6. The method according to claim 1 , wherein said coding by reference comprises coding a coding data item corresponding to an entry of at least one dictionary of references, wherein an entry of said dictionary of references gives identification information on an entry of the selected indexing dictionary, an item of positioning information and an item of length information.
6. The method according to claim 1 , wherein said coding by reference comprises coding a coding data item corresponding to an entry of at least one dictionary of references, wherein an entry of said dictionary of references gives identification information on an entry of the selected indexing dictionary, an item of positioning information and an item of length information. 7. The method according to claim 6 , wherein said identification information comprises an identifier of a dictionary among the plurality of indexing dictionaries, and an identifier of said entry identified within said selected indexing dictionary.