Arrow Research search

Author name cluster

Ravi Kothari

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

3 papers
1 author row

Possible papers

3

TIST Journal 2020 Journal Article

CNN-based Multiple Manipulation Detector Using Frequency Domain Features of Image Residuals

  • Divya Singhal
  • Abhinav Gupta
  • Anurag Tripathi
  • Ravi Kothari

Increasingly sophisticated image editing tools make it easy to modify images. Often these modifications are elaborate, convincing, and undetectable by even careful human inspection. These considerations have prompted the development of forensic algorithms and approaches to detect modifications done to an image. However, these detectors are model-driven (i.e., manipulation-specific) and the choice of a potent detector requires knowledge of the type of manipulation, something that cannot be known ( a priori ). Thus, the latest effort is directed towards developing model-free (i.e., generalized) detectors capable of detecting multiple manipulation types. In this article, we propose a novel detector capable of exposing seven different manipulation types in low-resolution compressed images. Our proposed approach is based on a two-layer convolutional neural network (CNN) to extract frequency domain features of image median filtered residual that are classified using two different classifiers—softmax and extremely randomized trees. Extensive experiments demonstrate the efficacy of proposed detector over existing state-of-the-art detectors.

IJCAI Conference 2015 Conference Paper

Analysis of Sampling Algorithms for Twitter

  • Deepan Subrahmanian Palguna
  • Vikas Joshi
  • Venkatesan Chakaravarthy
  • Ravi Kothari
  • LV Subramaniam

The daily volume of Tweets in Twitter is around 500 million, and the impact of this data on applications ranging from public safety, opinion mining, news broadcast, etc. , is increasing day by day. Analyzing large volumes of Tweets for various applications would require techniques that scale well with the number of Tweets. In this work we come up with a theoretical formulation for sampling Twitter data. We introduce novel statistical metrics to quantify the statistical representativeness of the Tweet sample, and derive sufficient conditions on the number of samples needed for obtaining highly representative Tweet samples. These new statistical metrics quantify the representativeness or goodness of the sample in terms of frequent keyword identification and in terms of restoring public sentiments associated with these keywords. We use uniform random sampling with replacement as our algorithm, and sampling could serve as a first step before using other sophisticated summarization methods to generate summaries for human use. We show that experiments conducted on real Twitter data agree with our bounds. In these experiments, we also compare different kinds of random sampling algorithms. Our bounds are attractive since they do not depend on the total number of Tweets in the universe. Although our ideas and techniques are specific to Twitter, they could find applications in other areas as well.