METADATA synchronization method with an audiovisual document using portions of frames and this metadata production device

The invention relates to a method for synchronizing a first metadata associated with an audiovisual document, the first metadata comprising a first signature of an audio frame and / or video of a sequence of the first document. Portions of the first document are included to provide a second document wherein the first metadata is no longer associated. A second metadata is first associated with the first document and the second metadata includes a second signature of the visual contents extracted from a portion of a frame of the sequence of the first document. Then, the first signature is detected in a sequence of the second audiovisual document. The second signature is then detected in the sequence of the second audiovisual document and the first metadata is synchronized with the second document using the second signature. In this way, the accuracy of synchronization between video content carried by the first signature is improved by the second signature and a new more accurate metadata is created.