ARTICLE IN PRESS Signal Processing Image Communication Windows Media Video 9 overview and applications Sridhar Srinivasan Pohsiang John Hsu Tom Holcomb Kunal Mukerjee Shankar L Regunathan Bruce Lin Jie Liang Ming Chieh Lee Jordi Ribas Corbera Windows Digital Media Division Microsoft Corporation Redmond WA 98052 USA Abstract Microsofts Windows Media 9 Series is a set of technologies that enables rich digital media experiences across many types of networks and devices These technologies are widely used in the industry for media delivery over the internet and other media and are also applied to broadcast high de nition DVDs and digital projection in theaters At the core of these technologies is a state of the art video codec called Windows Media Video 9 WMV 9 which provides highly competitive video quality for reasonable computational complexity WMV 9 is currently under standardization by the Society of Motion Picture and Television Engineers SMPTE and the spec is at the CD Committee Draft stage This paper includes a brief introduction to Windows Media technologies and their applications with a focus on the compression algorithms used in WMV 9 We present analysis experimental results and independent studies that demonstrate quality bene ts of WMV 9 over a variety of codecs including optimized implementations of MPEG 2 MPEG 4 and H 264 AVC We also discuss the complexity advantages of WMV 9 over H 264 AVC r 2004 Elsevier B V All rights reserved Keywords Video coding Windows media Codec standards 1 Introduction to windows media 1 1 A wide range of applications Windows Media 9 Series is the latest generation of digital media technologies developed by Microsoft 13 Although the origins of Windows Media focused on streaming compressed audio and video over the Internet to personal computers the vision moving forward is to enable effective delivery of digital media through any network to any device Fig 1 illustrates a variety of examples of how Windows Media technology is being used today In addition to Internet based applications e g subscription services video on demand over IP web broadcast etc content compressed with Windows Media codecs is being consumed by a wide range of wired and wireless consumer electronic devices e g mobile phones DVD players portable music players car stereos etc 27 Windows Media content can also be delivered to consumers in physical formats for instance Corresponding author E mail address jordir microsoft com J Ribas Corbera 0923 5965 see front matter r 2004 Elsevier B V All rights reserved doi 10 1016 j image 2004 06 005 ARTICLE IN PRESS 2 S Srinivasan et al Signal Processing Image Communication Fig 1 Examples of current Windows Media technology applications using the secure digital SD memory card 12 or on CD or DVD using the HighMATt format 24 Recently high de nition HD movies such as Terminator 2 and Step into liquid have been released commercially on DVDs using Windows Media and the DVD Forum has adopted the Windows Media Video 9 WMV 9 codec as mandatory for the next generation HD DVD format In the terrestrial and satellite broadcast space a recent project at the International Broadcasting Convention IBC demonstrated how to deliver Windows Media 9 Series content via DVB T and DVB S 21 As another example Windows Media technology is also used to compress movies in HD and multi channel audio for projection in commercial theaters For example the popular BMW Films and independent lms from the Sundance Festival were compressed and encrypted in Windows Media distributed electronically and projected digitally in numerous public theaters in the US 1 2 End to end delivery All of the applications mentioned thus far require a set of building blocks or components that permit the deployment of complete end toend solutions The fundamental components of Windows Media 9 Series are illustrated in Fig 2 and can be classi ed in three steps authoring distribution and playback In addition digital rights management DRM is a key component that is distributed across the entire media data path 1 2 1 Authoring Authoring is the process of creating and encoding digital media The basic encoding software provided by Microsoft is called Windows Media Encoder 9 Series It is a exible software encoder that can compress audio and video sources for live or on demand streaming by using the Windows Media codecs At the same time there are alternative encoding solutions provided by third parties that are built on top of the Windows Media porting kits e g hardware encoders from companies such as Harmonic Optibase Tandberg Television Texas Instruments etc or the Windows Media software development kits SDKs e g software encoders from companies like Accom Adobe Avid Discreet Quantel etc 1 2 2 Distribution The distribution of content compressed with Windows Media codecs over the Internet is generally done by a Windows Media Services server Windows Media Services version 4 1 is an optional component in Windows 2000 Server and Windows Media Services 9 Series is an optional component in Windows 2003 Server The new server supports more features for advertising and corporate scenarios and is twice as scalable it ARTICLE IN PRESS S Srinivasan et al Signal Processing Image Communication 3 Fig 2 End to end delivery of Windows Media content authoring distribution and playback The DRM system protects content based on policies set by the content owner doubles the number of customers that can receive a media clip at the same time A server can either stream the clip transmit it with as little delay as possible or download it transmit and store it over the internet into a user s playback device The transmission of the clip can be performed live for news sports concerts or similar events or on demand for music videos movies on demand and so on When streaming or transmitting a media clip the server adapts its throughput and re transmits lost packets intelligently using feedback from the network quality metrics For on demand streaming the latest server takes advantage of the additional bandwidth available above the average bit rate of the clip to reduce the start up delay In addition such server reduces the likelihood of losing the connection which manifests as playback glitches and re buffering to the viewer by sending more data to the playback device so that the device can continue playing even when there is network congestion A robust and scalable server is essential for Internet delivery but obviously having a
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