What is HD video?

The days of standard definition video are over. You have probably seen high-definition, or HD, on some of the videos you watch or printed on the box your television came in, and you may be wondering what makes HD quality video different.

In technical terms, HD video is any video with a resolution of 1280 x 720 or 1920 x 1080, denoted by 720p and 1080i/1080p respectively. These formats of video can display anywhere from 24 to 60 frames per second and are widescreen (16:9). If you are looking at information on a television, for example, you may notice the words progressive scan or interlace scan. Progressive scanning means the entire picture is drawn for every frame whereas interlace scanning, which is only for 1080 displays, is where half the lines are redrawn every other frame.

Here is the breakdown:

  • on average, standard digital television (SDTV) has 480 lines in the vertical display resolution compared to high-definition television's (HDTV) 1,080 or 720 lines. If you are having a hard time conceptualizing the difference, think about bed sheets. The higher thread count a set of sheets has, the softer those sheets will feel. A higher number of lines in the vertical display resolution is one of the things that gives you a clearer picture.
  • SDTVs usually have a refresh rate of 24, 30 or 50 frames per second versus HDTV's refresh rates of 60-600Hz, with hertz (Hz) meaning actions per second. Higher refresh rates do not change picture quality, but they do make the image smoother, tricking our eyes into seeing the flickering screen as continuous video.
  • Most standard televisions use interlaced scanning, which offers greater image resolution than progressive scanning when subjects are not in motion but loses up to half of the resolution when subjects move. On the other hand, high-definition televisions usually have a progressive scanning system, meaning quality is not sacrificed when subjects are moving on screen.

Once you have an HD television, or even without an HDTV, the next thing you will look at is HD content. You can find HD image sources on the Internet and video game consoles or through terrestrial broadcast, direct broadcast satellite and digital cable. Created for the purpose of high-definition video, Blu-ray discs provide ample digital storage for HD video content. The discs were designed to replace traditional DVDs but have largely not been adopted by the general public since their official release in June 2006. A proponent of Blu-ray, Sony designed the PlayStation 3 to play Blu-ray discs while Nintendo's new Wii U will support HD and the Xbox 360 already supports 1080p quality.

There are lots of online video streaming sites, like YouTube, Hulu and Vimeo, that offer HD video. Online, HD quality videos take longer to load, and the image quality of online HD videos is lower than that of broadcast HD, and occasionally poorer than DVD video, because of the heavy compression required.

How and where we watch HD quality videos is changing everyday due to advances in video technology. Whether you have a 50" Panasonic Viera or an Apple iPhone, HD is becoming the industry standard in video resolution, and it is important to know what makes high-definition different from the old standard.