This paper focuses on a user driven approach to improve video indexing. It consists in cumulating the large amount of small, individual efforts done by the users who access information, and to provide a community management mechanism to let users share the elicited knowledge. This technique is currently being developed in the "OPALES" environment and tuned up at the "Institut National de l'Audiovisuel" (INA), a National Video Library in Paris, to increase the value of its patrimonial video archive collections. It relies on a portal providing private workspaces to end users, so that a large part of their work can be shared between them. The effort for interpreting documents is directly done by the expert users who work for their own job on the archives. OPALES provides an original notion of "point of view" to enable the elicitation and the sharing of knowledge between communities of users, without leading to messy structures. The overall result consists in linking exportable private metadata to archive documents and managing the sharing of the elicited knowledge between users' communities. (Contains 22 references.) (Author/AEF)