Publications de Touradj Ebrahimi

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In recent years, light field technology has attracted the interest of academia and industry, thanks to the possibility of rendering 3D scenes in a more realistic and immersive way. In particular, light field displays have been consistently investigated for ...

We present a generic video codec, which is able to compress image sequences efficiently regardless of their input formats. In addition, this codec supports a wide range of bit rates, without significant changes in its main architecture. A multiresolution representation of the data is generated by a Gabor-like wavelet transform. The motion estimation is performed by a locally adaptive multigrid block-matching technique. This codec can handle both interlaced and progressive input sequences, the temporal redun

Quality assessment of images is of key importance for media applications. In this paper we present a new objective metric to predict the quality of images using deep neural networks. The network makes use of both the color information as well as frequency ...

The utilization of digital image sequences is becoming increasingly important in modern imaging applications, includingHDTV, interactive video, teleconferencing, telerobotics, and medical imaging. Due to the immense amountof data in image sequences, high compression coding methods are critical for efficient transmission and storage.Often, compression ratios exceeding 200:1 are required. Because these ratios are near the limits of conventionalcoding methods, we are investigating alternative methods which tak

Event-based computer vision is becoming very popular. With progress in sensing events, the volume of data produced has increased manyfold, and there is a need for compression. This paper introduces a novel deep-learning-based lossless event data compression codec. The idea is to represent the events as a point cloud with spatial dimensions x and y and temporal dimension t as its coordinates. Then, an adaptive octree structure is created to better compact the latter without introducing any loss by coding the

Automatic emotion recognition systems based on supervised machine learning require reliable annotation of affective behaviours to build useful models. Whereas the dimensional approach is getting more and more popular for rating: affective behaviours in continuous time domains, e.g., arousal and valence, methodologies to take into account reaction lags of the human raters are still rare. We therefore investigate the relevance of using machine learning algorithms able to integrate contextual information in th

The growing adoption of point clouds as an imaging modality has stimulated the search for efficient solutions for compression. Learning-based algorithms have been reporting increasingly better performance and are drawing the attention from the research com ...

The use of DNA molecules as a storage medium has been recently proposed as a solution to the exponentially increasing demand for data storage, achieving lower energy consumption while offering better lifespan and higher information density. The nucleotides composing the molecules can be regarded as quaternary symbols, but constraints are generally imposed to avoid sequences prone to errors during synthesis, archival, and sequencing. While the majority of previous works in the field have proposed methods for

Current increasing effort of broadcast providers to transmit UHD (Ultra High Definition) content is likely to increase demand for ultra high definition televisions (UHDTVs). To compress UHDTV content, several alter- native encoding mechanisms exist. In addition to internationally recognized standards, open access proprietary options, such as VP9 video encoding scheme, have recently appeared and are gaining popularity. One of the main goals of these encoders is to efficiently compress video sequences beyond

DNA molecules have been proposed as a support for long-term data storage. This enables a quaternary representation through the four nucleotides prevalent in the genetic material of living beings. Recently, the JPEG Committee launched a Call for Proposals for image coding algorithms in DNA support, retaining the top performer as its starting point for the development of a new standard. However, the process of storage and sequencing of molecules usually results in errors, but this additional challenge was not

Evidence from neuroscience and psychology supports the idea that synchronization among various sub-components of the organism is the key-point to emotional processes. This study investigates the way signals from the central nervous system interact with sig ...

The demand for data storage has grown exponentially over the past decades. Current archival solutions have significant shortcomings, such as high resource requirements and a lack of sufficient longevity. In contrast, research on DNA-based storage has been advancing notably due to its low environmental impact, larger capacity, and longer lifespan. This has led to the development of compression methods that adapted the binary representation of legacy JPEG images into a quaternary base of nucleotides while tak

Digital images have become an important source of information in the modern world of communication systems. In their raw form, digital images require a tremendous amount of memory. Many research efforts have been devoted to the problem of image compression in the last two decades. Two different compression categories must be distinguished: lossless and lossy. Lossless compression is achieved if no distortion is introduced in the coded image. Applications requiring this type of compression include medical im

Over the last few years, social network systems have greatly increased users’ involvement in online content creation and annotation. Since such systems usually need to deal with a large amount of multimedia data, it becomes desirable to realize an interact ...

The recent rise in interest in point clouds as an imaging modality has motivated standardization groups such as JPEG and MPEG to launch activities aiming at developing compression standards for point clouds. Lossy compression usually introduces visual arti ...

Extensive adoption of video surveillance, affecting many aspects of our daily lives, alarms the public about the increasing invasion into personal privacy. To address these concerns, many tools have been proposed for protection of personal privacy in image and video. However, little is understood regarding the effectiveness of such tools and especially their impact on the underlying surveillance tasks, leading to a tradeoff between the preservation of privacy offered by these tools and the intelligibility o

When human subjects assess the quality of multimedia data, high level perceptual processes such as Focus of Attention (FoA) and eye movements are believed to play an important role in such tasks. While prior art reports incorporation of visual FoA into obj ...

The past decades have witnessed rapid growth in imaging as a major form of communication between individuals. Due to recent advances in capture, storage, delivery and display technologies, consumers demand improved perceptual quality while requiring reduce ...

Shadow segmentation is a critical issue for systems aiming at extracting, tracking or recognizing objects in a given scene. Shadows can in fact modify the shape and colour of objects and therefore affect scene analysis and interpretation systems in many applications, such as video database search and retrieval, as well as video analysis in applications such as video surveillance. We present a shadow segmentation algorithm which includes two stages. The first stage extracts moving cast shadows in each frame

Accurate registration between real and virtual objects is critical for Augmented Reality (AR) applications. State of the art shows that no tracking device is individually adequate. We present a data fusion framework that combines orientation measurements of different tracker devices. It has been designed to work with a video based tracker subsystem and an inertial tracker. Thanks to its flexibility the system can use orientation measurements produced by any kind and number of trackers, no matter their rate

Touradj Ebrahimi

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A comprehensive framework for visual quality assessment of light field tensor displays

Motion-compensated generic coding of video based on a multiresolution data structure

A new objective metric to predict image quality using deep neural networks

Image sequence coding using concepts in visual perception

A learning-based lossless event data compression for computer vision applications

Prediction of Asynchronous Dimensional Emotion Ratings from Audiovisual and Physiological Data

Latent Space Slicing for Enhanced Entropy Modeling in Learning-Based Point Cloud Geometry Compression

Storing images and point clouds on DNA support with fountain codes with fountain codes

Comparison of compression efficiency between HEVC/H.265 and VP9 based on subjective assessments

DNA-based image storage with substitution and indel error correction

Implicit Affective Profiling of Subjects based on Physiological Data Coupling

Towards learning-based image compression for storage on DNA support

High-performance compression of visual information - A tutorial review - Part I : Still Pictures

Object-based Tag Propagation for Semi-automatic Annotation of Images

Subjective performance evaluation of bitrate allocation strategies for MPEG and JPEG Pleno point cloud compression

A framework for objective evaluation of privacy filters in video surveillance

Influence of audio-visual attention on perceived quality of standard definition multimedia content

On the Performance of Subjective Visual Quality Assessment Protocols for Nearly Visually Lossless Image Compression

Spatio-Temporal Shadow Segmentation and Tracking

Hybrid Tracking for Augmented Reality