Modelling dependency in multimedia streams

Expressing and analysing data dependency in multimedia streams is promising, since content-aware policies at a transport level would benefit from such services. In this paper we present a format-independent dependency model aimed at specifying, validating and reasoning about structural dependency in multimedia streams. Based on this model, we developed a universal dependency description language and a dependency validation service to serve as an infrastructure for content-aware transport layers. Driven by application knowledge, this special form of a cross-layer design enables lower layers to reason about the impact of data loss and drops during transmission while being unaware of the real data format.We outline, how this infrastructure can be used to build content-aware error protection policies and explain how applications need to specify dependency and prepare media streams in order to gain benefits from those policies. While costs and benefits of a dependency model are only quantifiable in conjunction with special policies, we report on the general worst-case costs of our model here.