A method is proposed for optimizing the bit rate of multimedia contents accessible by a plurality of user terminals connected to a radiocommunications network cell. The multimedia contents are stored in the form of a plurality of independent chunks on at least one multimedia contents server associated with at least one contents provider. The method includes the following steps, implemented in a device for optimizing the bit rate: receiving one request to obtain a multimedia description file, sent by a user terminal; obtaining a multimedia description file; modifying the multimedia description file on the basis of a piece of information representing a quality of delivery, delivering a modified multimedia description file; and transmitting the modified multimedia description file to the user terminal.