Haar-Wavelet-Based Just Noticeable Distortion Model for Transparent Watermark

Watermark transparency is required mainly for copyright protection. Based on the characteristics of human visual system, the just noticeable distortion (JND) can be used to verify the transparency requirement. More specifically, any watermarks whose intensities are less than the JND values of an image can be added without degrading the visual quality. It takes extensive experimentations for an appropriate JND model. Motivated by the texture masking effect and the spatial masking effect, which are key factors of JND, Chou and Li (1995) proposed the well-known full-band JND model for the transparent watermark applications. In this paper, we propose a novel JND model based on discrete wavelet transform. Experimental results show that the performance of the proposed JND model is comparable to that of the full-band JND model. However, it has the advantage of saving a lot of computation time; the speed is about 6 times faster than that of the full-band JND model

High dynamic range imaging implementation in scene monitoring under bad illumination

Unapređenje kvaliteta slike širenjem dinamičkog opsega u poslednje vreme se intenzivno koristi. Ovo za posledicu ima prisustvo znatno više detalja na slici, što je jako bitno u većini primena. Širenje dinamičkog opsega ima svoje granice i one su definisane fizičkim limitima senzora koji se koristi, tj. ograničenjima njegovog A/D konvertora. Kada je dinamički opseg scene značajno širi od dinamičkog opsega senzora, mnogi detalji neće biti adekvatno prikazani na slici. Međutim, ukoliko senzor inherentno podržava široki dinamički opseg, jasno se može uočiti da je snimljena slika kvalitetnija od one koja se dobija sa standardnog senzora...Improving image quality by expanding the dynamic range is extensively used recently. This results in the presence of significantly more details in the picture, which is very important for most applications. Expanding the dynamic range has its limits, and they are defined by the physical limits of sensor used, i.e. the limits of its A / D converter. When the dynamic range of the scene is significantly wider than the dynamic range of the sensor, many details will not be shown properly in the picture. However, if the sensor inherently supports wide dynamic range, it can be clearly noticed that the recorded image quality is higher than the one obtained with the standard sensors..

Novel source coding methods for optimising real time video codecs.

The quality of the decoded video is affected by errors occurring in the various layers of the protocol stack. In this thesis, disjoint errors occurring in different layers of the protocol stack are investigated with the primary objective of demonstrating the flexibility of the source coding layer. In the first part of the thesis, the errors occurring in the editing layer, due to the coexistence of different video standards in the broadcast market, are addressed. The problems investigated are ‘Field Reversal’ and ‘Mixed Pulldown’. Field Reversal is caused when the interlaced video fields are not shown in the same order as they were captured. This results in a shaky video display, as the fields are not displayed in chronological order. Additionally, Mixed Pulldown occurs when the video frame-rate is up-sampled and down-sampled, when digitised film material is being standardised to suit standard televisions. Novel image processing algorithms are proposed to solve these problems from the source coding layer. In the second part of the thesis, the errors occurring in the transmission layer due to data corruption are addressed. The usage of block level source error-resilient methods over bit level channel coding methods are investigated and improvements are suggested. The secondary objective of the thesis is to optimise the proposed algorithm’s architecture for real-time implementation, since the problems are of a commercial nature. The Field Reversal and Mixed Pulldown algorithms were tested in real time at MTV (Music Television) and are made available commercially through ‘Cerify’, a Linux-based media testing box manufactured by Tektronix Plc. The channel error-resilient algorithms were tested in a laboratory environment using Matlab and performance improvements are obtained