Nested sparse quantization for efficient feature coding

  • Authors:
  • Xavier Boix;Gemma Roig;Christian Leistner;Luc Van Gool

  • Affiliations:
  • Computer Vision Lab, ETH Zurich, Switzerland;Computer Vision Lab, ETH Zurich, Switzerland;Computer Vision Lab, ETH Zurich, Switzerland;Computer Vision Lab, ETH Zurich, Switzerland,KU Leuven, Belgium

  • Venue:
  • ECCV'12 Proceedings of the 12th European conference on Computer Vision - Volume Part II
  • Year:
  • 2012

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Abstract

Many state-of-the-art methods in object recognition extract features from an image and encode them, followed by a pooling step and classification. Within this processing pipeline, often the encoding step is the bottleneck, for both computational efficiency and performance. We present a novel assignment-based encoding formulation. It allows for the fusion of assignment-based encoding and sparse coding into one formulation. We also use this to design a new, very efficient, encoding. At the heart of our formulation lies a quantization into a set of k-sparse vectors, which we denote as sparse quantization. We design the new encoding as two nested, sparse quantizations. Its efficiency stems from leveraging bit-wise representations. In a series of experiments on standard recognition benchmarks, namely Caltech 101, PASCAL VOC 07 and ImageNet, we demonstrate that our method achieves results that are competitive with the state-of-the-art, and requires orders of magnitude less time and memory. Our method is able to encode one million images using 4 CPUs in a single day, while maintaining a good performance.