The patrimonial video collection of the Bibliothèque nationale de France constitutes a whole that is diversified on a technical level and qualitatively inhomogeneous, reflecting the publishers' production process. To conserve it and ensure its availability in the long term creates a real challenge for the Bibliothèque nationale de France, which for long seemed insurmountable. The massive dissemination of digital technologies and the imposition of the MPEG-2 standard make possible the implementation of a vast programme of permanent digitisation of the collection on magnetic analogical backup material, thus reconciling aspects until then antipathetic to preservation and ease of access. As well as not resolving the questions of "deontological" order inherent in all forms of transfer, digitisation does not dispense with the need to carry out actions in terms of preventive maintenance of backups. It also opens the door to other problems specific to "digital objects" and to their management, as well as to areas of investigation on the optical backup material.