Most users today are accustomed to operating VCRs and DVRs. There is an expectation that the device should enable the user to seek to a location in the audio or video stream. Minimally, Windows 7 logo requirements state that a DMR device must support time-based seeking for WMA and WMV content with ProfileIDs that are defined in NETMEDIA-0023 and NETMEDIA-0024. Support for seeking can be done locally by using cached content, through HTTP requests against the server or a combination of both (NETMEDIA-0070).
The time-based seek protocol for DMR devices and DMC device interactions is described in DLNA document CR13 (under the name ”controller-time seek operations”). CR13 will be published as Errata #3 to the DLNA 1.5 Guidelines. DMRs must follow the requirements for controller-time seek operations that are defined in CR13.
The Windows 7 NSS supports seeking to use a conventional HTTP range request as defined in section 14.35 of the HTTP 1.1 specification. It also supports the DLNA-defined HTTP extension header, TimeSeekRange.DLNA.org. Depending on the content type, the NSS provides none, one of the two, or both seek methods. The DMR must verify the appropriate seek method before it tries to seek within the content item.
Although the Windows 7 logo requirements require seek support for WMA and WMV profiles, for other profiles, DMR devices should support time-based seeking.
DLNA requires that DMRs be able to play and stop streams. Windows 7 logo requirements require that DMRs be able to pause as specified in the UPnP AVTransport specification (NETMEDIA-0071).
Volume Control Requirements
With digital media controllers controlling the playback experience, Windows 7 logo requirements state that it is mandatory that a DMR that can render audio must support volume control and conform with DLNA requirement 7.3.108 MM Renderer Volume Control (NETMEDIA-0072).
The baseline playback requirements provide a good user experience. To foster a great user experience, we advocate that DMR devices implement the following features in addition to the baseline requirements.
Choosing the Optimal RES Element
The Windows 7 NSS provides a DMR device with multiple RES elements, and the Windows 7 requirements state that the DMR must choose the RES element that it can play. Additionally, the DMR should select the RES element that provides the best playback experience. The DMR should weigh Quality of Service (QoS) into the selection criteria and determine the bit rate that best meets the client’s needs.
Fast Forward and Fast Rewind
Consumers are accustomed to being able to fast-forward and fast-rewind both audio and video content. Therefore, we recommend that DMR devices support ”trick modes.” Minimally, a DMR should support positive 2 and negative 2 play speed control of WMA and WMV content.
Some DMR devices enable more than just DMR functionality. If a DMR implements a media server control point (MSCP), then the DMR must either support search locally or support sending search requests in response to user action (NETMEDIA-0027). For example, if the DMR does not support local search, then the MSCP must also support sending CDS:Search requests in response to the user action. Search queries must support the following metadata properties:
DMR devices as consumer electronic devices should have the same robustness that the user experiences with a CD player. At a minimum, the DMR device must be able to play back its supported media type continuously for a 24-hour period without requiring user intervention (NETMEDIA-0048).
As previously stated, a DMR device must provide device description document metadata that indicates whether the device supports WoL. In addition to this requirement, if a DMR device implements one or more low-power modes of operation, the DMR device must support WoL (NETMEDIA-0076).
Wake on LAN Recommendations
Although DMR devices are not required to support WoL, we recommend that device manufacturers be proactive and implement WoL in all devices.
Windows 7 allows devices to modify the user’s ratings for a media item and to update the information on the server. If a DMR device allows editing the microsoft:userRatingInStars metadata attribute, then the DMR device must be able to notify digital media servers of the updated metadata by calling the UpdateObject method that the ContentDirectory service implements. The DMR device must call UpdateObject within 0.5 second of receiving approval of the change from the consumer.
User Experience Recommendations
The best user experience during playback includes displaying metadata that the user finds interesting about the currently playing item. The metadata for music should include the following:
During music playback, a DMR device should visually expose album art and metadata to the user.
If a DMR device includes a control point that allows for browsing files, then the DMR device should meet the recommendations that are described later in this document for digital media controllers.
Building a Great Digital Media Server
Windows 7 has embraced the DLNA 1.5 specification for devices. This means that the DLNA 1.5 DMS can interact with Windows Media Player as a DMP and Windows Media Player as a DMR.
For a DMS to work with Windows, it must comply with DLNA. A set of rules must be followed so that Windows can discover DLNA 1.5 servers and make them available to the consumer.
In DLNA, DMS devices are divided into two categories: mobile devices (M-DMS) and home DMSs. The Windows 7 logo requirements are relaxed for M-DMS devices because of mobile device memory constraints. In the future, manufacturers of M-DMS devices should enable the High Definition Media Server (HDMS) requirements, as they improve the user experience.