The Flexwave-Ii: A Wavelet-Based Compression Engine

The FlexWave-II has been developed as a dedicated image compression component for spaceborn applications, enabling a multitude of application scenarios, including lossless and lossy compression. The FlexWave-II provides scalable compression, allowing gradual enhancement or de gradation of the image quality in a programmable way. A wavelet-based compression scheme has been selected because of the intrinsic scalable characteristics. Moreover the compression criteria can be tuned separately for optimal measurement and visual data compression.The FlexWave-II provides full scalability features and high processing performance. It supports push-broom image processing. The wavelet transform engine is capable of computing up to 5 levels of wavelet transform with 5/3-, 9/3- or 9/7-tap wavelet filters, for image sizes as large as 1k x 1k pixels. On an FPGA implementation, clocked on 41 MHz, a processing performance of up to 10 Mpixels/second was measured. The wavelet compression engine allows two compression modes: a fixed compression ratio mode optimised for user-defined criteria and a fixed quantisation mode with user defined quantisation tables.