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The word-codeword mapping technique allows words to be managed in PPM modelling when a natural language text file is being compressed. The main idea for managing words is to assign them codes in order to improve the compression. The previous work was focused on proposing several mapping adaptive algorithms and evaluating them. In this paper, we propose a semi-static word-codeword mapping method that...
In Huffman-encoded data a bit error may propagate arbitrarily long. This paper introduces a method for limiting such error propagation to at most L bits, L being a parameter. It is required that the decoder knows the bit number currently being decoded. The method utilizes the inherent tendency of Huffman codes to resynchronize spontaneously and does not introduce any redundancy if such a resynchronization...
In this paper we study the adaptive prefix coding problem in cases where the size of the input alphabet is large. We present an online prefix coding algorithm that uses O(sigma1/lambda+epsiv) bits of space for any constants epsiv > 0, > 1, and encodes the string of symbols in O(loglog sigma) time per symbol in the worst case, where sigma is the size of the alphabet. The upper bound on the encoding...
This paper gives a novel wavelet image two-line (Wi2l) coder that is designed to fulfill the memory constraints of a typical wireless sensor node. The algorithm operates line-wisely on picture data stored on the sensor's flash memory card while it requires approximatively 1.5 kByte RAM to compress a monochrome picture with the size of 256 times 256 Bytes. The achieved data compression rates are the...
A current challenge in scientific computing is how to curb the growth of simulation datasets without losing valuable information. While wavelet based methods are popular, they require that data be decompressed before it can analyzed, for example, when identifying time-dependent structures in turbulent flows. We present adaptive coarsening, an adaptive subsampling compression strategy that enables...
Spatially scalable image coding algorithms are mostly based on linear filtering techniques that give a multi-resolution representation of the data. Reversible cellular automata can be instead used as simpler, non-linear filter banks that give similar performance. In this paper, we investigate the use of reversible cellular automata for lossy to lossless and spatially scalable coding of smooth multi-level...
The multicasting of an independent and identically distributed Gaussian source over a binary erasure broadcast channel is considered. This model applies to a one-to-many transmission scenario in which some mechanism at the physical layer delivers information packets with losses represented by erasures, and users are subject to different erasure probabilities. The reconstruction signal-to-noise ratio...
For the new signal acquisition methodology of compressive sensing (CS) a challenge is to find a space in which the signal is sparse and hence recoverable faithfully. Given the nonstationarity of many natural signals such as images, the sparse space is varying in time or spatial domain. As such, CS recovery should be conducted in locally adaptive, signal-dependent spaces to counter the fact that the...
We present a new lossy compressor for discrete sources. For coding a source sequence xn, the encoder starts by assigning a certain cost to each reconstruction sequence. It then finds the reconstruction that minimizes this cost and describes it losslessly to the decoder via a universal lossless compressor. The cost of a sequence is given by a linear combination of its empirical probabilities of some...
In most Wyner-Ziv video coding approaches, the temporal correlation of key frames is not exploited since they are simply intra encoded and decoded. In this paper, using the previously decoded key frame as the side information for the key frame to be decoded, we propose new methods of coding key frames in order to improve the rate distortion performance. These schemes which are based on switching between...
The H.264 encoder has input parameters that determine the bit rate and distortion of the compressed video and the encoding complexity. A set of encoder parameters is referred to as a parameter setting. We previously proposed two offline algorithms for choosing H.264 encoder parameter settings that have distortion-complexity performance close to the parameter settings obtained from an exhaustive search,...
Invertible integer transforms are essential for lossless source encoding. Using lifting schemes, we develop a new family of invertible integer transforms based on discrete generalized cosine transforms. The discrete generalized cosine transforms that arise in connection with compact semi-simple Lie groups of rank 2, are orthogonal over a fundamental region and have recently attracted more attention...
The paper thoroughly validates the proposed SID model on a broad dataset, showing significant accuracy improvements over SII models. Additionally, it is theoretically demonstrated that DVC systems that make SII assumptions suffer a performance penalty depending entirely on the correlation statistics of the video data.
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