A device (D) is dedicated to data stream processing within a communication satellite of a communication network. This device (D) comprises processing means (MT) whose job is, in the event of receipt of a first incoming data stream whose carrier exhibits a first modulation and comprising at chosen locations chosen insertion blocks, i) to detect the insertion blocks and at least one characteristic of the carrier of the first incoming stream, chosen from among its frequency, its phase, its timing and its amplitude, ii) to modulate, in accordance with the first modulation and having regard to each detected characteristic, data packets to be transmitted to a destination common with that of the first incoming stream, and iii) to replace with the modulated packets certain at least of the insertion blocks detected in the first incoming stream which has not been demodulated, so that the resulting stream is transmitted by the satellite, with its first original modulation, to the common destination so as to be demodulated therein as if it had been constituted by a single modulator.