Model and model update technique in a system for modeling the relationship of the bit rate of a transport stream and the bit rate of an elementary stream carried therein

A method and system are disclosed for controlling the generation of a systems layer stream, such as a transport stream, that carries a program made up of at least one elementary stream, such as an encoded audio signal or an encoded video signal. The systems layer stream is made up of serial segments, such as packets, which contain information specific to the systems layer, such as headers, and segments of elementary stream data. The bit rate of one or more of the elementary streams is adapted in accordance with a dynamically changing relation that relates the bit rate of such elementary streams to the bit rate of the portion of the systems layer stream that carries them.