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Isolated word recognition
Vodička, Radek ; Křupka, Aleš (referee) ; Sysel, Petr (advisor)
Main purpose of the thesis is to study the processes and methods of isolated words recognition. In the theoretical part a basic principals are explained. The practical part is about the program creating using these principles in practice. For isolated words recognition Hidden Markov Models (HMM) are used, for obtaining decision symptoms cepstral analysis is chosen.
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Protection of VoIP networks and their testing
Ulický, Ivan ; Sysel, Petr (referee) ; Krajsa, Ondřej (advisor)
Main goal of creating this diploma thesis is existence of increasingly amount of potential threats against IP voice networks (VoIP). The thesis is devoted to testing of various types of attacks and provides some possible solutions for this systems as well. The work points out to a various types of current attacks against either insecure or very little secure structures. The theoretical part is dedicated to analyse and description of wide spectrum of VoIP protocols including signaling protocols (SIP, IAX2), transport protocols (RTP, RTCP) and security protocols (SRTP, ZRTP, IPsec, SDES). Further attention is dedicated to the one of possible open source IP PBX solutions called Asterisk. There is shown a variety of possible attacks against this system due to its openness, because open systems always tend to be more susceptible for various attacks as they need an advanced administration and endless need for searching of new trends in area of security. The last block of the theoretical part is focused on common threats and types of attacks against VoIP networks. The practical part is about design and creation of web application called ,,VoIP Hacks using PHP” written in PHP scripting language and ist main task is to execute three basic attacks: eavesdropping, call drop and call flood. There is also a possibility of port scanning of selected network which is added as supplementary part of this application. The application can be comfortably managed from web browser user interface. All captured data can be displayed directly into the web browser. Tests of the application were performed on Google Chrome and Mozzila Firefox browsers. There is an accent placed on cooperation between the application and terminal linux programmes such as Tshark, BYE Teardown, INVITE flooder or Nmap, which all accept commands from web interface and interpret gained output values back to the web browser.
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Digital Audio Signal Feature Extraction and Modification in Dynamic Plane
Kramoliš, Ondřej ; Sysel, Petr (referee) ; Schimmel, Jiří (advisor)
This thesis deals with basic methods of root mean square and peak value measurement of a digital acoustic signal, algotithms to measure audio programme loudness and true-peak audio level according to recommendation ITU-R BS.1770-1 and digital systems for control of signal dynamic range. It shows achieved results of root mean square and peak value measurement and results of implementation of dynamic processor with general piecewise linear non-decreasing static curve and algorithms according to recommendation ITU-R BS.1770-1.
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Classification of transmission channels based on speech signal analysis
Báňa, Josef ; Sysel, Petr (referee) ; Atassi, Hicham (advisor)
The thesis examines the impact of VoIP transmission channel characteristics on speech parameters. It seeks ways of emulating properties of a selected VoIP transmission channel and creating a network emulation environment. Several scripts have been created in the Matlab development environment and used to modify and divide a continuous recording into parts identical to the original speeches, before passing through the transmission channel. Subsequently a database of speech recordings is created, as affected by selected characteristics - jitter, bandwidth, loss. Within these databases, symptoms are sought as the most evident characteristics of the transmission channel. Using correlation, symptoms are selected that are best suited for automated determination of the properties of transmission channel characteristics such as jitter, loss and bandwidth.
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Modeling of Linear Distortion of Audio Devices
Vrbík, Matouš ; Sysel, Petr (referee) ; Schimmel, Jiří (advisor)
Methods used for correction and modeling of frequency response of sound devices are discussed in this paper. Besides classic methods of digital filter design, more advanced and complex numerial methods are reviewed, Prony and Steiglitz-McBride in particular. This paper focuses on structure utilizing parallel sections of second-order IIR filters. Methods for calculating coefficients of this structure are presented and later implemented. For selected method, utilizing dual frequency warping, an interative algorithm for automatic calculation of parameters necessary to filter design is implemented - so called Particle Swarm Optimization. Six ways of evaluation filter design precision are presented and the results are compared. Functions realizing filter design are implemented in C++, MATLAB and Python. A VST module simulating the filter in real time is also provided.
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Multiplatform audio player
Malár, Ladislav ; Mach, Václav (referee) ; Sysel, Petr (advisor)
This master thesis deals with creating of the cross-platform audio player with the possibility of its use in the speech-language pathology clinic. The theoretical part is focused on the comparison of two multi-platform libraries, of which was one chosen for creating of the player. Subsequently on functionality SQLite database, which was also used as part of the final application. The basis of the practical part is the creation of the cross-platform audio player which is extended about database of patients and also extended about speech signal analysis with the help of VST plugin.
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Echo suppressor according to G.168 recommendation
Lajtkep, Tomáš ; Krajsa, Ondřej (referee) ; Sysel, Petr (advisor)
This master’s thesis deals with conditions and procedures of testing network echo cancellers according to recommendation ITU-T G.168. The point of it’s interest is design of test application which will perform the objective testing their basic and extended features in MATLAB. Theoretical section is concentrated on declaration the ground of echo cancellers and conditions of their testing. Procedures of particular tests follow in next part. The last section designs the testing function which results in entire application which tests submitted canceller and in chosen file write out the report and is also able to display results like graph.
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Lifetime Simulation of Wireless Sensor Network in Matlab
Chadim, Pavel ; Sysel, Petr (referee) ; Šimek, Milan (advisor)
This bachelor’s thesis is concerned with developing the energy model for wireless sensor network. The main features of wireless sensor networks include minimum energy consumption and the maximum date reliability. Furthermore work will be done in simulation lifetime of wireless sensor networks with the possibility to change parameters (error rate, transmission interval) which affects the power consumption of the node.
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