A method of forming a reduced compressed digital signal, in which the reduced compressed digital signal is formed from an initial compressed digital signal with several hierarchical levels which has been obtained by the compression, according to a hierarchical compression format, of a digital signal comprising data representing physical quantities. The initial signal thus compressed includes at least one header which includes information representing the configuration of the signal and the structure of the data therein, the configuration of the signal being defined by an initial set of parameters characterizing all the hierarchical levels of the signal. The method includes forming, from the at least one header of the initial compressed signal, at least one header of the reduced compressed signal which includes information representing a reduced configuration of the initial signal and the structure of the data in the compressed signal of reduced configuration, the reduced configuration being defined by a final set of parameters characterizing at least one of the hierarchical levels of the initial compressed signal. The compressed data is extracted corresponding to the final set of parameters from the initial compressed signal, and this data is inserted into the reduced compressed signal being formed.