In computer vision efficient multi-class classification is becoming a key problem as the field de... more In computer vision efficient multi-class classification is becoming a key problem as the field develops and the number of object classes to be identified increases. Often objects might have some sort of structure such as a taxonomy in which the mis-classification score for object classes close by, using tree distance within the taxonomy, should be less than for those far apart. This is an example of multi-class classification in which the loss function has a special structure. Another example in vision is for the ubiquitous pictorial structure or parts based model. In this case we would like the mis-classification score to be proportional to the number of parts misclassified. It transpires both of these are examples of structured output ranking problems. However, so far no efficient large scale algorithm for this problem has been demonstrated. In this work we propose an algorithm for structured output ranking that can be trained in a time linear in the number of samples under a mild assumption common to many computer vision problems: that the loss function can be discretized into a small number of values. We show the feasibility of structured ranking on these two core computer vision problems and demonstrate a consistent and substantial improvement over competing techniques. Aside from this, we also achieve state-of-the art results for the PASCAL VOC human layout problem.
Knowledge-based question answering relies on the availability of facts, the majority of which can... more Knowledge-based question answering relies on the availability of facts, the majority of which cannot be found in structured sources (e.g. Wikipedia info-boxes, Wikidata). One of the major components of extracting facts from unstructured text is Relation Extraction (RE). In this paper we propose a novel method for creating distant (weak) supervision labels for training a large-scale RE system. We also provide new evidence about the effectiveness of neural network approaches by decoupling the model architecture from the feature design of a state-of-the-art neural network system. Surprisingly, a much simpler classifier trained on similar features performs on par with the highly complex neural network system (at 75x reduction to the training time), suggesting that the features are a bigger contributor to the final performance.
Procedings of the British Machine Vision Conference 2011, 2011
We describe a two-stage method for detecting hands and their orientation in unconstrained images.... more We describe a two-stage method for detecting hands and their orientation in unconstrained images. The first stage uses three complementary detectors to propose hand bounding boxes. Each bounding box is then scored by the three detectors independently, and a second stage classifier learnt to compute a final confidence score for the proposals using these features. We make the following contributions: (i) we add context-based and skin-based proposals to a sliding window shape based detector to increase recall; (ii) we develop a new method of non-maximum suppression based on super-pixels; and (iii) we introduce a fully annotated hand dataset for training and testing. We show that the hand detector exceeds the state of the art on two public datasets, including the PASCAL VOC 2010 human layout challenge.
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Papers by Arpit Mittal