Chamira U. S. Edussooriya

Five-Dimensional Depth-Velocity Filtering for Enhancing Moving Objects in Light Field Videos

Five-dimensional (5-D) light field video (LFV) (also known as plenoptic video) is a more powerful form of representing information of dynamic scenes compared to conventional three-dimensional (3-D) video. In this paper, the 5-D spectrum of an object in an LFV is derived for the important practical case of objects moving with constant velocity and at constant depth. In particular, it is shown that the region of support (ROS) of the 5-D spectrum is a skewed 3-D hyperfan in the 5-D frequency domain, with the degree of skew depending on the velocity and depth of the moving object. Based on this analysis, a 5-D depth-velocity digital filter to enhance moving objects in LFVs is proposed, described and implemented. Further, by means of the commercially available Lytro light-field camera, LFVs of real scenes are generated and used to test and confirm the performance of the 5-D depth-velocity filters for enhancing such objects.

Low-Complexity Maximally-Decimated Multirate 3-D Spatio-Temporal FIR Cone and Frustum Filters

A low-complexity multirate 3-D spatio-temporal FIR cone and frustum filter structure is proposed having potential applications as a spatio-temporal directional filter. The cone filter structure employs a 1-D modified discrete Fourier transform (DFT) filter bank and 2-D spatial filters. The frustum filter having a double-frustum-shaped passband oriented along the temporal frequency axis is approximated by employing an appropriate subset of subbands. Low computational complexity is achieved by maximal decimation in the temporal dimension, and by employing the DFT-polyphase realization to implement the 1-D modified DFT filter bank. The cone and frustum filters are almost alias free, and provide near-perfect reconstruction. The reduction in computational complexity, relative to undecimated and under-decimated realizations, is numerically confirmed by means of a potential application involving the attenuation of strong broadband plane wave interference.

A 5-D IIR depth-velocity filter for enhancing objects moving on linear-trajectories in light field videos

A 5-D IIR depth-velocity filter is proposed for enhancing objects moving on linear trajectories, with constant velocity and at constant depth, in light field videos (also known as plenoptic videos). The passband of the proposed filter is a plane in the 5-D frequency domain and is realized by cascading three first-order 5-D IIR filters having 4-D hyperplanar passbands of appropriate orientations. Numerical simulation results are presented to confirm the performance of the proposed filter.

A LOW-COMPLEXITY 3D SPATIO-TEMPORAL FIR FILTER FOR ENHANCING LINEAR TRAJECTORY SIGNALS

A low-complexity 3D FIR filter is proposed for selectively enhancing severely corrupted linear trajectory spatio-temporal signals. The proposed 3D FIR filter is separable and consists of a 3D spatio-temporal wide-angle FIR cone filter between two 2D spatial variable-shift filters. Low complexity of the 3D spatio-temporal wide-angle FIR cone filter is achieved by exploiting the spatial-symmetry of the passband and by employing maximal decimation in the temporal dimension. Compared to existing techniques, the proposed 3D FIR filter provides significant reduction of the computational complexity for similar SINR improvement.

Under-decimated 3D FIR space-time cone filters using DFT polyphase filter banks for attenuation of radio frequency interference

It is shown that, by employing 2D FIR spatial filters and under-decimation, the computational time of 3D space-time polyphase cone filter banks may be significantly reduced. The resultant input-output 3D transfer function is almost alias-free and, further it is shown that the proposed cone filters can be used to effectively attenuate such stopband signals as radio frequency interference in radio astronomy applications.

Space-Time Digital Filtering of Radio Astronomical Signals using 3-D Cone Filters

In this paper, 3-D space-time (ST) processing is proposed as a technique to enhance signals of interest (SOIs) by attenuating near-over-the-horizon radio frequency interferences (RFIs) that exist on dense phased arrays used in the next generation of radio telescopes. The proposed approach is based on the difference between the regions of support (ROSs) in the 3-D frequency domain of the Fourier transforms of the SOIs and RFIs. A 3-D linear phase filter bank structure, consisting of 1-D FIR filters and 2-D circularly symmetric FIR filters, is employed to suppress the RFIs. The performance of the proposed 3-D ST filtering approach is illustrated using synthesized broadband (BB) SOIs and BB RFIs on dense aperture arrays (DAAs) and on focal plane arrays (FPAs). Results are presented that indicate the potential for successful mitigation of near-over-the-horizon BB RFIs without significantly distorting the BB SOIs. The advantage of the proposed ST filtering approach is its inherent capability of BB processing.

Using 1-D Variable Fractional-Delay Filters to Reduce the Computational Complexity of 3-D Broadband Multibeam Beamformers

A multibeam filter bank (MBFB) is proposed for recovering the broadband far-field signals received from multiple directions while rejecting interfering signals and noise. The MBFB consists of two sections. The first section employs variable fractional delays and independently steers the directions of the multiple beams. It achieves low complexity by using the Farrow structure. The second section achieves low complexity by maximal decimation methods and by exploiting the spatial symmetry of a 3-D double-frustum-shaped passband. Superior performance and lower complexity compared with previous methods are numerically confirmed for a typical narrow-angle broadband multibeam beamformer of the type that could be used in radio astronomy.

Enhancing Moving Objects in light field videos using 5-D IIR adaptive depth-velocity filters

The spectrum of an object moving in 5-D light field videos (also known as plenoptic videos) with constant velocity and at non-constant depth is analyzed. Based on this analysis, a novel 5-D IIR adaptive depth-velocity filter is proposed for enhancing such objects. The time-variant coefficients of the proposed 5-D IIR adaptive depth-velocity filter are derived in closed form. Numerical simulation results confirm the effectiveness of the proposed filter compared to 3-D IIR adaptive velocity filters and 4-D IIR adaptive depth filters.

Blended induction program for electronic engineering freshmen

This paper presents learning and teaching experiences gathered from an induction program conducted at the Department of Electronic and Telecommunication Engineering, University of Moratuwa, Sri Lanka for newly enrolled undergraduate students. The induction program, named as the pre-academic term, was an experimental effort to explore the applicability of blended leaning concepts to enhance the learning experience of Engineering freshmen, while enabling smooth transition from high school to university education. In addition to standard lectures, an integral part of the program was in-class demonstrations, where electronic circuits were assembled from scratch on a printed circuit board and demonstrated using a projected camera during the lectures. Organization, learning objectives, brief description of the example projects are presented along with a summary of formal student feedback. More than 85% of the freshmen indicated that the induction program helped them to smoothly begin the university education. A qualitative assessment in the laboratory work indicated that about 98% of the students successfully completed the assigned hands-on activities.

A novel 5-D depth---velocity filter for enhancing noisy light field videos

A 5-D depth–velocity filter is proposed for enhancing moving objects in noisy light field videos (LFVs) (also known as plenoptic videos). The proposed filter consists of an ultra-low complexity 5-D IIR depth filter and a 5-D FIR velocity filter. The 5-D IIR depth filter is employed to denoise a noisy LFV. The denoised LFV is then utilized to estimate the 3-D apparent velocity of the moving object of interest. The 5-D FIR velocity filter is designed based on the estimated 3-D apparent velocity and is used to enhance the moving object of interest while attenuating other interfering moving objects. Experimental results confirm the effectiveness of the proposed 5-D depth–velocity filter compared to previously reported 5-D depth–velocity filters.