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Web applications supporting education of audio signals generation and processing
Tkadlec, Vojtěch ; Schimmel, Jiří (referee) ; Rajmic, Pavel (advisor)
The main goal of the diploma thesis was the creation of 3 web applications for interactive support of studying courses in the area of digital signal processing using the programming language JavaScript, the markup language HTML, and the Web Audio API interface. The topics included additive synthesis, ADSR time envelope, amplitude modulation, and approximation of 1D signals using discrete cosine transform. The written part of the thesis also focuses on the tools used for the practical part of the thesis. For better understanding of the topics, four web applications were created, and a separate web application was created specifically for the topic of ADSR envelope.
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Handwriting recognition using neural network
Petr, Martin ; Surynek, Pavel (advisor) ; Pergel, Martin (referee)
Title: Handwriting recognition using neural network Author: Martin Petr Department: Department of Theoretical Computer Science and Mathematical Logic Supervisor: RNDr. Pavel Surynek, PhD. Supervisor's e-mail address: pavel.surynek@mff.cuni.cz Abstract: Pattern recognition finds its use in many fields whose development has been affected by computer science and computer technology. Among these, the conversion of handwritten or printed text into computer-encoded text has a particularly prominent position. In the presented work we propose a method for recognizing handwritten characters in real-time using feedforward neural network as the basic classification mechanism. Dealing with differences among individual instances of each handwritten character we thoroughly explored the possibility of suppressing these while emphasizing characteristics that are essential for successful recognition. For these purposes we employed discrete cosine transform, whose time-proven application in audio and video signal processing or even directly in the field of pattern recognition provided a convincing argument for us to use it in our work as well. As a means of suppressing variations among various writing instruments we proposed preprocessing of input images using binarization and skeletonization. The designed method was...
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Lossy Light Field Compression
Dlabaja, Drahomír ; Milet, Tomáš (referee) ; Bařina, David (advisor)
The aim of this paper is to propose, implement and evaluate a new lossy compression method for light field images. The proposed method extends the JPEG method to four dimensions and brings new ideas which lead to better compression performance. Correlation between light field views is exploited in both dimensions by four-dimensional discrete cosine transformation. The lossy part of the encoding is performed by quantization, similarly to the JPEG method. The proposed method is implemented as a program library in a C++ language. This paper compares the proposed method to JPEG, JPEG 2000 and HEVC intra image compression methods and HEVC video compression method. The results show that the proposed method outperforms the reference methods with images with a higher amount of views. HEVC video method is better for images with fewer views or for very low bitrates.
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New Transforms for JPEG Format
Svoboda, Stanislav ; Polok, Lukáš (referee) ; Bařina, David (advisor)
The discrete cosine transform (DCT) can be found in the heart of many image compression algorithms. Specifically, the JPEG format uses a lossy form of compression based on that transform. Since the standardization of the JPEG, many other transforms become practical in lossy data compression. This article aims to analyze the use of these transforms as the DCT replacement in the JPEG compression chain. Each transform is examined for different image datasets and subsequently compared to other transforms using the peak signal-to-noise ratio (PSNR) and SSIM. Our experiments show that an overlapping variation of the DCT, the local cosine transform (LCT), overcame the original block-wise transform at low bitrates. At high bitrates, the discrete wavelet transform employing the Cohen-Daubechies-Feauveau 9/7 wavelet offers about the same compression performance as the DCT.
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Image compression simultaneously in spatial and frequency domains
Vaněk, Martin ; Šorel, Michal (referee) ; Rajmic, Pavel (advisor)
This thesis is concerned with image compression. Firstly, JPEG lossy compression and origin of typical artifacts is explained. Then, some basic concepts are introduced and sparse representation of signals are presented. Then presentation of proximal algorithms is folowed and formulation of two optimazation problems, wchich removes typical artifacts on edges, created by JPEG compression. These problems are then solved by proximal algorithms.
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Image compression simultaneously in spatial and frequency domains
Vaněk, Martin ; Šorel, Michal (referee) ; Rajmic, Pavel (advisor)
This thesis is concerned with image compression. Firstly, JPEG lossy compression and origin of typical artifacts is explained. Then, some basic concepts are introduced and sparse representation of signals are presented. Then presentation of proximal algorithms is folowed and formulation of two optimazation problems, wchich removes typical artifacts on edges, created by JPEG compression. These problems are then solved by proximal algorithms.
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Handwriting recognition using neural network
Petr, Martin ; Surynek, Pavel (advisor) ; Pergel, Martin (referee)
Title: Handwriting recognition using neural network Author: Martin Petr Department: Department of Theoretical Computer Science and Mathematical Logic Supervisor: RNDr. Pavel Surynek, PhD. Supervisor's e-mail address: pavel.surynek@mff.cuni.cz Abstract: Pattern recognition finds its use in many fields whose development has been affected by computer science and computer technology. Among these, the conversion of handwritten or printed text into computer-encoded text has a particularly prominent position. In the presented work we propose a method for recognizing handwritten characters in real-time using feedforward neural network as the basic classification mechanism. Dealing with differences among individual instances of each handwritten character we thoroughly explored the possibility of suppressing these while emphasizing characteristics that are essential for successful recognition. For these purposes we employed discrete cosine transform, whose time-proven application in audio and video signal processing or even directly in the field of pattern recognition provided a convincing argument for us to use it in our work as well. As a means of suppressing variations among various writing instruments we proposed preprocessing of input images using binarization and skeletonization. The designed method was...
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Effect of Noise on Video Compression
Anton, Matyáš ; Drábek, Vladimír (referee) ; Bařina, David (advisor)
Videos are in fact image signals and as such, they are susceptible to distortions in the form of noise. This thesis' goal was to determine how the presence of noise can affect the results of image data compression as well as what impact might the lossy compression have on the noise present. Four contemporary compression formats were chosen, namely H.264, H.265, Motion JPEG 2000 and DIRAC, representing different approaches to the video compression, especially the contrast between a discrete cosine transform and a discrete wavelet transform.
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Hierarchical Coding of Moving Pictures
Špaček, Milan ; Rášo, Ondřej (referee) ; Schimmel, Jiří (advisor)
Bachelor‘s thesis deals with hierarchical coding – scaling – of moving pictures in currently widely used compression algorithms MPEG-2 and MPEG-4. Scaling is the process whereby the encoded data stream is divided into graduated layers, adapted especially to the possibilities of transmission media and capabilities of terminal devices. The content of the base layer is a signal with reduced quality. The content of one or more extension layers is a supplementary picture information, completing the signal to a full quality form. The decoder, depending on its abilities and external circumstances, can decode only the relevant layers from the received bitstream. The thesis focuses in the theoretical part on the detailed description of encoding and decoding video signal according to MPEG standards using three types of scalability. In the concrete, the spatial, qualitative SNR and Fine granular scalability are mentioned. In the practical part of thesis was created an educational application in Matlab environment with its own graphical user interface, which implements the functions performing spatial, qualitative SNR and Fine granular scalability. Based on the user-specified input parameters, it performs scaling the image and then displays the outputs of individual layers after scaling and after the image reconstruction. The input of the programme, in which a hierarchical coding is done, is the image in bitmap format with any size in RGB format.
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Digital image watermarking
Číka, Petr ; Krbilová, Izabela (referee) ; Makáň, Florian (referee) ; Němec, Karel (advisor)
Digital image watermarking has developed for the purpose of protecting intellectual property rights to multimedia data. The focus of this thesis is searching for an alternative solution of digital image watermarking methods. A detailed analysis of watermarking methods particularly in the frequency domain, and the modification of these methods are the main aim of this work. Improved performance in watermark extraction is one of the main goals. First, the common static image watermarking methods, possible attacks on the watermarked data and techniques for objective measurement of watermarked image quality are shortly introduced. Techniques which use the space domain for watermarking ar described in the next part of this work. It is about techniques which insert the watermark into the least significant bits of an image both in the RGB domain and in the YUV domain. The main part of the thesis depicts modified and newly developed static image watermarking methods in the frequency domain. These methods use various transforms and error-correction codes, by means of which the watermark robustness increases. All the methods developed are tested in MATLAB. Results together with tables and graphs are one part of work. The end of the thesis is devoted to a comparison of all the developed methods and their evaluation.
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