MHEG
From MythTV Official Wiki
MHEG is a type of Interactive TV used in DVB. It includes such things as an enhanced channel guide, access to additional video streams, and games. So far the MythTV implementation only contains support for the UK and New Zealand profiles.
New Zealand has also decided to adopt MHEG as part of its FreeView digital platform. They are using a modified version of the UK 1.0.6 profile. Initial support for the NZ Profile is included in 0.21