no code implementations • 23 Apr 2024 • Alaa Elobaid, Nathan Ramoly, Lara Younes, Symeon Papadopoulos, Eirini Ntoutsi, Ioannis Kompatsiaris
Biometric Verification (BV) systems often exhibit accuracy disparities across different demographic groups, leading to biases in BV applications.
no code implementations • 18 Mar 2024 • Dimitrios Karageorgiou, Giorgos Kordopatis-Zilos, Symeon Papadopoulos
In this work, we introduce OMG-Fuser, a fusion transformer-based network designed to extract information from various forensic signals to enable robust image forgery detection and localization.
no code implementations • 29 Feb 2024 • Christos Koutlis, Symeon Papadopoulos
The recently developed and publicly available synthetic image generation methods and services make it possible to create extremely realistic imagery on demand, raising great risks for the integrity and safety of online information.
1 code implementation • 17 Nov 2023 • Pietro Melzi, Ruben Tolosana, Ruben Vera-Rodriguez, Minchul Kim, Christian Rathgeb, Xiaoming Liu, Ivan DeAndres-Tame, Aythami Morales, Julian Fierrez, Javier Ortega-Garcia, Weisong Zhao, Xiangyu Zhu, Zheyu Yan, Xiao-Yu Zhang, Jinlin Wu, Zhen Lei, Suvidha Tripathi, Mahak Kothari, Md Haider Zama, Debayan Deb, Bernardo Biesseck, Pedro Vidal, Roger Granada, Guilherme Fickel, Gustavo Führ, David Menotti, Alexander Unnervik, Anjith George, Christophe Ecabert, Hatef Otroshi Shahreza, Parsa Rahimi, Sébastien Marcel, Ioannis Sarridis, Christos Koutlis, Georgia Baltsou, Symeon Papadopoulos, Christos Diou, Nicolò Di Domenico, Guido Borghi, Lorenzo Pellegrini, Enrique Mas-Candela, Ángela Sánchez-Pérez, Andrea Atzori, Fadi Boutros, Naser Damer, Gianni Fenu, Mirko Marras
Despite the widespread adoption of face recognition technology around the world, and its remarkable performance on current benchmarks, there are still several challenges that must be covered in more detail.
1 code implementation • 16 Nov 2023 • Stefanos-Iordanis Papadopoulos, Christos Koutlis, Symeon Papadopoulos, Panagiotis C. Petrantonakis
Online misinformation is often multimodal in nature, i. e., it is caused by misleading associations between texts and accompanying images.
1 code implementation • 20 Oct 2023 • Arjun Roy, Christos Koutlis, Symeon Papadopoulos, Eirini Ntoutsi
The generalization capacity of Multi-Task Learning (MTL) becomes limited when unrelated tasks negatively impact each other by updating shared parameters with conflicting gradients, resulting in negative transfer and a reduction in MTL accuracy compared to single-task learning (STL).
no code implementations • 19 Jul 2023 • Ioannis Sarridis, Jochen Spangenberg, Olga Papadopoulou, Symeon Papadopoulos
This paper presents a user study, involving 107 participants, predominantly journalists and human rights investigators, that explores the capability of Artificial Intelligence (AI)-based image filters to potentially mitigate the emotional impact of viewing such disturbing content.
no code implementations • 19 Jul 2023 • Ioannis Sarridis, Christos Koutlis, Symeon Papadopoulos, Christos Diou
This paper presents an in-depth analysis, with a particular emphasis on the intersectionality of these demographic factors.
1 code implementation • 15 Jun 2023 • Ed Pizzi, Giorgos Kordopatis-Zilos, Hiral Patel, Gheorghe Postelnicu, Sugosh Nagavara Ravindra, Akshay Gupta, Symeon Papadopoulos, Giorgos Tolias, Matthijs Douze
The problem comprises two distinct but related tasks: determining whether a query video shares content with a reference video ("detection"), and additionally temporally localizing the shared content within each video ("localization").
2 code implementations • 27 Apr 2023 • Stefanos-Iordanis Papadopoulos, Christos Koutlis, Symeon Papadopoulos, Panagiotis C. Petrantonakis
Multimedia content has become ubiquitous on social media platforms, leading to the rise of multimodal misinformation (MM) and the urgent need for effective strategies to detect and prevent its spread.
1 code implementation • 27 Apr 2023 • Ioannis Sarridis, Christos Koutlis, Symeon Papadopoulos, Christos Diou
To overcome these limitations, this work introduces FLAC, a methodology that minimizes mutual information between the features extracted by the model and a protected attribute, without the use of attribute labels.
Ranked #1 on HairColor/Bias-conflicting on CelebA
1 code implementation • 24 Apr 2023 • Pantelis Dogoulis, Giorgos Kordopatis-Zilos, Ioannis Kompatsiaris, Symeon Papadopoulos
New advancements for the detection of synthetic images are critical for fighting disinformation, as the capabilities of generative AI models continuously evolve and can lead to hyper-realistic synthetic imagery at unprecedented scale and speed.
no code implementations • 14 Apr 2023 • Nikolaos Giatsoglou, Symeon Papadopoulos, Ioannis Kompatsiaris
The recent wave of AI research has enabled a new brand of synthetic media, called deepfakes.
1 code implementation • 6 Apr 2023 • Christos Koutlis, Manos Schinas, Symeon Papadopoulos
Hate speech is a societal problem that has significantly grown through the Internet.
1 code implementation • 6 Apr 2023 • Giorgos Kordopatis-Zilos, Giorgos Tolias, Christos Tzelepis, Ioannis Kompatsiaris, Ioannis Patras, Symeon Papadopoulos
We introduce S$^2$VS, a video similarity learning approach with self-supervision.
Ranked #1 on Video Retrieval on FIVR-200K
no code implementations • 14 Mar 2023 • Emmanouil Krasanakis, Symeon Papadopoulos
Graph filters that transform prior node values to posterior scores via edge propagation often support graph mining tasks affecting humans, such as recommendation and ranking.
1 code implementation • 2 Mar 2023 • Stefanos-Iordanis Papadopoulos, Christos Koutlis, Symeon Papadopoulos, Panagiotis C. Petrantonakis
To address this, we perform a comparative study on existing and new Synthetic Misinformers that involves (1) out-of-context (OOC) image-caption pairs, (2) cross-modal named entity inconsistency (NEI) as well as (3) hybrid approaches and we evaluate them against real-world misinformation; using the COSMOS benchmark.
no code implementations • 14 Dec 2022 • Stefanos-Iordanis Papadopoulos, Christos Koutlis, Anastasios Papazoglou-Chalikias, Symeon Papadopoulos, Spiros Nikolopoulos
To this end, we develop a computer vision pipeline fine tuned on fashion imagery in order to extract relevant visual features along with the category and attributes of the garment.
no code implementations • 2 Dec 2022 • Maria Siopi, Giorgos Kordopatis-Zilos, Polychronis Charitidis, Ioannis Kompatsiaris, Symeon Papadopoulos
In this paper, we address the problem of image splicing localization with a multi-stream network architecture that processes the raw RGB image in parallel with other handcrafted forensic signals.
no code implementations • 1 Dec 2022 • Ioannis Sarridis, Christos Koutlis, Olga Papadopoulou, Symeon Papadopoulos
The sheer volume of online user-generated content has rendered content moderation technologies essential in order to protect digital platform audiences from content that may cause anxiety, worry, or concern.
1 code implementation • 20 Nov 2022 • Davide Alessandro Coccomini, Giorgos Kordopatis Zilos, Giuseppe Amato, Roberto Caldelli, Fabrizio Falchi, Symeon Papadopoulos, Claudio Gennaro
In this paper, we introduce MINTIME, a video deepfake detection approach that captures spatial and temporal anomalies and handles instances of multiple people in the same video and variations in face sizes.
Ranked #1 on Classification on ForgeryNet
1 code implementation • 17 Sep 2022 • Vasileios Iosifidis, Symeon Papadopoulos, Bodo Rosenhahn, Eirini Ntoutsi
Class imbalance poses a major challenge for machine learning as most supervised learning models might exhibit bias towards the majority class and under-perform in the minority class.
1 code implementation • 27 Jul 2022 • Stefanos-Iordanis Papadopoulos, Christos Koutlis, Symeon Papadopoulos, Ioannis Kompatsiaris
For fashion outfits to be considered aesthetically pleasing, the garments that constitute them need to be compatible in terms of visual aspects, such as style, category and color.
1 code implementation • 26 May 2022 • Christos Koutlis, Manos Schinas, Symeon Papadopoulos
To this end, we propose a methodology, called Visual Part Utilization, that utilizes the visual part of image memes as instances of the regular image class and the initial image memes as instances of the image meme class to force the model to concentrate on the critical parts that characterize an image meme.
1 code implementation • 20 May 2022 • Ioannis Sarridis, Christos Koutlis, Giorgos Kordopatis-Zilos, Ioannis Kompatsiaris, Symeon Papadopoulos
In this paper we introduce InDistill, a model compression approach that combines knowledge distillation and channel pruning in a unified framework for the transfer of the critical information flow paths from a heavyweight teacher to a lightweight student.
no code implementations • 27 Apr 2022 • Spyridon Baxevanakis, Giorgos Kordopatis-Zilos, Panagiotis Galopoulos, Lazaros Apostolidis, Killian Levacher, Ipek B. Schlicht, Denis Teyssou, Ioannis Kompatsiaris, Symeon Papadopoulos
Enabled by recent improvements in generation methodologies, DeepFakes have become mainstream due to their increasingly better visual quality, the increase in easy-to-use generation tools and the rapid dissemination through social media.
no code implementations • 8 Apr 2022 • Stefanos I. Papadopoulos, Christos Koutlis, Symeon Papadopoulos, Ioannis Kompatsiaris
We employ the product's target attributes time series as a proxy of temporal popularity patterns, mitigating the lack of historical data, while exogenous time series help capture trends among interrelated attributes.
Ranked #1 on Popularity Forecasting on SHIFT15M
1 code implementation • 29 Nov 2021 • Emmanouil Krasanakis, Symeon Papadopoulos, Ioannis Kompatsiaris
In this work, we aim to classify nodes of unstructured peer-to-peer networks with communication uncertainty, such as users of decentralized social networks.
no code implementations • 23 Nov 2021 • Apostolos Panagiotopoulos, Giorgos Kordopatis-Zilos, Symeon Papadopoulos
In this paper, we define the task of image localizability, i. e. suitability of an image for geolocation, and propose a selective prediction methodology to address the task.
1 code implementation • 18 Oct 2021 • Emmanouil Krasanakis, Symeon Papadopoulos, Ioannis Kompatsiaris, Andreas Symeonidis
We introduce pygrank, an open source Python package to define, run and evaluate node ranking algorithms.
no code implementations • 16 Jul 2021 • Simone Fabbrizzi, Symeon Papadopoulos, Eirini Ntoutsi, Ioannis Kompatsiaris
Hence, this work aims to: i) describe the biases that might manifest in visual datasets; ii) review the literature on methods for bias discovery and quantification in visual datasets; iii) discuss existing attempts to collect bias-aware visual datasets.
1 code implementation • 24 Jun 2021 • Giorgos Kordopatis-Zilos, Christos Tzelepis, Symeon Papadopoulos, Ioannis Kompatsiaris, Ioannis Patras
In this work, we propose a Knowledge Distillation framework, called Distill-and-Select (DnS), that starting from a well-performing fine-grained Teacher Network learns: a) Student Networks at different retrieval performance and computational efficiency trade-offs and b) a Selector Network that at test time rapidly directs samples to the appropriate student to maintain both high retrieval performance and high computational efficiency.
Ranked #2 on Video Retrieval on FIVR-200K
no code implementations • 17 May 2021 • Giorgos Kordopatis-Zilos, Panagiotis Galopoulos, Symeon Papadopoulos, Ioannis Kompatsiaris
In this paper, we address the problem of global-scale image geolocation, proposing a mixed classification-retrieval scheme.
no code implementations • 12 May 2021 • Polychronis Charitidis, Giorgos Kordopatis-Zilos, Symeon Papadopoulos, Ioannis Kompatsiaris
In this work, we present a deep learning-based approach for image tampering localization fusion.
1 code implementation • 17 Oct 2020 • Pavlos Avgoustinakis, Giorgos Kordopatis-Zilos, Symeon Papadopoulos, Andreas L. Symeonidis, Ioannis Kompatsiaris
For the robust similarity calculation between two videos, we first extract representative audio-based video descriptors by leveraging transfer learning based on a Convolutional Neural Network (CNN) trained on a large scale dataset of audio events, and then we calculate the similarity matrix derived from the pairwise similarity of these descriptors.
no code implementations • 2 Sep 2020 • Christos Koutlis, Symeon Papadopoulos, Manos Schinas, Ioannis Kompatsiaris
Multivariate time series forecasting is of great importance to many scientific disciplines and industrial sectors.
no code implementations • 12 Jun 2020 • Polychronis Charitidis, Giorgos Kordopatis-Zilos, Symeon Papadopoulos, Ioannis Kompatsiaris
In this paper, we propose a pre-processing step to improve the training data quality and examine its effect on the performance of DeepFake detection.
1 code implementation • ICCV 2019 • Giorgos Kordopatis-Zilos, Symeon Papadopoulos, Ioannis Patras, Ioannis Kompatsiaris
Subsequently, the similarity matrix between all video frames is fed to a four-layer CNN, and then summarized using Chamfer Similarity (CS) into a video-to-video similarity score -- this avoids feature aggregation before the similarity calculation between videos and captures the temporal similarity patterns between matching frame sequences.
Ranked #5 on Video Retrieval on FIVR-200K
no code implementations • SEMEVAL 2019 • Olga Papadopoulou, Giorgos Kordopatis-Zilos, Markos Zampoglou, Symeon Papadopoulos, Yiannis Kompatsiaris
In the effort to tackle the challenge of Hyperpartisan News Detection, i. e., the task of deciding whether a news article is biased towards one party, faction, cause, or person, we experimented with two systems: i) a standard supervised learning approach using superficial text and bag-of-words features from the article title and body, and ii) a deep learning system comprising a four-layer convolutional neural network and max-pooling layers after the embedding layer, feeding the consolidated features to a bi-directional recurrent neural network.
1 code implementation • 11 Sep 2018 • Giorgos Kordopatis-Zilos, Symeon Papadopoulos, Ioannis Patras, Ioannis Kompatsiaris
To create the dataset, we devise a process for the collection of YouTube videos based on major news events from recent years crawled from Wikipedia and deploy a retrieval pipeline for the automatic selection of query videos based on their estimated suitability as benchmarks.
no code implementations • IJCNLP 2017 • Bo Wang, Maria Liakata, Adam Tsakalidis, Spiros Georgakopoulos Kolaitis, Symeon Papadopoulos, Lazaros Apostolidis, Arkaitz Zubiaga, Rob Procter, Yiannis Kompatsiaris
We present a system for time sensitive, topic based summarisation of the sentiment around target entities and topics in collections of tweets.
1 code implementation • 23 Oct 2017 • Olga Papadopoulou, Markos Zampoglou, Symeon Papadopoulos, Ioannis Kompatsiaris
The detector is based almost exclusively on text-based features taken from previous work on clickbait detection, our own work on fake post detection, and features we designed specifically for the challenge.
no code implementations • 3 Aug 2016 • Sándor Darányi, Peter Wittek, Konstantinos Konstantinidis, Symeon Papadopoulos, Efstratios Kontopoulos
By using term distances as a measure of semantic relatedness vs. their PageRank values indicating social importance and applied as variable `term mass', gravitation as a metaphor to express changes in the semantic content of a vector field lends a new perspective for experimentation.
1 code implementation • 5 Feb 2009 • Symeon Papadopoulos, Andre Skusa, Athena Vakali, Yiannis Kompatsiaris, Nadine Wagner
There are numerous techniques adopting a global perspective to the community detection problem, i. e. they operate on the complete network structure, thus being computationally expensive and hard to apply in a streaming manner.
Data Analysis, Statistics and Probability Physics and Society