A method of processing a data stream includes taking a first number of samples of the data stream using a sampling clock over a first observation window and storing a stored data stream including the first number of samples in a data buffer. A length of the first observation window is determined by a reference clock. A measured number of cycles of the sampling clock are determined from the first number of samples. An error between an expected number of cycles of the sampling clock and the measured number of cycles of the sampling clock in the observation window is measured. The stored data stream corresponding to the first observation window is updated to contain a second number of samples by correcting the first number of samples with the error.