Dense Motion Field Estimation Research Articles

EasyFlow: increasing the convergence basin of variational image matching with a feature‐based cost

Dense motion field estimation is a key computer vision problem. Many solutions have been proposed to compute small or large displacements, narrow or wide baseline stereo disparity, or non‐rigid surface registration, but a unified methodology is still lacking. The authors introduce a general framework that robustly combines direct and feature‐based matching. The feature‐based cost is built around a novel robust distance function that handles keypoints and weak features such as segments. It allows us to use putative feature matches to guide dense motion estimation out of local minima. The authors’ framework uses a robust direct data term. It is implemented with a powerful second‐order regularisation with external and self‐occlusion reasoning. Their framework achieves state‐of‐the‐art performance in several cases (standard optical flow benchmarks, wide‐baseline stereo and non‐rigid surface registration). Their framework has a modular design that customises to specific application needs.

Pixel-wise video stabilization

In this paper, we present a novel video stabilization method with a pixel-wise motion model. In order to avoid distortion introduced by traditional feature points based motion models, we focus on constructing a more accurate model to capture the motion in videos. By taking advantage of dense optical flow, we can obtain the dense motion field between adjacent frames and set up a pixel-wise motion model which is accurate enough. Our method first estimates dense motion field between adjacent frames. A PatchMatch based dense motion field estimation algorithm is proposed. This algorithm is specially designed for similar video frames rather than arbitrary images to reach higher speed and better performance. Then, a simple and fast smoothing algorithm is performed to make the jittered motion stabilized. After that, we warp input frames using a weighted average algorithm to construct the output frames. Some pixels in output frames may be still empty after the warping step, so in the last step, these empty pixels are filled using a patch based image completion algorithm. We test our method on many challenging videos and demonstrate the accuracy of our model and the effectiveness of our method.

Motion Estimation in the 3-D Gabor Domain

Motion estimation methods can be broadly classified as being spatiotemporal or frequency domain in nature. The Gabor representation is an analysis framework providing localized frequency information. When applied to image sequences, the 3-D Gabor representation displays spatiotemporal/spatiotemporal-frequency (st/stf) information, enabling the application of robust frequency domain methods with adjustable spatiotemporal resolution. In this work, the 3-D Gabor representation is applied to motion analysis. We demonstrate that piecewise uniform translational motion can be estimated by using a uniform translation motion model in the st/stf domain. The resulting motion estimation method exhibits both good spatiotemporal resolution and substantial noise resistance compared to existing spatiotemporal methods. To form the basis of this model, we derive the signature of the translational motion in the 3-D Gabor domain. Finally, to obtain higher spatiotemporal resolution for more complex motions, a dense motion field estimation method is developed to find a motion estimate for every pixel in the sequence.

Estimation du champ de déplacement dense sur une séquence échocardiographique

Dense motion field estimation on a echocardiographic sequence. The estimation of the dense motion field is a first stage treatment often encountered in echocardiographic sequence diagnosis systems. Due to the low time sampling rate and the significant noise of such images, the usual methods based on the first order approximation of the optical flow constraint are inefficient. In this paper we propose a new method capable of dealing with these two problems by using the discrete form of this constraint. However, with this approach we are confronted with a non-convex minimization problem, dealt with by means of a continuation process. Finally, we present the results obtained on different echocardiographic sequences.

Object-based estimation of dense motion fields

Motion estimation belongs to key techniques in image sequence processing. Segmentation of the motion fields such that, ideally, each independently moving object uniquely corresponds to one region, is one of the essential elements in object-based image processing. This paper is concerned with unsupervised simultaneous estimation of dense motion fields and their segmentations. It is based on a stochastic model relating image intensities to motion information. Based on the analysis of natural images, a region-based model of motion-compensated prediction error is proposed. In each region the error is modeled by a white stationary generalized Gaussian random process. The motion field and its segmentation are themselves modeled by a compound Gibbs/Markov random field accounting for statistical bindings in spatial direction and along the direction of motion trajectories. The a posteriori distribution of the motion field for a given image sequence is formulated as an objective function, such that its maximization results in the MAP estimate. A deterministic multiscale relaxation technique with regular structure is employed for optimization of the objective function. Simulation results are in a good agreement with human perception for both the motion fields and their segmentations.