2020/07/06 by Johannes Ballé, Ballé, Johannes, Philip A. Chou +13 · 26 citations
Computer Science · Engineering · Mathematics · #FOS: Computer and information sciences #FOS: Electrical engineering #Image and Video Processing (eess.IV) #Information Theory (cs.IT) #cs.IT #eess.IV #electronic engineering #information engineering #math.IT
paper · pdf · doi:10.48550/arxiv.2007.03034
17 pages, 14 figures. Accepted for publication in IEEE Journal of Selected Topics in Signal Processing
arxiv created 2020/10/24 · arxiv updated 2020/10/27
We review a class of methods that can be collected under the name nonlinear transform coding (NTC), which over the past few years have become competitive with the best linear transform codecs for images, and have superseded them in terms of rate--distortion performance under established perceptual quality metrics such as MS-SSIM. We assess the empirical rate--distortion performance of NTC with the help of simple example sources, for which the optimal performance of a vector quantizer is easier to estimate than with natural data sources. To this end, we introduce a novel variant of entropy-constrained vector quantization. We provide an analysis of various forms of stochastic optimization techniques for NTC models; review architectures of transforms based on artificial neural networks, as well as learned entropy models; and provide a direct comparison of a number of methods to parameterize the rate--distortion trade-off of nonlinear transforms, introducing a simplified one.