Adaptive Streaming: a comparison

Adaptive live streaming represents a key advancement with respect to classic progressive download streaming such as the one employed by YouTube. With adaptive streaming the video source bit-rate is adapted on the fly so that the user can experience the maximum quality which is allowed by the time-varying available bandwidth.

An approach employed to implement adaptivity is the stream-switching technique that consists in encoding a video content at several bitrates and to dynamically switch among those videos to match the available bandwidth.

In the following the most important adaptive video streaming commercial solutions are briefly.

IIS Smooth Streaming (Demo)

IIS Smooth Streaming is a live adaptive streaming service provided by Microsoft. The streaming technology is available as a web-based solution by installing a plug-in that is available for Windows and iPhone OS 3.0. The streaming technology is codec agnostic and currently supports VC-1 and H.264 codecs. IIS Smooth Streaming employs stream-switching approach with different versions encoded with configurable bitrates and video resolutions up to 1080p. In the default configuration IIS Smooth Streaming encodes the video stream in seven layers resulting in a bitrate range from 300 kbps to 2.4 Mbps.

A demo is available at: http://www.iis.net/media/experiencesmoothstreaming.

Adobe Flash Dynamic Streaming (Demo)

Adobe's adaptive streaming solution is a web-based service available to all devices running a browser with Adobe Flash plugin. The server stores different streams of varying quality and size and switches among them during the playback adapting to user bandwidth and CPU. The service is provided using the RTMP streaming protocol. The supported video codecs are H.264 and VP6 which are available in Adobe Flash plugin. The advantage of AFDS is represented by the wide availability of Adobe Flash plugin at the client side.

A demo is available at: http://www.flashstreamworks.com/video/1080pfp9.html.

Akamai HD Network (Demo)

Akamai is the leader in the market of content delivery network and has recently launched an adaptive HDTV streaming service. The streaming technology is available for Adobe Flash, Microsoft Silverlight and available in most used we browsers for Windows, Mac and Linux. The video codec employed by Akamai HDTV is H264. Akamai HDTV employs stream-switching approach with three different versions encoded with bitrates ranging from 300 kbps up to 3.5Mbps with video resolutions from 180p up to 720p. The adaptation logic is implemented at the client side. The client estimates the network available bandwidth and select the video level to download by sending to the server a GET message.

A demo is available at http://wwwns.akamai.com/hdnetwork/demo/flash/default.html.

Apple HTTP Live Streaming

Apple has recently released a client-side HTTP adaptive live streaming solution. The server segments the video content into several pieces with configurable duration and video quality. The server exposes a playlist (.m3u8) containing all the available video segments. The client downloads consecutive video segments dynamically chosing the video quality using an undisclosed proprietary algorithm. The video codec employed is H264 using MPEG-2 TS container. Apple HTTP Live streaming is available on any device running iPhone OS 3.0 or later (including iPad), or any computer with QuickTime X or later installed, with support for encryption and authentication.

Move Networks (Demo)

Move Networks provides live adaptive streaming service to several TV networks such as ABC, FOX, Televisa, ESPN and others. A plugin is available for the most used web browsers for Windows and Mac OS X and has to be installed to access the service. Move Networks employs VP7, a video codec developed by On2, a company that has been recently acquired by Google. Adaptivity to available bandwidth is provided using the stream-switching approach. Five different versions of the same video are available at the server with bit rates ranging from 100 kbps up to 2200 kbps.

A demo is available at: http://www.movenetworkshd.com/.

Hulu (Demo)

Hulu is an online video service that offers a selection of shows, clips and movies. Hulu's selection of programming is provided by more than 225 content companies, including FOX, NBC Universal, ABC, Lionsgate, MGM, National Geographic, Paramount, A&E Television Networks, PBS, and Warner Bros. Television Group.

As stated in the official blog, Hulu player is written using Adobe Flash API and adopts an adaptive bitrate streaming. It employs a stream-switching approach with three different versions encoded with bitrates ranging from 640 kbps up to 1.6Mbps with video resolutions from 288p up to 480p.

A worldwide demo is available at: http://www.hulu.com/watch/183133/if-i-can-dream-perfume-guns-and-needles.

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