The Coherence toolkit offers the following multi-media related components:

• DLNA/UPnP Media Server (Coherence), which exports local files or online media to UPnP clients. There are many backends to fetch media from

  • local applications media collections, like those from Rythmbox or Banschee,
  • Audio-CD or DVB,
  • online services like Flickr, last.fm, YouTube, Picasa Web Albums and other.

  Due to the comprehensive plug-in architecture, these can easily be expanded.

  Coherence also contains an audio/video DLNA/UPnP MediaRenderer application, based on the GStreamer framework. It includes the source-code framework used by the other components. The media server supports Transcoding (experimental).

• Coherence-Config is a cross-platform GUI frontend for 'Coherence'.

• An image DLNA/UPnP MediaRenderer (Cadre), which can display pictures from the local filesystem or from a MediaServer.

• An application level proxy for UPnP devices (Mirabeau) which allows to share your UPnP content between two or more local networks over the Internet. It uses XMPP as a transport (work in progress).

• The UPnP-Inspector is a graphical UPnP Device and Service analyzer, and a debugging tool. Detected devices are displayed in a tree-view, where - amongst other things - actions can be called and state-variables be queried. It can also be used as a UPnP ControlPoint.

• Plugins or extensions for other applications to open them to the UPnP world, thanks to the framework (either as MediaServers, ControlPoints or MediaRenderers). This includes Totem, Nautilus, Eye Of Gnome, Rythmbox, Banshee, Elisa, amarok...

Additionally there is a command-line tool to work with UPnP Internet Gateway Devices (Puncher). Many routers offer an UPnP InternetGatewayDevice to query informations about the WAN connection, the link status, external IP address and to enable port-mappings that allow inbound connections to the local LAN. Puncher allows you interacting with these devices.

Developers get a framework written in Python with an emerging DBus API. This framework is designed to automate all UPnP-related tasks as much as possible and enable applications to participate in digital living networks, primarily the UPnP universe.

The core framework of Coherence provides:

• an SSDP server
• an MSEARCH client
• server and client for HTTP/SOAP requests
• server and client for Event Subscription and Notification (GENA)
• A device implementation dock

UPnP device implementations are pluggable. For instance, we can pick the MediaServer device and plug it into the core. Or attach the MediaRenderer device. Or attach both, or two MediaServers and a ControlPoint - this is the point where one of Coherence's particular features kicks in.

This probably makes more sense if we look at how UPnP devices are implemented within Coherence. On one side of the device we have the connectors to the core, but on the other side there is a dock for a backend to be plugged in. So a device implementation is generally a simple translation map between the the core and its backend.

As an example, a MediaServer connects to the core via the ContentDirectory and ConnectionManager services and bridges them to a filesystem backend. Or bridges them - let's say - to a less skimpy one, the MediaStore of a MediaCenter exposing its content in a way already presorted by album, artist, genre, etc.