A method of forming a derived digital signal from a compressed digital signal which has been obtained by compressing an original digital signal including original data representing physical quantities and grouped together in blocks of data ordered in the original signal. The method includes obtaining information contained in the compressed digital signal and representing the structure of the signal and the organization of the data therein, and from the information, forming a skeleton of the derived digital signal which at least partly includes this information and at least one leader and one body intended to subsequently contain compressed blocks of data, the skeleton thus formed being in accordance with a description syntax of the compressed signal.