Browsing by Subject "FIR filters"

Now showing 1 - 6 of 6

Open Access
Moving object detection in video by detecting non-Gaussian regions in subbands and active contours
(IEEE, 2003-09) Gök, M. Y.; Çetin, A. Enis
A multi-stage moving object detection algorithm in video is described in this paper. First, the camera motion is eliminated by motion compensation. An adaptive subband decomposition structure is then used to analyze the difference image. In the high-band subimages, moving objects which produce outliers are detected using a statistical test determining non-Gaussian regions. It turns out that the distribution of the subimage pixels is almost Gaussian in general. But, at the object boundaries the distribution of the pixels in the subimages deviates from Gaussianity due to the existence of outliers. Regions containing moving objects in the original image frame are detected by detecting regions containing outliers in subimages. Finally, active contours are initiated in these regions in the wavelet domain and object boundaries are accurately estimated.
Open Access
QR-RLS algorithm for error diffusion of color images
(SPIE, 2000) Unal, G. B.; Yardimci, Y.; Arıkan, Orhan; Çetin, A. Enis
Printing color images on color printers and displaying them on computer monitors requires a significant reduction of physically distinct colors, which causes degradation in image quality. An efficient method to improve the display quality of a quantized image is error diffusion, which works by distributing the previous quantization errors to neighboring pixels, exploiting the eye's averaging of colors in the neighborhood of the point of interest. This creates the illusion of more colors. A new error diffusion method is presented in which the adaptive recursive least-squares (RLS) algorithm is used. This algorithm provides local optimization of the error diffusion filter along with smoothing of the filter coefficients in a neighborhood. To improve the performance, a diagonal scan is used in processing the image.
Open Access
Restoration of error-diffused images using projection onto convex sets
(2001) Unal G.B.; Çetin, A.E.
In this paper, a novel inverse halftoning method is proposed to restore a continuous tone image from a given half-tone image. A set theoretic formulation is used where three sets are defined using the prior information about the problem. A new space-domain projection is introduced assuming the halftoning is performed using error diffusion, and the error diffusion filter kernel is known. The space-domain, frequency-domain, and space-scale domain projections are used alternately to obtain a feasible solution for the inverse halftoning problem which does not have a unique solution.
Open Access
Robust adaptive filtering algorithms for α-stable random processes
(Institute of Electrical and Electronics Engineers, 1999-02) Aydin, G.; Arıkan, Orhan; Çetin, A. Enis
A new class of algorithms based on the fractional lower order statistics is proposed for finite-impulse response adaptive filtering in the presence of α-stable processes. It is shown that the normalized least mean p-norm (NLMP) and Douglas' family of normalized least mean square algorithms are special cases of the proposed class of algorithms. A convergence proof for the new algorithm is given by showing that it performs a descent-type update of the NLMP cost function. Simulation studies indicate that the proposed algorithms provide superior performance in impulsive noise environments compared to the existing approaches.
Open Access
Sub-band equalization filter design for improving dynamic range performance of modulated wideband converter
(IEEE, 2017) Alp, Y. K.; Gök, Gökhan; Korucu, A. B.
In this work, we propose an iterative method to improve the dynamic range performance of the Modulated Wideband Converter (MWC), which is multi-channel sampling system for digitizing wideband sparse signals below the Nyquist limit without loss of information by using compressive sensing techniques. Our method jointly designs FIR filters for each subband to equalize the frequency response characteristics of the all sub-bands of the MWC. Obtained results from the extensive computer simulations of the MWC system show that the proposed method improves the dynamic range performance of the MWC system significantly.
Open Access
Theoretical investigation on exact blind channel and input sequence estimation
(IEEE, Piscataway, NJ, United States, 1999) Özdemir, A. K.; Arıkan, Orhan
Recent work on fractionally spaced blind equalizers have shown that it is possible to exactly identify the channel and its input sequence from the noise-free channel outputs. However, the obtained results are based on a set of over-restrictive constrainst on the channel. In this paper it is shown that the exact identification can be achieved in a broader class of channels.