A method for estimation of motion vector fields that includes detection of motion discontinuities and occlusion areas is presented. A cost function is formulated that incorporates coupled Markov random field models for the motion vector field, the motion discontinuity field and the occlusion field. The cost function is minimized by a deterministic iterative process. Application of this method to an image sequence with occlusion is described. Results of motion-compensated temporal interpolation for 4:1 field subsampling are presented and compared to motion estimation without occlusion processing.>

The authors examine one approach to the problem of estimating motion in varying illumination using a motion trajectory model and a spatio-temporal gradient approach which simultaneously estimates the motion field and the parameters describing the illumination field. Interpolation techniques are used to increase the estimation accuracy and flexibility. This method has been applied to several digital NTSC luminance sequences with synthetic and natural motion and with synthetic and natural illumination variation. Two experiments and their results are discussed.>

Sampling is a fundamental operation in all image communication systems. A time-varying image, which is a function of three independent variables, must be sampled in at least two dimensions for transmission over a one-dimensional analog communication channel, and in three dimensions for digital processing and transmission. At the receiver, the sampled image must be interpolated to reconstruct a continuous function of space and time. In imagery destined for human viewing, the visual system forms an integral part of the reconstruction process. This paper presents an overview of the theory of sampling and reconstruction of multidimensional signals. The concept of sampling structures based on lattices is introduced. The important problem of conversion between different sampling structures is also treated. This theory is then applied to the sampling of time-varying imagery, including the role of the camera and display apertures, and the human visual system. Finally, a class of nonlinear interpolation algorithms which adapt to the motion in the scene is presented.

Noise in television signals degrades both the image quality and the performance of image coding algorithms. This paper describes a nonlinear temporal filtering algorithm using motion compensation for reducing noise in image sequences. A specific implementation for NTSC composite television signals is described, and simulation results on several video sequences are presented. This approach is shown to be successful in improving image quality and also improving the efficiency of subsequent image coding operations.

Methods for sampling and reconstruction of NTSC video signals at twice the color subcarrier frequency are described and evaluated. A scheme for sampling NTSC signals is characterized by the horizontal sampling frequency and the spatiotemporal sampling structure. For a given sampling frequency, the sampling structure should be chosen to permit the best subjective reconstruction of the analog signal. This paper presents a three-dimensional analysis of sampling structures suitable for sampling NTSC signals at twice the color subcarrier frequency, and describes a method for designing the reconstruction filters. Three sampling schemes were simulated on a number of sequences of NTSC video, and evaluated in a subjective test. The field quincunx (QT) sampling structure was found to give best results. There was no detectable subjective difference between the original and reconstructed sequences in most cases. Minor degradations were detected for some critical images, upon close inspection.

Effects of nonideal filtering in the digital demodulation of the composite NTSC signal into luminance and chrominance components on the coding of the luminance component are discussed. The residual chrominance component is shown to cause degradation in prediction and/or motion detection algorithms which are based on line or frame difference signals. Simple techniques for reducing these effects using chrominance-band rejection filters are presented and the efficacy of these methods are verified by simulation.