DLNA clearly defines a minimal set of codecs that are required for interoperability and must be supported by a DMS. Because a DMS is used to store the consumer’s media files, it is essential to provide support for the various profiles that the consumer owns. For better interoperability, we recommend that a DMS provide support for WMV and WMA files.
Support for Windows Media Codecs
Windows Media Format codecs have been publically available for years and are an optional format in the DLNA specification.
Windows Media Audio Support
A DMS should support the following WMA profiles as specified in the DLNA 1.5 Media Formats specification (NETMEDIA-0022):
Windows Media Video Support
A DMS must support the following WMV profiles as specified in the DLNA 1.5 Media Formats specification (NETMEDIA-0021):
The WLP has few specific playback requirements for DMS devices that exceed the support that DLNA requires. Beyond basic SEEK support, Windows does make some recommendations.
Seeking to a specific location in a media file is a basic task for consumers. A DMS device must support DLNA HTTP time-seek requests from any media content in storage with ProfileIDs that belong to the sets that are defined in NETMEDIA-0021 and NETMEDIA-0022. A DMS device must support HTTP range requests (byte-based seeking) for all files in storage.
Trick Modes (Fast Forward/Fast Rewind)
A DMS device should support trick modes for Windows Media and other media formats. To do this, the DMS device should support different values of play speeds (advertised in the DNLA.ORG_PS parameter of the fourth field of protocolInfo). The Server-Side Playspeeds parameter is specified in the 7.3.35 MM ps-param (Server-Side PlaySpeeds Parameter) section of the DLNA 1.5 Specification.
Most users use Windows Media Player to filter their content quickly. For a DMS device to integrate with Windows 7, it is important that the DMS device exposes DLNA-defined search capabilities (NETMEDIA-0026) that use the following attributes:
For each attribute, the following operators must be supported:
DMSs are the backbone for connected media home networks. If users cannot access their content, the system fails. Microsoft We have defined the minimum requirements for the robustness of a DMS. A DMS device must be able to stream the supported media files continuously for 24 hours without requiring user intervention or degradation of quality of experience (NETMEDIA-0047). The DMS device should be able to stream for much longer periods of time, and future requirements will dictate that.
A DMS must be able to stream HD content. Although this requirement may be taxing to mobile devices, the reality is that more content is moving to HD (NETMEDIA-0053).
A good digital media server should be able to source at least 10 connections at the same time. The Windows 7 Logo Program requires that the server support at least two concurrent connections. This is especially important as users play content and download album art and other metadata at the same time (NETMEDIA-0054)
Similar to the DMR requirement, we recommend that a DMS device support a low-power mode of operation and WoL. Allowing a server to enter a low-power mode and awaken only when content is required is a smart, ecologically friendly design. As mentioned earlier, a DMS device must provide information in the device description document that states its support for WoL.
The WLP requires that a DMS device that implements one or more low-power modes must be able to resume to normal-power mode operation in response to receiving a broadcast Magic Packet. It is not a current requirement that the DMS device support a low-power mode of operation (NETMEDIA-0011).
To foster an improved user experience, the WLP requires that DMS devices implement the following features.
Most users’ music collections include album art with the media files. When user browse a library of music, they expect to see album art associated with their media files. Therefore, the Windows logo requirement NETMEDIA-0059 states that if album art is available for the music file, the DMS device must provide it.
In addition, the WLP requires that DMS devices filter album art from the queries for images (NETMEDIA-0029). Otherwise, users browsing their photo libraries are inundated with album art.
Users of Windows and Windows Media Player expect to browse through their libraries of content in thumbnail view. That means that thumbnails of videos and images appear in the library while the user is browsing. The WLP requires that if thumbnails are available, the server provide them to the client for videos and images (NETMEDIA-0060 and NETMEDIA-0061).
In addition to album art, users expect to see the metadata that is associated with their files. The WLP requires that a DMS device provide the common metadata attributes for music, video, and pictures (NETMEDIA-0032).
For improved functionality and searching, a DMS device should also provide support for these additional Microsoft attributes that are specified in the Windows Media Player compatibility document:
Building a Great Digital Media Controller
One of the more exciting parts of the model that was illustrated previously in Scenario 3 is the DMC. The DMC lets the user find the content on the server and send it to the DMR device within the home ecosystem.
Although this is one of the more important elements of the system, the actual Windows requirements for these devices are fairly limited. A DMC device must comply with DLNA and support Microsoft® Rally™ technologies.
In addition to the requirements that DLNA specifies, the WLP requires DMC devices to be able to wake up other devices. The DMC device controls the servers and the renderers, so if those devices are in sleep mode, the DMC device must be able to send magic packets to wake them up (NETMEDIA-0074).
Recommended Digital Media Controller Features
With so few requirements on DMC devices, OEMs can differentiate their DMCs by implementing suggested features. The following is a list of recommendations to consider.
User Experience: Playback
DMC devices should provide feedback to the user about the currently playing file. The feedback should include the following information:
In Scenario 3, DMC devices are designed to control the user experience, so it is important that the user is provided with the same type of controls as other consumer electronic devices. For example, the DMC should lets users play, pause, stop, fast forward, rewind, mute, and adjust the volume of the media they are consuming.
A great DMC device should let the user adjust and modify the volume of supported media renderers. The volume support should include MUTE and a slider for more detail. If the DMR does not support the volume control, the UI for this feature should be disabled.
Play / Pause / Stop
A DMC device should provide play, pause, and stop controls for all media types. The DMC device should enable the user to pause or stop the currently playing stream. In addition to providing the UI elements, the DMC device should forward the pause, stop, and play requests to the digital media renderer.
A DMC device that is acting as an MSCP should let the user navigate to a specific position in a media stream. The DMC device should enable the user to seek into a specified time position for audio and video types. In addition to providing the UI elements, the DMC device should forward the seek requests to the digital media renderer.
Fast Forward/Fast Rewind
A great DMC device should include trick mode support. If a DMR device indicates its ability to (fast/slow) forward or (fast/slow) rewind a stream, the DMC should enable the user to forward and rewind the currently playing stream. In addition to providing the UI elements, the DMC must forward the appropriate metadata and trick mode requests to the digital media renderer. The DMC should forward the Server-Side Playspeeds parameter to the DMR device as part of the transferred metadata in the SetAVTransportURI action. Forwarding this information to the DMR enables the DMR device to request those play speeds from the DMS device.
User Experience: Browse
Another key user experience is locating the files to stream. To provide a great user experience, a DMC device should enable the user to browse libraries, based on album art, video thumbnails, or image thumbnails. The visual hierarchy allows consumers to quickly navigate and find the files they are looking for.
Metadata and Ratings Update
In addition to displaying album art and thumbnails to the user, a DMC device should expose metadata for each media item. This should include the metadata that is mentioned in the playback experience and additional Microsoft specific metadata:
A DMC should also let the user change the userRatingsInStars. When the user makes a change to this field, the DMC should push this change back to the DMS by using the UPnP UpdateObject. This lets users change queries that are based on their preferences.
Glossary of Acronyms
The following table lists the acronyms used in this white paper.