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Audio signal restoration using the Plug-and-Play method
Švento, Michal ; Rajmic, Pavel (referee) ; Mokrý, Ondřej (advisor)
The topic of this thesis is the reconstruction of a digital audio signal that is corrupted in two ways, sample dropout and added noise. The classical approach to solving these problems are convex optimization algorithms, which are based on the sparsity of the audio signal. In this thesis, we try a new Plug-and-Play method that embeds a deep network, the denoiser, into conventional algorithms and attempt to solve these two distinct problems using a single algorithm. At the end of the paper, the algorithms are implemented and tested with the most common metrics and these results are evaluated. Modern methods have shown us that they can be more variable in the choice of parameters and offer more balanced solutions.
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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.
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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.
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Unfolded Low-rank + Sparse Reconstruction for MRI
Mokrý, Ondřej ; Vitouš, Jiří
We apply the methodology of deep unfolding on the problem of reconstruction of DCE-MRI data. The problem is formulated as a convex optimization problem, solvable via the primal–dual splitting algorithm. The unfolding allows for optimal hyperparameter selection for the model. We examine two approaches – with the parameters shared across the layers/iterations, and an adaptive version where the parameters can differ. The results demonstrate that the more complex model can better adapt to the data.
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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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Impulse noise detection in audio signals
Hůla, Josef ; Ištvánek, Matěj (referee) ; Mokrý, Ondřej (advisor)
Study disserts known method of detecting impulsive noise in audiosignal. Differential, filtering, autoregressive and ARMA methods are discussed. First, each method is theoretically examined and the character of impulsive disturbances is presented. Later an~implementation of each method is presented and results of their performance is compared. In order to have comparable results, the methods are tested on synthetic impulses with known position and duration and also on recordings containing real impulsive noise.
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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.
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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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Inconsistent Audio Declipping Performance Enhancement Based On Audio Inpainting
Mokrý, Ondřej ; Záviška, Pavel
Some of the state-of-the-art audio declipping methods are not consistent with the observedsignal, meaning that they do not keep the a priori undegraded (reliable) samples. These samples canbe directly substituted in the reconstructed signals, but this may create audible artifacts due to thesharp transitions between the declipped and the substituted parts. We propose two methods based onaudio inpainting, which deal with these transitions. As a result, we observe a significant improvementof the PEAQ ODG values, but only for some of the declipping algorithms considered.
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Restoration of missing audio signal samples using a psychoacoustic model
Švento, Michal ; Záviška, Pavel (referee) ; Mokrý, Ondřej (advisor)
This bachelor thesis deals with the reconstruction of short-time damaged audio signal. The signal is represented by sparse signal representation using discrete Gabor transform. Convex optimalization tools are used for the reconstruction. The optimalization problem is solved using the Douglas—Rachford and Chambolle—Pock algorithm. Psychoacoustic model is involved in algorithm to obtain better results in objective metrics. The comparison is realised by an objective method SDR, PEMO-Q and also subjectively.
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