Technology research and development in Hong Kong: hype or reality

Looks at the development of innovation and technology funding, infrastructure and achievements in Hong Kong in the past few years, and examine the potential areas where Hong Kong can excel and be a significant contributor to technology development. Comparison will be drawn from Finland, an economy of a size and GDP very similar to that of Hong Kong.published_or_final_versio

Vessel extraction under non-uniform illumination: A level set approach

Vessel extraction is one of the critical tasks in clinical practice. This communication presents a new approach for vessel extraction using a level-set-based active contour by defining a novel local term that takes local image contrast into account. The proposed model not only preserves the performance of the existing models on blurry images, but also overcomes their inability to handle nonuniform illumination. The efficacy of the approach is demonstrated with experiments involving both synthetic images and clinical angiograms. © 2006 IEEE.published_or_final_versio

Adaptive parallel video-coding algorithm

Parallel encoding of video inevitably frame rate gives varying rate performance due to dynamically changing video content and motion field since the encoding process of each macro-block, especially motion estimation, is data dependent. A multiprocessor schedule optimized for a particular frame with certain macro-block encoding time may not be optimized towards another frame with different encoding time, which causes performance degradation to the parallelization. To tackle this problem, we propose a method based on a batch of near-optimal schedules generated at compile-time and a run-time mechanism to select the schedule giving the shortest predicted critical path length. This method has the advantage of being near-optimal using compile-time schedules while involving only run-time selection rather than re-scheduling. Implementation on the IBM SP2 multiprocessor system using 24 processors gives an average speedup of about 13.5 (frame rate of 38.5 frames per second) for a CIF sequence consisting of segments of 6 different scenes. This is equivalent to an average improvement of about 16.9% over the single schedule scheme with schedule adapted to each of the scenes. Using an open test sequence consisting of 8 video segments, the average improvement achieved is 13.2%, i.e. an average speedup of 13.3 (35.6 frames per second).published_or_final_versio

An efficient parameterless quadrilateral-based image segmentation method

This paper proposes a general quadrilateral-based framework for image segmentation, in which quadrilaterals are first constructed from an edge map, where neighboring quadrilaterals with similar features of interest are then merged together to form regions. Under the proposed framework, the quadrilaterals enable the elimination of local variations and unnecessary details for merging from which each segmented region is accurately and completely described by a set of quadrilaterals. To illustrate the effectiveness of the proposed framework, we derived an efficient and high-performance parameterless quadrilateral-based segmentation algorithm from the framework. The proposed algorithm shows that the regions obtained under the framework are segmented into multiple levels of quadrilaterals that accurately represent the regions without severely over or undersegmenting them. When evaluated objectively and subjectively, the proposed algorithm performs better than three other segmentation techniques, namely, seeded region growing, K-means clustering and constrained gravitational clustering, and offers an efficient description of the segmented objects conducive to content-based applications. © 2005 IEEE.published_or_final_versio

Time domain analysis/resynthesis of musical tones based on polynomial interpolation techniques

The 3rd International Conference on Signal Processing, Beijing, China, 14-18 October 1996In this paper, a novel algorithm employing polynomial interpolation techniques is proposed for the analysis and resynthesis of musical tones, based on time domain information. This algorithm models a single period of oscillation as a series of features, with curves joining such features together. The trajectories of these features and the shape of the curves across the whole input signal can be parameterised, such that the signal can be analysed and resynthesised as a close approximation to the original. The current research introduced an alternative approach to analyse/resynthesise sampled musical signals in the frequency domain, one which characterises a signal by its physical structure rather than its frequency components. The results from this analysis can be used to further refine existing physical models of musical instruments.published_or_final_versio

Parallelization methodology for video coding - an implementation on the TMS320C80

This paper presents a parallelization methodology for video coding based on the philosophy of hiding as much communications by computation as possible. It models the task/data size, processor cache capacity, and communication contention, through a systematic decomposition and scheduling approach. With the aid of Petri-nets and task graphs for representation and analysis, it employs a triple buffering scheme to enable the functions of frame capture, management, and coding to be performed in parallel. The theoretical speedup analysis indicates that this method offers excellent communication hiding, resulting in system efficiency well above 90%. To prove its practicality, a H.261 video encoder has been implemented on a TMS320C80 system using the method. Its performance was measured, from which the speedup and efficiency figures were calculated. The only difference detected between the theoretical and measured data is the program control overhead that has not been accounted for in the theoretical model. Even with this, the measured speedup of the H.261 is 3.67 and 3.76 on four parallel processors (PPs) for QCIF and 352 × 240 video, respectively, which correspond to frame rate of 30.7 and 9.25 frames per second, and system efficiency of 91.8% and 94%, respectively. This method is particularly efficient for platforms with small number of parallel processors.published_or_final_versio

Quadrilateral-based region segmentation for tracking

We propose a novel quadrilateral based region segmentation method that is favorable for object tracking. Instead of using groups of pixels or regular blocks, it uses groups of connected quadrilaterals to represent regions. The proposed method derives the vertices of each quadrilateral from the edge map using the concept of center of masses. By merging the quadrilaterals, regions can be represented. The proposed method offers better data reduction than pixelwise region representation and better boundary approximation than block-based segmentation methods. Experimental results show that it generates a more reasonable region map, which is more suitable for object tracking, and a smaller number of regions than the seeded region growing, K-means clustering, and constrained gravitational clustering methods. © 2002 Society of Photo-Optical Instrumentation Engineers.published_or_final_versio

A Novel Quadrilateral-based Tracking Method

This paper proposes a novel tracking method based on quadrilateral-based segmentation. The tracking method matches quadrilaterals in a region with those in a reference frame to construct region correspondences, from which trajectory of each region can be obtained. The Table Tennis sequence has been used to evaluate the tracking method. Experiment results show that the proposed tracking method can track the ping-pong ball and the racket reasonably well over a series of images, indicating matching quadrilaterals to track region is a viable approach.published_or_final_versio

Recursive Cube of Rings: A new topology for interconnection networks

In this paper, we introduce a family of scalable interconnection network topologies, named Recursive Cube of Rings (RCR), which are recursively constructed by adding ring edges to a cube. RCRs possess many desirable topological properties in building scalable parallel machines, such as fixed degree, small diameter, wide bisection width, symmetry, fault tolerance, etc. We first examine the topological properties of RCRs. We then present and analyze a general deadlock-free routing algorithm for RCRs. Using a complete binary tree embedded into an RCR with expansion-cost approximating to one, an efficient broadcast routing algorithm on RCRs is proposed. The upper bound of the number of message passing steps in one broadcast operation on a general RCR is also derived.published_or_final_versio

Reduction of false sharing by using process affinity in page-based distributed shared memory mutiprocessor systems

In page-based distributed shared memory systems, a large page size makes efficient use of interconnection network, but increases the chance of false sharing, while a small page size reduces the level of false sharing but results in an inefficient use of the network. This paper proposes a technique that uses process affinity to achieve data pages clustering so as to optimize the temporal data locality on DSM systems, and therefore reduces the chance of false sharing and improves the data locality. To quantify the degree of process affinity for a piece of data, a measure called process affinity index is used that indicates the closeness between this piece of data and the process. Simulation results show that process affinity technique improves the execution performance as page size increases due to the effective reduction of fair sharing. In the best case an order of magnitude performance improvement is achieved.published_or_final_versio