Fine-tuning JPEG-XT compression performance using large-scale objective quality testing
The upcoming JPEG XT standard for High Dynamic Range (HDR) images defines a common framework for the lossy and lossless representation of high-dynamic range images. It describes the decoding process as the combination of various processing tools that can be combined freely. In this paper we analyze the coding efficiency of different decoding tools through a large scale objective quality testing using the HDR-VDP 2.2 objective metric. This evaluation is performed on a large database of 337 images, testing the effect of global and local tone mapping operators for various configurations, and for multiple combinations of quality parameters. The main findings are that using an inverse tone mapping operator for creating an HDR precursor image works well for global, but not for local operators, and that including refinement scans to increase the bit-depth of the extension layer provides substantial improvements for one of the encoding profiles and higher bit-rates.