Browsing by Author "Agathoklis, P"

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    A 3-D sparse FIR frustum filter for enhancing broadband plane waves
    (IEEE, 2019) Wijesekara, RT; Edussooriya, CUS; Bruton, LT; Agathoklis, P
    A 3-D FIR frustum filter having sparse coefficients is proposed for enhancing broadband plane waves received by uniform aperture arrays. Motivated by the design technique of 1-D interpolated FIR filters, the proposed filter is realized by cascading a spatially-upsampled 3-D FIR prototype filter having a frustum-shaped passband and a 3-D FIR masking filter having a parallelepiped passband. Sparsity of the filter coefficients is achieved through the spatial upsampling of the coefficients of the prototype filter and by hard-thresholding the coefficients of both prototype and masking filters. The proposed 3-D FIR frustum filter saves 39:5% multiplications and 66:6% additions compared to the state-of-the-art 3-D FIR frustum filters without degrading the performance in enhancing broadband plane waves.
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    Design and Implementation of 5-D IIR Depth Velocity Filters for Light Field Video Processing
    (Institute of Electrical and Electronics Engineers Inc., 2019) Wijenayake, C; Liyanage, N; Edussooriya, C; Seatang, H; Agathoklis, P; Bruton, L
    The design and hardware implementation of a lowcomplexity signal processing algorithm is proposed for real-time depth-velocity filtering in 5-D light field videos (LFVs). The proposed design is based on a stable 5-D infinite impulse response (IIR) digital filter having three cascaded sections, each synthesized using the concept of multidimensional passive network resonance. A novel semi-systolic hardware implementation is proposed. Each section of the filter is implemented and tested on a Xilinx Virtex-7 FPGA platform using Matlab based hardware co-simulation with both synthetic and real LFV signals. A realtime processing throughput of 467 LFV frames/s is implied with each section of the filter operating at 204, 164 and 115 MHz for input LFV frames of size 9×9×220×360.
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    Multi depth-velocity filters for enhancing multiple moving objects in 5-d light field videos
    (IEEE, 2020-07) Liyanage, N; Jayaweera, SS; Edussooriya, CUS; Wijenayake, C; Madanayake, A; Agathoklis, P; Bruton, L; Ambikairajah, E; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
    A moving object in a five-dimensional (5-D) light field video (LFV) can be selectively enhanced using the depth and the velocity of the object. In this paper, a 5-D depth-velocity (DV) filter is proposed to enhance multiple moving objects at different depths and with different velocities in an LFV. The 5-D DV filter is designed as a cascade of an infinite-extent impulse response multi-depth filter and a finite-extent impulse response multi-velocity filter. Experimental results obtained with numerically generated and real LFVs indicate that more than 15 dB improvement in signal-to-interference ratio can be achieved with the proposed 5-D multi DV filter compared to previously proposed multi depth-only filters.
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    Multi-depth filtering and occlusion suppression in 4-D light fields: Algorithms and architectures
    (Elsevier, 2020) Liyanage, N; Wijenayake, C; Edussooriya, C; Madanayake, A; Agathoklis, P; Bruton, LT; Ambikairajah, E
    Low-complexity signal processing algorithms and reconfigurable digital hardware architectures are proposed for multi-depth filtering and occlusion suppression in 4-D light fields (LFs). The proposed multi-depth-pass (MDP) and multi-depth-reject (MDR) 4-D filters allow simultaneous enhancement of planar objects at multiple desired depths and attenuation of planar objects at multiple undesired depths, thereby achieving electronically tunable multi-depth focusing. Partial-separability and recursive nature of the proposed MDP and MDR transfer functions ensure ultra-low hardware complexity suitable for real-time processing of large volume of input samples encountered in 4-D LFs. Filter synthesis details and examples with synthetic and real LFs of size 15  ×  15 × 434  ×  625 are presented. A generic framework encapsulating a multitude of possible digital hardware realizations is described, employing J-unfolding and look-ahead pipelining albeit with modifications as applicable to the underlying multi-dimensional signal flow graphs to obtain increased real-time throughput. Proof-of-concept digital designs are provided for the 2-passband case of a MDP filter verifying a real-time throughput of  ≈ 490 LFs of size 9  ×  9 × 434  ×  625 per second for filters operating at 135 MHz on a Xilinx Virtex-7 FPGA device.
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    Multi-Volumetric refocusing of light fields
    (IEEE, 2021) Jayaweera, SS; Edussooriya, CUS; Wijenayake, C; Agathoklis, P; Bruton, LT
    Geometric information of scenes available with fourdimensional (4-D) light fields (LFs) paves the way for postcapture refocusing. Light field refocusing methods proposed so far have been limited to a single planar or a volumetric region of a scene. In this paper, we demonstrate simultaneous refocusing of multiple volumetric regions in LFs. To this end, we employ a 4-D sparse finite-extent impulse response (FIR) filter consisting of multiple hyperfan-shaped passbands. We design the 4-D sparse FIR filter as an optimal filter in the least-squares sense. Experimental results confirm that the proposed filter provides 63% average reduction in computational complexity with negligible degradation in the fidelity of multi-volumetric refocused LFs compared to a 4-D nonsparse FIR filter
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    Real-time light field signal processing using 4D/5D linear digital filter FPGA circuits
    (IEEE, 2021) Edussooriya, CUS; Wijenayake, C; Madanayake, A; Liyanage, N; Premaratne, S; Vorhies, JT; Dansereau, DG; Agathoklis, P; Bruton, LT
    Light fields (LFs) and light field videos (LFVs) capture both angular and spatial variation of light rays emanating from scenes. This richness of information leads to novel applications such as post-capture refocusing, depth estimation and depth-velocity filtering which are not possible with images and videos. These capabilities come, however, with a significant increase in data to be processed. In order to fully exploit opportunities provided by LFs and LFVs, low-complexity signal processing algorithms that process LF and LFV data in realtime are required. In this paper, we survey such state-of-theart algorithms, in particular for depth filtering, refocusing and denoising of LFs and depth-velcoty filtering for LFVs, and future directions for these real-time LF an LFV processing algorithms.