Optical Flow and Trajectory Methods in Context

In this chapter we study the related fields of multi-frame optical flow and trajectories. Since the beginning of modern optical flow estimation methods, multiple frames have been used in an effort to improve the motion computation. We look at why most of these efforts have failed. More recently, researchers have stitched together sequences of optical flow fields to create trajectories. These trajectories are temporally coherent, a necessary property for virtually every real-world application of optical flow. New methods compute these trajectories directly using variational methods and low-rank constraints. We also identify the need for appropriate data sets and evaluation methods for this nascent field.