Optimizing MPEG-4 coding performance by taking post-processing into account

Centre for Multimedia Signal Processing, Department of Electronic and Information EngineeringRefereed conference paper2000-2001 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Regularized restoration of VQ compressed images with constrained least squares approach

Author name used in this publication: S. W. HongVersion of RecordPublishe

Decodage optimal oriente objet pour la suppression des effets de bloc dans les sequences dv et mpeg-2

Cet article propose une méthode de décodage permettant d'améliorer la qualité visuelle des séquences vidéos. Deux objectifs sont visés : la réduction des effets de bloc dans les séquences de type DV, M-JPEG et MPEG d'une part, la restitution des blocs perdus (dropout) par le système d'acquisition ou par le réseau d'autre part. La minimisation de critères appropriés permet une estimation et un traitement simultané du fond de la séquence et une segmentation spatio-temporelle des objets en mouvement. Un suivi temporel des objets permet ensuite de traiter chaque objet de manière indépendante et adaptée. La qualité de la séquence ainsi restituée par le décodeur est largement améliorée

Transform Domain-Based Perceptual Detection and Reduction of Blocking Artifacts

In this paper, provide a simple and effective method for measuring blocking artefacts with an ideal 2-D step function in this study. First, a basic edge detection technique for measuring blocking artefacts is proposed. The ideal 2-D step function is chosen based on the presence of blocking artefacts in the edge image. The blocking artefact reduction algorithm in frequency domain is designed to extract all of the parameters required to detect the presence of blocking artefacts and replace the optimal step function with a ramp function by replacing the coefficient of the first row of horizontal blocks with the coefficient of the shifted block. The proposed strategy was tested on various standard benchmark photos and found to increase the perceptual quality of JPEG compressed images after blocking artefact removal with the proposed method

FFT Bifurcation Analysis of Routes to Chaos via Quasiperiodic Solutions

The dynamics of a ring of seven unidirectionally coupled nonlinear Duffing oscillators is studied. We show that the FFT analysis presented in form of a bifurcation graph, that is, frequency distribution versus a control parameter, can provide a valuable and helpful complement to the corresponding typical bifurcation diagram and the course of Lyapunov exponents, especially in context of detailed identification of the observed attractors. As an example, bifurcation analysis of routes to chaos via 2-frequency and 3-frequency quasiperiodicity is demonstrated

Finite element based interpolation methods for spatial and temporal resolution enhancement for image sequences

Spatial resolution enhancement is a process for reconstructing a high resolution image from a low resolution image, whereas temporal resolution enhancement of encoded video aims of interpolating the skipped frames, making use of two successively received frames. In this thesis, a new image interpolation model, called the generalized image interpolation model , is developed in order to devise new techniques for spatial resolution enhancement of images, and temporal resolution enhancement of encoded video sequences. The interpolation model is based on the finite element method, and takes into account the unknown neighboring pixels, and therefore is capable of interpolating a collection of unknown pixels with an arbitrary shape, while providing a spatial continuity between the unknown pixels. Based on the generalized interpolation model, an edge-preserving iterative refinement scheme for spatial resolution enhancement of images is proposed. This scheme exploits not only the neighboring pixels whose values are known, but also takes into account those with unknown values. It is shown that the edge-preserving iterative refinement process maintains the smooth variation along a dominant edge in the up-scaled image. Simulation results show that the proposed scheme results in up-scaled images with subjective and objective qualities, which are better than those of the existing interpolation schemes. Further, the scheme is also shown to be capable of up-scaling an image by an arbitrary magnification factor, without resorting to extra steps, or the use of any conventional interpolation method. Next, error concealment-based MCI schemes are also presented for temporal resolution enhancement of encoded video sequences. These schemes are also based on the generalized image interpolation model, and need no pixel classification, thus reducing substantially the computational complexity. They are shown to be capable of concealing the errors in the homogeneous regions as well as in regions containing sharp edges. Experiments are carried out showing that the proposed schemes result in reconstructed frames having a better visual quality and a lower computational complexity than that provided by the existing techniques