Yui Chan - Academia.edu (original) (raw)

Papers by Yui Chan

2015 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2015

This paper presents fast and efficient intra prediction algorithms for screen content coding (SCC... more This paper presents fast and efficient intra prediction algorithms for screen content coding (SCC). The proposed algorithms focus on smooth regions frequently appeared in screen content videos, which have the characteristics of noiselessness. All the samples in a noiseless smooth region exhibit exactly the same pixel value. We then propose two intra coding techniques for noiseless smooth regions in SCC based on the smoothness of the boundary samples which are used for intra prediction. Our proposed algorithm can reduce computational complexity by at most 26.7% while keeping nearly the same video quality. Moreover, by removing the redundant coding bits for intra prediction modes, computational complexity can be further reduced to at most 53.3% in terms of encoding time with bitrate reduction up to 1.2%.

The 8th Annual IEEE International Conference on Nano/Micro Engineered and Molecular Systems, 2013

This paper analyzes the different reaction pathways that play major roles in the process of photo... more This paper analyzes the different reaction pathways that play major roles in the process of photocatalytic degradation, and presents a novel microfluidic photoelectrocatalytic reactor for selective control of them. This is accomplished by applying positive or negative bias potential to the photocatalytic reaction chamber and to select either the hole-driven or electron-driven oxidation pathway. The experimental results show that the negative bias exhibits higher performance in degrading the model chemical of methylene blue. Such selective control brings several important benefits. It provides another degree of freedom for photocatalysis, and enables detailed kinetic study on the reaction mechanisms. And, the bias eliminates the electron/hole recombination, which is one of the fundamental limits in conventional photocatalytic systems. In additional, the experiment shows that the bias produces a synergetic effect of electrocatalysis and photocatalysis and significantly enhances the degradation efficiency. The photoelectrocatalytic microreactor shows high stability and may be scaled up for high-performance water purification.

1999 IEEE International Conference on Acoustics, Speech, and Signal Processing. Proceedings. ICASSP99 (Cat. No.99CH36258), 1999

The conventional search algorithms for block matching motion estimation reduce the set of possibl... more The conventional search algorithms for block matching motion estimation reduce the set of possible displacements for locating the motion vector. Nearly all of these algorithms rely on the assumption: the distortion function increases monotonically as the search location moves away from the global minimum. Obviously, this assumption essentially requires that the error surface be unimodal over the search window. Unfortunately, this is usually not true in real-world video signals. In this paper, we formulate a criterion to check the confidence of unimodal error surface over the search window. The proposed Confidence Measure of Error Surface, CMES, would be a good measure for identifying whether the searching should continue or not. It is found that this proposed measure is able to strengthen the conventional fast search algorithms for block matching motion estimation. Experimental results show that, as compared to the conventional approach, the new algorithm through the CMES is more robust, produces smaller motion compensation errors, and requires simple computational complexity.

Proceedings of 2001 International Symposium on Intelligent Multimedia, Video and Speech Processing. ISIMP 2001 (IEEE Cat. No.01EX489), 2001

Page 1. Proceedings of 2001 International Symposium on Intelligent Multlmedla, Mdeo and Speech Pr... more Page 1. Proceedings of 2001 International Symposium on Intelligent Multlmedla, Mdeo and Speech Processing May 2-4 2001 Hong Kong Fast Search Algorithm for Edge-Oriented Block Matching Algorithm Yui-Lanz Chan, Ko-Chenug Hui and Wan-Chi Siu ...

Proceedings - International Conference on Image Processing, ICIP, 2010

2011 IEEE Visual Communications and Image Processing, VCIP 2011, 2011

In this paper, a fast algorithm is proposed to speed up the motion and disparity estimation in st... more In this paper, a fast algorithm is proposed to speed up the motion and disparity estimation in stereoscopic video coding. Based on the stereo-motion consistency constraint, an iterative search strategy is suggested to get the motion and disparity vectors simultaneously. A credible base vector selection scheme and an adaptive search range adjustment technique are designed to further strengthen the iterative search. Results show that the complexity can be significantly reduced compared to the JMVM full search with a negligible quality drop. I.

Science China Information Sciences, 2011

A network coding based hybrid ARQ algorithm for wireless video broadcast SCIENCE CHINA Informatio... more A network coding based hybrid ARQ algorithm for wireless video broadcast SCIENCE CHINA Information Sciences 54, 1327 (2011); Fast 2-D 8×8 discrete cosine transform algorithm for image coding Science in China Series F-Information Sciences 52, 215 (2009); An extended packetization-aware mapping algorithm for scalable video coding in finite-length fountain codes SCIENCE CHINA Information Sciences 56, 042311 (2013); Multiple description video coding based on residuum compensation Science in China Series F-Information Sciences 52, 1439 (2009);. RESEARCH PAPERS. SCIENCE CHINA Information Sciences

2013 IEEE China Summit and International Conference on Signal and Information Processing, ChinaSIP 2013 - Proceedings, 2013

Recent video coding standards such as high efficiency video coding (HEVC) and multi-view video co... more Recent video coding standards such as high efficiency video coding (HEVC) and multi-view video coding (MVC) can obtain significant gain from hierarchical prediction structures. Hierarchical B structure utilizes future reference frames, which induces high encoding delay. Comparatively, hierarchical P structure brings low-delay coding in which no future references are involved. The only hurdle of the lowdelay hierarchical P structure is the need of motion estimation in distant reference frames. To maintain a high coding efficiency, large search range for motion estimation was commonly adopted in distant reference pictures. Therefore, computational complexity will be increased dramatically. In this paper, motion vector composition is proposed in hierarchical P structure to shorten coding process. Simulation results reveal that the proposed scheme can achieve significant complexity savings.

Proceedings - International Conference on Image Processing, ICIP, 2006

Currently, the speed limit imposed on bridges under strong wind conditions is mostly determined b... more Currently, the speed limit imposed on bridges under strong wind conditions is mostly determined based on subjective experience. If the speed limit is set too low, the transportation system will be far from efficient. On the other hand, the safety of drivers cannot be guaranteed if the speed limit is set too high. The objective of this study is to simulate the performance of vehicles travelling on long-span bridges under severe wind events, with different speeds and different road conditions, and hence establish a realistic speed limit. A specially designed analytical model is proposed to study vehicle performance when travelling on long span bridges under strong wind loads. The physical components of the analytical model involve a 7-degrees-of-freedom vehicle; a bridge with 3D finite elements and stochastic and the correlated road roughness profiles. The winds loads acting on the physical components are simulated as stochastic wind velocity fields generated by using the spectral representation method. To more accurately predict the performance of the moving vehicle, the static and buffeting forces acting on the vehicle are also considered. The solution to the analytical model can be found using the vehicle-bridge interaction element concept. By introducing the vehicle and the road-weather characteristics, such as drag coefficient and frictional coefficient, a set of simplified vehicle stability equations are derived. The stability requirements are implemented into the analytical model to study the reliability of vehicles on long span bridges under strong wind loads. A real bridge example is used to study the effects of road roughness, vehicle speed, vehicle type and vehicle mass on the vehicle performance. Based on the above information, the speed limit for such a realistic long span bridge can be established. It is demonstrated that road roughness and the stiffness of the vehicle's suspension system are the key parameters that significantly influence the performance of the vehicle. The proposed model demonstrates that it can be used effectively to predict the speed limit on a bridge for a particular type of vehicle.

1995 International Conference on Acoustics, Speech, and Signal Processing

A new adaptive technique based on pixel decimation for estimating motion vector is presented. In ... more A new adaptive technique based on pixel decimation for estimating motion vector is presented. In traditional approach, a uniform pixel decimation is used. Since some pixels in each block do not enter into the matching criterion, this approach might limit the accuracy of the motion vector. In this paper, we select the most representative pixels based on image content in each block for the matching criterion. This is due to the fact thatt high activity in the luminance signal such as edges and texture contributes mainly to the matching criterion. Our approach can compensate the drawback in standard pixel decimation techniques. Computer simulations show that this technique is close to the performance of the exhaustive search with a significant reduction on computational complexity.

2008 International Conference on Neural Networks and Signal Processing, 2008

In modern video coding standards, they are mainly designed for normal forward playback. Recently,... more In modern video coding standards, they are mainly designed for normal forward playback. Recently, we have developed a macroblock-based reverse-play scheme for compressed video bitstreams. By exploiting the motion relationship between two adjacent frames, this scheme can significantly reduce the requirements on the decoder complexity and network bandwidth during reverse playback. However, the MB-based technique does not works well on traversing GOP boundaries reversely since no inter-frame prediction takes place between the last frame of one GOP and the first frame of its succeeded GOP. In this paper, by utilizing a new SP picture type in the H.264, we can solve the GOP discontinuity problem by building linkages across GOP boundaries. Instead of arranging the primary SPframe before the I-frame, a novel scheme is proposed to allocate various macroblocks within the GOP to be encoded as the SP type. This new arrangement for SP coding is specially designed for our macroblock-based reverse-play scheme and can be proved to eliminate the possible mismatch effect for reverse playback across GOP boundaries. With this allocation strategy, results from our experimental work confirm that the inherent GOP discontinuity problem can be avoided without introducing any mismatch between forward and reverse playback.

Signal Processing: Image Communication, 2014

Modern video coding standards are basically designed for forward playback only. Recently, we have... more Modern video coding standards are basically designed for forward playback only. Recently, we have developed a number of macroblock(MB)-based techniques to support reverse playback for compressed videos by exploiting the motion relationship between adjacent frames. Nevertheless, the MB-based techniques give no effect on traversing GOP boundaries reversely since no inter-frame prediction takes place between the last frame of one GOP and the first frame of its succeeded GOP. In this paper, we borrow ideas from the SP-picture concept in H.264 to establish linkages across GOP boundaries by encoding the last frame of each GOP as a primary SP-frame as well as its corresponding secondary SP-frame. During reverse playback across GOP boundaries, the secondary SP-frame is decoded by using the I-frame in its succeeded GOP as the motion-compensated frame. We believe that we are the first to consider SP-frames to build the linkage between two GOPs for reverse playback. Our scheme can also be used in any future coding standards that offer the similar coding mechanism of SP-frames. This approach can remarkably mitigate the required decoder complexity over 90% during reverse playback across GOP boundaries, but the straightforward implementation introduces serious drift errors. Therefore, as a further contribution of this paper, a novel scheme is designed to avoid the drift problem. Instead of arranging the primary SP-frame before the I-frame, the proposed scheme allocates various MBs within the GOP to be encoded as the SP-picture type. This completely new and unique arrangement for SP coding in which a primary SP MB and its corresponding secondary SP MB are no longer at the same time instant is specially designed for our MB-based techniques, and can be proved to eliminate the possible drift effect for reverse playback. With this allocation strategy, results from our experimental work show that the inherent GOP discontinuity problem can be avoided without introducing additional drift between forward and reverse playback.

Parkinsonism & Related Disorders, 2010

Lab on a Chip, 2012

This paper reports experimental studies using the photoelectrocatalytic effect to eliminate a fun... more This paper reports experimental studies using the photoelectrocatalytic effect to eliminate a fundamental limit of photocatalysis - the recombination of photo-excited electrons and holes. The fabricated reactor has a planar reaction chamber (10 × 10 × 0.1 mm(3)), formed by a blank indium tin oxide glass slide, an epoxy spacer and a BiVO(4)-coated indium tin oxide glass substrate. A blue light-emitting diode panel (emission area 10 × 10 mm(2)) is mounted on the cover for uniform illumination of the reaction chamber. In the experiment, positive and negative bias potentials were applied across the reaction chamber to suppress the electron/hole recombination and to select either the hole-driven or electron-driven oxidation pathway. The negative bias always exhibits higher performance. It is observed that under -1.8 V the degradation rate is independent of the residence time, showing that the accompanying electrolysis can solve the oxygen deficiency problem. The synergistic effect of photocatalysis and electrocatalysis is observed to reach its maximum under the bias potential of ± 1.5 V. The photoelectrocatalytic microreactor shows high stability and may be scaled up for high-performance water purification.

Journal of Visual Communication and Image Representation, 2012

The multiview video coding (MVC) extension of H.264/AVC is the emerging standard for compression ... more The multiview video coding (MVC) extension of H.264/AVC is the emerging standard for compression of impressive 3D and free-viewpoint video. The coding structure in MVC adopts motion and disparity estimation to exploit temporal and interview dependencies in MVC. It results in a considerable increase in encoding complexity. Most of the computational burden comes from uni-directional and bi-directional prediction. In this paper, an iterative search strategy is designed to speed up the uni-directional prediction in MVC. It can work with an adaptive search range adjustment through a confidence measure of a loop constraint to obtain both motion and disparity vectors jointly. Furthermore, a selective bi-directional prediction algorithm is proposed to enhance the coding performance by analyzing the statistical characteristics of bi-directional prediction in MVC. Experimental results demonstrate that, by using the proposed fast search, the temporal and interview redundancies of multiview video can be eliminated sufficiently with low complexity.

Journal of Visual Communication and Image Representation, 2004

Fast search algorithms for block motion estimation reduce the set of possible displacements for l... more Fast search algorithms for block motion estimation reduce the set of possible displacements for locating the motion vector. All algorithms produce some quality degradation of the predicted image. To reduce the computational complexity of the full search algorithm without introducing any loss in the predicted image, we propose a Hilbert-grouped partial distortion search algorithm (HGPDS) by grouping the representative pixels based on pixel activities in the hilbert scan. By using the grouped information and computing the accumulated partial distortion of the representative pixels before that of other pixels, impossible candidates can be rejected sooner and the remaining computation involved in the matching criterion can be reduced remarkably. In addition, we also suggest a smart search strategy which is an excellent complement of the HGPDS to form an efficient partial distortion search algorithm. The new search strategy rearranges the search order such that the most possible candidates are searched first and this rearrangement will increase the probability of early rejection of impossible motion vectors. Simulation results show that the proposed algorithm has a significant computational speed-up and is the fastest when compared to the conventional partial distortion search algorithms.

Journal of Toxicology and Environmental Health, Part A, 2009

Incense burning is common in Southeast Asia, where it is a traditional and ceremonial practice in... more Incense burning is common in Southeast Asia, where it is a traditional and ceremonial practice in deity worship and paying respect to ancestors. However, incense emissions are an important source of indoor air pollution in Asia, and may induce health problems to those exposed. In this in vitro study the effects of incense emissions on human DNA were investigated using the comet assay. Particulates in smoke from six kinds of incense were trapped in saline or ethanol and human lymphocytes were exposed under controlled conditions. Results showed that DNA damage, including strand breaks, was induced by both aqueous and ethanolic extracts of two samples. The ethanolic extract of one sample induced DNA damage, while no significant DNA damage was found in the remaining three samples. The mechanisms underlying DNA damage induced by incense emissions were also investigated. Catalase (CAT), sodium azide, and superoxide dismutase (SOD) were co-incubated with extract, which exerted significant DNA damaging effects. Results showed that CAT with or without SOD diminished DNA damage, whereas sodium azide did not seem able to reduce DNA damage. Data indicate there are potential adverse health effects of such exposure, particularly for temple workers.

Journal of Bridge Engineering, 2009

For a long-span coastal bridge structure, the corrosion initiation time is controlled by the spee... more For a long-span coastal bridge structure, the corrosion initiation time is controlled by the speed of chloride ions transfer and the depassivation process within the structure. These processes are significantly influenced by the actual variation of the environmental conditions on the concrete surface throughout its service life. From the regional climate characteristics through local climate conditions, the microclimate variation on the concrete surface is studied in this research. A set of realistic environmental condition profiles is proposed, based on the exposure conditions and the material properties of the components. Moreover, a 2D integrated corrosion performance assessment model is constructed to capture the change in environmental conditions and simulate the coupled diffusion process and the corrosion performance in the time domain. Two typical locations (Hong Kong and Michigan) are chosen as numerical examples for implementing the proposed corrosion performance assessment model, and control of the environmental factors of the various chloride exposures is highlighted. These factors are used to construct an integral empirical equation together with the general critical material and geometrical parameters.

IEEE Transactions on Multimedia, 2004

This paper presents a new frame-skipping transcoding approach for video combiners in multipoint v... more This paper presents a new frame-skipping transcoding approach for video combiners in multipoint video conferencing. Transcoding is regarded as a process of converting a previously compressed video bitstream into a lower bitrate bitstream. A high transcoding ratio may result in an unacceptable picture quality when the incoming video bitstream is transcoded with the full frame rate. Frame skipping is often used as an efficient scheme to allocate more bits to representative frames, so that an acceptable quality for each frame can be maintained. However, the skipped frame must be decompressed completely, and should act as the reference frame to the nonskipped frame for reconstruction. The newly quantized DCT coefficients of prediction error need to be recomputed for the nonskipped frame with reference to the previous nonskipped frame; this can create an undesirable complexity in the real time application as well as introduce re-encoding error. A new frame-skipping transcoding architecture for improved picture quality and reduced complexity is proposed. The proposed architecture is mainly performed on the discrete cosine transform (DCT) domain to achieve a low complexity transcoder. It is observed that the re-encoding error is avoided at the frame-skipping transcoder when the strategy of direct summation of DCT coefficients is employed. By using the proposed frame-skipping transcoder and dynamically allocating more frames to the active participants in video combining, we are able to make more uniform peak signal-to-noise ratio (PSNR) performance of the subsequences and the video qualities of the active subsequences can be improved significantly. Index Terms-Compressed-domain processing, frame skipping, video compression, video conferencing, video transcoding. I. INTRODUCTION W ITH the advance of video compression and networking technologies, multipoint video conferencing is becoming more and more popular [1]-[10]. In multipoint video conferencing, the conference participants are connected to a multipoint control unit (MCU) which receives video signals from several different participants, and then processes and transmits them to all participants. Multipoint video conferencing can be either "switched presence" or the "continuous Manuscript