SOURCEFORGE » RALF » 2014 Evaluation of videoconference and streaming

h1. Overview

Streaming is a multimedia flow received by an end-user while being provided by the provider. The end user can begin to play the data before the end of transmission by the provider. The media is stored in the RAM of the computer before the reading. There is different types of streaming, the live streaming (radio,television..) or the non live streaming (movies, CDs audio..).

For the transmission, different types of compression or protocols are used, we have for example the utilisation of mp3 or mp4. By contrast, the choice of the protocols is more complex. Indeed here is a list of protocols :

* Datagram protocols such as the User Data Protocol (UDP). UDP send the media stream as a series of small packets. UDP is simple and efficient however there is no mechanism to guarantee the delivery inside UDP. Therefore it is up to the receiving part to detect loss (in received data) and to recover data using error correction. In case of lost in the media stream, the stream may suffer a dropout. In conclusion, using UDP is efficient with a robust network.

* The Real Time Streaming Protocols (RTSP) such Real time Transport Protocol (RTP) and the Real time Transport Control Protocol (RTCP) were specifically designed to media stream. RTSP protocols runs over a variety of transport protocols.

* The HTTP adaptive bit rate streaming is based on HTTP progressive download. That another approach permits to have the advantages of a standard web protocol.

In our case of studies we use the HTTP adaptive bit rate streaming, therefore here is a presentation of its working.

Dynamic adaptive streaming over HTTP is an adaptive bit rate streaming who permits to high quality streaming of media over the Internet delivered from conventional HTTP web servers.

The content is made of various bit rate, the bit rate (therefore the quality of the media stream) depends on the networks conditions. 

When a segment is download the client selected automatically the next segment to download based on the current network condition.

The adaptive bit rate streaming provides to a client the best possible experience.

Here is figure who permits to see the behavior of the dynamic adaptive streaming over HTTP, there is multiple available bit rate “in” the web server, then according to the manifest, the user receive the bit rate corresponding to its network behavior.

!AdaptiveStreamingOverview.png!

The following curve permits to see a possible behavior of the available bit rate for a user, we see the dependance of the network congestion for the available bit rate (bandwidth).

!AdaptiveStreamingBitRate.png!