The invention relates to a device for demultiplexing coded data corresponding to multimedia objects. The data is organized in a bitstream divided into individually accessible portions--for instance Access Units for an MPEG-4 compliant bitstream--themselves subdivided into smaller data entities--SL-packets in the cited example--which all the demultiplexing operations are applied to. The operations are mainly, for all the data received at the input of the demultiplexing device: reading and formatting of a buffer, extraction of successive Access Unit segments, progressive reconstruction of a complete Access Unit, transmission of the Access Unit to an output buffer or file.