National Repository of Grey Literature 176 records found  previous11 - 20nextend  jump to record: Search took 0.01 seconds. 
Modern methods of reconstruction of saturated signals
Beránek, Šimon ; Smékal, Zdeněk (referee) ; Rajmic, Pavel (advisor)
This master's thesis deals with the problems of signal degradation caused by clipping and methods for its removal and signal restoration. Basics of mathematical formulations needed, signal processing and optimalization tasks are described. The goal of this thesis is the implementation of basic algorithms used for hard declipping and creating an audio database later used for testing these algorithms. These implementations are followed by modeling of soft clipping and later restored using the improved algorithms. The restorations are tested using the subjective hearing test MUSHRA and the results are statistically evaluated.
Image hashing using compressed sensing
Kopec, Peter ; Číka, Petr (referee) ; Rajmic, Pavel (advisor)
This thesis is devoted to the analysis and implementation of image hashing based on the article "Robust image hashing with compressed sensing and ordinal measures"[3]. Image hashing uses so-called perceptual hashing methods. These methods have great applications in computer vision science, and the properties of these methods allow us to compare the similarity of hashed images and classify these images into groups. We can use this comparison, for example, to search images on the Internet for various reasons. In the theoretical part, we will talk more about the properties of these hashing methods and describe the hashing method according to the mentioned paper, we will focus most on what is compressive sampling, saliency map and how we achieve it. In the practical part, we will prepare a test dataset using Python scripting language and implement the hashing method according to the mentioned article. Then we test this hashing method on this dataset and finally compare it with another hashing method.
Attacking biometric hashing via optimization techniques
Mlčáková, Kristýna ; Mokrý, Ondřej (referee) ; Rajmic, Pavel (advisor)
The thesis deals with biometric hashing, which is a two-factor authentication method that combines a secret key with biometric data in order to create a secure biomeric template for authentication purposes. The thesis first discusses the theoretical aspects of this issue and then focuses on the implementation of this concept. The paper also describes attacks on biometric hashing systems that are subsequently implemented. Practically performed attacks are based on the assumption that the attacker knows the user’s secret key and biohashes stored in the database. Two methods of attacks are applied. These methods are able to reconstruct the biometric data of an authorized user and related biohashes. Methods are based on 1-bit compressive sensing approach. The aim of the thesis is to evaluate the effectivity of the attacks on biometric hashing systems and to make a conclusion about the security of such systems.
Interactive web applications supporting education of 3D graphics
Priščák, Jaroslav ; Mokrý, Ondřej (referee) ; Rajmic, Pavel (advisor)
The use of interactive web applications has the potential to significantly improve the teaching of 3D computer graphics. By taking advantage of the convenience and accessibility of the web, these applications can provide students with more engaging and interactive learning. This thesis explores the development of such applications to help understand the fundamentals required for calculations such as normal vectors and tangent planes. Further, the thesis describes Phong's illumination model, the environmental and material parameters that affect the resulting light reflection. It then describes the different shading models such as flat, Gouraud and Phong shading models, describing the various advantages and disadvantages, the differences in computational complexity in determining the color of a fragment and individual pixels. It also explains the code on which these applets are built.
Image Edge Detection Using Convex Optimisation
Novosadová, Michaela ; Róka, Rastislav (referee) ; Dostál, Otto (referee) ; Rajmic, Pavel (advisor)
Detekce hran v obraze je jednou z nejdůležitějších technik v oblasti digitálního zpracování obrazu. Bývá používána, mimo jiné, jako první krok segmentace obrazu. I proto stále zůstává v oblasti zájmu vědců, kteří se snaží vyvíjet stále lepší detekční přístupy. Hlavním cílem této práce je nalezení vhodné metody detekce hran v obraze pomocí konvexní optimalizace. Navržená metoda je založená na řídkém modelování, a její hlavní část je formulována jako konvexní optimalizační problém, který je řešen pomocí proximálních algoritmů. Pro definici optimalizačního problému se předpokládá, že signál může být modelován jako přeparametrizovaný po částech polynomiální signál, který se skládá z disjunktních segmentů. Počet těchto segmentů je výrazně menší než je počet vzorků signálu, což vybízí k použití řídkosti. Návrh vhodného optimalizačního problému nejdříve probíhá na jednorozměrných signálech, jelikož implementace a porovnání jednotlivých algoritmů je pro jednorozměrné signály výrazně jednodušší a časově méně náročná, než pro dvojrozměrné. První část práce se věnuje představení základní teorie z oblasti zpracování signálu, řídkosti, konvexní optimalizace a proximálních algoritmů, a dále prezentuje průřez používanými metodami pro hranovou detekci v obraze. Druhá část práce se zaměřuje na návrh a následné vyhodnocení jednotlivých optimalizačních problémů pro segmentaci jednorozměrných syntetických signálů, které jsou poškozeny šumem. Vyhodnocení je provedeno jak z pohledu přesnosti detekce skoků tak i odšumění. Poslední část práce je věnována rozšíření nejlépe fungujícího přístupu k detekci skoků v jednorozměrném signálu pro použití na detekci hran v obraze. V této části je navržený přístup testován na standardizovaném datasetu obrázků, který obsahuje manuálně označené hrany od několika subjektů. Výsledky navržené metody jsou vyhodnoceny pomocí precision-recall křivek a jejich maximálního F skóre a následně porovnány s ostatními metodami hranové detekce.
Modern methods of reconstruction of saturated audio signals
Mikulášková, Aneta ; Mokrý, Ondřej (referee) ; Rajmic, Pavel (advisor)
This thesis presents a variety of soft clipping simulations and their respective de-clipping functions. A restoration method uses a Douglas-Rachford algorithm (already verified for hard de-clip). The algorithm is extended by inverse functions and simultaneous de-quantization is proposed. The simulations are applied to artificial signals, and audio samples, and the proposal is tested in the computing environment MATLAB. A restored signal is later evaluated by objective and subjective methods.
Web applications supporting education of audio signal processing
Malcher, Tomáš ; Mokrý, Ondřej (referee) ; Rajmic, Pavel (advisor)
This bachelors thesis deals with a creation of web applications using JavaScript language. These web applications should be helpful in signal processing classes by showing and explaining different phenomenons to students. Students can see how different parameters affect the outcome of said issue. The theory needed for understanding and implementation is covered by this thesis. Thesis covers key parts of the code of said web applications and the libraries used for their implementaition.
Demonstrational programs for music record processing
Jonáš, Petr ; Rajmic, Pavel (referee) ; Číž, Radim (advisor)
This bachelor’s thesis describes the processing of music records and signals. Demonstration programs were created in Matlab. In this thesis were created function of equalization, transposition and sound effects. In this thesis was created application for determining the similarity of signals. For both programs was created graphic user interface.
Innovation of digital image processing exercises
Honkyš, Jan ; Záviška, Pavel (referee) ; Rajmic, Pavel (advisor)
The bachelor thesis deals with innovation of lectures in the field of image processing. The innovation consists in the preparation of instructions for individual exercises in alternative programs, Adobe Photoshop CS6 Extended is now used in exercises. The first chapter deals with color models, spaces, color management and bitmap file formats. The second chapter introduces alternative bitmap editors – Adobe Photoshop CC 2021, GIMP, Affinity Photo, Zoner Photo Studio X, Corel PaintShop Pro 2022. Then they are compared according to several criteria, the cost for the school and students is considered and a selection of programs suitable for teaching image processing is made. In the next chapters, instructions for individual exercises are made in selected programs and an evaluation of the suitability of these programs for teaching is performed.
Modern methods of reconstruction of saturated audio signals
Mikulášková, Aneta ; Mokrý, Ondřej (referee) ; Rajmic, Pavel (advisor)
This thesis presents a variety of soft clipping simulations and their respective de-clipping functions. A restoration method uses a Douglas-Rachford algorithm (already verified for hard de-clip). The algorithm is extended by inverse functions and simultaneous de-quantization is proposed. The simulations are applied to artificial signals, and audio samples, and the proposal is tested in the computing environment MATLAB. A restored signal is later evaluated by objective and subjective methods.

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