A combination of the LZ78 method with a new scheme of model contexting is introduced. In the proposed scheme the hashing function is also used. This approach speeds up the searching process and has an improvement over...
详细信息
A combination of the LZ78 method with a new scheme of model contexting is introduced. In the proposed scheme the hashing function is also used. This approach speeds up the searching process and has an improvement over model contexting.
The authors use Kolmogorov complexity and compression algorithms to study DOS-DNA (DOS: defined ordered sequence). This approach gives quantitative and qualitative explanations of the regularities of apparently regula...
详细信息
The authors use Kolmogorov complexity and compression algorithms to study DOS-DNA (DOS: defined ordered sequence). This approach gives quantitative and qualitative explanations of the regularities of apparently regular regions. The authors present the problem of the coding of approximate multiple tandem repeats in order to obtain compression. Then the authors describe an algorithm that allows one to find efficiently approximate multiple tandem repeats. Finally, the authors briefly describe some of their results.< >
The paper addresses the problem of thresholding wavelet coefficients in a transform-based algorithm for still image compression. Processing data before the quantization phase is a crucial step in a compression algorit...
详细信息
The paper addresses the problem of thresholding wavelet coefficients in a transform-based algorithm for still image compression. Processing data before the quantization phase is a crucial step in a compression algorithm, especially in applications which require high compression ratios. In the paper, after a review on the applications of wavelets to image compression, a new solution to the problem of an accurate choice of thresholds is presented. It is based on the concept of local contrast and exploits the localization properties of wavelets and a maximization of the entropy to find the optimal threshold for the wavelet coefficients. The results are compared with standard thresholding techniques which do not include considerations about local distribution of pixel information within the image. At the end, examples of compression are given, where the algorithm includes the complete processing of transform coefficients (thresholding, quantization and coding).
Performance comparison between image compression methods is an activity difficult to realise because of the few standard environments for validation. The objective of this paper is to present OPENPRESS as a single ope...
详细信息
Performance comparison between image compression methods is an activity difficult to realise because of the few standard environments for validation. The objective of this paper is to present OPENPRESS as a single open platform for validation allowing the integration of most of the current and future image compression methods, to facilitate their comparison and validation on a common and coherent set of reference images. Another goal of OPENPRESS is to ensure a broad distribution of these compression methods to the potential users. For that purpose, the proposed environment involves advanced computer science techniques like distributed computing, platform-independent software engineering, client/server decomposition, etc.
The paper examines some one-dimensional lossy image compression schemes. To perform one-dimensional compression, an image is scanned into a one-dimensional array which is then compressed. Three types of scanning are c...
详细信息
The paper examines some one-dimensional lossy image compression schemes. To perform one-dimensional compression, an image is scanned into a one-dimensional array which is then compressed. Three types of scanning are considered: raster scan, Hilbert scan, and binary scan. Hilbert and binary scan are found to outperform raster scan. The methods considered for compression are integer wavelet transforms, a piecewise approximation with triggers (PAT) procedure introduced by Walach and Karnin (1986), and a modified PAT algorithm (MPAT). Wavelets outperform MPAT in compression, and MPAT in turn outperforms PAT; however, MPAT and PAT are computationally far simpler than wavelet transforms.
The authors introduce a new ECG compression algorithm, and a new distortion measure. The distortion measure, called the Weighted Diagnostic Distortion (WDD), is based on comparing PQRST complex features (such as: RR i...
详细信息
The authors introduce a new ECG compression algorithm, and a new distortion measure. The distortion measure, called the Weighted Diagnostic Distortion (WDD), is based on comparing PQRST complex features (such as: RR interval, QT interval, ST elevation, etc.) of the original ECG signal and the reconstructed one. The compression algorithm is based on analysis by synthesis coding. It consists of a beat codebook, long and short term predictors, and an adaptive residual quantizer. The compression algorithm uses the WDD measure in order to encode, by means of analysis by synthesis, every beat of the original ECG signal. The compression algorithm has been applied to the MIT-BIH Arrhythmia Database. A rate of approximately 100 bits per second has been achieved with a very good quality (WDD below 4%, and PRD below 8%).
An adaptive DCT-based image compression algorithm for radar images is proposed, tested and compared to JPEG and to classical coding algorithms for remote sensing imagery. The Modified Adaptive Discrete Cosine Transfor...
详细信息
An adaptive DCT-based image compression algorithm for radar images is proposed, tested and compared to JPEG and to classical coding algorithms for remote sensing imagery. The Modified Adaptive Discrete Cosine Transform (MADCT) scheme is proposed, which allows one to classify each image block by means of a threshold criterion based on AC and DC activity. The strategy of transmission of the DCT coefficients, the recovering process of blocks incorrectly discarded, and the bit-allocation phase have been properly designed to provide high compression of two classes of images: X-band real-aperture radar images for ship traffic control, and SAR images for browsing applications. The experimental results, in terms of PSNR and compression ratio, prove the superiority of the novel scheme with respect to standard coding techniques.
With an increasing use of implantable devices for the therapy of heart arrhythmia, the need arises for an efficient recording of cardiac signals with the limited resources of an implant. In this paper the authors pres...
详细信息
With an increasing use of implantable devices for the therapy of heart arrhythmia, the need arises for an efficient recording of cardiac signals with the limited resources of an implant. In this paper the authors present a new signal compression algorithm based on the Walsh-Hadamard Transform (WHT), which is suitable for realtime operation with minimal computational needs. Simulations with clinically measured data delivered compression ratios in the range 2.5-4 with just 4% PRD maximum distortion. This figures compare well to the results obtained with other (more complex) ECG compression techniques presented in the literature.
The target of this work is the high quality audio coding at low bit rate. It is shown how pyramid vector coding (PVC) can conveniently replace the classical Huffman coding technique in audio compression systems, provi...
详细信息
The target of this work is the high quality audio coding at low bit rate. It is shown how pyramid vector coding (PVC) can conveniently replace the classical Huffman coding technique in audio compression systems, providing also an advantage in the bit allocation procedure. The compression performances can be further improved by fixing an upper limit value to the vector components.
Volume data sets are becoming increasingly large and numerous with advances in acquisition methods and in computers. To date, the most commonly used lossless compression software for volume data sets are Lempel-Ziv-ba...
详细信息
Volume data sets are becoming increasingly large and numerous with advances in acquisition methods and in computers. To date, the most commonly used lossless compression software for volume data sets are Lempel-Ziv-based applications designed for text compression. We present an improved lossless volume compression algorithm based on Lempel-Ziv '77.
暂无评论