The fully adaptive prediction error coder (FAPEC) is an entropy coder that typically offers better results than the adaptive Rice compressor. It uses basic preprocessing stages such as delta preprocessing, but it can ...
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The fully adaptive prediction error coder (FAPEC) is an entropy coder that typically offers better results than the adaptive Rice compressor. It uses basic preprocessing stages such as delta preprocessing, but it can also be combined with a discrete wavelet transform. We describe a new algorithm called hierarchical pixel averaging (HPA). It divides an image into blocks of 16 x 16 pixels, which are subsequently divided into smaller blocks, up to the basic level where one block corresponds to one pixel. Average pixel values are determined for each level from which differential coefficients are extracted. HPA allows the introduction of controlled losses with several quality levels, also allowing to progressively decompress a given image from lower to higher quality. It achieves better resolution in sharp image edges when compared to other lossy algorithms. HPA is based on simple arithmetic operations, allowing a very simple (thus quick) implementation. It does not use any floating-point operations, which is an interesting feature for satellite or embedded data compression. We present a first implementation of HPA and the results obtained on a variety of images, both for the lossless and lossy cases with different quality levels. Our results indicate that HPA + FAPEC offer a performance comparable to that of CCSDS 122.0. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)
The Consultative Committee for Space Data Systems (CCSDS) 122.0 recommendation defines a particular image data compression algorithm for space. It is based on a discrete wavelet transform (DWT) algorithm followed by b...
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The Consultative Committee for Space Data Systems (CCSDS) 122.0 recommendation defines a particular image data compression algorithm for space. It is based on a discrete wavelet transform (DWT) algorithm followed by bit-plane encoder stage (BPE) based on Rice codes. The low complexity and memory efficiency of the algorithm makes it suitable for use onboard a spacecraft. On the other hand, fully adaptive prediction error coder (FAPEC) is a quick entropy coder aimed to achieve excellent compression ratios under almost any situation, including large fractions of outliers in the data and large sample sizes. A new image compression solution based on the DWT stage of the CCSDS 122.0 recommendation is presented, followed by our FAPEC entropy coder, thus removing the BPE stage. The purpose is to obtain a low-complexity algorithm for image compression able to provide similar or even better compression ratios than those obtained using the CCSDS 122.0 recommendation. A prototype of DWTFAPEC, the combination of the DWT stage with FAPEC, is presented here. Its lossless operation, as well as the results with a first lossy option with selectable quality using a wide variety of images, including the official CCSDS 122.0 image corpus as well as several astronomical and ground images, is tested. The results are satisfactory, achieving significantly better compression times. The lossless ratios are very close to those of the standard, while the lossy ratios are higher (for the same level of quality loss). Thus, DWTFAPEC can be used as an alternative to CCSDS 122.0 standard for space missions. c 2013 Society of Photo-Optical Instrumentation Engineers (SPIE)
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