A droplet ejection device includes a liquid ejection head, a supply flow path, a supply pump, and a supply flow path pressurizer. The apparatus generates an intermediate data stream in each of a plurality of stages into which an input data stream is divided in interpretation in the native environment and filters the intermediate data stream to generate a filtered data stream in the interpreter environment. ; growing on the MgO layer a low temperature growth layer made of ZnO group material at a substrate temperature of 500\xb0 C. The capacity setting device sets a first discharge capacity target value for the variable capacity compressor.