Distribution and Rendering of Real-Time Scene Based on the Virtual Reality System - Advances in Image and Graphics Technologies - page 195

of video source client, code server, streaming media server, data server, content dis-
tribution server, virtual scene server and ViWo client. The video source is divided
into fixed position monitor video source and mobile virtual reality client. The coding
server is responsible to code the raw data from the fixed position camera and transmit
code data to media server. As for the mobile devices, the local coding is used because
of the bandwidth limit. The coded data is sent to the media server which is responsi-
ble for packing the live stream, storing data flow and dispatching data to the edge
server node. At the same time, all the streaming resource is registered on the virtual
scene server through communication with the media server. The client obtains re-
source list from the virtual scene server and then requests streaming flow from the
edge content delivery server. When the edge content delivery server is requested for
data flow, resource is checked if existed in the local cache. If the data is existed in the
local, data will be directly read and then sent to client. Otherwise, the edge content
delivery server will request data from the media server. This way Request delay and
stress to backbone is reduced for a large number of requests.

Fig. 1. The overall system design

3.1 Design for Streaming Media Server Module

As mentioned in the overall architecture above, the streaming media server in the
system is responsible for data reception, stream Package, preservation and distribu-
tion. The video frame encoded can be received according to a uniform protocol and it
can also increase the expansion sexual system access of the device. The coded data
flow will be packed to flash video tag. It's important to indicate that the flash video
tag is organized to a Group of Picture (GOP) structure that is started at key frame and
maintains about a size of 40 frames. The index file that records GOP file location and
timestamp is saved in the memory to response to client's request for flash video
through the protocol of RTMP [10] . Similar to the protocol RTMP, the encoded frame
also needs to be packed to MPEG-TS slice, the file of m3u8 format that records the