Research Of Real-time Transmission Technology Of Streaming Media For Sample Image Of Electronic Probe

With the rapid development of the computer technology and network communication technology, national large-scale scientific instruments networked-sharing has achieved some results, but at present there are still the prominent problems of large scientific instruments in general lack of resources, uneven distribution and low utilization rate. Large-scale scientific instruments networked-sharing needs to further promote. Electronic Probe is a widely used large scientific instrument, and sample image analysis during the experiment of such instruments is an important part. Sample images of electronic probe are real-time transmitted to remote users in video stream means remote workers can observe the real-time video of sample images not to the site, and it is of great significance to electronic probe networked-sharing.Based on the analysis of the development of the domestic and international of scientific instruments such as electron probe and streaming media, we find there are some problems in the remote transmission and coding of sample image. In coding, most of the sample image transmitted in image; sample image transmitted in video using H.264 video encoding technology is rarely used. In data transmission, the main used transport protocol is TCP Protocol and RTP (Real-time Transport Protocol) suitable for real-time transmission of streaming media is not found in the literature. Purpose of this thesis is to make real-time transmission technology of streaming media be applied to the sample image remote transmission of electron probe, and to improve the performance of the sample images remote transmission.Based on DirectShow streaming media technology development platform and VC++6.0 development platform, using COM components, network communication, video coding and other technologies, this thesis develops a real-time transmission scheme for sample image video stream of electron probe, and implements the server and client software.The server is responsible for capturing the sample image video stream of electron probe, coding, sending and responding to client requests. Specific functions of each module are achieved as following:(1)Acquisition Module of Sample Image Video StreamAccording to the characteristic of the sample image video source of electron probe, the RGB signal of sample image can be captured by VGA video capture card, by video capture Filter, sample image video can be acquired from VGA video capture card.(2)Coding Module of Sample Image Video StreamFor cutting down video bit rate of transmission and realizing real-time transmission to multi-client under the conditions of the limited bandwidth, highly active coding algorithm is needed for the compression of sample image. By studying with open source X264 in accordance with H.264 video coding standard, and optimizing the encoder, an X264 coding Filter is designed realizing high compression of sample image.(3)Sending Module of Sample Image Video StreamFor improving the real-time of remote transmission of sample image, a protocol which uses high transmission rate is needed. By studying with real-time transmission protocol which is fit for streaming media transmission, and JRTPLIB based on RTP lib which is open source, a send Filter based on RTP is designed realizing X264 encoding data packing and sending according to RFC3984.(4)Management Module of ServerManagement module of Server is responsible for accepting and rejecting the connection request from clients, starting remote video real-time transmission thread and realizing functions of adding and deleting clients.The client is responsible for receiving the sample image video stream, decoding and display, and connecting to the server and other functions. Specific functions of each module are achieved as following:(1)Receiving Module of Sample Image Video StreamVideo stream receiving module is used to receive the video stream sended from server. The buffer pool technology is utilized for real-time receiving of RTP data packets, making it unpacked and recombined into NAL units, and transmitting the NAL units to the video decoding module.(2)Decoding Module of Sample Image Video StreamDecoding module is used to real-time decode the NAL units, sended by receiving module of the video, through calling H.264 decoding library, and send it to display module of sample image video stream.(3)Display Module of Sample Image Video StreamDisplay module is used to receive the video data compressed by decoding module, and call Rendering Filter of DirectShow for real-time display.(4)Management Module of ClientsManagement module is responsible for sending a connection request to the server, starting the video connection to receive real-time threads when server permits, and disconnecting the connection to the server to stop receiving the video stream.This thesis focuses on the H.264 video coding standard, RTP Protocol, and the RTP payload format for H.264. Several open-source library are utilized for the H.264 coding of the sample image video, and RTP data transmission of the coding data according to RFC3984 standard, as well as H.264 video decoding and display. Transmission of real-time and stability is realized via local area network testing. H.264 video coding standard and RTP is applied to the remote transmission of sample image video of electron probe, and multi-client real-time transmission is achieved in this thesis, making a step forward to the research of real-time transmission of sample image video of electron probe.