A flexible interface that enables an application to communicate directly with processing modules to easily control the processing of streaming data. The interface provides basic commands for applications to use to communicate with processing modules and provides the flexibility to adapt to changing standards. The interface enable an application to set the type of input and output data formats of a processing module and control when the processing module processes input data and generates output data. The processing modules enurmerate its capabilities by category, by media type, or by both category and media type. Processing modules are registered by class ID, category, whether the application needs a key, the number and types of input data types, and the number and type of output data types to register.