Precisely. OTA terrestrial HD signals are MPEG-2, typically at 19 Mb/sec. The satellite and cable providers often convert to MPEG-4 (nothing wrong with that) and reduce the bandwidth (and that's where the problems begin).

My parents used to have AT&T U-verse (TV over DSL). They moved and can't get U-verse in their new place, but it comes with free (analog) basic cable. Solution? They have an OTA antenna to get HD local channels and the free cable for what it's got. My father, he of the massively maladjusted TV settings who wouldn't know contrast from brightness or color from tint, was blown away by how much better terrestrial HD is than the same channels through AT&T U-verse.