Optimal adapted weighting of wavelet coefficients for on-board coding of satellite images

Satellite images offer a large amount of information but require on-board compression because of the weight and memory constraints of on-board equipment. Moreover, this compression must be integrated in a bit rate control scheme. In order to guarantee a high local quality on some critical areas, the authors have developed an adapted encoder, based on a wavelet transform and which integrates a local quality constraint within a bit rate control. This encoder realizes coding and bit rate regulation in the same time by using an EZW (Embedded Zerotree of Wavelet) algorithm. Because of memory constraints, this regulation only deals with a little part of the image, namely sixty-four lines. Before looking forward how they define and how they integrate the notion of quality within the bit rate regulation loop, they must describe the artifacts which appear when coding satellite images