A data processing system is provided comprising a main processor operable to perform a plurality of data processing tasks, a data engine having a data engine core operable to perform a number of said plurality of data processing tasks on behalf of said main processor and a data stream processing unit providing a data communication path between said main processing unit and said data engine core. The data stream processing unit has a control interface operable to receive from said data engine core at least one command and a data stream controller operable to receive at least one input data stream and to perform at least one operation on said at least one input data stream to generate at least one output data stream comprising a sequence of data elements. The data stream processing unit is responsive to said at least one command from said data engine core to control said data stream controller to perform said at least one operation.