This demonstration presents an audio based audio-visual synchronization method and its real-time application. In everyday applications, videos and sounds are often recorded separately without time code. In this situation, an editor has to synchronize videos and sounds manually, and that work is usually complicated. Our system synchronizes videos and sounds automatically in real-time by comparing features between an audio signal embedded in a video and a sound recorded separately. Features are extracted from audio based on time differential of short-time spectra. A video will be play-backed by following a separately recorded sound signal while all calculations are executed in real-time.