"High-definition" is the abbreviation for "high-definition." HDTV is a type of television that uses progressive or interlaced scanning, a widescreen (16:9) aspect ratio, and a height resolution of 720 or 1080 pixels. HD can refer to either 720p or 1080p when live-streaming. This means that some viewers will be left frustrated by inevitable buffering and small video sizes. But have no fear because there are solutions to these problems. While there are many devices you can use to stream videos, HD video quality on all devices is still a problem.