditional prediction modes, while a data reuse strategy between rate estimation and entropy coding minimizes the overall hardware resources required for the system. Experimental results show that, compared with a 4K@120fps JPEG-XS encoder, HLC achieves the same throughput while using only half the LUT resources and delivers BD-PSNR improvements of 3.461dB, 3.299dB, and 5.312dB on gaming, natural, and text content datasets, respectively.