We showcase that different image manipulation filters excel at unveiling different types of manipulations and provide complementary forensic traces. To take advantage of this, we propose two ways for merging the outputs of such filters to perform more accurate image manipulation localization and detection.
- Related publications [mmm24a]
- Software package [download source code]

We combine a camera motion detection method, two saliecy detection methods for generating frame-level saliency maps, a salient event detection approach for extracting traditional 2D+time video volumes from the 360-degrees video, and an adapted state-of-the-art video summarization method, to transform 360-degrees videos to video summaries that are suitable for traditional video distribution channels.
- Related publications [mmm24b]
- Software package [download source code]

We investigate the application of filter pruning on two already small and compact face detectors, EXTD (Extremely Tiny Face Detector) and EResFD (Efficient ResNet Face Detector). The main pruning algorithm that we utilize is Filter Pruning via Geometric Median (FPGM). We show that we can further reduce the model size of already lightweight face detectors, with limited accuracy loss, or even with a small accuracy gain for low pruning rates.
- Related publications [wacvw24]
- Software package [download source code]

We introduce Masked Feature Modelling (MFM) for the unsupervised pretraining of a Graph Attention Network (GAT) block. MFM utilizes a pretrained Visual Tokenizer to reconstruct masked features of objects within a video, leveraging the MiniKinetics dataset. We then incorporate the pre-trained GAT block into a state-of-the-art bottom-up supervised video-event recognition architecture, ViGAT, to improve the model's accuracy in a smaller target dataset.
- Related publications [ism23]
- Software package [download source code]

RL-DiVTS is a new reinforcement-based method for video thumbnail selection, that relies on estimates of the frames' aesthetic quality, representativeness and visual diversity, made with the help of tailored reward functions. It integrates a novel diversity-aware Frame Picking mechanism that performs a sequential frame selection and applies a reweighting process to demote frames that are visually-similar to the already selected ones.
- Related publications [icip23]
- Software package [download source code]

TAME is a method for post-hoc explanation of DCNN-based image classifiers. TAME learns to generate explanation maps by introducing a multi-branch hierarchical attention mechanism. This mechanism is trained end-to-end along with the original (frozen) DCNN, to derive class activation maps (CAMs) using the feature maps (FMs) coming from multiple layers of the original DCNN. After training, explanation maps can be computed in a single forward pass.
- Related publications [ism2022a] (see also [eccvw22] for a related earlier method)
- Software package [download source code]

Gated-ViGAT combines bottom-up (object) information, a new frame sampling policy and a gating mechanism for video event recognition. The frame sampling policy uses weighted in-degrees (WiDs), derived from the adjacency matrices of graph attention networks (GATs), and a dissimilarity measure to select the most salient and diverse frames. The gating mechanism fetches the selected frames and commits early exiting when an adequately confident decision is achieved.
- Related publications [ism2022b] (see also [access22] for a related earlier method)
- Software package [download source code]

The problem we address is the creation of an explanation mask, which indicates the parts of the video that influenced the most the estimates of a video summarization network about the frames' importance. We examine various attention-based signals and we evaluate their performance in combination with different replacement functions, and utilizing measures that quantify the capability of explanations to spot the most and least influential parts of a video.
- Related publications [ism2022c] [acmmm23] (see also [icmr22] for the CA-SUM summarizer that we used as the basis)
- Software package [download source code]

We provide code and associated materials for two learning-based eXplainable AI (XAI) methods, L-CAM-Fm and L-CAM-Img, for DCNN image classifiers. Our methods receive as input an image and a class label and produce as output the image regions that the DCNN has focused on in order to infer this class. Both methods use an attention mechanism (AM), trained end-to-end along with the original (frozen) DCNN, to derive class activation maps (CAMs) from the last convolutional layer's feature maps (FMs).
- Related publications [eccvw22]
- Software package [download source code]

This software can be used for training our deep learning architecture called ViGAT, which utilizes an object detector together with a Vision Transformer (ViT) backbone network to derive object and frame features, and a head network to process these features for the task of event recognition and explanation in video. Our ViGAT method makes unique contributions in the areas of bottom-up event recognition and explainable AI for video understanding.
- Related publications [access22]
- Software package [download source code]

We provide the implementation of our T-times-V method for free-text-based video retrieval. Our method learns how to combine multiple diverse textual and visual features towards generating multiple joint feature spaces, which encode text-video pairs into comparable representations. It also introduces an additional softmax operation at the retrieval stage, for revising the query-video similarities inferred by the trained network.
- Related publications [eccvw22]
- Software package [download source code]

This software can be used for training a deep learning architecture, which estimates frames' importance by integrating a concentrated attention mechanism and utilizing information about the frames' uniqueness and diversity. Training is performed in an unsupervised manner. After being on a collection of videos, the CA-SUM model is capable of producing summaries for unseen videos, according to a user-specified time-budget about the summary duration.
- Related publications [icmr22]
- Software package [download source code]

This software can be used for training a deep learning architecture which estimates the frames' importance after modeling their dependencies with the help of global and local multi-head attention mechanisms that integrate a positional encoding component. Training is performed in a supervised manner (using human-generated video summaries). After being trained, the PGL-SUM model can produce representative summaries for unseen videos, according to a user-specified time-budget about the summary duration.
- Related publications [ism21a]
- Software package [download source code]

This software can be used for training a deep learning architecture for video thumbnail selection, taking under consideration the representativeness and the aesthetic quality of the video frames. Training is fully-unsupervised, based on a combination of adversarial and reinforcement learning. After being trained on a collection of videos, the Video Thumbnail Selector is capable of selecting a set of representative video thumbnails for unseen videos.
- Related publications [icmr21]
- Software package [download source code]

This is an implementation of our fast video cropping method, which allows adapting an input video to a different aspect ratio while staying focused on the original video's main subject. Our method utilizes visual saliency to find the regions of attention in each frame, and employs a filtering-through-clustering technique as well as temporal filters to select the main region of focus and produce a smooth sequence of cropped frames.
- Related publications [icip21]
- Software package [download source code]

This is an implementation of ObjectGraphs, our novel bottom-up video event recognition and explanation approach. It combines object detection, a graph convolutional network (GCN) and a long short-term memory (LSTM) network for performing video event recognition as well as for identifying the objects that contributed the most to the event recognition decisions, thus providing explanations for the latter.
- Related publications [cvprw21]
- Software package [download source code]

This is an implementation of our latest video summarization method, presented in our paper "AC-SUM-GAN: Connecting Actor-Critic and Generative Adversarial Networks for Unsupervised Video Summarization", IEEE Trans. on Circuits and Systems for Video Technology (IEEE TCSVT), 2020 (early access). This is, to date, our most complete and best-performing method for video summarization.
- Related publications [csvt20]
- Software package [download source code]

We provide the code for our paper "Structured Pruning of LSTMs via Eigenanalysis and Geometric Median for Mobile Multimedia and Deep Learning Applications", Proc. 22nd IEEE Int. Symposium on Multimedia (ISM), Dec. 2020. This code can be used for generating more compact LSTMs, which is very useful for mobile multimedia applications and deep learning applications in other resource-constrained environments.
- Related publications [ism20]
- Software package [download source code]

We provide an implementation of our video summarization evaluation method presented in our publication "Performance over Random: A Robust Evaluation Protocol for Video Summarization Methods", Proc. 28th ACM Int. Conf. on Multimedia (ACM MM '20). This software can be used for evaluating automatically-generated video summaries using the Performance over Random (PoR) evaluation protocol.
- Related publications [acmmm2020]
- Software package [download source code]

We provide an implementation of our extended dual encoding network for ad-hoc video search, presented at ACM ICMR 2020. This network makes use of more than one encodings of the visual and textual content, as well as two different attention mechanisms.
- Related publications [icmr2020]
- Software package [download source code]

This is an implementation of our filter pruning framework for DCNNs, presented at the IEEE ICME 2020 Mobile Multimedia Computing Workshop. This framework compresses noisy or less discriminant filters in small fractional steps, utilizing a class-separability criterion and an asymptotic schedule for the pruning rate and scaling factor, so that the selected filters' weights are gradually reduced to zero.
- Related publications [icme2020]
- Software package [download source code]