Cool-chic 5.0: Faster Encoding and Inter-Feature Entropy Modeling for Overfitted Image Compression

TL;DR

Cool-chic 5.0 is an overfitted image codec that achieves superior compression with significantly reduced encoding iterations and lower decoding complexity, outperforming state-of-the-art codecs.

Contribution

This paper introduces Cool-chic 5.0 with an improved decoder and optimization, reducing encoding iterations by tenfold and lowering decoding complexity while maintaining competitive compression performance.

Findings

Outperforms all overfitted codecs with 10x fewer encoding iterations.

Achieves -11% rate reduction over H.266/VVC.

Decoding complexity is 250 times lower than modern autoencoders.

Abstract

Overfitted codecs compress an image by learning a decoder tailored to the content during the encoding. As such, they trade increased encoding complexity for strong compression performance and low decoding complexity. This work introduces Cool-chic 5.0, the latest version in the Cool-chic series of overfitted codecs, featuring an updated decoder architecture and an improved optimization process. Cool-chic 5.0 outperforms all overfitted codecs with 10 times less encoding iterations. It offers -11% rate reduction compared to the state-of-the-art conventional codec H.266/VVC. It is also competitive with modern autoencoders such as MLIC++ while featuring a decoding complexity 250 times lower. This work is made open-source at https://github.com/Orange-OpenSource/Cool-Chic.