1. A method for modelling a set of transform coefficients, the method being performed by a device and comprising: determining at least one boundary coefficient value; determining one or more parameters for a first distribution model for transform coefficients of the set the magnitudes of which are greater than one of the boundary coefficient values; determining parameters for at least one further distribution model for transform coefficients of the set the magnitudes of which are less than the one of the boundary coefficient values; and performing a device operation on at least part of a composite distribution model which is a composite of the first distribution model and the at least one further distribution model having the respective determined parameters.