Controlling the focus and input events in multimedia applications

Abstract

Multimedia applications can contain other embedded multimedia applications specified using the same or different languages. Therefore, during an application presentation there must be a mechanism to rule which language players and media players control commands (events) coming from input devices, and which ones control the focus on their related child objects, in a given moment of time. This paper presents a hierarchical control model addressing this mechanism. The proposal aims at supporting declarative languages targeting both Web and Digital TV applications. The model is first presented in its general scope. Then, its potential use by some standard declarative hypermedia languages (HTML-based, SMIL and NCL) is discussed. Since NCL has adopted the model in its standard specification, the discussion targeting NCL is more detailed, showing how the NCL player, part of the reference implementation of Ginga middleware, has been developed. NCL and Ginga are ITU-T H.761 Recommendation for IPTV services and part of the ISDB-T standards.