Multistream compression is based on a transformation significantly different from the ones commonly used for data compression. This Master thesis concerns with the use of said method for the compression of text files written in natural language. The main goal of the thesis is to find suitable preprocessing methods for text transformation, which would enable the Multistream compression to achieve better compression ratios, together with searching for the best methods for coding of individual streams. The practical part of the thesis deals with the implementation of several transformation algorithms into the XBW project.

The topic of the thesis has been chosen based on efforts of an unnamed company for better data warehouse optimisation. Since the ETL process at the company has been changed, which led to the migration to Teradata database system, it would be appropriate to perform both the operation optimisation, as well as capacity optimisation. The first part of the thesis describes the Teradata concept and its architecture. This part particularly focuses on the Statistics which belong to the system operation optimisation. The main part of the thesis subsequently deals with Compression. Teradata uses several types of compression. The practical part brings the application of Multi Value Compression which has been performed via an appropriate tool. In order for the generated scripts to work correctly, they had to be adjusted. Additionally, defect reporting was performed and the communication with the development team also took place. The results of the table compression is compared with the estimations. The compression was applied on the production environment. The BLC process consisted of appropriate tables identification and compression testing. Based on the results of the testing, recommendations have been established.

The most of existing text compression methods is based on the same base concept. First the Input text is divided into sequence of text units. These text units cat be single symbols, syllables or words. When compressing large text files, searching for redundancies over longer text units is usually more effective than searching over the shorter ones. But if we choose words as base units we cannot anymore catch redundancies over symbols and syllables. In this paper we propose a new text compression method called Hierarchical compresssion. It constructs hierarchical grammar to store redundancies over syllables, words and upper levels of text. The code of the text then consists of code of this grammer. We proposed a strategy for constructing hierarchical grammar for concrete input text and we proposed an effective way how to encode it. Above mentioned our proposed method is compared with some other common methods of text compression.

This thesis deals with possible and realized decompression and playing of video on platforms, using FPGA unit. For implementation of this player is used platform FITKit, which has integrated VGA connector and large enough RAM memory. It uses a hard drive as memory medium with FAT32 file system.

Generators of pseudorandom sequences are widely used objects, not in the least place because of their application in stream ciphers. One of the ways to improve resistance to different types of attack is to use compression on the generated sequence in order to remove redundant information, that might lead to an attack against the generator. In this work we try to explore from a wider perspective the theoretical foundations for compressing pseudorandom sequences created thus far. Using this general view we will examine some known attacks against the PRN generators and look for a way to resist such attacks.

The mission of the Technology Transfer Programme Office is to increase impact on a society by transferring technologies developed by the European Space Agency. Method and Apparatus for compressing time series is a patented compression algorithm designed to be efficient as its purpose is to run on deep space probes or satellites. The algorithm is inspired by a method for fractal terrain generation, namely the midpoint displacement algorithm. This work introduces fractals, their application and modifying the patented algorithm, in order to achieve greater compression. The modification lies in modifying the displacement mechanism. The modified algorithm is capable of reducing data up to 25 %, compared to the patented algorithm. The modification made the algorithm less efficient. In large-scale test, performed on Rosetta spacecraft telemetry, the modified algorithm achieved around 5 % higher compression.

The semestral thesis describes ECG signal compression methods designed to modify the data for transmission via communication channels. The thesis contains an introduction to Ethernet and explanation of communication in the network. The transport protocols TCP and UDP are discussed in more detail. In the practical part of the thesis was created two separate applications. The first application in the sender's computer opens a text file with the ECG signal. Loaded ECG signal is filtered by cascade of filters to eliminate interference. The resulting signal is displayed. A part of the application is the R wave detection, calculating the length of RR interval and heart rate. The application also allows to compress an ECG signal. ECG signal is sent via Ethernet network via UDP protocol for individual samples. Applications in the recipient's computer receives signal samples from the network. Recieved compressed data is reconstructed. The resulting ECG signal is displayed and there are again detected R waves, the length of RR intervals and sampling frequency are calculated.

The aim of this thesis was introducing the options of conversion between OTDM and WDM technologies. Since this issue is rather extensive, first of all the principle of optical transmission system is described. One chapter presents the effects influencing the optical transmissions. Material absorption, linear and nonlinear scattering and bending losses are mentioned in terms of fiber losses, followed by description of waveguide, chromatic and polarization-mode dispersion of optical fibers. Last part of the chapter presents nonlinear effects, including self-phase modulation, cross-phase modulation and four-wave mixing. The practical part of the thesis deals with multichannel systems. The principles of frequency, space a hybrid multiplexing are explained. Multichannel systems with optical time domain multiplexing and waveguide multiplexing are described in detail and compared. The elements of the transmission chain of multiplex, such as different types of lasers, detectors, modulators, optical amplifiers, splitters, couplers, MUX and DEMUX are discussed. The next part of the thesis was aimed at suggesting the model of mutual conversion between OTDM and WDM systems. First of all, the previously performed experiments concerning the conversion between OTDM and WTM were evaluated. Then the model of OTDM/WDM/OTDM conversion was designed, with explanation of its parts and their function. The general recommendations for practical implementation were are also included. Due to the limited amount of time reserved for access to the simulation program Optsim, the simulations were performed only for certain parts of the proposed conversion model. At the end of the thesis, the proposed model is evaluated.

Ztrátová komprese signálů EKG je užitečná a v současnosti stále se rozvíjející oblast. Stále se vyvíjí nové a nové kompresní algoritmy. V této oblasti ale chybí standardy pro hodnocení kvality signálu po kompresi. Existuje tedy sice mnoho různých kompresních algoritmů, které ale buď nelze objektivně porovnat vůbec, nebo jen zhruba. V oblasti komprese navíc nikde není popsáno, zda mají na výkon kompresních algoritmů vliv patologie, popřípadě jaký. Tato dizertační práce poskytuje přehled všech nalezených metod pro hodnocení kvality signálů EKG po kompresi. Navíc bylo vytvořeno 10 nových metod. V rámci práce byla provedena analýza všech těchto metod a na základě jejích výsledků bylo doporučeno 12 metod vhodných pro hodnocení kvality signálu EKG po kompresi. Také je zde představen nový kompresní algoritmus „Single-Cycle Fractal-Based (SCyF)“. Algoritmus SCyF je inspirován metodou založenou na fraktálech a využívá jednoho cyklu signálu EKG jako domény. Algoritmus SCyF byl testován na čtyřech různých databázích, přičemž kvalita signálů po kompresi byla vyhodnocena 12 doporučenými metodami. Výsledky byly porovnány s velmi populárním kompresním algoritmem založeným na vlnkové transformaci, který využívá metodu „Set Partitioning in Hierarchical Trees (SPIHT)“. Postup testování zároveň slouží jako příklad, jak by měl vypadat standard hodnocení výkonu kompresních algoritmů. Dále bylo statisticky prokázáno, že existuje rozdíl mezi kompresí fyziologických a patologických signálů. Patologické signály byly komprimovány s nižší efektivitou a kvalitou než signály fyziologické.

Purpose of this thesis is to describe the context-based compression methods and their application to multimedia data. There is described the principle of arithmetic coding and prediction by partial matching method, including creation of the probability model. There are also described multimedia data and the basic principles of their compression. The next section presents compression methods, that I implemented at work and their results.