Supported Streaming Protocols - Design Guidelines and Considerations for Building Windows Certified Network Media Devices

Since the 1920s when radio stations started regular broadcasting in the U.S., the home is a place of entertainment where media has played an important role. Recent Nielsen reports show that the average user watches television approximately 4 hours and 30 minutes per day. If we add other forms of entertainment such as DVDs, CDs, gaming, and Internet, we realize that media entertainment has become a primary activity for home users.
Media has experienced a transformation. Media existed as analog waves that were transmitted over radio and television broadcasting systems, or stored in vinyl records and magnetic tapes. Radio and television are moving to digital formats, and digital media in the form of pictures, music, and videos are kept in computers and other storage devices such as PCs, network-attached storage (NAS) devices, or digital video recorders (DVRs). Users have embraced digital media technologies at a fast pace. The 32-mm camera was invented in 1936. Starting around 1995, casual users have replaced their analog cameras with digital cameras. It is not unusual to find users who have thousands of digitized pictures that are stored in PCs, iPods, network-attached storage devices, and other home devices.
Since the advent of MP3 players, users are accumulating digital music at an equally fast pace. Many families have converted all their CDs to digital music to use it in MP3 players and iPods. Personal video is digital, easy to access, and an important social component, as Web sites such as YouTube show. Most digital cameras record directly in digital formats, which means that users can add hundreds of video files to their content libraries.
Because users keep media libraries with hundreds of pictures, music, and videos in storage devices at home, it is important to provide the means to access content easily and conveniently. For example, a user who tries to view a video that is stored in a PC might prefer to see the video on the large-screen living room television. Fortunately, together with the developments in digital media, home networking technology is making inroads into the home.
The 802.11 standard was finalized in 1997, and its adoption and use have grown exponentially since its introduction. Market research reports indicate that home network equipment sales grew by 15 percent between 2006 and 2007. It is estimated that by the end of 2008, the number of installed home networks worldwide will reach 200 million.
Home networks are used primarily for family members to share Internet access and printers, but they are migrating into a new function: connecting all media devices in the home to improve the quality of home-based entertainment activities.
There are many technological alternatives to develop a network platform for media devices. Home media devices are manufactured by many recognized vendors. Users enjoy the diversity of prices, quality, and features that the consumer electronics companies provide for media devices, but they also expect uniform usage scenarios and experiences. Therefore, a model for developing a network connectivity platform is to create a suite of baseline standards that provide a connectivity infrastructure but leave room for innovative products. In this way, vendors from heterogeneous industries—for example, consumer electronics, computers, and communication—can design products that interconnect well but that can be differentiated in the market.
The Digital Living Network Alliance (DLNA) has developed a suite of standards that provide a balanced approach to network connectivity for media devices. The standards are based on the following interconnection technologies:
802.11 a/b/g and Ethernet for physical connectivity.
TCP/IP for network connectivity.
UPnP for device discovery and communications.
HTTP for the transfer of control messages and the transfer of content.
MPEG-2 and MPEG-4 for media formats.
DLNA also recognizes optional components that add significant value to the platform: additional media formats such as Windows Media Audio (WMA) and Windows Media Video (WMV), Real-Time Transfer Protocol (RTP) as a secondary streaming protocol, non-streaming scenarios such as upload and download, and other alternatives.
The DLNA architecture categorizes devices according to their roles in the network. Windows 7 is designed to interact with many of the device classes that DLNA introduced. Specifically, Windows 7 interoperates with the following device classes:
Digital media servers—devices that act as the sources of content in the network.
Digital media players—devices that can browse, select, and play content from digital media server (DMS) devices in the network.
Digital media renderers—devices that can receive control actions and play content from DMS devices in the network.
Digital media controllers—devices that can browse and select content from any DMS, and then send control actions and play requests to any digital media renderer (DMR).
Some device classes in this list have a mobile equivalent. The mobile equivalent for a DMS is an M-DMS. Similarly, the mobile equivalent for a digital media player (DMP) is an M-DMP, and for a digital media controller (DMC) is an M-DMC. There is no mobile equivalent for a DMR. The important difference between home devices and their mobile equivalents is in the supported media formats. Although home devices support formats such as Motion Picture Experts Group (MPEG-2) and Linear Pulse Code Modulation (LPCM), mobile devices support formats such as MPEG-4 (Part 10), advanced audio coding (AAC), and MP3. Windows 7 computers support media formats for both home and mobile devices. Therefore, this paper makes no difference between home devices and mobile equivalents.
Windows media device connectivity in the home started with the release of a Windows XP application named Windows Media Connect (WMC). This application implemented a UPnP Media Server and used standard HTTP protocols for streaming. Devices that implemented UPnP media renderers, and were Plays for Sure certified, interoperated with WMC. This application became a component of Windows Media® Player with the release of Windows Media Player 11 named Network Sharing Services (NSS) that incorporates most elements that are necessary to interact with the first version of DLNA digital media players. Although WMC and Windows Media Player NSS implement mostly a media server component, the new NSS version in Windows 7 includes DMS, DMR, DMP, and DMC functionality. Furthermore, the new version includes a rich list of optional DLNA features, including transcoding, support for multiple new media formats, and download support.
With the expanded scope of the Windows 7 platform, the PC becomes a comprehensive networked media device that can interoperate seamlessly with DLNA devices and with many popular non-DLNA devices. Furthermore, the Windows 7 PC is versatile because of the large number of supported media formats and its powerful hardware accelerated transcoding engine. With these advances, we hope to bring a premier media-sharing experience to users who embrace the new era of digital living.
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