M. Emoto

M. Hasegawa

National Institute for Fusion Science (NIFS-Repository)

QUEST experiment is executed with thecollaboration of many universities in Japan, and thescientists are remotely taking part in this experiment fromvarious places in Japan. For example, the data acquisitionand archiving system is operating in NIFS which locatesabout 1,000 km apart from the experiment site, and thescientists can retrieve to analyze the acquired in their roomwithout visiting the site1).However, in order to realize smooth remotecooperation, they have to know the situation in theexperiment site in real time, and the voice and video playimportant roles. Therefore, the authors have installed a webcamera (Panasonic BB-HCM715) in the control room ofthe experiment site, and the user could view the situation ofthe control room while they stay in their room. However,because the web camera is not so powerful that the numberof the connections is limited and it cannot send the videoimages to all the participants.Therefore, the authors have developed a relay serverto redistribute the video images retrieved from the webcamera to the clients. Fig.2 shows the overview of thescheme. The web camera can be controlled from the webbrowser using CGI (Common Gateway Interface), and itsAPI (Application Program Interface) is open to use. Usingthe API, the relay server connects to the web camera andreceives the video images as Motion JPEG (MJPEG).When a client connects to the relay server, the relay servercopies the frames of the original image and sent them to theclient. Different from other video format, such as MPEG-2or MPEG-4, each frame of MJPEG is independent and it iseasy to copy the current frame image without calculatingfrom the previous frames.Using a relay server, the video can be sent to themore clients than the web camera. However, as the numberof the client increases, the relay server cannot handle all ofthe clients. This is because the connection between theclient and server is unicast, or one-to-one communication,and the server and the network loads are proportional to thenumber of the connections. On the other hand, there is atechnology called IP multicast. Using IP multicast, datapackets are sent to the multiple clients at same time, and theload doesn’t depend on the number of the clients. Therefore,the authors considered IP multicast as a promisingtechnology for the remote participation, feasibility of IPmulticast to send video images has been studied.In order to send the video images using IP multicast,the author have tested a network camera that had a GigEVision interface. GigE Vision is a standard interface tocontrol the network attached video camera. In order todevelop an application to control GigE Vision application,A&B Software’s Active GigE was adopted. It is an Active-X component, and the developer can incorporate it intotheir own software just by drag-and-drop. However,evaluating the performance, the authors found theapplication was not fast enough to send the smooth videoimages. Therefore, to enhance the performance, the authorshave been studying other options to use GigE Vision.1) Nakanishi, H. et al.: Fus. Eng. Des., 82, (2007) 1203Fig.1 web camera installed in the control roomMJPEGFig 2. Relay Server538§60. Study of Video Monitoring System for Remote ParticipationEmoto, M.,  Hasegawa, M. (Kyushu Univ.)

Study of Video Monitoring System for Remote Participation

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