Publications by Touradj Ebrahimi

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.

Video transcoding is an important step to enable interoperability between different networks, terminals, applications, and services for video communication. This paper studies the influence of typical video transcoding artifacts due to frame rate reduction ...

Nowadays, image and video are the data types that consume most of the resources of modern communication channels, both in fixed and wireless networks. Thus, it is vital to compress visual data as much as possible, while maintaining some target quality leve ...

In this paper, we present a no-reference blur metric for images and video. The blur metric is based on the analysis of the spread of the edges in an image. Its perceptual significance is validated through subjective experiments. The novel metric is near real-time, has low computational complexity and is shown to perform well over a range of image content. Potential applications include optimization of source coding, network resource management and autofocus of an image capturing device.

Recently deep learning based image compression has made rapid advances with promising results based on objective quality metrics. However, a rigorous subjective quality evaluation on such compression schemes have rarely been reported. This paper aims at pe ...

High dynamic range (HDR) imaging is able to capture a wide range of luminance values, closer to what the human eye can perceive. However, for capture and display technologies, it is important to answer the question on the significance of higher dynamic range for user preference. This paper answers this question by investigating the added value of higher dynamic range via a rigorous set of subjective experiments using paired comparison methodology. Video sequences at four different peak luminance levels were

Replica detection is a prerequisite for the discovery of copyright infringement and detection of illicit content. For this purpose, content-based systems can be an efficient alternative to watermarking. Rather than imperceptibly embedding a signal, content-based systems rely on content similarity concepts. Certain content-based systems use adaptive classifiers to detect replicas. In such systems, a suspected content is tested against every original, which can become computationally prohibitive as the number

For augmented reality applications, accurate estimation of the camera pose is required. An existing video-based markerless tracking system, developed at the ITS, presents several weaknesses towards this goal. In order to improve the video tracker, several feature point extraction and tracking techniques are compared in this project. The techniques with best performance in the framework of augmented reality are applied to the present system in order to prove system s enhancement. A new implementation for fea

Studying emotions has become increasingly popular in various research fields. Researchers across the globe have studied various tools to implicitly assess emotions and affective states of people. Human computer interface systems specifically can benefit fr ...

Modern cameras can be used to capture high dynamic range (HDR) images by taking multiple low dynamic range (LDR) pictures at different exposure settings. However, DSLR cameras often store the multiple exposure pictures, which increases storage requirements ...

Mini-drones are increasingly used in video surveillance. Their areal mobility and ability to carry video cameras provide new perspectives in visual surveillance which can impact privacy in ways that have not been considered in a typical surveillance scenar ...

This work concerns the developing of new perceptual metrics for 3D watermarking quality assessment. Any water- marking algorithm, to be effective, requires that the distortions is inevitably introduces into the watermarked media is imperceptible. This requirements is particularly severe for watermarking of 3D objects where the visual quality of the original model has to be preserved, i.e. the visual aspect of the watermarked object have to be the same of the original one. Several methods based on the knowle

For augmented reality applications, accurate estimation of the camera pose is required. An existing video-based marker tracking system developed at the ITS presents some limitations when the marker is completely or partially occluded. The objective of this project is to improve the tracking of the camera on those cases. For this purpose, the tracking of the marker is extended to that of natural feature points around the marker's environment. The extension to natural features works as follows. Feature point

When a stereo pair is formed from a decoded view and a synthesized view, it is unclear how the overall quality of the stereo pair should be assessed through objective quality metrics. In this paper, this problem is addressed considering a 3D video represen ...

A compression technique based on an expansion is presented. The elementary functions of the expansion form a class of pyramidal Gabor functions covering the frequency domain in octave bands. The image sequence is coded by differentially coding selected coefficients of this expansion. Simulation results show sequences reconstructed with good quality for a bit rate less than 64 Kbit/s.

The Dynamic Vision System (DVS) is a novel image acquisition system that works only when there is a brightness change in a pixel, resulting in a stream of events including timestamps, spatial coordinates and the sign of the bright- ness change (increase or ...

In the past few years sharing photos within social networks has become very popular. In order to make these huge collections easier to explore, images are usually tagged with representative keywords such as persons, events, objects, and locations. In order ...

In this paper, we present an original non-linear subdivision scheme suitable for univariate data, plane curves and discrete triangulated surfaces, while keeping the complexity acceptable. The proposed technique is compared to linear subdivision methods having an identical support. Numerical criteria are proposed to verify basic properties, such as convergence of the scheme and the regularity of the limit function.

We consider dense networks of surveillance cameras capturing overlapped images of the same scene from different viewing directions, such a scenario being referred to as multi-view. Data compression is paramount in such a system due to the large amount of c ...

Space missions are often equipped with several high definition sensors that can autonomously collect a potentially enormous amount of data. The bottleneck in retrieving these often precious datasets is the onboard data storing capability and the communication bandwidth, which limit the amount of data that can be sent back to Earth. In this paper, we propose a method based on the analysis of brain electrical activity to identify the scientific interest of experts towards a given image in a large set of image

The performance of objective quality metrics for high-definition (HD) video sequences is well studied, but little is known about their performance for ultra-high definition (UHD) video sequences. This paper analyzes the performance of several common object ...

Touradj Ebrahimi

Chat with Graph Search

Impact of video transcoding artifacts on the subjective quality

Learning-based Image Coding: Early Solutions Reviewing and Subjective Quality Evaluation

A No-Reference Perceptual Blur Metric

Perceptual Quality Study On Deep Learning Based Image Compression

Subjective Evaluation of Higher Dynamic Range Video

Hierarchical Indexing using R-trees for Replica Detection

Robust Feature Point Extraction and Tracking for Augmented Reality

EEG correlates of different emotional states elicited during watching music videos

Evaluation of JPEG XT for high dynamic range cameras

Privacy in Mini-drone Based Video Surveillance

Watermarked 3D Object Quality Assessment

Camera Tracking using natural feature point matching for Augmented Reality

Quality Assessment of a Stereo Pair Formed From Decoded and Synthesized Views Using Objective Metrics

Video coding using a pyramidal Gabor expansion

Event Data Stream Compression Based on Point Cloud Representation

Geotag Propagation in Social Networks Based on User Trust Model

Non-linear subdivision using local spherical coordinates

Recent Advances in Multi-view Distributed Video Coding

Implicit Retrieval Of Salient Images Using Brain Computer Interface

Benchmarking of quality metrics on ultra-high definition video sequences