HGTV HD, a 1080i HD channel, originally did not simulcast its parent channel, but featured programming separate from HGTV.
On March 31, 2008, HGTV, along with the Food Network, launched its HD simulcast of its SD feed. SD programs on the HD feed are stretched to fill the screen rather than presented in their original 4:3 aspect ratio.
Read more about this topic: HGTV (United States)