Late Fusion and Calibration for Multimedia Event Detection Using Few Examples (Author's Manuscript)
SRI International Menlo Park United States
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The state-of-the-art in example-based multimedia event detection MED rests on heterogeneous classifiers whose scores are typically combined in a late-fusion scheme. Recent studies on this topic have failed to reach a clear consensus as to whether machine learning techniques can outperform rule-based fusion schemes with varying amount of training data. In this paper, we present two parametric approaches to late fusion a normalization scheme for arithmetic mean fusion logistic averaging and a fusion scheme based on logistic regression, and compare them to widely used rule-based fusion schemes. We also describe how logistic regression can be used to calibrate the fused detection scores to predict an optimal threshold given a detection prior and costs on errors. We discuss the advantages and shortcomings of each approach when the amount of positives available for training varies from 10 positives 10Ex to 100 positives 100Ex. Experiments were run using video data from the NIST TRECVID MED 2013 evaluation and results were reported in terms of a ranking metric the mean average precision mAP and R0, a cost-based metric introduced in TRECVID MED 2013.
- Statistics and Probability