information which is used to specify coding parameters and is therefore sent in smaller quantities than the main error prediction signal is sometimes called side information.  Variations on coding may include trade-offs between the amount of this side information and the amount needed for the error prediction signal.

For example, the use of three types of encoded pictures in MPEG 2 allows a certain reduction in the amount of error prediction information, but this must be supplemented by side information identifying the type of each picture.