Showing papers by "Fabrizio Granelli published in 2000"

Low-complexity post-processing for artifact reduction in block-DCT based video coding

Abstract: Most widespread video coding algorithms (such as MPEG, H.261, H.263) employ DCT coding for data compression but introduce annoying artefacts due mainly to the independent quantization of the coefficients in each block, that are especially visible at medium and low bitrates. Within this framework, post-processing appears to be a practical solution for visual enhancement of compressed video. In this paper, an adaptive anisotropic spatial-variant FIR filtering procedure is proposed. The filter kernels are selected on the basis of a pixel classification procedure that performs a block-DCT coefficients energy analysis and an edge extraction. The analysis of the transform coefficients matrix allows one to extract information about spatial characteristics, while the edge information provide the basis for the estimation of the position of the local visual artifact. Accurate filtering results were obtained during experiments that outperform those obtained with other existing approaches.

Minimax Based Regulation of Change Detection Threshold in Video-Surveillance Systems

Abstract: Thanks to the increasing development of complex vision systems, it becomes strictly necessary to introduce quantitative performance evaluation methods Such methods should make it possible both comparing results provided by different surveillance systems and selecting optimal parameters for each one, depending on the specific functionality of a system and on the particular characteristics of the monitored environment In this contribution, it is shown that Receiver Operating Characteristics [1] (ROC) curves provide a well assessed tool that can be used for the above purpose In literature ROC curves have been used for performance evaluation of image processing algorithms: in [2] for evaluation of edge detection algorithms and in [3] for evaluation of artificial neural networks for medical imaging

Adaptive post-processing error concealment based on feedback from a video-surveillance system

Abstract: An effective real-time post-processing algorithm for error recovery in noise corrupted JPEG bit streams integrated into an existing remote video-surveillance system is presented. The algorithm exploits information extracted by the video-surveillance system in order to detect corrupted frames and to recover them, enhancing the performances of the system, without compromising the real-time behavior of the application. Results show the validity of the presented approach.

Post-processing for real-time quality enhancement of MPEG-coded video sequences

Abstract: In this paper, a novel adaptive spatial-variant FIR filter is proposed for the reduction of compression artifacts in MPEG coding. The selection of the appropriate filtering kernel is performed by a classification of the processed regions based both upon the distribution of the energy among the transform coefficients and on the distance from edge pixels, extracted with the Sobel operator. Experimental results show that the proposed algorithm outperforms existing enhancement approaches, especially when constraints on low-complexity and real-time processing are compelling.