What is High Definition?

Boy does this make for some great discussions on the boards and mailing lists. Even technical folks seem to have strong feelings that conflict with each other. Seems the actual definition of “High Definition” is up for debate.

Let’s get the basics out of the way so we can dive into the deepest depths of the debate and discussion. According to Wikipedia, we have three things to consider when deciding whether a video is actually “high definition.”

  • The number of lines in the vertical display resolution.
  • The scanning system: progressive scanning (p) or interlaced scanning (i).
  • The number of frames or fields per second.

The number of lines in the vertical display is typically what we use when discussing HDTV. 1080p and 720p both refer to the number of lines – top to bottom – in the display and the scanning system (in this case progressive is indicated with the “p”).

You might also come across folks that are discussing 480p. This is the native resolution of a standard DVD, and is considered by many as “enhanced definition.” Even though some TVs can upscale smaller formats – 480p is not considered HD.

So, HD is defined by the number of pixels in the display. As most of us will find out, or have found out already, the number of pixels doesn’t dictate quality. Put a low quality signal through a nice HDTV and you get mud – hard to even watch. Many of the folks shooting video these days are using HD equipment to record and edit the video. This typically makes the video look better on both HD and standard definition TVs.

To experience a bit of why the debate exists, take a look at the price ranges for video cameras that boast “HD” capabilities. Some on the lower end might have all the pixels necessary to be defined as HD, but have terrible quality. If you’re in the market for a video camera, you should pay attention to other distinguishing features as well, such as the number of CCDs (Charge Coupled Devices) in the camera. The cameras with 3 CCDs offer much higher quality than a 1 CCD camera (for more information in this regard check out the page on Wikipedia on Three CCDs). We’ll save additional discussion on this for a future blog on choosing a video camera.

Here is the definition of HD as shared by Ben Waggoner, a very well known video expert with Microsoft and author of Compression for Great Digital Video. From an email just over a week ago:

“At Microsoft we’ve decided as a matter of policy that we won’t use a HD logo or terminology for anything that’s not at least 1280 wide or 720 tall. For example, some of our sporting event Silverlight players has a HD logo that only lights up when it’s receiving a 720p stream, and is dimmed at lower bitrates. In cases where there’s stuff we think is notably good, but not full HD (like the NCAA March Madness live streams) we may use a “HQ” logo or terminology to indicate the higher quality streams. But we’re going to do our part holding the line on the real definition of HD.”

According to Ben, who I trust, “Full HD is already available via the internet.”

So, HD is really limited to only two sizes: 1280×720 and 1920×1080. I’m pretty sure this is correct 🙂

If you want to learn more about screen resolutions in general, visit the Wikipedia page on Display Resolution. Included on this webpage is the following list for current resolutions for Televisions.

  • SDTV: 480i (NTSC uses an analog system of 486i split into two interlaced fields of 243 lines)
  • SDTV: 576i (PAL, 720×576 split into two interlaced fields of 288 lines)
  • EDTV: 480p (720×480 progressive scan)
  • EDTV: 576p (720×576 progressive scan)
  • HDTV: 720p (1280×720 progressive scan)
  • HDTV: 1080i (1920×1080 split into two interlaced fields of 540 lines)
  • HDTV: 1080p (1920×1080 progressive scan)

If you really want to dig into the technical details of HD, I would suggest taking a look at Ben Waggoners page here on Understanding HD Formats.


Posted by Chuck Ebbets   @   30 November 2009

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