The present invention relates in particular to a synchronization system and process. The synchronization system comprises a specification unit for specifying synchronization signals associated with an audiovisual programme, the latter comprising an audiovisual content and control information, a recognition unit for recognizing these synchronization signals in a stream carrying this programme transmitted via a broadcasting network, by recognizing at least one extracted portion of the audiovisual content, and an activation unit triggering an action in case of detection of these signals. The specification unit prepares and transmits to the recognition unit recognition elements making it possible to obtain this extracted portion, which comprise instructions for extracting the portion of content from at least one stream of an audiovisual programme previously received by the recognition unit via the broadcasting network. In variants, the recognition elements are obtained independently of the specification unit. Applications to interactive television and to automatic recordings.