3,664 research outputs found
Focus Is All You Need: Loss Functions For Event-based Vision
Event cameras are novel vision sensors that output pixel-level brightness
changes ("events") instead of traditional video frames. These asynchronous
sensors offer several advantages over traditional cameras, such as, high
temporal resolution, very high dynamic range, and no motion blur. To unlock the
potential of such sensors, motion compensation methods have been recently
proposed. We present a collection and taxonomy of twenty two objective
functions to analyze event alignment in motion compensation approaches (Fig.
1). We call them Focus Loss Functions since they have strong connections with
functions used in traditional shape-from-focus applications. The proposed loss
functions allow bringing mature computer vision tools to the realm of event
cameras. We compare the accuracy and runtime performance of all loss functions
on a publicly available dataset, and conclude that the variance, the gradient
and the Laplacian magnitudes are among the best loss functions. The
applicability of the loss functions is shown on multiple tasks: rotational
motion, depth and optical flow estimation. The proposed focus loss functions
allow to unlock the outstanding properties of event cameras.Comment: 29 pages, 19 figures, 4 table
A lower bound for topological entropy of generic non Anosov symplectic diffeomorphisms
We prove that a generic symplectic diffeomorphism is either Anosov or
the topological entropy is bounded from below by the supremum over the smallest
positive Lyapunov exponent of the periodic points. We also prove that
generic symplectic diffeomorphisms outside the Anosov ones do not admit
symbolic extension and finally we give examples of volume preserving
diffeomorphisms which are not point of upper semicontinuity of entropy function
in topology
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