A method for extracting a subset of data from an ordered set of bi-dimensional matrices (data arrays) such as a sequence of pictures or a multi-dimensional matrix, for instance, is implemented by dedicated hardware that may be used each time it is necessary to extract a subset of data from a data array. For each matrix of data, the method calculates very quickly row and column indices of border data of the portion to be extracted, which are obtained by arithmetical operations among row and column indices of vertices of a closed area of interest. The method is implemented in a device for selectively transferring a data stream sampled at a certain bit-rate to a microprocessor unit or to a memory receiving the data stream at a different rate.