CRC calculation for PSI data

Dear All, For some reason, I am trying to separate PSI information from .ts data which follows MPEG-2 standard. When I am trying to get, PAT data, some times I am getting wrong data, but the version of the PAT table is not changing. So, I have decided to check the CRC value of the data. But, I couldn't find a correct algorithm for calculating CRC of MPEG Data.So, could any of you please guide me in this. Thanks in advance..... Regards & Thanks, Satyanarayana KVP.