An information processing apparatus having a device which processes data at a rate exactly adjusted relative to the rate of a data supplying device without requiring a common clock signal. A writing unit writes data into a buffer memory. When a first half of the buffer memory has become filled with data, a starter makes a reading unit start reading data from the buffer memory. A writing time measurement unit and a reading time measurement unit respectively measure the writing time required to write data in the buffer memory and the reading time required to read data from the buffer memory starting from the first storage location to the exact middle storage location of the buffer memory. A controller controls the rate at which data is read from the buffer memory based on the relationship between the writing time and the reading time.