2,784 research outputs found
Identifying First-person Camera Wearers in Third-person Videos
We consider scenarios in which we wish to perform joint scene understanding,
object tracking, activity recognition, and other tasks in environments in which
multiple people are wearing body-worn cameras while a third-person static
camera also captures the scene. To do this, we need to establish person-level
correspondences across first- and third-person videos, which is challenging
because the camera wearer is not visible from his/her own egocentric video,
preventing the use of direct feature matching. In this paper, we propose a new
semi-Siamese Convolutional Neural Network architecture to address this novel
challenge. We formulate the problem as learning a joint embedding space for
first- and third-person videos that considers both spatial- and motion-domain
cues. A new triplet loss function is designed to minimize the distance between
correct first- and third-person matches while maximizing the distance between
incorrect ones. This end-to-end approach performs significantly better than
several baselines, in part by learning the first- and third-person features
optimized for matching jointly with the distance measure itself
Angular Scale Expansion Theory And The Misperception Of Egocentric Distance In Locomotor Space
Perception is crucial for the control of action, but perception need not be scaled accurately to produce accurate actions. This paper reviews evidence for an elegant new theory of locomotor space perception that is based on the dense coding of angular declination so that action control may be guided by richer feedback. The theory accounts for why so much direct-estimation data suggests that egocentric distance is underestimated despite the fact that action measures have been interpreted as indicating accurate perception. Actions are calibrated to the perceived scale of space and thus action measures are typically unable to distinguish systematic (e.g., linearly scaled) misperception from accurate perception. Whereas subjective reports of the scaling of linear extent are difficult to evaluate in absolute terms, study of the scaling of perceived angles (which exist in a known scale, delimited by vertical and horizontal) provides new evidence regarding the perceptual scaling of locomotor space
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