Stream generating apparatus and method of supplying frame sync signal used for stream generating apparatus

A stream generating apparatus includes an acquirer which acquires from an external source a reference signal synchronized with the video signal, a self-driven counter which has a first count mode in which the number of clocks in the frame period is counted in synchronization with a reference signal acquired by the acquirer thereby to generate and supply a first frame sync signal to the first and second signal processing units, and a second count mode in which the number of clocks in the frame period is counted independently not in synchronization with the reference signal thereby to generate and supply a second frame sync signal to the first and second signal processing units, and a controller which switches a count mode between either from the first count mode to the second count mode or from the second count mode to the first count mode based on predetermined conditions.