We know that DVD brought a revolution in video and audio experience compare with VCD times, but with the technology developed with each passing day and people's increasing demand; we need screen wider and image quality higher, so the HD generated.
What's HD format?
HD video refers to any video system of higher resolution than standard-definition (SD) video, and most commonly involves display resolutions of 1,280*720 pixels (720p) or 1,920*1,080 pixels (1080i/1080p).