Jacek Nieweglowski

Jacek Nieweglowski; Moncef Gabbouj

Abstract Weighted Medians with integer weights are widely used nonlinear operators in signal processing. Weighted median filters belong to the class of stack filters. Since each stack filter is uniquely specified by its corresponding positive Boolean function, the latter can be used to analyze the behavior of the filter. On the other hand, weighted medians are usually represented by a given set of weights. In this paper, weighted medians are first extended to include weighted median operators with positive real-valued weights. It is shown that any real weighted median is equivalent to an integer weighted median. As a consequence, a sensitivity analysis can always be performed to represent real weighted medians by finite precision weighted medians. This result proves very useful if one realizes that optimal adaptive weighted medians are usually real-valued. Conversion algorithms are presented to find the positive Boolean function representing a given weighted median and a set of weights of a weighted median representing a given positive Boolean function if feasible.

Jacek Nieweglowski; Timo Moisala; Petri Haavisto

A new method for temporal interpolation of video sequences is proposed. For each pair of original frames a new frame is created by averaging frames obtained by motion compensated warping of original frames. The parameters of the geometrical transformation applied to original frames are determined by the motion in the sequence. The advantage of the proposed method is that it can compensate for various motion types such as translations, rotations, and scaling. The primary application of the presented algorithm is the frame interpolation of video sequences coded at very low bitrates where the warping scheme ran also he used for motion compensated prediction. In that case the decoder does not have to perform motion estimation but can use motion vectors from encoder for frame interpolation.<<ETX>>

Jacek Nieweglowski; Lin Yin; Moncef Gabbouj; Y. Neuvo

The authors present a procedure based on quadratic programming for finding the optimal weighted order statistic filter under the mean absolute error criterion satisfying imposed structural constraints. In this way, filters are obtained that simultaneously meet the desired detail preservation constraints and give a good noise attenuation. The algorithm is characterized by low computational complexity and simplicity in constraint formulation. The method is capable of handling large window size problems.<<ETX>>

Marta Karczewicz; Jacek Nieweglowski; Petri Haavisto

This paper discusses the problem of motion compensated prediction in a segmentation based video coding scheme. The problem is considered in the framework of a generic video coder utilizing spatial image segmentation and a polynomial model of the motion vector field for each image region. It is shown that very impressive reductions in prediction error can be achieved by this approach compared to traditional block matching. The cost of encoding the motion information is also addressed. We derive an analytical method for the reduction of the number of motion coefficients, which is optimal is the sense of the least increase in the prediction error. Finally, we derive a low complexity method for motion assisted merging of regions resulting from spatial segmentation which leads to a dramatic reduction in the number of regions.

Jacek Nieweglowski; Petri Haavisto

A new method for temporal prediction of image sequences is proposed. In the proposed method the motion of a selected set of individual pixels, instead of blocks, is estimated. The resulting low resolution estimate of the motion vector field is interpolated using an adaptive scheme. This yields piecewise smooth motion vector field. The proposed prediction scheme can compensate various types of motion and deformations. It can also be incorporated in current hybrid video compression systems with little additional complexity and no change in the bit stream syntax. It is shown that the proposed scheme improves the peak signal-to-noise ratio of the prediction by up to 1.9 dB compared to conventional methods.

T. G. Campbell; Mika Grundstrom; Jacek Nieweglowski

The transmission of Digital High Definition Television signal over terrestrial broadcast channel imposes severe requirements on the signal. The system has to handle very large variations of Signal-to-Noise Ratio depending on the distance between transmitter and the receiver and the quality of receiving equipment e.g. antenna. It should provide the HDTV quality picture whenever possible and viewable picture in very poor conditions. One possible solution to this problem is the system providing easily retrievable standard resolution signal embedded in the HDTV signal. In this paper we consider the design of the channel coding part of the system as well as joint optimization of source and channel coding. The results of the simulations of such a system are also included.

Jacek Nieweglowski; T.G. Campbell; P. Haavisto

Jacek Nieweglowski; Mustafa Ali Tûrker; Ossi Kalevo; Petri Haavisto

Jacek Nieweglowski; Ali Tuerker; Ossi Kalevo; Petri Haavisto

Jacek Nieweglowski; Ali Tuerker; Ossi Kalevo; Petri Haavisto