Publications by Evangelos Alexiou

Benchmarking of objective quality metrics for point cloud compression

Touradj Ebrahimi, Evangelos Alexiou, Davi Nachtigall Lazzarotto

Point cloud is a promising imaging modality for the representation of 3D media. The vast volume of data associated with it requires efficient compression solutions, with lossy algorithms leading to larger bit-rate savings at the expense of visual impairmen ...

IEEE2021

On Block Prediction For Learning-Based Point Cloud Compression

Touradj Ebrahimi, Evangelos Alexiou, Davi Nachtigall Lazzarotto

Point clouds are among popular visual representations for immersive media. However, the vast amount of information generated during their acquisition requires effective compression for practical applications. Although relevant activities from standardizati ...

IEEE2021

Perceptual Quality of Point Clouds with application to Compression

Evangelos Alexiou

Modern information technologies and human-centric communication systems employ advanced content representations for richer portrayals of the real world. The newly adopted imaging modalities offer additional information cues and permit the depiction of real ...

EPFL2021

Comparison of Remote Subjective Assessment Strategies in the Context of the JPEG Pleno Point Cloud Activity

Evangelos Alexiou

In this work we compare two different options to perform on-line subjective quality assessment experiments in the context of the Call for Evidence on JPEG Pleno Point Cloud Coding. A deep-learning based point cloud codec submitted to the Call was tested ag ...

IEEE2021

Towards a Point Cloud Structural Similarity Metric

Touradj Ebrahimi, Evangelos Alexiou

Point cloud is a 3D image representation that has recently emerged as a viable approach for advanced content modality in modern communication systems. In view of its wide adoption, quality evaluation metrics are essential. In this paper, we propose and ass ...

IEEE2020

PointXR: A Toolbox for Visualization and Subjective Evaluation of Point Clouds in Virtual Reality

Touradj Ebrahimi, Evangelos Alexiou, Nanyang Yang

In this study, we explore the use of virtual reality to subjectively evaluate the visual quality of point cloud contents. To this aim, we develop the PointXR toolbox, a set of Unity applications that can host experiments under variants of interactive and p ...

IEEE2020

Quality Evaluation Of Static Point Clouds Encoded Using MPEG Codecs

Touradj Ebrahimi, Evangelos Alexiou

This paper presents a quality evaluation study of point cloud codecs that have been recently standardised by the MPEG committee. In particular, a subjective experiment to assess their performance in terms of bitrate against visual quality is designed and r ...

IEEE2020

A comprehensive study of the rate-distortion performance in MPEG point cloud compression

Touradj Ebrahimi, Irene Viola, Evangelos Alexiou

Recent trends in multimedia technologies indicate the need for richer imaging modalities to increase user engagement with the content. Among other alternatives, point clouds denote a viable solution that offers an immersive content representation, as witne ...

2019

Point cloud quality evaluation: Towards a definition for test conditions

Touradj Ebrahimi, Rafael Xavier Meriade Duarte, Evangelos Alexiou

Recently stakeholders in the area of multimedia representation and transmission have been looking at plenoptic technologies to improve immersive experience. Among these technologies, point clouds denote a volumetric information representation format with i ...

2019

Exploiting user interactivity in quality assessment of point cloud imaging

Touradj Ebrahimi, Evangelos Alexiou

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 ...

2019

Towards Modelling of Visual Saliency in Point Clouds for Immersive Applications

Touradj Ebrahimi, Evangelos Alexiou, Peisen Xu

Modelling human visual attention is of great importance in the field of computer vision and has been widely explored for 3D imaging. Yet, in the absence of ground truth data, it is unclear whether such predictions are in alignment with the actual human vie ...

2019

Point Cloud Quality Assessment Metric Based on Angular Similarity

Touradj Ebrahimi, Evangelos Alexiou

The rise of immersive technologies has been recently fuelled by emerging applications which employ advanced content representations. Among various alternatives, point clouds denote a promising solution which has recently drawn a significant amount of inter ...

2018

Point Cloud Subjective Evaluation Methodology based on 2D Rendering

Touradj Ebrahimi, Evangelos Alexiou

Point clouds are one of the most promising technologies for 3D content representation. In this paper, we describe a study on quality assessment of point clouds, degraded by octree-based compression on different levels. The test contents were displayed usin ...

2018

A novel methodology for quality assessment of voxelized point clouds

Touradj Ebrahimi, Evangelos Alexiou

Recent trends in multimedia technologies indicate a significant growth of interest for new imaging modalities that aim to provide immersive experiences by increasing the engagement of the user with the content. Among other solutions, point clouds denote an ...

SPIE-INT SOC OPTICAL ENGINEERING2018

Point cloud subjective evaluation methodology based on reconstructed surfaces

Touradj Ebrahimi, Evangelos Alexiou

Point clouds have been gaining importance as a solution to the problem of efficient representation of 3D geometric and visual information. They are commonly represented by large amounts of data, and compression schemes are important for their manipulation ...

SPIE-INT SOC OPTICAL ENGINEERING2018

Benchmarking of Objective Quality Metrics for Colorless Point Clouds

Touradj Ebrahimi, Evangelos Alexiou

Recent advances in depth sensing and display technologies, along with the significant growth of interest for augmented and virtual reality applications, lay the foundation for the rapid evolution of applications that provide immersive experiences. In such ...

IEEE2018

Impact of Visualisation Strategy for Subjective Quality Assessment of Point Clouds

Touradj Ebrahimi, Evangelos Alexiou

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 ...

2018

On subjective and objective quality evaluation of point cloud geometry

Touradj Ebrahimi, Evangelos Alexiou

Point clouds have emerged as a promising solution for immersive representation of 3D contents. In this paper an interactive subjective quality assessment for point clouds is proposed. Quality assessment of geometry information in point clouds subject to re ...

2017

On the performance of metrics to predict quality in point cloud representations

Touradj Ebrahimi, Evangelos Alexiou

Point clouds are a promising alternative for immersive representation of visual contents. Recently, an increased interest has been observed in the acquisition, processing and rendering of this modality. Although subjective and objective evaluations are cri ...

Spie-Int Soc Optical Engineering2017

Towards subjective quality assessment of point cloud imaging in augmented reality

Touradj Ebrahimi, Evgeniy Upenik, Evangelos Alexiou

Recently, there has been an increased interest in capture, processing and rendering of visual content in form of point clouds. Among other challenges, subjective and objective quality evaluation of point clouds are still open problems. Most proposed subjec ...

2017