Introduction

 UPnP is an open standards based architecture based on TCP/IP and web technologies to provide control and data transfer between networked devices.

Devices that implement UPnP provide the following functionality,

  • Discovery
  • Control
  • State Eventing

Discovery is the automatic mechanism for (interested) devices to be notified when a UPnP device online status changes.

Control of a device is achieved by remote invocation of actions provided by the services implemented by the device.

State Evening provides an automatic mechanism for (subscribed) devices to be notified when a device's state changes.


UPnP AV Architecture

The main goals of the AV architecture are,

  • Support for arbitrary transport protocol and media formats
  • Ability for content streaming without intervention of the control point
  • Ability for control points implementations to be independent of transport protocols and media formats

Below shows the three players involved in the distribution (Media Server), playback (Media Renderer) and control (Control Point) of digital media.

The control point discovers the media server and media renderer and using the services provided by the media server and media renderer performs actions to create a link between the media server and media renderer (using a commonly supported transport protocol and media format) enabling the media renderer to playback the selected media.

Media Server

A compliant UPnP AV Media Server implements the following services,

  • Content Directory (Required)
  • Connection Manager (Required)
  • AV Transport (Optional)

The role of the media server is to allow a control point to browse, using the Content Directory service, the catalogue of media indexed by the server. Once some media has been selected, the media server establishes a connection with the selected media renderer and transfers the media to the media renderer using the appropriate transport protocol.

Media Renderer

A compliant UPnP AV Media Renderer implements the following services,

  • Rendering Control (Required)
  • Connection Manager (Required)
  • AV Transport (Optional)

The role of the media renderer is to 'render' the digital media into something consumable by the end user, e.g. convert a music file into an analogue signal for playback through speakers, converting a movie file into an audio and video stream for playback on a TV etc.

Control Point

The role of a control point is to discover all devices that the control point can control and provide an interface for the control of the discovered devices. An AV control point will provide a method of browsing a media server's catalogue of media and will perform all the necessary setup tasks to enable a user defined media renderer to playback the selected media.


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