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Home VoIP
Bílek, Tomáš ; Ščuglík, František (referee) ; Ráb, Jaroslav (advisor)
The thesis explores practical applications of VoIP technology at home, in combination with the opensource private branch exchange Asterisk. A substantial part of this work is the documentation of the functioning of the main parts of public switched telephone networks (PSTN) and VoIP networks. Also described are the principles of voice digitization, commonly used codecs and several VoIP protocols. The last part of the thesis focuses on the design, practical realization and verification of two home VoIP installations.
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Comparison of Multimedia Signal Compression Possibilities
Špaček, Milan ; Mišurec, Jiří (referee) ; Škorpil, Vladislav (advisor)
Thesis deals with multimedia signal comparison of compression options focused on video and advanced codecs. Specifically it describes the encoding and decoding of video recordings according to the MPEG standard. The theoretical part of the thesis describes characteristic properties of the video signal and justification for the need to use recording and transmission compression. There are also described methods for elimination of encoded video signal redundancy and irrelevance. Further on are discussed ways of measuring the video signal quality. A separate chapter is focused on the characteristics of currently used and promising codecs. In the practical part of the thesis were created functions in Matlab environment. These functions were implemented into graphic user interface that simulates the activity of functional blocks of the encoder and decoder. Based on user-specified input parameters it performs encoding and decoding of any given picture, composed of images in RGB format, and displays the outputs of individual functional blocks. There are implemented algorithms for the initial processing of the input sequence including sub-sampling, as well as DCT, quantization, motion compensation and their inverse operations. Separate chapters are dedicated to the realisation of codec description in the Matlab environment and to the individual processing steps output. Further on are mentioned compress algorithm comparisons and the impact of parameter change onto the final signal. The findings are summarized in conclusion.
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Codec Detection from Speech
Jon, Josef ; Matějka, Pavel (referee) ; Černocký, Jan (advisor)
Tato práce se zabývá detekcí kodeků z komprimovaného řečového signálu. Cílem bylo zjistit, jaké charakteristiky rozlišují jednotlivé kodeky a následně vytvořit prostředí vhodné pro experimenty s různými typy a konfiguracemi klasifikátorů. Použity byly Support vector machines a především neuronové sítě, které byly vytvořeny pomocí nástroje Keras. Hlavním přínosem této práce je experimentální část, ve které je analyzován vliv různých parametrů neuronové sítě. Po nalezení nejvhodnější kombinace parametrů dosáhla síť přesnosti klasifikace přes 98% na testovací sadě obsahující data z 6 kodeků.
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Error protection of data transmission using BCH Codes
Kašpar, Jaroslav ; Křivánek, Vítězslav (referee) ; Němec, Karel (advisor)
The thesis Data transmission error-protection with BCH codes deals with a large class of random-error correcting cyclic codes which are able to protect binary data and can be used for example in data storages, high speed modems. Bose, Chaudhuri and Hocquenghem (BCH) codes operate over algebraic structures called Galois fields. The BCH encoding is the same as cyclic encoding and can be done with linear feedback shift register but decoding is more complex and can be done with different algorithms - in this thesis there are two algorithms for decoding Peterson and Berlekam-Massey mentioned. The aim of this thesis is to find BCH code which is able to correct t = 6 independent errors in up to data sequence n = 150 bits, then peruse possible realizations of the codecs and set criteria for the best realization, then design and test this realization. This thesis is split into three main parts. In the first part there are encoding and decoding methods of the BCH code generally described. The second part deals with selecting of the right code and realization. There was chosen BCH (63,30) code and realization with FPGA chip. In the last part is described design of BCH encoder and decoder and compilation in the Altera design software.
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Video mixer/translator for web-based videoconference system
Hutar, Jan ; Balík, Miroslav (referee) ; Číka, Petr (advisor)
Bachelor s thesis specialises in a basic description, comparing and processing of video standards H.264 and VP8 in real time. Particularly it concerns a support of videoconfe- rence systems working with those mutually incompatible standards. The work enquires and tests two most considerable software devices convenient with basic requirements for working with video in real time and available with LGLP licence respectively FFmpeg and GStreamer. The thesis suggests practice video mix implementation of data input and the way of code translation into required outgoing stream. FFmpeg tool has been used for realization and message of mixer/translator and simple interface has been established available from web browser with assistance of HTML, PHP and Javascript.
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Streaming of compressed multimedia content
Tesař, Pavel ; Číka, Petr (referee) ; Müller, Jakub (advisor)
The topic of the master's thesis is about transmission of multimedia via network with help of compression’s algorithm used in codec MPEG-4 part 10 and Real Time Protocol (RTP). First part of this master thesis will be familiarization with basic terms about multimedia. It will be queried about techniques of compression axioms for audio and video, justification for necessary use of compression in transmitting multimedia via network. Also, here will be subscribed principles and properties of Real Time Protocol, which was designed for multimedia stream. From the start, competent codec for implementation of two applications (client, server) with read raw video and audio data, will choose the following : compression with help of codec Theora (Vorbis), transfer via network in RTP packets, decode and play at visual form for end user. Complete subscription of implementation for both applications written in programming languages C/C++ and Java, will be certain. The basic overview about this problematic experience with implementation, which were here concluded, are the reasons for reading this master thesis.
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Microcontroller based system for voice transfer
Kapitančik, Maroš ; Kaczmarczyk, Václav (referee) ; Bradáč, Zdeněk (advisor)
The aim of this thesis have to introduce us with digitalized transmission of speech with limited data flow and construct device witch can comunicate on this level. Theoretical part is describing base creation of sound human preception and issues with digitizing. Proposed device uses hardware codec VS1063a. Coding is applied with IMA ADPCM. Scale of incoming analog audio signal can be up to 4kHz. Inside system is controled by microcontroler, witch take care about others parts. For comunication with other moduls is used wireless transceivers module. Software part describes confuguration and selected options of every individual part. Next is explained principle of entire system. For comunication was implemented packet data structure. This implementation raised data flow but saved error state in transmit.
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Lossless Video Compression
Kafka, Jan ; Polok, Lukáš (referee) ; Bařina, David (advisor)
This thesis is about the lossless video compression using 3D prediction. At first is introduced the necessary theory about image data modification. This part serves to define important terms, which are needed to start the creative work itself. Then several variants of codec's structure proposals follow, as well as the choice of methods and description of expected characteristics. Here we can get the first idea how the codec works. Then there is a description of some implementation's details, which could give a detailed insight into the codec's inner architecture. In the last part of the work, the implemented codec is tested and its characteristics are compared to another lossless codecs. The result is that the own codec, using the 3D prediction, can defeat all other tested codecs with its compression ratio.
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