Distribution and Rendering of Real-Time Scene Based on the Virtual Reality System - Advances in Image and Graphics Technologies - page 196

path of slice file is transported through the protocol of HLS [11] . At the same time,
encoded data is stored in the local data server. If the live streaming is finished, media
data saved in the data server can also be requested by the client.

Fig. 2. Modules of media server

Table 1. Request method for RTMP and HLS protocol

URI Explanation

rtmp://ip:port/chanel/datarate.flv/live Flash live stream on specified

channel and datarate

rtmp://ip:port/video/filename.flv&dr=datarate Flash Video stream on specified

datarate

http://ip:port/chanel/datarate.ts/live Mpeg-tsLive stream on specified

channel and datarate

http://ip:port/video/filename.m3u8&dr=datarate Mpeg-ts video stream on speci-

fied datarate

3.2 Data Caching and Load Balancing for Distribution Server

When the edge distribution server is requested by client, the cache is checked if the
data exists in the local cache. In the virtual reality system, if the request is hit on the
local server, the data flow will be directly sent to client. Otherwise, the edge distribu-
tion server will turn to the central media server to request data. The requested data
flow is saved in the local server so that the edge distribution server doesn't need to
request data if next client requests the same data flow. In case there is no enough sto-
rage space for the cache of the data flow in the local server, the resource that is not
recently used will be replaced. Replacement policy in the virtual reality system is
more complicated than the traditional content distribution network because the data is
continuously requested within the region. The visited frequency of Virtual scene, last
request time of media streaming and times of recently visited are all key factors