The scheduler is responsible for managing the plugins at runtime. The main responsabilities are: Preparing the plugins so they can be scheduled. Monitoring state changes and enabling/disabling the element in the chain. Choosing an element as the entry point for the pipeline. Selecting and distributing the global clock. The scheduler is a plugable component, this means that alternative schedulers can be written and plugged into GStreamer. The default scheduler uses cothreads to schedule the plugins in a pipeline. Cothreads are fast and lightweight user-space threads. There is usually no need to interact with the scheduler directly, however it some cases it is feasable to set a specific clock or force a specific plugin as the entry point in the pipeline.