An Improved DC Recovery Method from AC Coefficients of DCT-Transformed Images

Motivated by the work of Uehara et al. [1], an improved method to recover DC coefficients from AC coefficients of DCT-transformed images is investigated in this work, which finds applications in cryptanalysis of selective multimedia encryption. The proposed under/over-flow rate minimization (FRM) method employs an optimization process to get a statistically more accurate estimation of unknown DC coefficients, thus achieving a better recovery performance. It was shown by experimental results based on 200 test images that the proposed DC recovery method significantly improves the quality of most recovered images in terms of the PSNR values and several state-of-the-art objective image quality assessment (IQA) metrics such as SSIM and MS-SSIM.Comment: 6 pages, 6 figures, ICIP 201

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Secure Computing with the MPEG RVC Framework

Recently, the ISO/IEC standardized a dataflow-programming framework called Reconfigurable Video Coding (RVC) for the specification of video codecs. The RVC framework aims at providing the specification of a data-driven system at a high abstraction level so that the functionality (or behaviour) of the system become independent of the implementation details. The idea is to specify a system so that only the functionality (or behaviour) of the algorithms are explicitly expressed via their input and output interfaces, and the implementation choice (conversion of implementation-independent abstract solution to implementation-dependent solution) can then be made only once specific target platform has been chosen. With this approach, one abstract design can be used to automatically create implementations towards multiple target platforms. Although RVC was developed with the perspective of video codecs, it can serve as a general-purpose framework for domains beyond multimedia codecs. This motivated us to research: 1) if and how RVC can benefit other domains like secure computing? 2) can applications in other domain help evolve RVC to make it an even more general and useful solution?In this thesis, we report our investigations on applying the methodology, standardized by the MPEG RVC framework, to develop secure computing systems from the domains of cryptography and multimedia security, leading to the conclusion that the attractive features of the RVC approach can successfully be applied to another field than multimedia coding.In order to study if the RVC is a good choice for the development of secure computing systems, we started our work with the development of a Crypto Tools Library (CTL) based on RVC, which covers a number of widely used ciphers and cryptographic hash functions such as AES, Triple DES, ARC4 and SHA-2. By combining CTL with video tool library (a standard library defined by the RVC standard), a non-standard RVC-based H.264/AVC encoder and a non-standard RVC-based JPEG codec, we further demonstrated the benefits of using RVC to develop different kinds of multimedia security applications, which include joint multimedia encryption-compression schemes, digital watermarking and image steganography in JPEG compressed domain. Moreover, two security protocols were also implemented and deployed to demonstrate how one can do hardware/software co-design easily with RVC. Our performance benchmarking results on the RVC-based AES and SHA-2 implementations in both C and Java and on the above mentioned multimedia security applications revealed that the automatically generated implementations can achieve a comparable performance to some manually-written reference implementations. Since RVC also naturally supports parallelization of applications on multi-core systems, we also conducted a comparative study to evaluate the amount of performance gain cryptographic and multimedia security applications can achieve on multi-core platforms.In a nutshell, our study has shown that RVC can be used as a general-purpose implementation-independent development framework for diverse data-driven applications with different complexities and highlighted some areas where RVC requires some improvements to become more and more general-purpose. These areas include 1) investigating better ways to support human interactions in dataflow programming paradigm (e.g., supporting event handlers by modelling humans as a special functional units), 2) supporting code generation for many-core systems, 3) enhancement of code generation and simulation tools to support large-scale RVC systems (with thousands to millions of components), and 4) enhancement of design space exploitation tools to support automated parallelization of RVC applications

Energy and distortion analysis of video compresion schemes for wireless video sensor networks

Wireless Video Sensor Networks (WVSNs) - a type of WSNs - comprise of sensor nodes that can capture, process and communicate video frames. The battery powered sensor nodes have limited hardware resources while video processing and communication are resource intensive tasks i.e., require high- end processors, large memory and bandwidth. Video encoding is a popular method used to reduce the communication overhead but being an inherently complex process it results in higher com- putational energy-drain on video sensor nodes. This establishes an interesting computation-communication tradeoff for energy efficient video communication (encoding and transmission) in WVSNs. In this paper, we study this computation-communication tradeoff under Intel-imote2 based single-hop and multi-hop video sensor networks testbed by empirically evaluating selected imple- mentations of the MPEG-4 (Part 2) and H.264/AVC encoders. The analysis has been carried out to characterize the performance of encoders in terms of energy efficiency, compression efficiency and video distortion. The experimental results show that in single-hop WVSNs, MPEG-4 is energy efficient over H.264 whilst in multi- hop WVSNs, H.264 is energy efficient over MPEG-4

Performance Benchmarking of RVC based Multimedia Specifications

The Reconfigurable Video Coding (RVC) framework was developed to specify video codecs as abstract and as much as possible implementation-agnostic descriptions, which are supposed to be processed by code synthesis tools to automatically generate implementations for different target languages and platforms. However, there are still questions about if the run-time performance of these automatically generated RVC-based codec implementations is good enough to run efficiently on different target platforms. In this paper, we present a performance benchmarking study on various RVC-based multimedia specifications (H.264/AVC and JPEG codecs, and four multimedia security systems based on these codecs), which covers the following two aspects: 1) the run-time performance against their corresponding non-RVC implementations on a single-core machine; 2) the performance gain these RVC-based implementations on a dual-core machine. Based on our benchmarking results, which show that RVC-based multimedia implementations achieve adequate/acceptable performance, we conclude that RVC has the potential to become a general-purpose but still performance-efficient development framework for many application domains

Secure Computing with the MPEG RVC Framework

Recently, ISO/IEC standardized a dataflow-programming framework called Reconfigurable Video Coding (RVC) for the specification of video codecs. The RVC framework aims at providing the specification of a system at a high abstraction level so that the functionality (or behavior) of the system become independent of implementation details. The idea is to specify a system so that only intrinsic features of the algorithms are explicitly expressed, whereas implementation choices can then be made only once specific target platforms have been chosen. With this system design approach, one abstract design can be used to automatically create implementations towards multiple target platforms. In this paper, we report our investigations on applying the methodology standardized by the MPEG RVC framework to develop secure computing in the domains of cryptography and multimedia security, leading to the conclusion that the RVC framework can successfully be applied as a general-purpose framework to other fields beyond multimedia coding. This paper also highlights the challenges we faced in conducting our study, and how our study helped the RVC and the secure computing communities benefited from each other. Our investigations started with the development of a Crypto Tools Library (CTL) based on RVC, which covers a number of widely used ciphers and cryptographic hash functions such as AES, Triple DES, ARC4 and SHA-2. Performance benchmarking results on the RVC-based AES and SHA-2 implementations in both C and Java revealed that the automatically generated implementations can achieve a comparable performance to some manually-written reference implementations. We also demonstrated that the RVC framework can easily produce implementations with multi-core support without any change to the RVC code. A security protocol for mutual authentication was also implemented to demonstrate how one can build heterogeneous systems easily with RVC. By combining CTL with Video Tool Library (a standard library defined by the RVC standard), a non-standard RVC-based H.264/AVC encoder and a non-standard RVC-based JPEG codec, we further demonstrated the benefits of using RVC to develop different kinds of multimedia security applications, which include joint multimedia encryption-compression schemes, digital watermarking and image steganography in JPEG compressed domain. Our study has shown that RVC can be used as a general-purpose implementation-independent development framework for diverse data-driven applications with different complexities

Energy Efficient Video Compression for Wireless Sensor Networks

Wireless video sensor networks are anticipated to be deployed to monitor remote geographical areas. To save energy in bit transmissions/receptions over a video sensor network, the captured video content needs to be encoded before its transmission to the base station. However, video encoding is an inherently complex operation that can cause a major energy drain at battery-constrained sensors. Thus a systematic evaluation of different video encoding options is required to allow a designer to choose the most energy-efficient compression technique for a given video sensing application scenario. In this paper, we empirically evaluate the energy efficiencies of predictive and distributed video coding paradigms for deployment on real-life sensor motes. For predictive video coding, our results show that despite its higher compression efficiency, inter video coding always depletes much more energy than intra coding. Therefore, we propose to use image compression based intra coding to improve energy efficiency in the predictive video coding paradigm. For distributed video coding, our results show that the Wyner-Ziv encoder has consistently better energy efficiency than the PRISM encoder. We propose minor modifications to PRISM and Wyner-Ziv encoders which significantly reduce the energy consumption of these encoders. For all the video encoding configurations evaluated in this paper, our results reveal the counter-intuitive and important finding that the major source of energy drain in WSNs is local computations performed for video compression and not video transmission