When inputted pixels from an input DMA unit, a packing unit outputs data package. One data package consists of α inputted pixels. A memory control unit writes, on a write line memory at a write interval, the data package that is outputted by the packing unit. The write interval is α times longer than an input interval at which the pixels are inputted into the packing unit. During the writing process, the memory control unit reads out another data package from a read line memory at a read interval that is the same as the input interval. In addition, the memory control unit treats the write line memory as the read line memory, after completing the writing process. Alternatively, the memory control unit treats the read line memory as the write line memory, after completing the reading process.