| 摘要 |
There is provided a method of playing audio content of an audio-visual presentation to a viewer of video content of the audio-visual presentation in synchronisation with the video content, wherein playback of the audio content is synchronised with the displayed video content based on at least one ultrasonic synchronisation signal (400) received during display of the video content. The method comprises receiving and digitising an ultrasonic signal comprising the at least one ultrasonic synchronisation signal (400), the at least one ultrasonic synchronisation signal encoding a respective timecode through modulation of one or more ultrasonic carrier signals (410-1 to 410-8), wherein a first ultrasonic carrier signal which has been amplitude modulated to encode a logical "1" or a logical "0" in each of a plurality of data-carrying segments (412) of the amplitude modulated first ultrasonic carrier signal is received and digitised. Each of the data carrying segments (412) is followed by a non-data-carrying segment (414), in which the amplitude of the first ultrasonic carrier signal does not exceed a predetermined threshold. A digitised ultrasonic synchronisation signal in the digitised ultrasonic signal is identified, and the identified digitised ultrasonic synchronisation signal is decoded to determine the corresponding timecode by processing the digitised ultrasonic synchronisation signal to identify the data-carrying segments (412), and extracting the corresponding timecode from the identified data-carrying segments (412). A playback point in the stored audio content is then determined based on the determined timecode, and the stored audio content is played to the viewer from the determined playback point such that the audio content is played in synchronisation with the displayed video content. |
