A Mobile Real-time Video System Using RTMP

发布时间：2018-04-19 18:22

 
Abstract—This paper introduces a mobile real-time video system which is different from other existing real-time video system that is mainly based on wired computers. The system proposed in paper is basically designed to enable users under wireless circumstances to publish what they are capturing with their mobile devices and also watch what others are capturing. The system mainly contains mobile devices with a Flex [1] client application on them, a media server which handles live streams using RTMP [2] (Real-Time Messaging Protocol), and a web server which used to deal with HTTP requests.
 
Keywords- real-time; mobile; Flex; RTMP
 
I.      INTRODUCTION
Today there are many real-time video system using various technologies and protocols. People can watch, for example, live NBA games not only in front of TV, but also in front of a computer. However, there is a trending that mobile devices are becoming more and more important because their mobility enables people to use them whenever and wherever they need them. Besides, in existing real-time video systems, users are usually receivers who receive what is provided, rather than providers who are able to share precious moments to others in a real time way.
This paper comes up with a real-time video system that enables people to not only watch live video with their mobile devices but also be providers who make their moments live and share with friends and families by using mobile devices. There are mainly three parts in this system:
(1)   Media server: Media server is a server that deals with live video streaming including input streaming which comes from providers’ mobile devices and output streaming distributed to receivers who request live videos. The choice of media server is fundamentally based on the protocol used in this system to transmit live video streaming. There are many protocols for streaming media, such as RTP/RTCP [3], RTSP [4], RTMP, and so on. Because the protocol chosen here is RTMP, we use Red5 [5] which is primarily designed for RTMP as our media server.
(2)   Flex client application: The Flex client application mentioned here is software application installed on mobile devices and used as client for users to communicate with media server and web server. The reason we use Flex which is provided by Adobe to develop the client is that it has convenient interfaces of video encoding and transmission when  the  video  file format is  FLV and  the  transmission protocol is RTMP (FLV and RTMP are also developed by Adobe).
(3)   Web server: Web server is a server that deals with HTTP requests which contains commands of users, such as signing in, getting live video list, and so on. Also web server is in charge of managing database according to requests from users.
This article is organized as follows: Section II addresses about the related work. Section III addresses the system architecture and shows each part of the system in details. Section IV addresses the system implementation to present the whole process of how the system works in details. Section V draws conclusions and introduces some future work.
II.     RELATED WORK
 
A.    Protocols
There are mainly two popular kinds of basic protocols used for streaming media today, (1) RTP/RTCP which can work on both UDP and TCP but mainly UDP, and (2) RTMP which only works on TCP.
RTP (Real-time Transport Protocol) defines a standardized packet format for delivering audio and video over IP networks [6]. RTP is primarily designed for video teleconference applications. Now it is widely used in television services, web-based push-to-talk and telephony. For RTP, RTCP works as a controller which monitors transmission statistics and quality of service (QoS) and helps to synchronize multiple streams. Because RTP is mainly based on UDP which is simple and fast but lack control over congestion of network, there are many researches dealing with congestion control of RTP using RTCP. And as its unfair competition with TCP streams in bandwidth, many kinds of TCP-friendly protocols emerge to enable media streams based on UDP to be smoother and compete more fairly with TCP streams, such as TFRC [7] (TCP-Friendly Rate Control).
RTMP is a TCP-based protocol for streaming audio, video, and data over the Internet smoothly between a Flash player and a server. As it is based on TCP, the congestion control is much better than RTP based on UDP.
B.    Applications
The most common applications using streaming media technology are video teleconference, VOD (Video on Demand), live video, and video call.
…..
 
V.    CONCLUSION AND FUTURE WORK
This paper presents a mobile real-time video system using RTMP. This system mainly intends to enable users to publish live videos and watch live videos of others with mobile devices. Also users can watch live videos with computers on website we built. The propose of designing this kind of system is different from both video calls which happens between only two persons and watching live broadcast in front of a computer which lacks of mobility and individuality. Rather, this system basically realizes that people can share things immediately whenever and wherever they want in form of live video if they have access to network.
In future work, firstly, as this system is a client-server system, the bottleneck of system mainly underlies in the capability of media server, that is, when the number of user grows to a level that surpasses the capability of media server, media server may run down. Secondly, as bandwidth is limited, especially the bandwidth for streams from media server out to users, we need to do further research on video encoding to improve compression ratio of video data before being transmitted. Thirdly, feedback from users may contain some advisable suggestions and some bugs, according to which we will improve our system.
 
ACKNOWLEDGMENT
Wireless Ubiquitous Business Environment, Architecture, Key Technology Research and Demonstration Based on Web (No. 2012ZX03005008); the Fundamental Research Funds for the Central Universities
 
REFERENCES
[1]   Flex introduction. http://www.adobe.com/pr oducts/flex.html
[2] RTMP Specification 1.0. http://wwwimages.adobe.com/www.adobe.c om/content/dam/Adobe/en/devnet/rtmp/pdf/rtmp_specification_1.0.p df.
[3] RFC 3550, Standard 64, RTP: A Transport Protocol for Real-Time Applications.
[4] RFC 2326, Real Time Streaming Protocol (RTSP), IETF, 1998. [5]    Red5 introduction. http://www.red5.org/.
[6]  http://en.wikipedia.org/wiki/Real-time_Transport_Protocol.
[7] RFC 5348, TCP Friendly Rate Control  (TFRC):  Protocol Specification.
[8] Wichian Premchaiswadi, Anucha Tungkasthan, Nipat Jongsawat. Enhancing Learning Systems by using Virtual Interactive Classrooms and Web-based Collaborative Work. IEEE EDUCON Education Engineering 2010¬—The Future of Global Learning Engineering Education.
[9]   http://live.video.sina.com.cn/room/nba/.
[10]  www.skype.com/.
[11] Adobe Air introduction. http://www.adobe.com/products/air.html.



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