Study of No-Reference Video Quality Metrics for HEVC Compression, Journal of Telecommunications and Information Technology, 2016, nr 1

The paper proposes a No-Reference (NR) quality assessment measurement originally developed for H.264, used for High Efficiency Video Coding (HEVC). In particular, authors present an investigation of NR metrics to objectively estimate the perceptual quality of a set of processed video sequences. The authors take into account typical distortions introduced by the block-based coding approaches like HEVC codec. The underlying processing used for the quality assessment considers the blockiness caused by the boundaries of each coded block and the blurring as a lack of spatial details. The correlation between the NR quality metrics and the well-known and most widely used objective metric, the Video Quality Model (VQM), is performed to validate the quality prediction accuracy based on the provided scores. The Pearson correlation coefficients obtained stand for promising results for different types of videos

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Perceptually Adaptive Lagrangian Multiplier for HEVC Guided Rate-Distortion Optimization

International audienceRecent video coding standards typically use the Rate-distortion optimization (RDO) method, which is essential to appropriately perform mode decisions during encoding process. The newest standard High Efficiency Video Coding (HEVC) introduces complex encoding structures and strong dependency between coding units. Particularly, the Lagrangian multiplier is a primary factor in RDO procedure, which directly affects the ratedistortion (R-D) performance and is defined for an entire video frame. This paper proposes a novel approach for perceptually guiding the RDO process in HEVC. The reference encoder does not consider effectively the perceptual characteristics of the input video and further, the visual sensitivity of each coding tree unit (CTU) in a frame. Inspired by the mechanisms of the human visual system, the proposed solution is a CTU-level adjustment of Lagrangian value based on a set of complementary perceptual features. The proposed scheme concerns important visual information of a CTU and its temporal dependency with adjacent blocks. Feature extraction is implemented in the frequency domain using efficient spatio-temporal analysis. In our experiments, we opted a perceptual Mean Squared Error (MSE) metric and Structural Similarity (SSIM) index. According to perceptual MSE metric, the BD-rate savings using the Bjontegaard delta measurements, were fairly convincing over the state-of-theart HEVC software HM16.12; 4.41% and 6.14% for Random Access (RA) and Low Delay (LD) encoding settings, respectively. Using SSIM, the BD-Rate achieved 6.95% and 9.86% for RA and LD settings, respectively. The proposed method further demonstrates a superior R-D performance over a compared approach adopting a similar scheme

Towards Perceptually Guided Rate-Distortion Optimization For HEVC

International audienceThis paper proposes a novel approach for perceptually guiding the rate-distortion optimization (RDO) process within the High Efficiency Video Coding (HEVC) standard. The reference codec does not consider effectively the perceptual characteristics of the input video and further, the particular perceptual sensitivity of each coding tree unit (CTU) inside a frame. The corresponding frame-level Lagrangian multiplier depends only on the quantization parameter. Inspired by the mechanisms of the human visual system, the proposed solution is a CTU-Ievel adjustment of the standard Lagrangian value based on a set of complementary measured features. These measures rely on the spatial and temporal analysis of the current CTU in the frequency domain. Based on perceptual quality indices and Bjontegaard delta measurements, over several resolutions of tested video sequences, the proposed method demonstrates a promising coding performance according to the rate-distortion compromise

BLIND IMAGE QUALITY ASSESSMENT IN THE COMPLEX FREQUENCY DOMAIN

International audienceIn this paper, we propose a no-reference (NR) image quality assess- ment (IQA) metric that operates in the complex frequency domain. A set of features are developed to model the natural scene statistics without depending on any specific visual distortion. The proposed approach relies on a statistical analysis of the transformed image, involving the importance of the phase and magnitude provided by the underlying complex coefficients. We further investigate the cor- relation between the different image spatial-frequency resolutions, i.e., representations under different scales and orientations in order to extract the directional features and energy distributions of an im- age. The validation of the NR metric is performed on a variety of challenging IQA databases and the obtained results show good cor- relation with subjective scores. Besides, the obtained performance is highly competitive compared to the top-performing NR IQA met- rics

Perceptual Video Content Analysis and Application to HEVC Quantization Refinement

International audienceIn this paper, we propose a set of perceptual features aiming to consistently describe the visual information. The measurement is performed in the complex frequency domain according to human visual system (HVS) mechanisms. The aim is to explore the performance of these features in a video coding scheme. Particularly, we consider the High Efficiency Video Coding (HEV C) standard as it introduces several efficient tools along with new coding structures. The quantization parameter (QP) is an essential factor that affects the coding performance and has a relationship the Lagrangian multiplier. Based on extracted measures, a perceptual factor is proposed to adjust the Lagrangian multiplier and subsequently, the QP is refined over the adjusted value. The achieved BD-rate savings over several resolutions of video sequences, using the Bjontegaard metric, show the promising coding efficiency of the proposed method with regard to an adequate rate-distortion (R-D) compromise. We opted for the Structural SIMilarity (SSIM) metric to carry out a perceptual R-D comparison. The R-D curves demonstrate that the obtained bitrate savings are associated to convenient quality measures, compared to HEVC anchor and a state-of-the-art QP refinement model

Nephrotic syndrome and Guillan-barre syndrome: A rare association in child

Only few cases of nephrotic syndrome associated with Guillain-Barre Syndrome (GBS) have been reported in the adult and pediatric literature. A 3-year-old boy was initially admitted to our hospital following five days of progressive weakness of his extremities, fatigue, right leg pain and numbness. There was no past history of renal or neurological disease. Cerebro-spinal fluid studies showed a protein level of 92 mg/dL and a white cell count of 1 per high-power field. The diagnosis of GBS was verified with a nerve conduction velocity test as well as. The GBS symptoms improved gradually on intravenous immunoglobulin. Three weeks later, he deve-loped severe proteinuria and edema; laboratory investigation showed nephrotic syndrome which responded to steroid therapy. Renal biopsy showed minimal change glomerulonephritis. He re-mained free of proteinuria during his 20 months of follow-up

Multi-Institutional Breast Cancer Detection Using a Secure On-Boarding Service for Distributed Analytics

The constant upward movement of data-driven medicine as a valuable option to enhance daily clinical practice has brought new challenges for data analysts to get access to valuable but sensitive data due to privacy considerations. One solution for most of these challenges are Distributed Analytics (DA) infrastructures, which are technologies fostering collaborations between healthcare institutions by establishing a privacy-preserving network for data sharing. However, in order to participate in such a network, a lot of technical and administrative prerequisites have to be made, which could pose bottlenecks and new obstacles for non-technical personnel during their deployment. We have identified three major problems in the current state-of-the-art. Namely, the missing compliance with FAIR data principles, the automation of processes, and the installation. In this work, we present a seamless on-boarding workflow based on a DA reference architecture for data sharing institutions to address these problems. The on-boarding service manages all technical configurations and necessities to reduce the deployment time. Our aim is to use well-established and conventional technologies to gain acceptance through enhanced ease of use. We evaluate our development with six institutions across Germany by conducting a DA study with open-source breast cancer data, which represents the second contribution of this work. We find that our on-boarding solution lowers technical barriers and efficiently deploys all necessary components and is, therefore, indeed an enabler for collaborative data sharing