Rivendell includes two modules specially optimized for performing automatic operations: the RDCatch and RDAirPlay modules. However, these two modules take radically different approaches in how they go about organizing and controlling operations, so a few words regarding each may be in order here.

RDCatch is aimed at executing actions on the basis of a strict time-based schedule, referred to as an event list. Each action (which can be a recording, a play out, an upload or download, a macro execution or an operation on an audio switcher device) executes on the basis of its scheduled time in the event list, independently of all other actions. As such, RDCatch is often best suited for use in settings such as network head end operations or 'auxiliary' roles at broadcast stations, where the transitions between events are generally not an important part of the presentation.

RDAirPlay takes a very different approach, in that most events are organized into one or more playlists or logs. A Rivendell log is a list of one or more carts, organized in chronological order. As the name implies, RDAirPlay is optimized for use in situations where the transitions between the various program elements are a key part of the delivery and presentation of the content, such as in live air play environments.

Of course, it's entirely possible to use both modules, even together on the same machine at the same time – the Linux OS makes for a very robust and capable multitasking system. In this chapter, we will take a look at the capabilities of RDCatch.