Browsing by Author "Wong, Stephan"

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Citation Count: Jafari, Aref...et al. (2014). "A combined spatial and frequency based texture model for organsegmentation in computed tomography examinations" Journal Of Medical Imaging And Health Informatics, Vol.4, No.2, pp.230-236.
A combined spatial and frequency based texture model for organsegmentation in computed tomography examinations
(Amer Scientific Publishers, 2014) Jafari, Aref; Hassanpour, Reza; Shahbahrami, Asadollah; Wong, Stephan
The organ segmentation in computed tomography (CT) examination is a tedious and error prone task. The local similarity of the pixels from different organs, and the differences between the pixels of the same organ observed in different examinations are two most challenging problems affecting the segmentation process. In this study, statistical and spectral texture properties are combined with the a-priori knowledge about the human body to develop a model for reliably segmenting organs in CT examinations. The main goal of the developed model is fusing local and global statistics to support spatial-frequency analysis and to maximize the simultaneous localization of energy in both spatial and frequency domains. The feature space dimension is reduced by means of a wrapper technique applied as a pre-processing filter. The proposed classifier utilizes a linear combination (ensemble) of two support vector machines (SVM) where the first SVM classifies the input samples according to their textural information and the second one correct the results of the first classifier by searching the spatial information of those samples in a statistical atlas.
Citation Count: Choupani, Roya; Wong, Stephan; Tolun, Mehmet R., "A drift-reduced scheme for hierarchical wavelet coding scalable video transmissions", 2009 First International Conference On Advances In Multimedia, (2009).
A drift-reduced scheme for hierarchical wavelet coding scalable video transmissions
(IEEE, 2009) Choupani, Roya; Wong, Stephan; Tolun, Mehmet R.
Scalable video coding allows for the capability of (partially) decoding a video bitstream when faced with communication deficiencies such as low handwidth or loss of data resulting in lower video quality. As the encoding is usually based on perfectly reconstructed frames, such deficiencies result in differently decoded frames at the decoder than the ones used in the encoder and, therefore, leading to errors being accumulated in the decoder. This is commonly referred to as the drift error. Drift-free scalable video coding methods also suffer from the low performance problem as they do not combine the residue encoding scheme of the current standards such as MPEG-4 and H.264 with scalability characteristics. We propose a scalable video coding method which is based on the motion compensation and residue encoding methods found in current video standards combined with the scalability property of discrete wavelet transform. Our proposed method aims to reduce the drift error while preserving the compression efficiency. Our results show that the drift error has been greatly reduced when a hierarchical structure for frame encoding is introduced.
Citation Count: Choupani, Roya; Wong, Stephan; Tolun, Mehmet R. "Adaptive Embedded Zero Tree for Scalable Video Coding", World Congress On Engıneering, Wce 2011, Vol Iı, pp. 1567-1571, (2011).
Adaptive Embedded Zero Tree For Scalable Video Coding
(Int Assoc Engineers-Laeng, 2011) Choupani, Roya; Wong, Stephan; Tolun, Mehmet R.; 1863
Video streaming over the Internet has gained popularity during recent years mainly due to the revival of video-conferencing and video-telephony applications and the proliferation of (video) content providers. However, the heterogeneous, dynamic, and best-effort nature of the Internet cannot always guarantee a certain bandwidth for an application utilizing the Internet. Scalability has been introduced to deal with such issues (up to a certain point) by adapting the video quality with the available bandwidth. In addition, wavelet based scalability combined with representation methods such as embedded zero trees (EZWs) provides the possibility of reconstructing the video even when only the initial part of the streams have been received. EZW prioritizes the wavelet coefficients based on their energy content. Our experiments however, indicate that giving more priority to low frequency content improves the video quality at a specific bit rate. In this paper, we propose a method to improve on the compression rate of the EZW by prioritizing the coefficients by combining each frequency sub-band with its energy content. Initial experimental show that the first two layers of the generated EZW are about 22.6% more concise.
Citation Count: Choupani, Roya; Wong, Stephan; Tolun, Mehmet. "Hierarchical SNR Scalable Video Coding with Adaptive Quantization for Reduced Drift Error",10th International Conference on Computer Vision Theory and Applications (VISAPP-2015), pp.117-123, 2015.
Hierarchical SNR Scalable Video Coding with Adaptive Quantization for Reduced Drift Error
(2015) Choupani, Roya; Wong, Stephan; Tolun, Mehmet
In video coding, dependencies between frames are being exploited to achieve compression by only coding the differences. This dependency can potentially lead to decoding inaccuracies when there is a communication error, or a deliberate quality reduction due to reduced network or receiver capabilities. The dependency can start at the reference frame and progress through a chain of dependent frames within a group of pictures (GOP) resulting in the so-called drift error. Scalable video coding schemes should deal with such drift errors while maximizing the delivered video quality. In this paper, we present a multi-layer hierarchical structure for scalable video coding capable of reducing the drift error. Moreover, we propose an optimization to adaptively determine the quantization step size for the base and enhancement layers. In addition, we address the trade-off between the drift error and the coding efficiency. The improvements in terms of average PSNR values when one frame in a GOP is lost are 3.70(dB) when only the base layer is delivered, and 4.78(dB) when both the base and the enhancement layers are delivered. The improvements in presence of burst errors are 3.52(dB) when only the base layer is delivered, and 4.50(dB) when both base and enhancement layers are delivered.
Citation Count: Choupani, Roya; Wong, Stephan; Tolun, Mehmet. "Hierarchical SNR Scalable Video Coding with Adaptive Quantization for Reduced Drift Error", 10th International Conference on Computer Vision Theory and Applications, pp. 117-123, 2015.
Hierarchical SNR Scalable Video Coding with Adaptive Quantization for Reduced Drift Error
(2015) Choupani, Roya; Wong, Stephan; Tolun, Mehmet
In video coding, dependencies between frames are being exploited to achieve compression by only coding the differences. This dependency can potentially lead to decoding inaccuracies when there is a communication error, or a deliberate quality reduction due to reduced network or receiver capabilities. The dependency can start at the reference frame and progress through a chain of dependent frames within a group of pictures (GOP) resulting in the so-called drift error. Scalable video coding schemes should deal with such drift errors while maximizing the delivered video quality. In this paper, we present a multi-layer hierarchical structure for scalable video coding capable of reducing the drift error. Moreover, we propose an optimization to adaptively determine the quantization step size for the base and enhancement layers. In addition, we address the trade-off between the drift error and the coding efficiency. The improvements in terms of average PSNR values when one frame in a GOP is lost are 3.70(dB) when only the base layer is delivered, and 4.78(dB) when both the base and the enhancement layers are delivered. The improvements in presence of burst errors are 3.52(dB) when only the base layer is delivered, and 4.50(dB) when both base and enhancement layers are delivered.
Citation Count: Choupani, Roya; Wong, Stephan; Tolun, Mehmet R., "Multiple description coding for SNR scalable video transmission over unreliable networks", Multimedia Tools And Applications, Vol69, No.3, pp.843-858, (2014).
Multiple description coding for SNR scalable video transmission over unreliable networks
(Springer, 2014) Choupani, Roya; Wong, Stephan; Tolun, Mehmet R.
Streaming multimedia data on best-effort networks such as the Internet requires measures against bandwidth fluctuations and frame loss. Multiple Description Coding (MDC) methods are used to overcome the jitter and delay problems arising from frame losses by making the transmitted data more error resilient. Meanwhile, varying characteristics of receiving devices require adaptation of video data. Data transmission in multiple descriptions provides the feasibility of receiving it partially and hence having a scalable and adaptive video. In this paper, a new method based on integrating MDC and signal-to-noise ratio (SNR) scalable video coding algorithms is proposed. Our method introduces a transform on data to permit transmitting them using independent descriptions. Our results indicate that on average 1.71dB reduction in terms of Y-PSNR occurs if only one description is received.
Citation Count: Choupani, Roya; Wong, Stephan; Tolun, Mehmet R. "Multiple Description Scalable Coding for Video Transmission over Unreliable Networks", Embedded Computer Systems: Architectures, Modeling, and Simulation, pp. 58-67, 2009.
Multiple Description Scalable Coding for Video Transmission over Unreliable Networks
(2009) Choupani, Roya; Wong, Stephan; Tolun, Mehmet R.; 1863
Developing real time multimedia applications for best effort networks such as the Internet requires prohibitions against jitter delay and frame loss. This problem is further complicated in wireless networks as the rate of frame corruption or loss is higher in wireless networks while they generally have lower data rates compared to wired networks. On the other hand, variations of the bandwidth and the receiving device characteristics require data rate adaptation capability of the coding method. Multiple Description Coding (MDC) methods are used to solve the jitter delay and frame loss problems by making the transmitted data more error resilient, however, this results in reduced data rate because of the added overhead. MDC methods do not address the bandwidth variation and receiver characteristics differences. In this paper a new method based on integrating MDC and the scalable video coding extension of H.264 standard is proposed. Our method can handle both jitter delay and frame loss, and data rate adaptation problems. Our method utilizes motion compensating scheme and, therefore, is compatible with the current video coding standards such as MPEG-4 and H.264. Based on the simulated network conditions, our method shows promising results and we have achieved up to 36dB for average Y-PSNR.
Citation Count: Choupani, Roya; Wong, Stephan; Tolun, Mehmet (2013). "Optimized Multiple Description Coding for Temporal Video Scalability", Advances in Intelligent Systems and Computing, Vol. 225, No. 1, pp. 167-176.
Optimized Multiple Description Coding for Temporal Video Scalability
(2013) Choupani, Roya; Wong, Stephan; Tolun, Mehmet
The vast application of video streaming over the Internet requires video adaptation to the fluctuations of the available bandwidth, and the rendering capabilities of the receiver device. On the other hand, the available video coding standards are designed for optimum bit rate which makes them susceptible to packet losses. A combination of video adaptation methods and error resilient methods can make the video stream more robust against networking problems. In this paper, an optimization for combining scalable video coding with multiple description coding schemes have been proposed. Our proposed method is capable of creating balanced descriptions with optimum coding efficiency.
Citation Count: Choupany, Roya; Wong, Stephan; Tolun, Mehmet (2011). "Scalable video transmission over unreliable networks using multiple description wavelet coding", 7th International Conference on Digital Content, Multimedia Technology and Its Applications, IDCTA 201116 August 2011through 18 August 2011, pp. 5-10.
Scalable video transmission over unreliable networks using multiple description wavelet coding
(2011) Choupany, Roya; Wong, Stephan; Tolun, Mehmet; 1863
Scalable video coding (SVC) and multiple description coding (MDC) are the two different adaptation schemes for video transmission over heterogenous and best-effort networks such as the Internet. We present a new approach to combine the advantages of SVC and MDC to provide reliable video communication over a wider range of communication networks and/or satisfy application requirements. Our proposed method utilizes 3D discrete wavelet transform and a modified embedded zero tree data structure to group the coefficients in different descriptions. The proposed method reduces the impact of the drift error by organizing the frames in a hierarchical structure.
Citation Count: Choupani, Roya; Wong, Stephan; Tolun, Mehmet, "Unbalanced multiple description wavelet coding for scalable video transmission", Journal of Electronic Imaging, Vol. 21, No. 4, (2012)
Unbalanced Multiple Description Wavelet Coding for Scalable Video Transmission
(IS&T & SPIE, 2012) Choupani, Roya; Wong, Stephan; Tolun, Mehmet R.; 21259
Scalable video coding and multiple description coding are the two different adaptation schemes for video transmission over heterogeneous and best-effort networks such as the Internet. We propose a new method to encode video for unreliable networks with rate adaptation capability. Our proposed method groups three dimensional discrete wavelet transform coefficients in different descriptions and applies a modified embedded zero tree data for rate adaptation. The proposed method optimizes the bit-rates of the descriptions with respect to the channel bit rates and the maximum acceptable distortion. The experimental results in the presence of one description loss indicate that on average the videos at the rate of 1000 Kbit/s are reconstructed with Y-component of peak signal to noise ratio (Y-PSNR) value of 36.2 dB. The dynamic allocation of descriptions to the network channels is optimized for rate distortion minimization. The improvement in term of Y-PSNR achieved by rate distortion optimization has been between 0.7 and 5.3 dB in different bit rates. (c) 2012 SPIE and IS&T. [DOI: 10.1117/1.JEI.21.4.043006]
Citation Count: Choupani, Roya; Wong, Stephan; Tolun, Mehmet. Using wavelet transform self-similarity for effective multiple description video coding, 2015 10th International Conference on Information, Communications and Signal Processing (ICICS), 2016.
Using wavelet transform self-similarity for effective multiple description video coding
(IEEE, 2016) Choupani, Roya; Wong, Stephan; Tolun, Mehmet
Video streaming over unreliable networks requires preventive measures to avoid quality deterioration in the presence of packet losses. However, these measures result in redundancy in the transmitted data which is utilized to estimate the missing packets lost in the delivered portions. In this paper, we have used the self-similarity property if the discrete wavelet transform (DWT) to minimize the redundancy and improve the fidelity of the delivered video streams in presence of data loss. Our proposed method decomposes the video into multiple descriptions after applying the DWT. The descriptions are organized in such a way that when one of them is lost during transmission, it is estimated using the delivered portions by means of self-similarity between the DWT coefficients. In our experiments, we compare video reconstruction in the presence of data loss in one or two descriptions. Based on the experimental results, we have ascertained that our estimation method for missing coefficients by means of self-similarity is able to improve the video quality by 2.14dB and 7.26dB in case of one description and two descriptions, respectively. Moreover, our proposed method outperforms the state-of-the-art Forward Error Correction (FEC) method in case of higher bit-rates.
Citation Count: Hassanpour, Reza; Wong, Stephan; Shahbahrami, Asadollah (2008). "Vision-based hand gesture recognition for human computer interaction: A review", MCCSIS'08 - IADIS Multi Conference on Computer Science and Information Systems; Proceedings of Interfaces and Human Computer Interaction 2008, pp. 125-132.
Vision-based hand gesture recognition for human computer interaction: A review
(2008) Hassanpour, Reza; Wong, Stephan; Shahbahrami, Asadollah
Evolution of user interfaces shapes the change in the human-computer interaction. With the rapid emergence of threedimensional (3-D) applications; the need for a new type of interaction device arises as traditional devices such as mouse, keyboard, and joystick become inefficient and cumbersome within these virtual environments. Intuitive and naturalness characteristics of "Hand Gestures" in human computer interaction have been the driving force and motivation to develop an interaction device which can replace current unwieldy tools. This study is a survey on the methods of analyzing, modeling and recognizing hand gestures in the context of human-computer interaction. Taxonomy of the methods based on the applications that they have been developed for and the approaches that they have used to represent gestures is presented. Direction of future developments is also discussed.
Citation Count: Choupani, Roya; Wong, Stephan; Tolun, Mehmet R. (2008). "Weighted embedded zero tree for scalable video compression", Proceedings of the 2008 International Conference on Image Processing, Computer Vision, and Pattern Recognition, IPCV 2008, 14 July 2008 through 17 July 2008, pp. 681 - 684.
Weighted embedded zero tree for scalable video compression
(2008) Choupani, Roya; Wong, Stephan; Tolun, Mehmet R.
Video streaming over the Internet has gained popularity during recent years mainly due to the revival of videoconferencing and videotelephony applications and the proliferation of (video) content providers. However, the heterogeneous, dynamic, and best-effort nature of the Internet cannot always guarantee a certain bandwidth for an application utilizing the Internet. Scalability has been introduced to deal with such issues (up to a certain point) by intelligently separating any information stream into multiple streams. The reception of one, several, or all stream influences the perceived quality of the information as basic, improved, or best, respectively. In addition, wavelet-based scalability combined with representation methods such as embedded zero trees (EZWs) improves the decode-ability of the stream even when only the initial part of the streams have been received. In this paper, we propose a method to improve on the compression rate of the EZW for scalability purposes by reducing the number of levels used in the tree. Therefore, the proposed method should be able to deal more efficiently with the mentioned scalability issues in low bandwidth network. Initial experimental show that the first two layers of the generated EZW are about 22.6% more concise.