The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Yunglyul Lee - One of the best experts on this subject based on the ideXlab platform.
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a Postprocessing method for reducing quantization effects in low bit rate moving picture coding
IEEE Transactions on Circuits and Systems for Video Technology, 1999Co-Authors: Hyunwook Park, Yunglyul LeeAbstract:The reconstructed images from highly compressed MPEG data have noticeable image degradations, such as blocking artifacts near the block boundaries, corner outliers at crosspoints of blocks, and ringing noise near image edges because the MPEG quantizes the transformed coefficients of 8/spl times/8 pixel blocks. A Postprocessing algorithm is proposed to reduce quantization effects, such as blocking artifacts, corner outliers, and ringing noise, in MPEG-decompressed images. The proposed Postprocessing algorithm reduces the quantization effects adaptively by using both spatial frequency and temporal information extracted from the compressed data. The blocking artifacts are reduced by one-dimensional (1-D) horizontal and vertical low-pass filtering (LPF), and the ringing noise is reduced by two-dimensional (2-D) signal-adaptive filtering (SAF). A comparison study of the peak signal-to-noise ratio (PSNR) and the computation complexity analysis between the proposed algorithm and the MPEG-4 VM (verification model) Postprocessing algorithm is performed by computer simulation with several image sequences. According to the comparison study of PSNR and computation complexity analysis, the proposed algorithm shows better performance than the VM Postprocessing algorithm, whereas the subjective image qualities of both algorithms are similar.
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blocking effect reduction of jpeg images by signal adaptive filtering
IEEE Transactions on Image Processing, 1998Co-Authors: Yunglyul Lee, H C Kim, Hyunwook ParkAbstract:A Postprocessing algorithm is proposed to reduce the blocking artifacts of Joint Photographic Experts Group (JPEG) decompressed images. The reconstructed images from JPEG compression produce noticeable image degradation near the block boundaries, in particular for highly compressed images, because each block is transformed and quantized independently. The blocking effects are classified into three types of noises in this paper: grid noise, staircase noise, and corner outlier. The proposed Postprocessing algorithm, which consists of three stages, reduces these blocking artifacts efficiently. A comparison study between the proposed algorithm and other Postprocessing algorithms is made by computer simulation with several JPEG images.
Mei-yin Shen - One of the best experts on this subject based on the ideXlab platform.
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fast compression artifact reduction technique based on nonlinear filtering
International Symposium on Circuits and Systems, 1999Co-Authors: Mei-yin Shen, Jongwon Kim, C Jay C KuoAbstract:A computationally efficient Postprocessing technique to reduce compression artifacts in low-bit-rate video coding is presented in this research. Blocking and ringing effects are two major compression artifacts observed in the block DCT-based video codec, such as H.263, when the coding bit rate becomes low. Reduction of these artifacts can significantly improve the overall visual quality of decoded video. A new table-lookup method and a nonlinear filtering approach are adopted to remove the blocking and ringing effects, respectively. Experiments employing H.263+TMN8 anchor bit-streams are performed to show that the proposed Postprocessing technique can alleviate the coding artifacts efficiently with a low computational complexity.
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real time Postprocessing technique for compression artifact reduction in low bit rate video coding
SPIE's International Symposium on Optical Science Engineering and Instrumentation, 1998Co-Authors: Mei-yin ShenAbstract:A computationally efficient Postprocessing technique to reduce compression artifacts in low-bit-rate video coding is proposed in this research. We first formulate the artifact reduction problem as a robust estimation problem. Under this framework, the artifact-free image is obtained by minimizing a cost function that accounts for smoothness constraints as well as image fidelity. Instead of using the traditional approach that applies the gradient descent search for optimization, a set of nonlinear filters is proposed to determine the approximating global minimum to reduce the computational complexity so that real-time Postprocessing is possible. We have performed experimental results on the H.263 codec and observed that the proposed method is effective in reducing severe blocking and ringing artifacts, while maintaining a low complexity and a low memory bandwidth.
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Review of Postprocessing Techniques for Compression Artifact Removal
Journal of Visual Communication and Image Representation, 1998Co-Authors: Mei-yin Shen, C.-c. Jay KuoAbstract:Low bit rate image/video coding is essential for many visual communication applications. When bit rates become low, most compression algorithms yield visually annoying artifacts that highly degrade the perceptual quality of image and video data. To achieve high bit rate reduction while maintaining the best possible perceptual quality, Postprocessing techniques provide one attractive solution. In this paper, we provide a review and analysis of recent developments in Postprocessing techniques. Various types of compression artifacts are discussed first. Then, two types of Postprocessing algorithms based on image enhancement and restoration principles are reviewed. Finally, current bottlenecks and future research directions in this field are addressed.
Hyunwook Park - One of the best experts on this subject based on the ideXlab platform.
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a Postprocessing method for reducing quantization effects in low bit rate moving picture coding
IEEE Transactions on Circuits and Systems for Video Technology, 1999Co-Authors: Hyunwook Park, Yunglyul LeeAbstract:The reconstructed images from highly compressed MPEG data have noticeable image degradations, such as blocking artifacts near the block boundaries, corner outliers at crosspoints of blocks, and ringing noise near image edges because the MPEG quantizes the transformed coefficients of 8/spl times/8 pixel blocks. A Postprocessing algorithm is proposed to reduce quantization effects, such as blocking artifacts, corner outliers, and ringing noise, in MPEG-decompressed images. The proposed Postprocessing algorithm reduces the quantization effects adaptively by using both spatial frequency and temporal information extracted from the compressed data. The blocking artifacts are reduced by one-dimensional (1-D) horizontal and vertical low-pass filtering (LPF), and the ringing noise is reduced by two-dimensional (2-D) signal-adaptive filtering (SAF). A comparison study of the peak signal-to-noise ratio (PSNR) and the computation complexity analysis between the proposed algorithm and the MPEG-4 VM (verification model) Postprocessing algorithm is performed by computer simulation with several image sequences. According to the comparison study of PSNR and computation complexity analysis, the proposed algorithm shows better performance than the VM Postprocessing algorithm, whereas the subjective image qualities of both algorithms are similar.
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blocking effect reduction of jpeg images by signal adaptive filtering
IEEE Transactions on Image Processing, 1998Co-Authors: Yunglyul Lee, H C Kim, Hyunwook ParkAbstract:A Postprocessing algorithm is proposed to reduce the blocking artifacts of Joint Photographic Experts Group (JPEG) decompressed images. The reconstructed images from JPEG compression produce noticeable image degradation near the block boundaries, in particular for highly compressed images, because each block is transformed and quantized independently. The blocking effects are classified into three types of noises in this paper: grid noise, staircase noise, and corner outlier. The proposed Postprocessing algorithm, which consists of three stages, reduces these blocking artifacts efficiently. A comparison study between the proposed algorithm and other Postprocessing algorithms is made by computer simulation with several JPEG images.
Wei Gong - One of the best experts on this subject based on the ideXlab platform.
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a review on statistical Postprocessing methods for hydrometeorological ensemble forecasting
Wiley Interdisciplinary Reviews: Water, 2017Co-Authors: Qingyun Duan, Chiyuan Miao, Wei GongAbstract:Computer simulation models have been widely used to generate hydrometeorological forecasts. As the raw forecasts contain uncertainties arising from various sources, including model inputs and outputs, model initial and boundary conditions, model structure, and model parameters, it is necessary to apply statistical Postprocessing methods to quantify and reduce those uncertainties. Different Postprocessing methods have been developed for meteorological forecasts (e.g., precipitation) and for hydrological forecasts (e.g., streamflow) due to their different statistical properties. In this paper, we conduct a comprehensive review of the commonly used statistical Postprocessing methods for both meteorological and hydrological forecasts. Moreover, methods to generate ensemble members that maintain the observed spatiotemporal and intervariable dependency are reviewed. Finally, some perspectives on the further development of statistical Postprocessing methods for hydrometeorological ensemble forecasting are provided. WIREs Water 2017, 4:e1246. doi: 10.1002/wat2.1246 For further resources related to this article, please visit the WIREs website.
Sebastian Lerch - One of the best experts on this subject based on the ideXlab platform.
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neural networks for Postprocessing ensemble weather forecasts
Monthly Weather Review, 2018Co-Authors: Stephan Rasp, Sebastian LerchAbstract:AbstractEnsemble weather predictions require statistical Postprocessing of systematic errors to obtain reliable and accurate probabilistic forecasts. Traditionally, this is accomplished with distri...
