Adaptive postprocessing algorithms for low bit rate video signals

A new adaptive postprocessing algorithm to enhance the quality of a noisy video sequence is presented. The algorithm recognizes that the visibility of noise depends on local signal characteristics. It therefore classifies the video signal into different classes and uses separate nonlinear filters matched to each class. The most general version of the algorithm employs motion-compensated frame averaging to improve picture quality in a first stage. A classification algorithm subsequently divides subblocks of pixels in the averaged frame into four classes: edge, smooth, nonsmooth with motion and nonsmooth without motion. Spatial algorithms that perform multilevel median filtering, double median filtering, and median filtering are used for pixels belonging to edge, smooth, and nonsmooth with motion categories. Pixels in the nonsmooth, unmoving category are left unfiltered to preserve corresponding image texture. In a simpler version of this four-class system, the motion cues and motion-compensated frame averaging are eliminated, and the purely spatial filtering is based on a three-class algorithm. When used at the output of a 3-D subband coder at 384 kbps, the spatial postfilter was shown to provide a consistent gain in subjectively evaluated picture quality. Twenty-five viewers participated in an experiment involving three coded sequences. In a pairwise comparison of postfiltered and unfiltered sequences, the postfiltered version was judged to be better in 63 out of 75 instances.     

Rankboost $$+$$ + : an improvement to Rankboost

Machine Learning - Rankboost is a well-known algorithm that iteratively creates and aggregates a collection of “weak rankers” to build an effective ranking procedure. Initial work on...     

Magnetic Flux Alignment Studies on Entrapped Ferrofluid Nanoparticles in Poly Vinyl Alcohol Matrix

Highly surface active super paramagnetic colloidal suspensions of nano crystalline ferrofluid have been synthesized through wet-chemical route. Entrapment of magnetic domains presented in the nano ferrofluid in a polymer matrix like poly vinyl alcohol film was accomplished by developing polymer composite film in between two magnetic poles by solvent casting method. Similarly poly vinyl alcohol-ferrofluid composite films were also developed in the absence of magnetic field. Atomic force microscopy image of nano-composite film makes it clear that the film developed in the absence of magnetic field possesses randomly oriented domains, whereas film developed with magnetic field shows well aligned flux lines. The characteristics and nature of forces acting between magnetic domains along the magnetic flux lines were explored from magnetic force microscopy imaging. The number of flux lines developed in the polymer matrix was observed to be directly proportional to applied external magnetic field. Approximate number of magnetic lines passing through unit area of composite film was evaluated from line profile data analysis of atomic force microscopy image. The particle sizes of the nanoparticles encapsulated in the polymer matrix were found to be in the range of 10- 20 nm. Scanning electron microscopy micrographs confirm aggregation of ferrofluid particles of ribbon like morphology along the magnetic flux lines. Magnetic properties of the entrapped nanoparticles in polymer matrix film were analyzed using vibrating sample magnetometer at room temperature. The super paramagnetic nature and other magnetic properties were evaluated from the hysteresis loop.     

Using FORAY Models to Enable MPSoC Memory Optimizations

With the technology advances it becomes feasible to implement a large multiprocessor system on a single chip. In such Systems-on-Chip (SoCs), a significant portion of energy is spent in the memory subsystem. There are several approaches reducing this energy, including the ones at physical, architecture and algorithmic levels. Classical approaches, including algorithmic and some architectural approaches, use static analysis and transformation of the application source code. However, often it is not possible to perform static analysis and optimization of a program’s memory access behavior unless the program is written in an easily analyzable form, e.g., free from pointer arithmetic. In this paper, we introduce the FORAY model of a program that allows aggressive analysis of the application’s memory behavior and enables such optimizations on arbitrary code which are not possible to apply otherwise. We then present FORAY-GEN: an automated profile-based approach for extraction of the FORAY model from the original program. We also outline our approach in applying FORAY-GEN for multiprocessor SoCs. We demonstrate how FORAY-GEN enhances applicability of other memory subsystem optimization approaches, resulting in an average of two times increase in the number of memory references that can be analyzed by existing static approaches.     

Exploring Energy Efficient Architectures for RLWE Lattice-Based Cryptography

Journal of Signal Processing Systems - Quantum computers are imminent threat to secure signal processing because they can break the contemporary public-key cryptography schemes in polynomial time....     

Computational fluid dynamic investigation of liquid rack cooling in data centres

Relying on thermal air management in a data centre is becoming less effective as heat densities from the Information Technology (IT) equipment continue to rise. Direct liquid cooling is more efficient at transferring the waste heat, but requires liquid loops passing as close as possible to the heat source. A new Computational Fluid Dynamics (CFD) strategy is developed for data centre scenarios where a liquid loop heat exchanger is attached at the rear of server racks (back doors), which can avoid the need to separate the cold and hot air streams in traditional hot/cold aisle arrangements. The effectiveness of additional fans in the back door heat exchangers is investigated using the three-dimensional CFD model of a simplified three-aisle, six-rack data centre configuration.