Evolving JPEG color data compression standard

Abstract

An international team of technical experts, the Joint Photographic Experts Group (JPEG), has been working for the past four years on a color image data compression standard for use worldwide in a variety of still image applications. This joint committee operated under ISO/IEC JTCl/SC2/Working Group 8 (Coded Representation of Picture and Audio Information) until it recently moved to a new working group, ISO/IEC JTC1/SC2/WG10 (Photographic Image Coding). The work is being done jointly with a special rapporteur group on image communication within CCITT Study Group VIII. Within the United States, work in support of this international activity is focused within the U.S. picture coding committee, Accredited Standards Committee X3 Technical Committee X3L3 (formerly Task Group X3L2.8). Other standards applications groups are eagerly awaiting the completion of JPEG in order to effectively incorporate color images into their application environments. JPEG's intensive technical research and refinement stages have been completed and an International Standards Organization (ISO) Committee Draft for the evolving JPEG data compression standard has been submitted for international balloting. Extensive testing of the applicability to various environments is in progress. Companies are beginning to announce JPEG software or hardware availability, even though they recognize that the JPEG algorithm may change. This paper will provide a critical review of the evolving JPEG color image data compression standard. A history of JPEG is given first, followed by the steps still needed for adoption of JPEG as an international image data compression standard. Then the JPEG »toolkit» is explored with additional detail on the entropy coders and data interleave conventions. In the results section, the compression performance numbers on the JPEG test images are given for the baseline Huffman sequential coding system both with and without resynchronization. The arithmetic coding results are given for the sequential DCT-based mode with and without resynchronization, several progressive DCT-based processes and the sequential lossless mode. The final section briefly notes some applications and implementations of JPEG.