In an audio-video synchronous playback control system which outputs coded audio data to an external audio decoding device so as to be decoded and played back by the external audio decoding device while playing back video data maintaining synchronization with the audio data playback of the external audio decoding device, an audio information analysis section figures out the size of one unit of the coded audio data and the size of audio data which is obtained by decoding the one unit of the coded audio data. A silent data generation section generates silent data of a size corresponding to the size of audio data. The video data playback of the video decoding/output section is controlled based on the amount of the silent data which are played back or processed by the audio output section.