title: An Analysis of Contemporary JPEG2000 Codecs for Image Format Migration
creators: William Palmer Peter May Peter Cliff
abstract: Despite the importance of web archives for the access to historical information published on the Internet, human interaction with web archives systems has not been thoroughly addressed. The web archive search user interface presented on this paper was derived from several rounds of development and usability testing over the Portuguese Web Archive search user interface (available at archive.pt). We present our findings gathered while adapting a typical web search user interface to the context of web archive search.  We describe how we adapted a typical search user interface to address full-text and URL search over web-archived data, highlighting the unexpected problems detected during us- ability testing of our interface and current limitations for future work. The obtained results from usability testing showed that the average user satisfaction with our user in- terface was 70%. The obtained results from anonymous user satisfaction questionnaires yield a 84.3% score. This paper presents results of an analysis of different implementations of the JPEG2000 standard, specifically part 1: JP2, an image format that is currently popular within the digital preservation community. In particular we are interested in the effect different JPEG2000 codecs (encoders and decoders) have on image quality in response to lossy compression. We focus on three main codec libraries for analysis - Kakadu, JasPer and OpenJPEG - migrating 932 TIFF newspaper images to lossy JPEG2000 files using 2:1 and 4:1 compression ratios, and monitor image quality using PSNR. We look at the combination of encoder/decoder pairs and find that using OpenJPEG for both gives the best quality results, albeit with the slowest execution time. We also find that in some circumstances, particularly when a JasPer encoder is used, in order to retain image quality of the decoded image, the best choice of decoder may not be the same codec used to create the JPEG2000; based on these results, the encoding library is therefore recommended technical preservation metadata to retain.
keywords: jpeg2000 tiff migration codec psnr image quality generational loss lisbon