Progressive vs Interlaced Video Explained

Along with all of the different HDTV resolutions (480p, 720p, 1080i) there is also the progressive ‘p’ and interlaced ‘i’ aspect of the video. Here’s what you need to know about each.

Interlaced video is drawn on your TV screen by first showing you the odd lines of the image and the even lines of the image within 1/60 of a second leaving you with the full picture with some occasional flicker and maybe some distortion.

Progressive video is drawn on your TV screen by showing you the full image at once going left from right in 1/60 of a second giving you a more stable image with less flicker and distortion.

You will often see people discussing whether 720p or 1080i is the best HD resolution. The 1080i has a higher resolution and will have better quality but since it is interlaced video it will be more unstable. The 720p has lower resolution but since it is progressive the image will be more stable and possible less distortion. I think your preference will depend on how your eyes view the images – the 1080i is too jumpy or unstable for some people and they prefer the 720p resolution.

CNET has a nice write-up on progressive scan and offers some good technical details:

Progressive scan works in the same manner as your computer monitor. It writes one full frame of video from left to right across the screen every 1/60 of a second. Since the entire image is drawn at one time--as opposed to an interlaced image where the even lines are drawn first, followed by the odd lines--a progressively scanned video image looks more stable than an interlaced one. Progressive scan also introduces fewer motion artifacts, such as jagged diagonal lines and movement in fine detail, into the picture.

To read more about progressive scan DVD players, check out home theater hi-fi’s great write-up that goes into progressive vs interlaced and what the real differences you may see between your DVD player doing the progressive scan or your TV:

Many current progressive players fall back into a very watchable but very soft video mode when they aren't sure whether the source is film or not. In the worst case, the entire film will look excessively soft, which means they're getting exactly no benefit at all from their progressive player.

So what’s your preference – 720p or 1080i?