Emerging practical schemes indicate that algebraic mixing of different packets by means of random linear network coding can increase the throughput and robustness of streaming services over wireless networks. However,...
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Emerging practical schemes indicate that algebraic mixing of different packets by means of random linear network coding can increase the throughput and robustness of streaming services over wireless networks. However, concerns with the security of wireless video, in particular when only some of the users are entitled to the highest quality, have uncovered the need for a network coding scheme capable of ensuring different levels of confidentiality under stringent complexity requirements. We show that the triple goal of hierarchical fidelity levels, robustness against wireless packet loss and efficient security can be achieved by exploiting the algebraic structure of network coding. The key idea is to limit the encryption operations to a critical set of network coding coefficients in combination with multi-resolution video coding. Our contributions include an information-theoretic security analysis of the proposed scheme, a basic system architecture for hierarchical wireless video with network coding and simulation results.
作者：
Franques, VTUSAF
Res Lab Munit Directorate Eglin AFB FL 32542 USA
Recently, a new image compression algorithm was developed which employs wavelet transform and a simple binary linear quantization scheme with an embedded coding technique to perform data compaction. This new family of...
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ISBN:
(纸本)081942840X
Recently, a new image compression algorithm was developed which employs wavelet transform and a simple binary linear quantization scheme with an embedded coding technique to perform data compaction. This new family of coder, Embedded Zerotree Wavelet (EZW), provides a better compression performance than the current JPEG coding standard for low bit rates. Since The Embedded Zerotree Wavelet coding algorithm emerged, all of the published coding results related to this coding technique are on monochrome images. In this paper the author has enhanced the original coding algorithm to yield a better compression ratio [2], and has extended the wavelet-based zerotree coding to color images. Color imagery is often represented by several components, such as RGB, in which each component is generally processed separately. With color coding, each component could be compressed individually in the same manner as a monochrome image, therefore requiring a threefold increase in processing rime. Most image coding standards employ de-correlated components, such as YlQ or Y, C-B, C-R, and subsampling of the 'chroma' components, such coding technique is employed here. Results of the coding, including reconstructed images and coding performance, will be presented.
A novel encoder based on an enhanced Laplacian pyramid is proposed for compression of Medical grey-scale images: major details are prioritized through an adaptive decision rule embedded in a uniform threshold quantize...
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A novel encoder based on an enhanced Laplacian pyramid is proposed for compression of Medical grey-scale images: major details are prioritized through an adaptive decision rule embedded in a uniform threshold quantizer with noise feedback. The major benefit of this content-driven feedback quantizer is that significant features are straightforwardly propagated throughout the pyramid, thus enhancing compactness and visual quality of the reduced-resolution versions progressively associated with the code stream. Nevertheless, the reconstruction error is determined only by the size of the quantization step at the base level of the pyramid, thereby making it possible for the maximum absolute reconstruction error to be easily and strongly upper-bounded (near-lossless compression), as often required in archiving medical images, for diagnostic and legal purposes. Both lossless and lossy coding show favorable comparisons with JPEG in objective terms, i.e., compression ratios and distortion plots. Lossy coding outperforms JPEG also subjectively, due to the absence of visual impairments and diagnostic artifacts even at very low rates. This feature is also evidenced in a preliminary ROC analysis on a set of X-ray chest images. The pyramid encoder produces compressed images whose diagnostic quality seems to be comparable, for medium rates, to that of the uncompressed versions, and superior to that of the JPEG coded versions. (C) 1997 Elsevier Science B.V.
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