Sony's RoomLink system broadens the enjoyment of videos, music, photographs and other media by allowing consumers to link a variety of devices via a home network. To enhance the compatibility of home networking devices, including products based on Sony's RoomLink system, a group of manufacturers have established the DLNA design guidelines and introduced the DLNA Certified logo.
DLNA
The Digital Living Network Alliance, or DLNA, (http://www.dlna.org/jp) is an organization established to enhance the interoperability of home networks. The organization issues design guidelines to support the seamless sharing of video, music, photographs and other content through home networks. It also issues a logo for use on products that qualify under these guidelines.
Sony established the DLNA in June 2003 after convincing other manufacturers of the need to improve interoperability through industry-level standardization initiatives. Sony continues to play a leading role in the organization, and a Sony executive is Chairman of the DLNA Board of Directors. Today there are over 240 members, including the world's leading manufacturers of electrical appliances, mobile equipment and computers, as well as developers of software, devices, services and applications, and content providers. By supplying a wide variety of DLNA-compliant products, these manufacturers are helping to raise awareness of DLNA as an industry standard for home networking.
Design Guidelines for Seamless Content Sharing within the Home
The DLNA has established a basis for home network interoperability by formulating design guidelines based on various widely used open standards, such as HTTP, UPnP (*1), XML and MPEG. The DLNA protocol stack (*2) is shown in Figure 1.
*1 Universal plug and play: Technical specifications to allow computers, peripheral devices, AV equipment, electrical appliances and other equipment to be connected and provide functions via networks
*2 A layered software structure consisting of selected protocols required to provide functions on a network
Connecting Devices to a Home Network/Device Discovery
The network layer consists of Ethernet, a LAN protocol widely used for home networking and Internet access, and an IP network based on wireless LAN technology. Devices on the home network are discovered using DHCP, which automatically assign IP addresses, and SSDP as defined in the UPnP Device Architecture. It is also possible to retrieve the names and functions of devices, and this information can then be used to select devices.
Server Content Discovery/Media Format Compatibility Checking
Using the structure defined in UPnP AV, it is possible to obtain a list of videos, music, photographs stored on a selected device, together with metadata related to this content. The guidelines also stipulate formats, including video formats, such as MPEG-2 and AVC/H.264 (the new MPEG-4 standard) and audio formats, such as linear PCM and MPEG-2 AAC, as well as media format profile IDs representing these formats.
Content Transfer
At the content transfer stage, compatible content can be selected by using media format profile IDs to check compatibility between the server and the player. The selected content is transferred by HTTP. Copyright protection technology, such as DTCP-IP, is used when premium content is transferred.
Design guidelines formulated by DLNA cover the connection of devices to home networks, the discovery of other devices, the discovery of content on servers, media format compatibility checking and content transfers. Their purpose is to allow the seamless sharing of content within the home.
In September 2005, a home network transfer protocol for the ARIB standard for digital broadcasting in Japan was adopted. This protocol, which is based on the DLNA design guidelines and the DTCP-IP standard, will allow broadcast content and other information received through digital tuners to be transferred through a home network.
