The media streaming server technology have been developed in the recent past using free software and open source approaches. But commercial approaches are preferred by certain multimedia big enterprises. These enterprises dominate the mobile media delivery business. For this reason we think it is interesting to discover the main characteristics of the principal commercial platforms to deliver mobile video streaming to mobile devices and its main key features: Media and delivery components. We will give our vision on: Real Networks’ Helix Media delivery components based on RTSP and Microsoft’s IIS Media Services based on HTTP. The aim of this book chapter is to provide detailed insight into these different streaming approaches and how these platforms and protocols aid in building flexible streaming applications for mobile devices. A comparison among these approaches is also provided and also we present the delivery of video streaming to Apple mobile devices in the two commercial approaches.
TopIntroduction
The last ten years has seen an explosion of new mobile devices: from handhelds to smart telephones. All of them able to receive High Definition (HD) video from a video Server (live video or stored video). The techniques the media servers used to deliver information to the mobile devices is name live, streaming or progressive download. Each technique is implemented by a particular protocol and several delivery techniques in the Server. We center our attention in the protocol and Server technology for delivery information to mobile devices.
The most difficult task of streaming audio and video over a network is maintaining a continuous presentation to the user in a highly changeable environment. Buffering is caused when the client runs out of data in the buffer and must wait for more to arrive. The client will always run out of data if the bit rate of the incoming stream exceeds the current available bandwidth. The actual bandwidth at any given point is determined by network conditions and traffic, which are constantly fluctuating. The delivery of information to mobile devices is very hard due to the heterogeneity of these kinds of devices (Macias, E. & Suarez A., 2010). We first analyze the particular characteristics of mobile devices that differentiate them for other kind of devices:
They have reduced resources: display, processor and memory. That means the multimedia contents must be adapted to be delivered to them. Standards like 3rd Generation Partnership Project (3GPP), Moving Picture Experts Group (MPEG), H.264 and codecs like Advanced Audio Coding (AAC), Adaptive Multi-Rate Speech (AMR) and Flash can be used for mobile devices. The information must be encapsulated in a determined container (for example, MPEG-2 transport stream container) compatible with the mobile device player.
They naturally use wireless technologies (for example, Wireless Fidelity (WiFi)) and mobile networks (for example, Universal Mobile Telecommunications System (UMTS)) to communicate. These technologies suffer from fluctuating bandwidth that may occur due to network congestion or the handover causing several problems to the delivery of media information (Suarez, A. et al., 2009).
They use proprietary (Symbian, Apple iOS and Windows Phone …) or open source operating systems (Android) and players.
The protocols traditionally used for video delivery are the following:
Live video. The video is sent using User Datagram Protocol (UDP) or Real Time Protocol (RTP).
Streaming. The Real Time Streaming Protocol (RTSP) is the first used (Schulzrinne, H. et al., 1998). A recent variation of this protocol is Real Time Messaging Protocol (RTMP) that is a proprietary solution of Adobe that runs over Transmission Control Protocol (TCP), for streaming audio, video and data over the Internet, between a Flash player and a Flash media server. A key benefit with RTSP / RTMP is its ability to provide multicast support. They are the only alternatives for streaming scenarios inside a corporate network where delivery to many customers is required without initiating new connections for each user.
In the last three years, adaptive Hyper Text Transfer Protocol (HTTP) streaming solutions for live and on demand content have appeared on the market mainly because HTTP does not have the same firewall and Network Address Translator (NAT) traversal problems as traditional streaming. Moreover, HTTP is not likely disallowed by routers and firewall settings. No ports need to be opened that are commonly closed by default. This is one of the main motives why Apple developed the protocol for its mobile internet devices. Important to note here is that YouTube chooses to offer HTTP Live Streams for iPhone visitors. Because of this, the HTTP live streaming technology suddenly gained a huge installed base, as all the video’s on YouTube are also available through this streaming technology.