ETSI TS 103 320 specifies the GEM Companion Screen Service Framework, which is addressing the Phase 1 and 1+ of DVB's companion screen requirements. These requirements ask for extensions of the GEM middleware specification ETSI TS 102 728 [1], to support information exchange and synchronization between the companion screen and the primary service.

The Companion Screen Service Framework provides the infrastructure for GEM companion services that offer their functionality to companion devices in the home network. GEM companion services allow broadcasters and content providers to dynamically provide companion services that integrate screen devices, such as mobile phones, tablets, PCs etc. into the viewing experience.

GEM companion services can be deployed via regular GEM applications and enable the broadcaster and content provider to dynamically add companion services, thus augmenting the experience of the viewer to companion devices.

These companion devices can communicate with the GEM companion services via standardized protocols (e.g. UPnP, REST, WebSockets) or can chose to implement proprietary communication protocols.

The framework defines a common discovery mechanism based on the UPnP Application Management Service for these services.

The companion screen service framework as defined by the present document is orthogonal to GEM profiles and versions and can be used on all GEM platforms and derived platforms (MHP, OCAP, BD-J).