Bit rate and local quality control using a rate/distortion criterion for on-board satellite images compression

The method we present is developed as part of an onboard satellite images compression with target ratios greater than 6. Such a compression is required because of the weight and memory constraints of on-board equipment and must be integrated in a bit rate control scheme. In order to guarantee a high local quality on some critical areas, we have developed an adapted encoder which integrates a local quality constraint within a bit rate control. This encoder, based on a progressive transmission of information by using an EZW algorithm, realizes coding and bit rate regulation in the same time. Actually, our encoder is a quite different from Shapiro´s one due to the integration of Regions Of Interest (ROI) by setting up a classification map. Such a technique allows to limit artifacts on ROI without creating too much degradation on the rest of the image.