A. Vincent

Sungkyunkwan University, Sŏul, Seoul, South Korea

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Publications (47)25.68 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In the stereoscopic high-definition (HD) frame-compatible formats, the separate left and right views are reduced in resolution and packed to fit within the same video frame as a conventional two-dimensional high-definition signal. Since they do not require additional transmission bandwidth and entail limited changes to the existing broadcasting infrastructure, these formats have been suggested for 3DTV. However, the convenience of frame-compatible formats comes at the expense of lower picture quality of the 3D signal. In this study, we evaluated the loss in picture quality of two frame-compatible formats: 1080i Side-by-Side and 720p Top/Bottom, using a subjective assessment experiment.
    Multimedia and Expo (ICME), 2012 IEEE International Conference on; 01/2012
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    ABSTRACT: In the stereoscopic frame-compatible format, the separate high-definition left and high-definition right views are reduced in resolution and packed to fit within the same video frame as a conventional two-dimensional high-definition signal. This format has been suggested for 3DTV since it does not require additional transmission bandwidth and entails only small changes to the existing broadcasting infrastructure. In some instances, the frame-compatible format might be used to deliver both 2D and 3D services, e.g., for over-the-air television services. In those cases, the video quality of the 2D service is bound to decrease since the 2D signal will have to be generated by up-converting one of the two views. In this study, we investigated such loss by measuring the perceptual image quality of 1080i and 720p up-converted video as compared to that of full resolution original 2D video. The video was encoded with either a MPEG-2 or a H.264/AVC codec at different bit rates and presented for viewing with either no polarized glasses (2D viewing mode) or with polarized glasses (3D viewing mode). The results confirmed a loss of video quality of the 2D video up-converted material. The loss due to the sampling processes inherent to the frame-compatible format was rather small for both 1080i and 720p video formats; the loss became more substantial with encoding, particularly for MPEG-2 encoding. The 3D viewing mode provided higher quality ratings, possibly because the visibility of the degradations was reduced.
    SPIE-SDA; 01/2011
  • Demin Wang, Liang Zhang, A. Vincent
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    ABSTRACT: Motion-compensated frame rate up-conversion is used to convert video/film materials of low frame rates to a higher frame rate so that the materials can be displayed with smooth motion and high-perceived quality. It consists of two key elements: motion estimation and motion-compensated frame interpolation. It requires accurate motion trajectories to ensure quality results and low computational cost to ensure practical applications. This paper presents a novel motion estimation algorithm that combines the accuracy of maximum a posteriori probability (MAP) estimation with the speed of hierarchical block-matching algorithm (BMA). This MAP estimation uses three consecutive pictures, instead of the conventional two, and one previously estimated motion field to exploit the temporal correlation between motion fields and to determine motion in occluded areas. The optimization of the MAP estimation is performed using full-search and implemented by means of look-up tables. The full search ensures that the optimization converges to the global minimum, while the look-up tables dramatically reduce the computational cost. Experimental results show that the proposed algorithm provides motion trajectories that are much more accurate than those obtained using either the full-search BMA or hierarchical BMA alone. Also, it is much faster than the full-search BMA.
    IEEE Transactions on Broadcasting 07/2010; · 2.09 Impact Factor
  • F. Speranza, A. Vincent, R. Renaud
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    ABSTRACT: In this study we evaluated the bit-rate efficiency of current hardware H.264 encoders as compared to that of established MPEG-2 hardware encoders. To estimate bit-rate efficiency, we measured the subjective video quality of MPEG-2 encoded material processed at three bit rates: 8, 12, and 16 Mbps, and determined the bit-rate at which H.264 encoded material produced similar subjective video quality. The MPEG-2 and H.264 bit rates that resulted in the same perceived video quality were used to estimate bit-rate efficiency.
    IEEE Transactions on Broadcasting 01/2010; · 2.09 Impact Factor
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    ABSTRACT: Motion-compensated frame rate up-conversion (MC-FRUC) consists of two key elements: motion estimation and motion-compensated frame interpolation. The motion estimation algorithm presented in , which is used in the MC-FRUC method proposed in this paper, provides unidirectional motion trajectories. The advantage of this motion estimation algorithm, besides its accuracy, is that it provides information on occlusions. However, motion compensation along unidirectional motion trajectories yields overlaps, holes, and blocking artifacts. To solve these problems, this paper presents two new algorithms for unidirectional motion-compensated frame interpolation: irregular-grid expanded-block weighted motion compensation (IEWMC) and block-wise directional hole interpolation (BDHI). The IEWMC is used to reduce the blocking artifacts and solve the problem of overlapping blocks. The BDHI preserves local texture and edges while filling holes. Experimental results show that the IEWMC outperforms conventional motion compensation, and the BDHI is better than the repeated median filter that is often used to fill holes. The performance of the proposed MC-FRUC, that uses the two new algorithms and the unidirectional motion estimation algorithm, is evaluated against three existing MC-FRUC techniques: a typical bi-directional algorithm, an object-based algorithm, and a commercial plug-in product. Experimental results show that the quality of the pictures interpolated using the proposed MC-FRUC method is much higher than those interpolated using the three existing MC-FRUC techniques.
    IEEE Transactions on Broadcasting 01/2010; 56(2):142-149. · 2.09 Impact Factor
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    ABSTRACT: The curved wavelet transform (CWT) was developed to enhance compactness of the wavelet transform (WT) representation. Curve determination is critical for the CWT because a well-defined curve set can increase the performance gain in terms of the rate-distortion (R-D). Conventionally, the image to be encoded is divided into blocks and the curve orientation in each block is independently determined through the minimization of its high-pass CWT energy. In this paper, we propose an R-D optimization algorithm for the curve determination, in which variable block size and the impact of neighboring blocks are taken into account. To reduce the computational cost, an alternative sampling strategy is exploited. Experiment results with natural images show that the proposed algorithm can provide better image quality, measured objectively or subjectively, compared to the conventional CWT coding algorithm. Importantly, the proposed approach overcomes the hurdles of computational cost and optimization at the global level opens the door for further performance enhancements of applications with the CWT.
    Image Processing (ICIP), 2009 16th IEEE International Conference on; 12/2009
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    ABSTRACT: In this paper, we propose a region-adaptive quantization scheme and progressive side information/channel noise modeling for Wyner-Ziv video coding. The proposed region-adaptive quantization scheme can enhance coding performance and provide an additional functionality of region of interest (ROI) coding. It also improves the accuracy of channel noise modeling by using previously decoded bit-plane information. Simulation results show that the proposed region-adaptive quantization scheme is especially suitable for static sequences, and the progressive side information/channel noise modeling works well in dynamic scenes.
    Broadband Multimedia Systems and Broadcasting, 2009. BMSB '09. IEEE International Symposium on; 06/2009
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    ABSTRACT: This paper presents a new distributed video coding (DVC) scheme where the DC and the AC coefficients of DCT transform are separately encoded and transmitted. The DC coefficients are first transmitted to the decoder and compared with their corresponding DC coefficients found in the side information derived within the decoder. The result of the comparison is then transmitted back to the encoder and used to decide whether the AC coefficients of a block need to be transmitted. Experimental results show that the proposed scheme can significantly improve the performance, while maintaining a low computational complexity at the encoder.
    Electrical and Computer Engineering, 2009. CCECE '09. Canadian Conference on, St-Johns, Canada; 05/2009
  • Demin Wang, Liang Zhang, Andre Vincent
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    ABSTRACT: Motion estimation is being utilized more and more in video post-production and display for a wide range of applications. These applications require accurate motion trajectories at low computational cost. This paper presents a novel motion estimation algorithm that combines the accuracy of MAP estimation with the speed of hierarchical block-matching algorithm (BMA). This MAP estimation uses three consecutive pictures, instead of the conventional two, and one previously estimated motion field to exploit the temporal correlation between motion fields and to determine motion in occluded areas. The optimization of the MAP estimation is performed using full search and implemented by means of look-up tables. The full search ensures that the optimization converges to the global minimum, while the look-up tables dramatically reduce the computational cost. Experiment results show that the proposed algorithm provides motion trajectories that are much more accurate than those obtained using the full-search BMA and hierarchical BMA. It is much faster than the full-search BMA, but slower than the hierarchical BMA.
    01/2009;
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    ABSTRACT: This paper presents an extension of the maximum likelihood estimation sample consensus (MLESAC) by introducing an online validation of individual correspondences, which is based on the Law of Large Numbers (LLN). The outcomes of the samples, each considered a random event, are analyzed for useful information regarding the validities of individual correspondences. The information from the individual samples that have been processed is accumulated and then used to guide subsequent sampling and to score the estimate. To evaluate the performance of the proposed algorithm, the proposed method was applied to the problem of estimating the fundamental matrix. Experimental results with the Oxford image sequence, Corridor, showed that for a similar consensus the proposed algorithm reduced, on average, the Sampson error by about 13% and 12% in comparison to the RANSAC and the MLESAC estimator, while the associated number of samples decreased by about 14% and 15%, respectively.
    Advances in Visual Computing, 5th International Symposium, ISVC 2009, Las Vegas, NV, USA, November 30 - December 2, 2009, Proceedings, Part I; 01/2009
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    ABSTRACT: In the last few years distributed video coding (DVC) has become a new paradigm for video compression where the encoding process needs to be simple. DVC allows for the development of new applications where the computational complexity and the amount of memory inside the video encoder are limited. In this paper, we introduce a new data representation and coding method for DVC systems. The proposed method consists of an adaptive binary representation based on the maximum difference between the source picture and the side information. This adaptive representation provides a reduction of bitrate without any loss of information, while maintaining the low complexity of the encoder. Experimental results show a significant increase in performance over conventional DVC methods.
    Proceedings of the International Conference on Image Processing, ICIP 2009, 7-10 November 2009, Cairo, Egypt; 01/2009
  • Liang Zhang, Demin Wang, A. Vincent
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    ABSTRACT: A novel data structure is proposed for magnitude-ordering 3-D wavelet transform coefficients. This data structure consists of temporal 1-D orientation trees followed by spatial 2-D orientation trees. Based on this data structure, a coding algorithm is developed for the embedded coding of 3-D wavelet transform coefficients. Experiment results confirm that the proposed coding algorithm outperforms a conventional algorithm that uses asymmetric 3-D orientation trees.
    IEEE Transactions on Broadcasting 10/2008; · 2.09 Impact Factor
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    ABSTRACT: All existing video coding standards are based on block-wise motion compensation and block-wise DCT. At high levels of quantization, block-wise motion compensation and transform produces blocking artifacts in the decoded video, a form of distortion to which the human visual system is very sensitive. The latest video coding standard, H.264/AVC, introduces a deblocking filter to reduce the blocking artifacts. However, there is still visible distortion after the filtering when compared to the original video. In this paper, we propose a non-conventional filter to further reduce the distortion and to improve the decoded picture quality. Different from conventional filters, the proposed filter is based on a machine learning algorithm (decision tree). The decision trees are used to classify the filter's inputs and select the best filter coeffcients for the inputs. Experimental results with 4 × 4 DCT indicate that using the filter holds promise in improving the quality of H.264/AVC video sequences.
    Proc SPIE 01/2008;
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    ABSTRACT: Wavelet-based video coding has received much attention and emerged as a viable alternative to the traditional DCT-based hybrid coding scheme. This paper presents a wavelet-based video codec, its fast implementation, and its compression efficiency. The codec consists of motion-compensated temporal filtering (MCTF), 2-D spatial wavelet transform, and extended SPIHT for wavelet coefficient coding. It exploits a new signal extension method and sub-sampling rule to improve the performance of the MCTF. Experimental results show that the codec performs as well as H.264 High Profile (reference software JM10.1 with I and P picture types) in terms of PSNR and bit rates. It generally provides a better subjective picture quality than H.264 because it does not suffer from blocking artefacts.
    01/2007;
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    ABSTRACT: A framework for virtual view synthesis based on multiple images is presented in this paper. Compared to conventional view synthesis based on stereoscopic image pairs, a postprocessing algorithm for disparity refinement is added to exploit information contained in multiple images captured with a multi-view camera configuration. The principle for disparity refinement is examined, leading to the development of a novel algorithm. Experimental results show that the newly developed algorithm can improve image quality of synthesized virtual views with a PSNR gain of up to 0.65 dB.
    Proceedings of the 2007 IEEE International Conference on Multimedia and Expo, ICME 2007, July 2-5, 2007, Beijing, China; 01/2007
  • Demin Wang, Liang Zhang, A. Vincent
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    ABSTRACT: The conventional motion-compensated temporal wavelet transform using the 5/3 filter produces GOP-boundary artifacts, i.e., a drop in picture quality at the boundaries of groups of pictures (GOP). A simple and efficient method is proposed in this paper to reduce the GOP-boundary artifacts and improve the overall performance of the transform. With this method, a group of pictures to be temporally transformed is extended by boundary repetition to one side and by symmetrical extension to the other side. The sub-sampling rule changes from one level to another during the multi-level transform. In addition, a non-uniform quantization scheme is employed. This method does not require any additional computation or memory. Experimental results of video coding with six test sequences show that this method outperforms the conventional method, providing a coding gain of 0.27 dB in terms of average PSNR and up to 1.95 dB in terms of minimum PSNR
    IEEE Transactions on Broadcasting 10/2006; · 2.09 Impact Factor
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    ABSTRACT: The conventional two-dimensional wavelet transform used in existing image coders is usually performed through one-dimensional (1-D) filtering in the vertical and horizontal directions, which cannot efficiently represent edges and lines in images. The curved wavelet transform presented in this paper is carried out by applying 1-D filters along curves, rather than being restricted to vertical and horizontal straight lines. The curves are determined based on image content and are usually parallel to edges and lines in the image to be coded. The pixels along these curves can be well represented by a small number of wavelet coefficients. The curved wavelet transform is used to construct a new image coder. The code-stream syntax of the new coder is the same as that of JPEG2000, except that a new marker segment is added to the tile headers. Results of image coding and subjective quality assessment show that the new image coder performs better than, or as well as, JPEG2000. It is particularly efficient for images that contain sharp edges and can provide a PSNR gain of up to 1.67 dB for natural images compared with JPEG2000.
    IEEE Transactions on Image Processing 09/2006; 15(8):2413-21. · 3.20 Impact Factor
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    Wei Li, G. Gagnon, Hong Liu, A. Vincent
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    ABSTRACT: The throughput of IP (UDP and TCP) data transmission over terrestrial ATSC DTV channels was evaluated. A testbed was developed for this purpose. Various issues affecting the throughput of IP data transmission over DTV channels were analyzed, such as channel noise, traffic load, IP packet size and return link capacity. Results obtained from these tests offer valuable information for broadcasters who plan to implement datacasting services over ATSC DTV systems.
    IEEE Transactions on Broadcasting 07/2006; · 2.09 Impact Factor
  • SMPTE journal: publication of the Society of Motion Picture and Television Engineers 04/2006; · 0.07 Impact Factor
  • D. Wang, L. Zhang, A. Vincent
    Picture Coding Symposium 2006. 04/2006;