A Parallel implementation of an mpeg-2 encoder using message-passing

The days of film are waning as digital cameras and digital video cameras are becoming commonplace. Uncompressed digital video can consume large amounts of space, making it cumbersome to store efficiently. A method of video compression was developed by the Motion Pictures Expert Group (MPEG), and is now an international standard with the International Organization for Standardization (ISO). This thesis deals with the MPEG-2 Video standard, ISO/IEC 13818-2 [2]. The goal of this thesis is to explore the applications of MPEG-2 encoding in a parallel processing paradigm. To achieve this, a sequential MPEG-2 software encoder was obtained from the MPEG Software Simulation Group (MSSG) [18] and modified to be run, in parallel, on a cluster of single-processor Linux workstations using the Message Passing Interface (MPI) [11, 10, 3]. A multi-threaded pipeline of the encoding process was created using Pthreads [6]. The resulting pipelined parallel encoder has been shown to produce compliant elementary MPEG-2 bitstreams for progressive video sequences. Results of simulation showed that the parallel encoder always performed better than the sequential version as the number of processors scaled. However, it did not exhibit the ideal linear speedup that all parallel programs aim to achieve. This is due to the program executing on a set of resources not ideal for the multi-threaded pipeline. The ensuing chapters will provide the motivation for this work, and an overview of MPEG in addition to parallel processing and programming. Also forthcoming will be how it was achieved and the results produced. Supplementary applications of this work will also be discussed

Transport of video over partial order connections

A Partial Order and partial reliable Connection (POC) is an end-to-end transport connection authorized to deliver objects in an order that can differ from the transmitted one. Such a connection is also authorized to lose some objects. The POC concept is motivated by the fact that heterogeneous best-effort networks such as Internet are plagued by unordered delivery of packets and losses, which tax the performances of current applications and protocols. It has been shown, in several research works, that out of order delivery is able to alleviate (with respect to CO service) the use of end systems’ communication resources. In this paper, the efficiency of out-of-sequence delivery on MPEG video streams processing is studied. Firstly, the transport constraints (in terms of order and reliability) that can be relaxed by MPEG video decoders, for improving video transport, are detailed. Then, we analyze the performance gain induced by this approach in terms of blocking times and recovered errors. We demonstrate that POC connections fill not only the conceptual gap between TCP and UDP but also provide real performance improvements for the transport of multimedia streams such MPEG video

ベクトル型スーパーコンピュータのためのメモリ指向型最適化戦略に関する研究

Tohoku University小林広明課

Progress in Landslide Research and Technology, Volume 1 Issue 1, 2022

This open access book provides an overview of the progress in landslide research and technology and is part of a book series of the International Consortium on Landslides (ICL). The book provides a common platform for the publication of recent progress in landslide research and technology for practical applications and the benefit for the society contributing to the Kyoto Landslide Commitment 2020, which is expected to continue up to 2030 and even beyond to globally promote the understanding and reduction of landslide disaster risk, as well as to address the 2030 Agenda Sustainable Development Goals

On finite-difference time-domain sub-gridding algorithms for efficient modelling of ground-penetrating radar

Introducing finely detailed models of GPR antennas into finite-difference time-domain forward models often results in large computation overheads. In many cases the solution becomes intractable. The overhead increases due to the larger size of the model. This is as a result of the increase in spatial and temporal sampling required by the antenna geometry and the conditionally stable nature of the FDTD method respectively. This problem is compounded for predictive applications where the model-parameter space is non-linear and solutions derived from heuristic optimisation schemes require multiple simulation runs. To overcome this issue this work presents a novel sub-gridded FDTD approach to model for the first time realistic descriptions of GPR antennas in half-space type problems. The sub-gridding is performed using Huygens Sub-Gridding (HSG). This method does not limit the sub-gridding ratio and therefore a wide range of applications are possible. Also, a new method is developed called the Switched Huygens Sub-Gridding (SHSG). This method significantly improves upon the stability of the HSG, and has a superior computational performance. In addition, it is simpler to implement and optimise its performance owing to the simple nature of its stabilisation mechanism. In resonant problems, stability is shown to increase by a factor of 5.6. And computational speed is increased by a factor of 28 and 17 for a realistically modelled antenna over a buried water-filled plastic pipe using the SHSG and HSG respectively. Furthermore, a novel effective permittivity scheme is developed for Debye media that can be applied to dielectric-dispersive and dispersive-dispersive interfaces. This technique resolves the issue of reduction in accuracy at material interfaces outside sub-gridded regions. And it can be used to increase the accuracy of the FDTD method for dispersive materials generally. The relative error is reduced from 5% to 0.6% for the field transmitted and received by a Hertzian dipole over a dispersive half-space containing a water pipe. In addition, analytical results confirm a significant increase in accuracy for a range of soil types. Moreover, these advances are implemented in open-source package gprMax and will be made available in a forthcoming release. The implementations take advantage of parallel architectures and are therefore very efficient. In addition, these advances are general and can be applied to several problems in GPR and to many problems in computational electrodynamics

Exploring Processor and Memory Architectures for Multimedia

Multimedia has become one of the cornerstones of our 21st century society and, when combined with mobility, has enabled a tremendous evolution of our society. However, joining these two concepts introduces many technical challenges. These range from having sufficient performance for handling multimedia content to having the battery stamina for acceptable mobile usage. When taking a projection of where we are heading, we see these issues becoming ever more challenging by increased mobility as well as advancements in multimedia content, such as introduction of stereoscopic 3D and augmented reality. The increased performance needs for handling multimedia come not only from an ongoing step-up in resolution going from QVGA (320x240) to Full HD (1920x1080) a 27x increase in less than half a decade. On top of this, there is also codec evolution (MPEG-2 to H.264 AVC) that adds to the computational load increase. To meet these performance challenges there has been processing and memory architecture advances (SIMD, out-of-order superscalarity, multicore processing and heterogeneous multilevel memories) in the mobile domain, in conjunction with ever increasing operating frequencies (200MHz to 2GHz) and on-chip memory sizes (128KB to 2-3MB). At the same time there is an increase in requirements for mobility, placing higher demands on battery-powered systems despite the steady increase in battery capacity (500 to 2000mAh). This leaves negative net result in-terms of battery capacity versus performance advances. In order to make optimal use of these architectural advances and to meet the power limitations in mobile systems, there is a need for taking an overall approach on how to best utilize these systems. The right trade-off between performance and power is crucial. On top of these constraints, the flexibility aspects of the system need to be addressed. All this makes it very important to reach the right architectural balance in the system. The first goal for this thesis is to examine multimedia applications and propose a flexible solution that can meet the architectural requirements in a mobile system. Secondly, propose an automated methodology of optimally mapping multimedia data and instructions to a heterogeneous multilevel memory subsystem. The proposed methodology uses constraint programming for solving a multidimensional optimization problem. Results from this work indicate that using today’s most advanced mobile processor technology together with a multi-level heterogeneous on-chip memory subsystem can meet the performance requirements for handling multimedia. By utilizing the automated optimal memory mapping method presented in this thesis lower total power consumption can be achieved, whilst performance for multimedia applications is improved, by employing enhanced memory management. This is achieved through reduced external accesses and better reuse of memory objects. This automatic method shows high accuracy, up to 90%, for predicting multimedia memory accesses for a given architecture