Publications by Touradj Ebrahimi

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The recent advances in light field imaging are changing the way in which visual content is captured, processed and consumed. Storage and delivery systems for light field images rely on efficient compression algorithms. Such algorithms must additionally tak ...

In this work, a performance evaluation of AVC Intra and JPEG2000 in terms of rate-distortion performance is conducted. A set of High Definition sequences with different spatial resolutions is used for this purpose. Results obtained show quite competitive p ...

In 2019, the JPEG Standardization Committee initiated JPEG AI to define the first image coding specifications, taking advantage of an end-to-end learning-based coding approach. The JPEG AI specifications will be soon published as an international standard ...

Shadows are often integral parts of natural scenes and their identification is an important task in image analysis. In this paper, we propose an algorithm for recognition of shadows cast by objects on the scene's background. The proposed approach is based on the use of color information by means of photometric invariant color transformations. The method is divided into two levels: first, object and shadow edges are extracted from the RGB components and only object edges from the invariant features; then, ed

In this report we benchmark the plane-to-plane objective quality metric. This is, a metric that measures the angular similarity of tangent planes between two point cloud models and relies on normal vectors that are carried with associated pairs of points. Evidently, the performance of the metric depends by default on the normal vectors and the way they approximate the underlying surfaces. Thus, to shed some light on the impact of the normal estimation algorithm selection and configuration in the performance

Change detection is a temporal segmentation tool aiming at identifying changes in image sets or image sequences at two different times. Many change detection algorithms have been proposed over the past decade for the generation of video objects in a wide range of applications, ranging from interactive multimedia to remote surveillance. Most of these algorithms are tailored to the specific application at hand. Therefore there is a need of a general model for change detection which could support the choice of

The JPEG committee (Joint Photographic Experts Group, formally known as ISO/IEC SC29 WG1) is currently in the process of standardizing JPEG XS, a new interoperable solution for low-latency, lightweight and visually lossless compression of image and video. ...

New techniques for redundancy removal of quantized coefficients of a wavelet transform are discussed. Several strategies are developed to improve the redundancy reduction stage in subband/wavelet based image compression. The influence of the scanning path in coding the coefficients of the subbands after transformation are pointed out and solutions are proposed for exploiting the correlation between the coefficients in a more efficient way. New methods are also proposed to encode the address of non zero coef

JPEG image coding standard has been a dominant format in a wide range of applications in soon three decades since it has been released as an international standard. The landscape of applications and services based on pictures has evolved since the original ...

The detection of digital face manipulation in video has attracted extensive attention due to the increased risk to public trust. To counteract the malicious usage of such techniques, deep learning-based deepfake detection methods have been developed and ha ...

The objective of Universal Multimedia Access (UMA) is to permit any user equipped with whatever device the access to multimedia information. To handle the problems of UMA, two different approaches are commonly used: store variations of the same content and send the most appropriate one, and store the original content and adapt it on-the-fly. In this project a UMA environment using a mixture of both approaches is proposed. The tools allowing to reach this goal are: an Annotation Tool which describes media us

In this paper, we present a video encoding scheme that uses object-based adaptation to deliver surveillance video to mobile devices. The method relies on a set of complementary video adaptation strategies and generates content that matches various appliance and network resources. Prior to encoding, some of the adaptation strategies exploit video object segmentation and selective filtering in order to improve the perceived quality. Moreover, object segmentation enables the generation of automatic summaries a

Today, several alternatives for compression of digital pictures and video sequences exist to choose from. Beside internationally recognized standard solutions, open access options like the VP8 image and video compression have recently appeared and are gaining popularity. In this paper, we present the methodology and the results of the rate-distortion performance analysis of VP8. The analysis is based on the results of subjective quality assessment experiments, which have been carried out to compare the two

This paper reports results of subjective and objective quality assessments of responses to a grand challenge on light field image compression. The goal of the challenge was to collect and evaluate new compression algorithms for light field images. In total ...

Point clouds are a new modality for representation of plenoptic content and a popular alternative to create immersive media. Despite recent progress in capture, display, storage, delivery and processing, the problem of a reliable approach to subjectively a ...

As immersive technologies target to provide higher quality of multimedia experiences, it is important to understand the quality of experience (QoE) perceived by users from various multimedia rendering schemes, in order to design and optimize human-centric ...

We propose a smart camera which performs video analysis and generates an MPEG-7 compliant stream. By producing a content-based metadata description of the scene, the MPEG-7 camera extends the capabilities of conventional cameras. The metadata is then directly interpretable by a machine. This is especially helpful in a number of applications such as video surveillance, augmented reality and quality control. As a use case, we describe an algorithm to identify moving objects and produce the corresponding MPEG-

A significant number of pictures are posted to social media sites or exchanged through instant messaging and cloud-based sharing services. Most social media services offer a range of access control mechanisms to protect users privacy. As it is not in the b ...

Point clouds have recently emerged as a promising and practical solution to code 3D visual information for immersive applications. Among other challenges, objective and subjective quality assessments are still open problems for this type of visual data rep ...

Perceptual prefiltering is the process of enhancing relevant portions of an image or of a video, and of simplifying contextual information in order to improve the perceived quality or the compression ratio. In this paper, we discuss the results of subjective quality evaluation experiments performed to assess the impact of perceptual prefiltering on video coding and we propose an objective quality metric that mimics the behavior of human observers. The predicted performance of the proposed metric is consiste

Touradj Ebrahimi

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Impact of interactivity on the assessment of quality of experience for light field content

On Comparing Image and Video Compression Algorithms

JPEG AI: The First International Standard for Image Coding Based on an End-to-End Learning-Based Approach

Cast Shadow Recognition in Color Images

Benchmarking of the plane-to-plane metric

Classification of change detection algorithms for object-based applications

Overview of the JPEG XS core coding system subjective evaluations

New techniques for subband/wavelet transform coefficient coding applied to still image compression

Comprehensive assessment of image compression algorithms

Impact of Video Processing Operations in Deepfake Detection

Design and Implementation of a Universal Multimedia Access Environment

Surveillance Video for Mobile Devices

Performance analysis of VP8 image and video compression based on subjective evaluations

Objective and subjective evaluation of light field image compression algorithms

Exploiting user interactivity in quality assessment of point cloud imaging

Modeling Immersive Media Experiences by Sensing Impact on Subjects

Recent Advances in MPEG-7 Cameras

Privacy-Preserving Photo Sharing based on a Public Key Infrastructure

Impact of Visualisation Strategy for Subjective Quality Assessment of Point Clouds

Evaluating Perceptually Prefiltered Video