Translational Motion Model Research Articles

Investigation on convergence behaviors of the differential method for 2-D motion parameter estimation

We investigate convergence behaviors of the differential method for estimation of 2-D motion parameters. While the differential method has been widely researched for motion compensated predictive video coding, little attention has been paid to its convergence properties. Based on the nonseparable exponential covariance image model, we derive theoretical estimates of update terms for translational and affine motion models. The effects of noise, spatial correlation, choice of spatial gradient measures, and the size of a region, are quantitatively analyzed in relation to the convergence speed. Some empirical results are presented to verify the analysis.

On spatial adaptation of motion-field smoothness in video coding

Most motion-compensation methods dealt with in the literature make strong assumptions about the smoothness of the underlying motion field. For instance, block-matching algorithms assume a blockwise-constant motion field and are adequate for translational motion models; control-grid interpolation assumes a blockwise bilinear motion field and captures zooming and warping fairly well. Time-varying imagery, however often contains both types of motion (as well as others), and hence exhibits a high degree of spatial variability of its motion-field smoothness properties. We develop a simple method to spatially adapt the smoothness of the motion field. The proposed method demonstrates substantial improvements in video quality over a wide range of bit rates. To this end, we introduce the notion of a motion field that is characterized by a set of labels. The labels provide the flexibility to adaptively switch between two different motion models locally. The individual motion models have very different smoothness properties. The switched framework for motion compensation performs significantly better than each of its constituent motion models, in terms of both visual quality and signal-to-noise ratio (0.3-0.7 dB on the average). Finally, we develop an extension of this method that enhances the overlapped block motion compensation scheme by allowing spatial adaptation of the window function.

Electric fields associated with moving phase boundaries during martensitic transformation

Phase transformations in metals are considered in terms of non-equilibrium continuum thermodynamics. The evolution of a heterophase system in thermal and electric fields is described by a self-consistent set of differential equations. Special attention is paid to the thermoelectric properties of phase boundaries. A one-dimensional model for uniform translational motion of a plane interface is developed, the spatial distributions of temperature and electric charge, current and potential are calculated.

Constructing cylindrical panoramic image usingequidistant matching

An efficient algorithm for constructing cylindrical panoramic image mosaics from a near pure panning camera is proposed. The algorithm uses equidistant matching for image alignment, which uses a translational motion model. It also allows the effective focal length of the camera to be estimated efficiently by a bisection method.

DCT-based motion estimation

We propose novel discrete cosine transform (DCT) pseudophase techniques to estimate shift/delay between two one-dimensional(1-D) signals directly from their DCT coefficients by computing the pseudophase shift hidden in DCT and then employing the sinusoidal orthogonal principles, applicable to signal delay estimation remote sensing. Under the two-dimensional (2-D) translational motion model, we further extend the pseudophase techniques to the DCT-based motion estimation (DXT-ME) algorithm for 2-D signals/images. The DXT-ME algorithm has certain advantages over the commonly used full search block-matching approach (BKM-ME) for application to video coding despite certain limitations. In addition to its robustness in a noisy environment and low computational complexity, O(M(2)) for an MxM search range in comparison to the O(N(2) . M(2)) complexity of BKM-ME for an NxN block, its ability to estimate motion completely in DCT domain makes possible the fully DCT-based motion-compensated video coder structure, which has only one major component in the feedback loop instead of three as in the conventional hybrid video coder design, and thus results in a higher system throughput. Furthermore, combination of the DCT and motion estimation units can provide space for further optimization of the overall coder. In addition, the DXT-ME algorithm has solely highly parallel local operations and this property makes feasible parallel implementation suitable for very large scale integration (VLSI) design. Simulation on a number of video sequences is presented with comparison to BKM-ME and other fast block search algorithms for video coding applications even though DXT-ME is completely different from any block search algorithms.

Two-stage motion compensation using adaptive global MC and local affine MC

This paper describes a high-efficiency video coding method based on ITU-T H.263. To improve the coding efficiency of H.263, a two-stage motion compensation (MC) method is proposed, consisting of global MC (GMC) for predicting camera motion and local MC (LMC) for macroblock prediction. First, global motion such as panning, tilting, and zooming is estimated, and the global-motion-compensated image is produced for use as a reference in LMC. Next, LMC is performed both for the global-motion-compensated reference image and for the image without GMC. LMC employs an affine motion model in the context of H.263's overlapped block motion compensation. Using the overlapped block affine MC, rotation and scaling of small objects can be predicted, in addition to translational motion. In the proposed method, GMC is adaptively turned on/off for each macroblock since GMC cannot be used for prediction in all regions in a frame. In addition, either an affine or a translational motion model is adaptively selected in LMC for each macroblock. Simulation results show that the proposed video coding technique using the two-stage MC significantly outperforms H.263 under identical conditions, especially for sequences with fast camera motion. The performance improvements in peak-to-peak SNR (PSNR) are about 3 dB over the original H.263, which does not use the two-stage MC.

Image sequence coding using multiple-level segmentation and affine motion estimation

A very low bit-rate video codec using multiple-level segmentation and affine motion compensation is presented. The translational motion model is adequate to motion compensate small regions even when complex motion is involved; however, it is no longer capable of delivering satisfactory results when applied to large regions or the whole frame. The proposed codec is based on a variable block size algorithm enhanced with global motion compensation, inner block segmentation, and a set of motion models used adaptively in motion compensation. The experimental results show that the proposed method gives better results in terms of the bit rate under the same PSNR constraint for most of the tested sequences as compared with the fixed block size approach and traditional variable block size codec in which only translational motion compensation is utilized.

A Microscopic Model for Diffusion of a Polymer Chain in the Entangled Regime

In the entangled regime the reptation concept [1,2] is the most successful in describing the dynamical behavior of a single chain. Using scaling concepts some quantities such as translational diffussion coefficient for the polymer center of mass D_{tr}, and renewal time {\tau} [3] have been calculated in the reptation model. This model is used for representing the low-frequency motions of a polymer molecule in a fluid of entangled chains, neglecting rapid relaxation processes that are attributed to local conformal transitions of backbone. Helfand and collabrators have studied the kinetics of conformational transitions in chain molecules, and they find that single-bond rotations followed by the compensating rearrangement of neigboring units are predominantly responsible for local motions [4]. Such models have also been considered by Erman and co-workers [5]. The purpose of this study to understand reptation at a microscopic level. We consedir rapid relaxation processes, that are singlet- or double -bond rotations; motion along the contour of the chain is due to displacments caused by rearangements of the neighboring units. We recover the usual scaling behavior of the diffusion coefficients and relaxation times with the chain mass. Moreover, the effective activation energy that is found from the local jump model for translational motion of the chain center of mass compares favorably with experiment and is independent of the molecular weight for large enough chains [6]. We are also able to account for the apparent temperature of this "activation energy".

Closing the loop: detection and pursuit of a moving object by a moving observer

We present an integrated system which is able to pursue a moving object and maintain the object centered in the image by controlling a robot-head. The system contains three parts: independent motion detection, tracking, and control of a robot-head. This paper focuses on the detection mechanism, and briefly discusses the tracking and control issues. The system runs continuously in time and updates the object localization at a frame-rate of 25 Hz. The moving object can be tracked, although the observer performs an unknown independent motion, involving both translation and rotation. We focus on a simple motion detection algorithm, since computational cost is of major importance for real-time systems with feedback. The algorithm is noniterative and computationally inexpensive. The running time complexity is O ( n) for an image containing n pixels. The image-processing takes place on a MaxVideo 200 pipeline processor, and the head control algorithm is running on a Transputer T800 network. Some offline experimental results are presented, where comparisons are made between affine and translational image motion models.

Reptation of a polymer chain by conformal transitions in the entangled regime.

We study a model for reptation, where motion along the contour of the chain is due to displacements caused by singlet- or double-bond rotations (local jumps) followed by rearrangements of the neighboring units, rather than ``kink motion.'' We recover the usual scaling behavior of the diffusion coefficients and relaxation times with the chain mass. Moreover, the effective activation energy that is found from the local jump model for translational motion of the chain center of mass compares favorably with experiment and is independent of the molecular weight for large enough chains. (c) 1995 The American Physical Society

Departures from the soft collision model for Dicke narrowing: Raman measurements in the Q branch of D2

With high quality spectral data, we have observed departures from the soft collision model for translational motion, in the transition region from Doppler broadening to Dicke narrowing. The departures are in agreement with theoretical calculations based on the Boltzmann equation. The implications of the results concerning the dynamics of fluids are discussed. In addition we show that the mass diffusion constant describes the translational diffusion of the optical coherence and we give precise measurements of the broadening coefficients of the Q(0) to Q(6) lines.

Molecular dynamics and interactions in liquids, molecular crystals and molecular complexes: Mori three variable theory and computer simulation of translational motions in molecular fluids

The itinerant oscillator model for translational stochastic motion in molecular and atomic fluids is developed using a Mori continued fraction representation of the velocity autocorrelation function C v (t). The initial generalised Langevin equation is solved in terms of the velocity probability density function and the van Hove self correlation function G s( r ,t). These are then compared with their equivalents derived independently from molecular dynamics and experimental sources. In particular C v (t) is compared with velocity a.c.f's computed from an atom-atom intermolecular potential using molecular dynamics methods for four different interatomic separations. The non-Gaussian characteristics of the p.d.f.'s above are investigated using simulations of a.c.f.'s of moments of v such as the a.c.f. of kinetic energy. It is concluded that some form of rotation /translation coupling is needed in order that the initial equation may be made more realistic.

Paramagnetic relaxation reagents as a probe for translational motion of liquids

Use of the paramagnetic relaxation reagent tris- (acetylacetonato) chromium(III) [Cr(acac)3] proves capable of probing the solution structure of organic liquids. The theory describing the relaxation effects of this chelate is presented, wherein it is assumed that the nuclear spin–lattice relaxation mechanism is due to the modulation of the electron–nuclear dipole–dipole interaction. The electronic relaxation time Te1 (or τs) and the mutual translational motion of the paramagnetic species and the solvent molecules, in our case carbon tetrachloride, are considered the only causes of this modulation. Since for the paramagnetic molecules it is possible to calculate the electronic relaxation times, such systems are well defined for the description of translational diffusion. It is found that a jump diffusion model for translational motion explains the experimental data with jump distances comparable to the diameter of the solvent molecules.

ChemInform Abstract: CARBON‐13 NMR STUDY OF MOLECULAR REORIENTATION IN GLYCEROL

The 13C spin‐lattice relaxation time T1 has been measured as a function of temperature by the PRFT technique in a sample of carefully dried glycerol. Data were taken between 267 and 339°K and the results fitted to a theoretical description of relaxation involving unlike spins which are undergoing anisotropic reorientation. The best fit gave a ratio of rotational diffusion coefficients of 1:5:200 and an activation energy for molecular reorientation of 2.41±0.05 kcal/mole. The results indicate that it is not necessary to invoke a continuous distribution of correlation times in order to describe the relaxation behavior. A speculative model for rotational and translational motion, consistent with the results of previous studies, is presented.

Carbon-13 NMR study of molecular reorientation in glycerol

The 13C spin-lattice relaxation time T1 has been measured as a function of temperature by the PRFT technique in a sample of carefully dried glycerol. Data were taken between 267 and 339°K and the results fitted to a theoretical description of relaxation involving unlike spins which are undergoing anisotropic reorientation. The best fit gave a ratio of rotational diffusion coefficients of 1:5:200 and an activation energy for molecular reorientation of 2.41±0.05 kcal/mole. The results indicate that it is not necessary to invoke a continuous distribution of correlation times in order to describe the relaxation behavior. A speculative model for rotational and translational motion, consistent with the results of previous studies, is presented.

A comparative study of the motions of methane molecules and argon atoms in liquid and high-pressure gas states by neutron scattering

The microscopic motions in methane in the liquid state, T = 102 K, and in the high-pressure gas state at 1640 bar, T = 295 K, as well as in high-pressure argon at 1815 bar, T = 295 K, mixed with methane of partial pressure of 82 bar were investigated by scattering of slow neutrons of wavelengths 4.18 and 4.73 Å. The data were carefully corrected for instrumental effects and multiple scattering in sample and container walls. The corrected data were compared to a few simple models for the micro-dynamics: Langevin diffusion and argon-type motion for the centre-of-mass motion, Langevin diffusion and free rotation for the rotational motion. Translational and rotational motions were supposed to be uncoupled. The centre-of-mass motion described as the argon-type of motion was derived from existing experimental data on liquid argon by use of the law of corresponding states. It is found that the molecular motions in liquid methane are well described by the argon type of centre-of-mass motion combined with the Langevin type of rotational diffusion. In contrast, the Langevin-diffusion model for both translational and rotational motion fits the data reasonably well in high-pressure methane as well as in high-pressure argon. It is, however, fair to state that a model for rotational motion inbetween free rotation and Langevin rotational diffusion would give the best fit to the gas data. It is thus demonstrated that a clear distinction exists between the dynamics of the liquid and the high-pressure gas forms of argon and methane. The experiments on high-pressure argon and methane are the first ones to reveal a case in which Langevin diffusion describes the translational motions in a dense fluid to a very good approximation. A comparison of the values of the diffusion constants obtained from these neutron studies to values calculated by use of Enskog's theory as well as other data is carried through. The various values of the diffusion constants agree reasonably well. The gap between microscopic and macroscopic measurements of the diffusion constant is thereby overbridged.