Trajectory saliency detection using consistency-oriented latent codes from a recurrent auto-encoder

TL;DR

This paper introduces a novel unsupervised method for detecting dynamic salient trajectories in videos by learning compact latent codes with a recurrent auto-encoder that captures normal motion patterns and identifies deviations.

Contribution

It proposes a new trajectory saliency detection approach using consistency-oriented latent codes from a recurrent auto-encoder, outperforming existing methods on real datasets.

Findings

Outperforms existing trajectory saliency detection methods

Effective in real-world pedestrian trajectory scenarios

Utilizes a nearly unsupervised learning framework

Abstract

In this paper, we are concerned with the detection of progressive dynamic saliency from video sequences. More precisely, we are interested in saliency related to motion and likely to appear progressively over time. It can be relevant to trigger alarms, to dedicate additional processing or to detect specific events. Trajectories represent the best way to support progressive dynamic saliency detection. Accordingly, we will talk about trajectory saliency. A trajectory will be qualified as salient if it deviates from normal trajectories that share a common motion pattern related to a given context. First, we need a compact while discriminative representation of trajectories. We adopt a (nearly) unsupervised learning-based approach. The latent code estimated by a recurrent auto-encoder provides the desired representation. In addition, we enforce consistency for normal (similar) trajectories through the auto-encoder loss function. The distance of the trajectory code to a prototype code accounting for normality is the means to detect salient trajectories. We validate our trajectory saliency detection method on synthetic and real trajectory datasets, and highlight the contributions of its different components. We show that our method outperforms existing methods on several scenarios drawn from the publicly available dataset of pedestrian trajectories acquired in a railway station (Alahi 2014).