Publications de Touradj Ebrahimi

Chattez avec Graph Search

Posez n’importe quelle question sur les cours, conférences, exercices, recherches, actualités, etc. de l’EPFL ou essayez les exemples de questions ci-dessous.

AVERTISSEMENT : Le chatbot Graph n'est pas programmé pour fournir des réponses explicites ou catégoriques à vos questions. Il transforme plutôt vos questions en demandes API qui sont distribuées aux différents services informatiques officiellement administrés par l'EPFL. Son but est uniquement de collecter et de recommander des références pertinentes à des contenus que vous pouvez explorer pour vous aider à répondre à vos questions.

Recent years have witnessed significant advance- ment in face recognition (FR) techniques, with their applications widely spread in people’s lives and security-sensitive areas. There is a growing need for reliable interpretations of decisions of such systems. Existing studies relying on various mechanisms have investigated the usage of saliency maps as an explanation approach, but suffer from different limitations. This paper first explores the spatial relationship between face image and its deep representa

Quality is a fundamental concept closely linked to measuring performance in systems, products and services. Any compression and representation technique in audiovisual signals needs metrics of quality, not only in their design stage but also in demonstrating their superior performance when compared to state of the art. Some believe that the main reason for the failure of previous waves of 3D was the lack of a minimum quality requirement in 3D. It is therefore important to consider mechanisms of 3D vision in

This paper reports the details and results of a subjective and objective quality evaluation assessing responses to an MPEG call for evidence (CfE) on high dynamic range (HDR) and wide color gamut video coding. Five HDR video contents, compressed at four bi ...

In recent years, significant advancements in face recognition have been witnessed thanks to the rapid development of artificial intelligence. Despite remarkable performance, predictions made by such techniques tend to be challenging to explain. Considering ...

Subjective quality assessment is widely used to understand and to study human perception of multimedia quality and as a basis for developing objective metrics to automatically predict the quality of audiovisual presentations. There are several recognized international protocols and procedures for reliable assessment of quality in multimedia systems and services, with emphasis on speech, audio and video modalities. However, the aspect of certification is not yet well understood in this context. This paper di

Crowdsourcing is becoming a popular cost effective alternative to lab-based evaluations for subjective quality assessment. However, crowd-based evaluations are constrained by the limited availability of display devices used by typical online workers, which makes the evaluation of high dynamic range (HDR) content a challenging task. In this paper, we investigate the feasibility of using low dynamic range versions of original HDR content obtained with tone mapping operators (TMOs) in crowdsourcing evaluations

Pose-invariant face recognition has become a challenging problem for modern AI-based face recognition systems. It aims at matching a profile face captured in the wild with a frontal face registered in a database. Existing methods perform face frontalizatio ...

This work addresses the problem of studying and characterizing topology changes between resulting and reference segmentation masks in video sequences. In particular, the goal of this paper is to examine the impact of individual and combined artifacts found in video object segmentation applications (e.g., added regions and holes). Added regions and holes artifacts are synthetically generated and inserted in a segmentation mask. We performed a psychophysical experiment in which human subjects were asked to ra

Recently, short animated image sequences have become very popular in social networks. Most animated images are represented in GIF format. In this paper we propose an animated JPEG format, called aJPEG, which allows the standard JPEG format to be extended in a backward compatible way in order to cope with animated images. After presenting the proposed format, we illustrate it using two prototype applications: the first in form of a GIF-to-aJPEG converter on a personal computer and the second in form of an aJ

Plenoptic content is becoming increasingly popular thanks to the availability of acquisition and display devices. Thanks to image-based rendering techniques, a plenoptic content can be rendered in real time in an interactive manner allowing virtual navigation through the captured scenes. This way of content consumption enables new experiences, and therefore introduces several challenges in terms of plenoptic data processing, transmission and consequently visual quality evaluation. In this paper, we propose

We present an algorithm for tracking video object which is based on an hybrid strategy. This strategy uses both object and region information to solve the correspondence problem. Low level descriptors are exploited to track object s regions and to cope wit ...

Evaluation of the performance of video segmentation algorithms is important in both theoretical and practical considerations. This paper addresses the problem of video segmentation assessment, through both subjective and objective approaches, for the specific application of video surveillance. After an overview of the state of the art technique in video segmentation objective evaluation metrics, a general framework is proposed to cope with application dependent evaluation assessment. Finally, the performanc

Feature selection is a machine learning technique that has many interesting applications in the area of brain- computer interfaces (BCIs). Here we show how automatic relevance determination (ARD), which is a Bayesian feature selection technique, can be app ...

Wyner-Ziv (WZ) video coding is an emerging video coding paradigm based on two major Information Theory results: the Slepian-Wolf and Wyner-Ziv theorems. One of the most interesting and used WZ video coding architectures makes use of a feedback channel (FC) ...

The image compression field is witnessing a shift in paradigm thanks to the rise of neural network-based models. In this context, the JPEG committee is in the process of standardizing the first learning-based image compression standard, known as JPEG AI. W ...

Tremendous progress has been made in audiovisual technologies in the last decades. Consequently, new technologies quality measures evolve and trend to be more user-centric. This is the reason why the Quality of Experience (QoE) assessment is presently meaningful and challenging, especially for users typical experiences during multimedia content consumption. Such an evaluation is the aim of this paper. More specifically, the Sense of Presence (SoP) was explored in place of QoE as it is a factor influencing t

MPEG-7 camera extends the capabilities of conventional cameras by analyzing its scene in order to generate a contentbased description according to the recently approved MPEG- 7 standard. This gives to the camera a large variety of current and potential applications, such as surveillance, augmented reality, and virtual display. This paper provides an overviewof what is meant by an MPEG-7 camera, discusses the above mentioned applications, and provides an implementation example of such a camera using existing

With the increasing use of multimedia technologies, image compression requires higher performance as well as new features. To address this need in the specific area of still image encoding, a new standard is currently being developed, the JPEG2000. It is not only intended to provide rate-distortion and subjective image quality performance superior to existing standards, but also to provide functionality that current standards can either not address efficiently or not address at all.

In this paper, we present a system for image replica detection. More specifically, the technique is based on the extraction of 162 features corresponding to texture, color and gray-level characteristics. These features are then weighted and statistically normalized. To improve training and performances, the features space dimensionality is reduced. Lastly, a decision function is generated to classify the test image as replica or non-replica of a given reference image. Experimental results show the effective

This paper introduces a personalized content preparation and delivery framework for universal multimedia access. This framework has a wealth of potential applications in broadcasting, the World Wide Web and mobile telecommunication. Content preparation deals with the generation of summaries by automatic video analysis techniques, and with the annotation of content using MPEG 7 for search and retrieval and SMIL for interactive video. The use of open standards favors interoperability with third-party applicat

Touradj Ebrahimi

Chattez avec Graph Search

Explainable Face Verification via Feature-Guided Gradient Backpropagation

3D Video Quality Assessment

Subjective and Objective Evaluation of HDR Video Coding Technologies

Improving Perturbation-based Explanation Methods with Application to Face Recognition

Towards certification of 3D video quality assessment

Crowdsourcing evaluation of high dynamic range compression

Pose-Invariant Face Recognition via Feature-Space Pose Frontalization

Impact of Topology Changes in Video Segmentation Evaluation

Towards an animated JPEG

A new approach to subjectively assess quality of plenoptic content

Tracking Video Objects in Cluttered Background

Application Dependent Video Segmentation Evaluation - A Case Study for Video Surveillance

Bayesian Feature Selection Applied In a P300 Brain- Computer Interface

Studying Error Resilience Performance for a Feedback Channel Based Transform Domain Wyner-Ziv Video Codec

On the impact of learning-based image compression on computer vision tasks

Towards prediction of Sense of Presence in immersive audiovisual communications

MPEG-7 Camera

JPEG2000: The upcoming still image compression standard

Image Replica Detection based on Binary Support Vector Classifier

Personalized Content Preparation and Delivery for Universal Multimedia Access