A stream of data is accessed from a memory system by an autonomous memory access engine, converted on the fly by the memory access engine, and then presented to a processor for data processing. A portion of a lookup table (LUT) containing converted data elements is preloaded into a lookaside buffer associated with the memory access engine. As the stream of data elements is fetched from the memory system each data element in the stream of data elements is replaced with a respective converted data element obtained from the LUT in the lookaside buffer according to a content of each data element to thereby form a stream of converted data elements. The stream of converted data elements is then propagated from the memory access engine to a data processor.