In measuring the resistance value of an output buffer, a supply voltage is supplied to a first P-channel transistor in its source through an ammeter provided within an IC tester, a ground potential is supplied from the IC tester to a first N-channel transistor in its source, and a voltmeter provided within the IC tester is connected to a first external output terminal. The conversion can also use the filtered lower bit depth video for tone mapping and tone mapping derivation. When it is determined that there is no overlapping period, a high speed control is performed for controlling electromagnetically driven valves.