Abstract: A method and a system for filtering a data stream in a telecom-munications network. The objective of the invention is to provide a filtering mechanism for a data stream whereby the amount of data in the stream is reduced without using compression and with a minimal loss of channel in-formation content. The system comprises two logically different memories. The first memory (201) is used to store channel control information and the second memory (202) to store channel information according to the control channel information stored in the first memory. The fill rate of the first memory is monitored and the content of the second memory is checked by the control unit (200).