Question about TV show reruns

[Mace Dolex]

So thanks to the advent of DVD's we can all now enjoy our favorite TV shows from our childhood up to the present in complete box sets fully restored and unedited after years of having to endure TV shows once they hit rerun heaven are sometimes painfully trimmed to add commercials from network affiliates.

So my question, is there any information on who or what group of people have the arduous task of combing through countless TV shows and having to edit every episode of every TV sitcom, drama, action show in order to fit more commercial time?

There are some sitcoms I grew up watching in reruns where I never knew were edited but then there are other sitcoms that are sloppily trimmed in where you can hear the laughtrack bleed through that you know a joke was cut.