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DLNA Expands Interoperability Guidelines

Portland, Ore. — The Digital Living Network Alliance (DLNA) has extended its interoperability guidelines to new home devices, including networked printers and handheld remotes, and to mobile devices such as cellphones and portable media players (PMPs).

DLNA’s mission is to make it possible for digital content to be shared seamlessly among DLNA-certified PCs, consumer electronics and mobile devices by setting minimum compatibility standards.

The new guidelines will:

— enable DLNA-certified networked printers to print out images displayed on compliant devices such as TVs and cellphones.

—add “push” devices to provide more convenient control of networked devices in the home. Networked remote controls and cellphones, for example, would be able to discover devices on the network, discover the content on the devices, and push content from one device to another for viewing or listening. Previously the guidelines allowed only for devices that pulled content from other devices for local viewing or listening.

—enable transfer of audio, video and digital images back and forth between home devices and mobile devices, which can include cellphones, PMPs and car A/V systems.

Now that the expanded guidelines have been approved, DLNA is developing testing procedures to ensure interoperability among compliant devices, said board member Bob Taylor. The procedures should be finalized by the third or fourth quarters, and testing of products for commercial release could potentially begin weeks after that, he said.

Testing of devices under the previous guidelines is underway, and the first U.S.-market products incorporating them will likely be available in the fall, Taylor said.

Under the original suite of guidelines, DLNA-certified media servers and renderers (such as digital media adapters, or DMAs) must incorporate Microsoft’s universal plug-and-play technology for media management and automatic discovery of a device, its content and the format of its content; use HTTP 1.0/1.1 for media transport; and use the IPv4 Protocol Suite for the network stack.

The discovery process enables DMAs to identify the formats in which content is stored on a networked server, such as a PC, and whether that content is in a format that the DMA supports. If so, the content is transferred automatically in that format. If not, the server automatically transcodes the content into a DLNA-mandatory format for transfer. The server, for example, might transcode an MP3 file into mandatory uncompressed PCM for transfer to the DMA. Because products will usually support multiple formats, however, the devices “will make the best choice to minimize translation,” Taylor said.

For servers and DMAs, mandatory formats for transferring media are JPEG for images, PCM for audio and MPEG-2 for video. Devices need only incorporate the format that applies to them. An audio device, for example, doesn’t have to incorporate ability to display JPEG images. A device such as TV or PC, however, must incorporate all three at a minimum.

For connectivity, DLNA-certified DMAs and servers must incorporate 802.3i (10BaseT Ethernet) or 802.3u (100BaseT Fast Ethernet), or one of the Wi-Fi-certified 802.11 wireless standards (802.11a, b or g), or a combination of these physical-layer interfaces.

DLNA-certified servers and DMAs can also support the following optional media formats:

Imaging: GIF, TIFF, PNG.

Audio: MP3, WMA9, AC-3, AAC, ATRAC3plus.

Video: MPEG-1, MPEG-4, WMV9.

Printer additions: For printers, the mandatory technologies remain the same, with the JPEG media format becoming a mandatory printer language for DLNA-certified printers. JPEG will supplement the proprietary printer languages that each printer maker currently embeds in its printers, making it unnecessary for suppliers to load dozens of printer drivers for each printer vendor onto devices such as TVs and cellphones, Taylor explained.

Remotes: For handheld remote control of content, the handheld device will incorporate either Bluetooth or one of the wireless IEEE 802.11a/b/g standards to talk to a wireless access point to control an Ethernet-networked or wireless-networked DMA and server, said Taylor.

Mobile devices: For mobile devices, DLNA makes some changes to the mandatory media formats. The mandatory formats still include PCM and JPEG, but the mandatory video format changes from MPEG-2 to MPEG-4 (also called AVC) because the latter doubles the compression rate and allows for lower bit rates, Taylor said. Although MPEG-4 is mandatory on the mobile side and MPEG-2 is mandatory on the home device side, Taylor cited two reasons for an expected lack of interoperability problems. First, many chipsets simultaneously support MPEG-2 and MPEG-4. Second, in the event that a home DMA doesn’t support MPEG-4, then users can buy a Media Interoperability Unit (MIU), developed under the mobile specs to perform format conversions from MPEG-4 to MPEG-2.

An MIU might also be necessary to transcode audio from mobile devices for transfer to the home network. That’s because most portable devices don’t store uncompressed PCM. The MIU would transcode a portable device’s compressed formats — such as MP3 and AAC — to PCM for transfer to home devices, Taylor said. Portable devices could easily be designed to perform the transcoding themselves, however, because the devices already have the capability to uncompress compressed formats for playback through headphones.

For mobile device connectivity, DLNA added Bluetooth as one of three mandatory connectivity requirements. DLNA mobile devices must incorporate wired Ethernet; one of the Wi-Fi-certified 802.11 wireless standards (802.11a, b or g); or Bluetooth using its file-transfer profile, which is normally used to transfer data files between, for example, a phone and laptop. As a result, consumers won’t have to select from a menu of different Bluetooth profiles to transfer music, video or images, Taylor said.

Although cellphones or PMPs with wired Ethernet ports are unlikely to be developed, Taylor admitted, the guidelines anticipate combination Wi-Fi/cellular phones and Wi-Fi-equipped PMPs.