Tammam Tillo

Transform Coding Techniques for Lossy Hyperspectral Data Compression

Transform-based lossy compression has a huge potential for hyperspectral data reduction. Hyperspectral data are 3-D, and the nature of their correlation is different in each dimension. This calls for a careful design of the 3-D transform to be used for compression. In this paper, we investigate the transform design and rate allocation stage for lossy compression of hyperspectral data. First, we select a set of 3-D transforms, obtained by combining in various ways wavelets, wavelet packets, the discrete cosine transform, and the Karhunen-Loegraveve transform (KLT), and evaluate the coding efficiency of these combinations. Second, we propose a low-complexity version of the KLT, in which complexity and performance can be balanced in a scalable way, allowing one to design the transform that better matches a specific application. Third, we integrate this, as well as other existing transforms, in the framework of Part 2 of the Joint Photographic Experts Group (JPEG) 2000 standard, taking advantage of the high coding efficiency of JPEG 2000, and exploiting the interoperability of an international standard. We introduce an evaluation framework based on both reconstruction fidelity and impact on image exploitation, and evaluate the proposed algorithm by applying this framework to AVIRIS scenes. It is shown that the scheme based on the proposed low-complexity KLT significantly outperforms previous schemes as to rate-distortion performance. As for impact on exploitation, we consider multiclass hard classification, spectral unmixing, binary classification, and anomaly detection as benchmark applications

Progressive 3-D coding of hyperspectral images based on JPEG 2000

In this letter we propose a new technique for progressive coding of hyperspectral data. Specifically, we employ a hybrid three-dimensional wavelet transform for spectral and spatial decorrelation in the framework of Part 2 of the JPEG 2000 standard. Both onboard and on-the-ground compression are addressed. The resulting technique is compliant with the JPEG 2000 family of standards and provides competitive performance with respect to state-of-the-art techniques.

Redundant Slice Optimal Allocation for H.264 Multiple Description Coding

In this paper, a novel H.264 multiple description technique is proposed. The coding approach is based on the redundant slice representation option, defined in the H.264 standard. In presence of losses, the redundant representation can be used to replace missing portions of the compressed bit stream, thus yielding a certain degree of error resilience. This paper addresses the creation of two balanced descriptions based on the concept of redundant slices, while keeping full compatibility with the H.264 standard syntax and decoding behavior in case of single description reception. When two descriptions are available still a standard H.264 decoder can be used, given a simple preprocessing of the received compressed bit streams. An analytical setup is employed in order to optimally select the amount of redundancy to be inserted in each frame, taking into account both the transmission condition and the video decoder error propagation. Experimental results demonstrate that the proposed technique favorably compares with other H.264 multiple description approaches.

Sliding-Window Raptor Codes for Efficient Scalable Wireless Video Broadcasting With Unequal Loss Protection

Digital fountain codes have emerged as a low-complexity alternative to Reed-Solomon codes for erasure correction. The applications of these codes are relevant especially in the field of wireless video, where low encoding and decoding complexity is crucial. In this paper, we introduce a new class of digital fountain codes based on a sliding-window approach applied to Raptor codes. These codes have several properties useful for video applications, and provide better performance than classical digital fountains. Then, we propose an application of sliding-window Raptor codes to wireless video broadcasting using scalable video coding. The rates of the base and enhancement layers, as well as the number of coded packets generated for each layer, are optimized so as to yield the best possible expected quality at the receiver side, and providing unequal loss protection to the different layers according to their importance. The proposed system has been validated in a UMTS broadcast scenario, showing that it improves the end-to-end quality, and is robust towards fluctuations in the packet loss rate.

Multiple Description Image Coding Based on Lagrangian Rate Allocation

In this paper, a novel multiple description coding technique is proposed, based on optimal Lagrangian rate allocation. The method assumes the coded data consists of independently coded blocks. Initially, all the blocks are coded at two different rates. Then blocks are split into two subsets with similar rate distortion characteristics; two balanced descriptions are generated by combining code blocks belonging to the two subsets encoded at opposite rates. A theoretical analysis of the approach is carried out, and the optimal rate distortion conditions are worked out. The method is successfully applied to the JPEG 2000 standard and simulation results show a noticeable performance improvement with respect to state-of-the art algorithms. The proposed technique enables easy tuning of the required coding redundancy. Moreover, the generated streams are fully compatible with Part 1 of the standard

A novel multiple description coding scheme compatible with the JPEG2000 decoder

We propose a novel technique to generate rate-distortion optimized multiple descriptions of images, exploiting the rate-allocation strategy embedded in the JPEG2000 encoder. The proposed scheme can be applied to any encoding algorithm, given that the rate allocation is based on code-block truncation. The method yields excellent performance in terms of both central and side distortion, outperforming state-of-the art techniques. Moreover, the single description decoding is fully compatible with the JPEG2000 Part 1 decoder.

A New Low Complexity KLT for Lossy Hyperspectral Data Compression

Transform-based lossy compression has a huge po- tential for hyperspectral data reduction. In this paper we propose a lossy compression scheme for hyperspectral data based on a new low-complexity version of the Karhunen-Lo` eve transform, in which complexity and performance can be balanced in a scalable way, allowing one to choose the best trade off that better matches a specific application. Moreover, we integrate this transform in the framework of Part 2 of the JPEG 2000 standard, taking advantage of the high coding efficiency of JPEG 2000, and exploiting the interoperability of an international standard. Hyperspectral imaging amounts to collecting the energy reflected or emitted by ground targets at a typically very high number of wavelengths, resulting in a data cube consisting of tens to hundreds of bands. These data have become increas- ingly popular, since they enable plenty of new applications, in- cluding detection and identification of surface and atmospheric constituents present, analysis of soil type, agriculture and forest monitoring, environmental studies and military surveil- lance. The data are usually acquired by a remote platform (a satellite or an aircraft), and then downlinked to a ground sta- tion. Due to the huge size of the datasets, compression is nec- essary to match the available transmission bandwidth. In the past, scientific data have been almost exclusively compressed by means of lossless methods, in order to preserve their full quality. However, more recently, there has been an increasing interest in their lossy compression. Many of these techniques are based on decorrelating transforms, in order to exploit spatial and inter-band (i.e., spectral) correlation, followed by a quantization stage and an entropy coder. Examples include the

Data-Dependent Pre- and Postprocessing Multiple Description Coding of Images

Multiple description coding can be implemented as pre- and postprocessing to all standards for image and video communications, with obvious advantages. This can be achieved by generating two subsets from the original data; a controllable amount of extra redundancy between the descriptions has to be inserted to help the estimation of the possibly lost description from the received one. This redundancy can be in the form of spatial oversampling. In this paper, we propose and develop a mathematical framework for two descriptions pre- and postprocessing methods, which exploit the correlation characteristics of the visual data in order to better implement the multiple description coding paradigm. Simulation results show a noticeable performance improvement of both the proposed methods with respect to state-of-the art algorithms, in terms of both rate/redundancy/distortion tradeoff and computational complexity

Multiple Description Coding for H.264/AVC With Redundancy Allocation at Macro Block Level

In this paper, a novel multiple description video coding scheme is proposed to insert and control the redundancy at macro block (MB) level. By analyzing the error propagation paths, the relative importance of each MB is determined. The paths, in practice, depend on both the video content and the adopted video coder. Considering the relative importance of the MB and the network status, an unequal protection for the video data can be realized to exploit the redundancy effectively. In addition, a simple and effective approach is introduced to tune the quantization parameter for the variable rate coding case. The whole scheme is implemented in H.264/AVC by employing its coding options, thus generating descriptions that are compatible with the baseline profile and extended profile of H.264/AVC. Due to its general property, the proposed approach can be employed for other hybrid video codecs. The results demonstrate the advantage of the proposed approach over other H.264/AVC multiple description schemes.

Hyperspectral Image Compression Employing a Model of Anomalous Pixels

We propose a new lossy compression algorithm for hyperspectral images, which is based on the spectral Karhunen-Loeve transform, followed by spatial JPEG 2000, which employs a model of anomalous pixels during the compression process. Results on Airborne Visible/Infrared Imaging Spectrometer scenes show that the new algorithm provides better rate-distortion performance, as well as improved anomaly detection performance, with respect to the state of the art.