A method of processing an input data stream including at least one data peak (2), comprising: detecting at least one peak (2) in the input data stream having an apex with an amplitude above a predetermined threshold (4); and extrapolating (30) the segment of the peak which has an amplitude above the predetermined threshold (7, 8), based on a shape characteristic of the peak (2), to estimate the amplitude of the segments of the peak which have an amplitude less than said threshold (15, 16).