subs will slightly cut off at the begining and the end of the sentece

Does any one know when using tmpenc , what aspect to use in aime with subs, the porblem i get the begining of the sentence the first few letters are cut off and at the end aswell. I think this is an aspect ratio problem, has anyone had this problem? any input will help. (i converting these to Mpeg2 for dvd playback@ 4:3 aspect ratio)