The Renderer Objects — dLeyna 0.8.2 documentation

# The Renderer Objects

dleyna-renderer-service exposes a separate D-Bus object for each DMR it detects on the LAN. These objects serve three purposes:

1. They allow the client to retrieve information about the DMR, such as its name, the URL of its icon, its manufacturer, the currently playing content, etc.

2. They allow the client to manipulate the DMR, i.e., to play a given URL, to play, pause and stop, etc.

3. They can be used to implement two box push.

Each renderer object exposes three separate interfaces: org.mpris.MediaPlayer2, org.mpris.MediaPlayer2.Player and com.intel.dLeynaRenderer.PushHost.

## com.intel.dLeynaRenderer.RendererDevice

### Methods

The com.intel.dLeynaRenderer.RendererDevice interface currently exposes two methods:

Cancel() -> void

  Cancels all requests a client has outstanding on that server.

GetIcon(s RequestedMimeType, s Resolution) -> (ay Bytes, s MimeType)

  Returns the device icon bytes and mime type according to the RequestedMimeType and Resolution parameters. Both RequestedMimeType and Resolution parameters are currently reserved for future use and should be set as an empty string.

### Properties

The `com.intel.dLeynaRenderer.RendererDevice` interface exposes information about the DMR via a number of D-Bus properties. These properties are described below:

Name | Type | m/o [1] | Description
--- | --- | --- | ---
DeviceType | s | m | The UPnP type of the device, e.g., urn:schemas-upnp-org:device:MediaServer:1
UDN | s | m | The Unique Device Name of the server.
FriendlyName | s | m | The friendly name of the media server.
IconURL | s | o | A URL pointing to an icon that graphically identifies the server
Manufacturer | s | m | A string identifying the manufacturer of the server
ManufacturerUrl | s | o | A URL pointing to the manufacturer’s web site.
ModelDescription | s | o | A description of the server.
ModelName | s | m | The model name of the server.
ModelNumber | s | o | The server’s version number
SerialNumber | s | o | The server’s serial number
PresentationURL | s | o | The presentation URL of the server, i.e., a link to it’s HTML management interface.
ProtocolInfo | s | m | A string that identifies all of the file formats and network protocol combinations that the renderer supports. [2]
DeviceClasses | as | o | A list of supported device classes, such as DMR-1.5, etc.

The ProtocolInfo property identifies the types of URLs the renderer is capable of playing. The example value given above indicates that the renderer is capable of retrieving (via HTTP) and playing/displaying audio MP4 and JPEG files. Now the astute among you might notice that the information provided by the ProtocolInfo property is already available via the standard MPRIS SupportedMimeTypes and SupportedUriSchemes properties. This is true, however ProtocolInfo is still useful as its value is specifically formatted to make it easy to write a certain type of application called a Digital Media Controller (DMC).

When you write a DMC you instruct a DMR to play a media file exposed by a Digital Media Server (DMS). DMSs often publish the same piece of media content in a number of formats, exposing a separate URL for each format. The DMC can use the ProtocolInfo of his chosen renderer to determine which of the many formats is most suitable for the renderer and having done this to determine which URL to use. If the DMC uses dleyna-server-service to browse the contents of DMSs, it can achieve this simply by identifying the dleyna-server-service D-Bus object of the file it wishes to play, and then invoking this object’s GetCompatibleResource method, passing the renderer’s ProtocolInfo string as a parameter. This method will then return the most suitable URL for the renderer.

## org.mpris.MediaPlayer2

This interface is part of the MPRIS standard and is documented in the MRPIS D-Bus Interface Specification document [MPRIS]. As the interface is well described in this document, this section will focus on the peculiarities of dleyna-renderer-service’s implementation of this interface rather than the interface itself.

The main points of interest are:

- The methods Raise and Quit are implemented but they do nothing. The CanRaise and CanQuit properties necessarily return false.

- The property HasTrackList is always set to false. This is because TrackLists are not yet implemented. Hopefully, this will change in the future.

- The property CanSetFullscreen is always set to false and Fullscreen is not implemented.

- The DesktopEntry is not implemented.

## org.mpris.MediaPlayer2.Player

Like `org.mpris.MediaPlayer2`, `org.mpris.MediaPlayer2.Player` is a standard MPRIS2 interface and is already documented in the MRPIS2 specification. Consequently, this section will only describe the peculiarities of dleyna-renderer-service’s implementation of this interface. The main points of interest are noted below:

- The LoopStatus property is not implemented.

- The Shuffle property is not implemented.

- The Seek signal is not implemented yet.

- The first parameter to SetPosition is ignored, and any valid D-Bus path can be specified as its value.

- PropertiesChanged signals are emitted via the `org.freedesktop.DBus.Properties` interface of a renderer object instance when `org.mpris.MediaPlayer2.Player` interface properties value change.

### Additional Properties

Some new properties have been added, they are described below:

Name | Type | m/o [1] | Description
--- | --- | --- | ---
TransportPlaySpeeds | ad | m | Allowed play speed values supported by the renderer. It allows clients to set the Rate property with a value that will be accepted by the DMR.
CurrentTrack | u | m | The sequence number of the currently selected track.
NumberOfTracks | u | m | The number of tracks in the currently selected media.
Mute | b | o | The mute setting of the master audio channel. New in version 0.0.2.
CanByteSeek | b | m | Whether the client can control the playback position using ByteSeek and SetBytePosition.
BytePosition | x | o | The current track position in bytes.

### Methods

New methods have been added, they are described below:

GotoTrack(u TrackNumber) -> void

  Performs a seek operation to the specified track number.

OpenUriEx(s Uri, s Metadata) -> void

  Same as the OpenUri method of the org.mpris.MediaPlayer2.Player MPRIS2 standard interface, with an additional parameter Metadata to specify the DIDL-Lite XML description of the item to be opened. New in version 0.0.2.

OpenNextUri(s Uri, s Metadata) -> void

  Same as OpenUriEx method but for enabling an early download of the next object. New in version 0.2.0.

SetUri(s Uri, s Metadata) -> void

  Same as OpenUriEx except that it doesn’t automatically play the media. You need to explicitely call the Play method. New in version 0.2.0.

ByteSeek(x Offset) -> void

  Same as Seek but parameter Offset is not expressed in seconds but in bytes, and allows to set the seekmode by using “X_DLNA_REL_BYTE” unit. New in version 0.2.1

SetBytePosition(o TrackID, x Position) -> void

  Same as SetPosition but parameter Position is not expressed in seconds but in bytes, and allows to set the seekmode by using “X_DLNA_REL_BYTE” unit. New in version 0.2.1

## org.mpris.MediaPlayer2.TrackList

Not (yet) implemented

## org.mpris.MediaPlayer2.Playlists

Not (yet) implemented

## com.intel.dLeynaRenderer.PushHost

DMRs participate in two different DLNA use cases. Three Box System and two Box Push. In the three Box System a DMC instructs a DMR to play a URL hosted by a DMS. In two Box Push, an application pushes content it has created or downloaded directly to a renderer. In two Box Push the DMS is not involved at all and this presents a problem as DMRs do not really support the concept of Push. Rather than pushing files to a DMR, the client passes it a URL and then instructs the DMR to pull the content from the URL. For this to work, a web server must be running somewhere to host the URL. In the 3 Box System the role of the web server is played by the DMS. Unfortunately, as we have seen, in 2 Box Push there is no DMS. So who is to host the content to be pushed?

Conceptually, each application that wishes to push a file to a DMR could start its own web server on which it could temporarily host the file to be pushed. However, this is complicated for application developers and also wasteful of system resources. Potentially, every application that can create of download content can push this content to DMRs. As, these applications can legitimately run simultaneously having them run their own web servers would consume unnecessary system resources.

dleyna-renderer-service solves these problems by providing both a web server and simple APIs that can be used by clients to host files on this server. As only one instance of dleyna-renderer-service runs at any one time (well currently only one can run per user session) we avoid the proliferation of web servers. These push APIs are provided by the com.intel.dLeynaRenderer.PushHost interface which is implemented by all renderer objects.

### Methods

`com.intel.dLeynaRenderer.PushHost` contains two methods which are described in below.

HostFile(s path) -> s

  Hosts a file on dleyna-renderer-service’s web server. The parameter path should be a full path to the local file to be hosted, e.g., /home/user/Podcasts/pod.mp3. The value returned is the URL of the newly hosted file.

RemoveFile(s path) -> void

  Stops hosting the file whose full path is passed as parameter to this function.

dleyna-renderer-service only runs a web server when files are being hosted. Once all clients have stopped hosting files, either by calling RemoveFile or by exiting, dleyna-renderer-service will shut down its web server. Actually, dleyna-renderer-service may run more than one web server if multiple DMRs are accessed over different interfaces. When a client chooses to host a file for a given renderer, dleyna-renderer-service checks to see if a web server is already running on the interface through which this renderer is accessible. If it is not it starts a new web server. It follows that if clients try to host multiple files for multiple renderers running on different interfaces, dleyna-renderer-service may actually run multiple servers. However, it will only run one server per interface, and the server will be shutdown as soon as it no longer has any files to host.

Footnotes

[1] (1,2)

m/o indicates whether the property is optional or mandatory.

[2]

The idea behind the ProtocolInfo property is a little complicated and requires further discussion. The Protocol info field is a comma separated list of protocol info values. Each protocol info value consists of 4 fields separated by colons. Unfortunately, the format is too complex to describe in this document. The reader is referred to the UPnP Connection Manager Service Template document [CM2] and the DLNA Guidelines [DLNA] where it is described extensively. However, an example protocol info value is presented below, to give the reader an idea of what such a string might look like:

`"http-get:*:audio/mp4:DLNA.ORG_PN=AMR_WBplus,http-get:*:image/jpeg:DLNA.ORG_PN=JPEG_MED"`