Hadi
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Paper accepted: Elsevier Signal Processing: Reversible Data Hiding for Color Images Based on Pixel Value Order of Overall Process Channel Correlation

Journal Website

Authors: Ningxiong Maoa (Southwest Jiaotong University), Hongjie Hea (Southwest Jiaotong University), Fan Chenb (Southwest Jiaotong University), Lingfeng Qua (Southwest Jiaotong University), Hadi Amirpour (Alpen-Adria-Universität Klagenfurt, Austria), and Christian Timmerer (Alpen-Adria-Universität Klagenfurt, Austria)

Abstract: Color image Reversible Data Hiding (RDH) is getting more and more important since the number of its applications is steadily growing. This paper proposes an efficient color image RDH scheme based on pixel value ordering (PVO), in which the channel correlation is fully utilized to improve the embedding performance. In the proposed method, the channel correlation is used in the overall process of data embedding, including prediction stage, block selection and capacity allocation. In the prediction stage, since the pixel values in the co-located blocks in different channels are monotonically consistent, the large pixel values are collected preferentially by pre-sorting the intra-block pixels. This can effectively improve the embedding capacity of RDH based on PVO. In the block selection stage, the description accuracy of block complexity value is improved by exploiting the texture similarity between the channels. The smoothing the block is then preferentially used to reduce invalid shifts. To achieve low complexity and high accuracy in capacity allocation, the proportion of the expanded prediction error to the total expanded prediction error in each channel is calculated during the capacity allocation process. The experimental results show that the proposed scheme achieves significant superiority in fidelity over a series of state-of-the-art schemes. For example, the PSNR of the Lena image reaches 62.43dB, which is a 0.16dB gain compared to the best results in the literature with a 20,000bits embedding capacity.

Keywords—Reversible data hiding, color image, pixel value ordering, channel correlation

5g_Kaerntner_Fog_Logo
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Paper accepted @ IEEE ISM´2022: Semantic-Aware View Prediction for 360-Degree Videos at the 5G Edge

IEEE ISM’2022 (https://www.ieee-ism.org/)

Authors: Shivi Vats, Jounsup Park, Klara Nahrstedt, Michael Zink, Ramesh Sitaraman, and Hermann Hellwagner

Abstract: In a 5G testbed, we use 360° video streaming to test, measure, and demonstrate the 5G infrastructure, including the capabilities and challenges of edge computing support. Specifically, we use the SEAWARE (Semantic-Aware View Prediction) software system, originally described in [1], at the edge of the 5G network to support a 360° video player (handling tiled videos) by view prediction. Originally, SEAWARE performs semantic analysis of a 360° video on the media server, by extracting, e.g., important objects and events. This video semantic information is encoded in specific data structures and shared with the client in a DASH streaming framework. Making use of these data structures, the client/player can perform view prediction without in-depth, computationally expensive semantic video analysis. In this paper, the SEAWARE system was ported and adapted to run (partially) on the edge where it can be used to predict views and prefetch predicted segments/tiles in high quality in order to have them available close to the client when requested. The paper gives an overview of the 5G testbed, the overall architecture, and the implementation of SEAWARE at the edge server. Since an important goal of this work is to achieve low motion-to-glass latencies, we developed and describe “tile postloading”, a technique that allows non-predicted tiles to be fetched in high quality into a segment already available in the player buffer. The performance of 360° tiled video playback on the 5G infrastructure is evaluated and presented. Current limitations of the 5G network in use and some challenges of DASH-based streaming and of edge-assisted viewport prediction under “real-world” constraints are pointed out; further, the performance benefits of tile postloading are disclosed.

 

Hadi
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Paper accepted @ IEEE TIP: Advanced Scalability for Light Field Image Coding

IEEE Transactions on Image Processing (TIP)
Journal Website

 

Authors: Hadi Amirpour (Alpen-Adria-Universität Klagenfurt, Austria), Christine Guillemot (INRIA, France), Mohammad Ghanbari (University of Essex, UK), and Christian Timmerer (Alpen-Adria-Universität Klagenfurt, Austria)

Abstract: Light field imaging, which captures both spatial and angular information, improves user immersion by enabling post-capture actions, such as refocusing and changing view perspective. However, light fields represent very large volumes of data with a lot of redundancy that coding methods try to remove. State-of-the-art coding methods indeed usually focus on improving compression efficiency and overlook other important features in light field compression such as scalability. In this paper, we propose a novel light field image compression method that enables (i) viewport scalability, (ii) quality scalability, (iii) spatial scalability, (iv) random access, and (v) uniform quality distribution among viewports, while keeping compression efficiency high. To this end, light fields in each spatial resolution are divided into sequential viewport layers, and viewports in each layer are encoded using the previously encoded viewports. In each viewport layer, \revision{the} available viewports are used to synthesize intermediate viewports using a video interpolation deep learning network. The synthesized views are used as virtual reference images to enhance the quality of intermediate views. An image super-resolution method is applied to improve the quality of the lower spatial resolution layer. The super-resolved images are also used as virtual reference images to improve the quality of the higher spatial resolution layer.
The proposed structure also improves the flexibility of light field streaming, provides random access to the viewports, and increases error resiliency. The experimental results demonstrate that the proposed method achieves a high compression efficiency and it can adapt to the display type, transmission channel, network condition, processing power, and user needs.

Keywords—Light field, compression, scalability, random access, deep learning.

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GMSys 2023: First International ACM Green Multimedia Systems Workshop, 7 – 10 June 2023, Vancouver, Canada

The threat of climate change requires a drastic reduction of global greenhouse gas (GHG) emissions in several societal spheres. Thus, this also applies to reducing and rethinking the energy consumption of digital technologies. Video streaming technology is responsible for more than half of digital technology’s global impact [ref]. There is rapid growth, also now with digital and remote work has become more mainstream, in the amount of video data volume, processing of video content, and streaming which affects the rise of energy consumption and its associated GHG emissions.

The International Workshop on Green Multimedia Systems 2023 (GMSys 2023) aims to bring together experts and researchers to present and discuss recent developments and challenges for energy reduction in multimedia systems. This workshop focuses on innovations, concepts, and energy-efficient solutions from video generation to processing, delivery, and further usage.

Find further info at https://athena.wp.itec.aau.at/events-gmsys23/

 

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Paper accepted: Context-aware Community Evolution Prediction in Online Social Networks

Athors: Alexander Lercher, Nishant Saurabh, Radu Prodan

The 15th IEEE International Conference on Social Computing and Networking
http://www.swinflow.org/confs/2022/socialcom/

Abstract: Community evolution prediction enables business-driven social networks to detect customer groups modeled as communities based on similar interests by splitting them into temporal segments and utilizing ML classification to predict their structural changes. Unfortunately, existing methods overlook business contexts and focus on analyzing customer activities, raising privacy concerns. This paper proposes a novel method for community evolution prediction that applies a context-aware approach to identify future changes in community structures through three complementary features. Firstly, it models business events as transactions, splits them into explicit contexts, and detects contextualized communities for multiple time windows. Secondly, it %it performs feature engineering by uses novel structural metrics representing temporal features of contextualized communities. Thirdly, it uses extracted features to train ML classifiers and predict the community evolution in the same context and other dependent contexts. Experimental results on two real-world data sets reveal that traditional ML classifiers using the context-aware approach can predict community evolution with up to three times higher accuracy, precision, recall, and F1-score than other baseline classification methods (i.e., majority class, persistence).

Scientific Pre-kickoff Meeting Graph-Massivizer

A pre-kickoff meeting for Graph-Massivizer took place on November 4, 2022, at Vrije Universiteit Amsterdam. Ana Lucia Varbanescu, Michael Cochez, Alexandru Iosup, and Radu Prodan discussed the scientific goals of the Graph Massivizer project and how to exceed them.

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Graphmassivizer @ Austrian Science Blog Schrödingerskatze.at

A new online article about Graphmassivizer has been published in the Science blog; check it out HERE.

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Paper accepted: CNN-assisted Road Sign Inspection on the Computing Continuum

2022 IEEE/ACM 2nd Workshop on Distributed Machine Learning for the Intelligent Computing Continuum (DML-ICC) In conjuction with IEEE/ACM UCC 2022 December 6-9, 2022 | Vancouver, Washington, USA

Authors: Narges Mehran (Alpen-Adria-Universität Klagenfurt) and Radu Prodan (Alpen-Adria-Universität Klagenfurt)

Abstract: Processing rapidly growing data encompasses complex workflows that utilize the Cloud for high-performance computing and the Fog and Edge devices for low-latency communication. For example, autonomous driving applications require inspection, recognition, and classification of road signs for safety inspection assessments, especially on crowded roads. Such applications are among the famous research and industrial exploration topics in computer vision and machine learning. In this work, we design a road sign inspection workflow consisting of 1) encoding and framing tasks of video streams captured by camera sensors embedded in the vehicles, and 2) convolutional neural network (CNN) training and inference models for accurate visual object recognition. We explore a matching theoretic algorithm named CODA [1] to place the workflow on the computing continuum, targeting the workflow processing time, data transfer intensity, and energy consumption as objectives. Evaluation results on a real computing continuum testbed federated among four Cloud, Fog, and Edge providers reveal that CODA achieves 50%-60% lower completion time, 33%-59% lower CO2 emissions, and 19%-45% lower data transfer intensity compared to two stateof-the-art methods.

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Paper accepted: MCOM-Live: A Multi-Codec Optimization Model at the Edge for Live Streaming

29th International Conference on MultiMedia Modeling
9 – 12 January 2023 | Bergen, Norway

Daniele Lorenzi (Alpen-Adria-Universität Klagenfurt), Farzad Tashtarian (Alpen-Adria-Universität Klagenfurt), Hadi Amirpour (Alpen-Adria-Universität Klagenfurt), Christian Timmerer (Alpen-Adria-Universität Klagenfurt), and Hermann Hellwagner (Alpen-Adria-Universität Klagenfurt)

Abstract:

HTTP Adaptive Streaming (HAS) is the predominant technique to deliver video contents across the Internet with the increasing demand of its applications. With the evolution of videos to deliver more immersive experiences, such as their evolution in resolution and framerate, highly efficient video compression schemes are required to ease the burden on the delivery process. While AVC/H.264 still represents the most adopted codec, we are experiencing an increase in the usage of new generation codecs (HEVC/H.265, VP9, AV1, VVC/H.266, etc.). Compared to AVC/H.264, these codecs can either achieve the same quality besides a bitrate reduction or improve the quality while targeting the same bitrate. In this paper, we propose a Mixed-Binary Linear Programming (MBLP) model called Multi-Codec Optimization Model at the edge for Live streaming (MCOM-Live) to jointly optimize (i) the overall streaming costs, and (ii) the visual quality of the content played
out by the end-users by efficiently enabling multi-codec content delivery. Given a video content encoded with multiple codecs according to a fixed bitrate ladder, the model will choose among three available policies, i.e., fetch, transcode, or skip, the best option to handle the representations. We compare the proposed model with traditional approaches used in the industry. The experimental results show that our proposed method can reduce the additional latency by up to 23% and the streaming costs by up to 78%, besides improving the visual quality of the delivered segments by up to 0.5 dB, in terms of PSNR.

MCOM architecture overview.