Mathias Larsson

Efficient methods for encoding regions of interest in the upcoming JPEG2000 still image coding standard

The general method for generating the regions of interest (ROI) mask needed for encoding ROI in the upcoming JPEG2000 still image coding standard is presented. A simple method for the generation of the ROI mask for rectangular-shaped ROI is then proposed. Finally, to simplify the decoder when dealing with arbitrary shaped ROIs, a method for ROI coding that does not require any shape information to be transmitted to the decoder is described. A small coding penalty is associated with this method, while it makes it possible to have arbitrarily shaped ROI without the need of shape information and ROI mask generation at the decoder. The proposed methods have been included in the Final Committee Draft of JPEG2000 Part 1.

JPEG 2000 still image coding versus other standards

JPEG 2000, the new ISO/ITU-T standard for still image coding, is about to be finished. Other new standards have been recently introduced, namely JPEG-LS and MPEG-4 VTC. This paper puts into perspective the performance of these by evaluating JPEG 2000 versus JPEG-LS and MPEG-4 VTC, as well as the older but widely used JPEG. The study concentrates on compression efficiency, although complexity and set of supported functionalities are also evaluated. Lossless compression efficiency as well as the lossy rate-distortion behavior is discussed. The principles behind each algorithm are briefly described and an outlook on the future of image coding is given. The results show that the choice of the “best” standard depends strongly on the application at hand.

Region of interest coding in JPEG2000 for interactive client/server applications

This paper presents an approach which allows an efficient on-the-fly decoding of regions of interest of an already encoded image without need for a complete decoding/encoding process. The basic method is compatible with the wavelet based compression scheme adopted for the JPEG2000 standard and has been already adopted in a previous verification model. This technique is specially of value in interactive client/server applications linked through narrowband networks, in which the client can request the server to tailor more efficiently the transmission of the desired information at little processing cost. Simulation results show significant improvement in reduction of transmission time and enhanced flexibility at the expense of a very small complexity and bit rate overhead.