Why is the i or p ( interlace or progressive scan) at the 1080 lines and not the 1920 lines HDTV?

Question

I mean, why doesn't it say 1920i or 1920p? Why does it have to say 1080i or 1080p? Or just 1920i/1080i or 1920/1080p?

Answer 1

Because the lines of pixels are processed horizontally and not vertically.  No, as the horizontal lines build on top of each other the vertical lines work their way up.  Only one direction needs to be processed.

Answer 2

The distinction between interlaced and progressive is between horozontal lines, not verticle. When the image is interlaced the screen is alternating between the odd and even HORIZONTAL lines. That is why we count Horizontal lines for the rating.

Also resolution is a rating transplanted from computer monitors as analog TVs never used to give a Verticle line rating only Horizontal and we would look for a TV with as many "lines" as we could instead of a high "resolution." Also strictly speaking there is no requirement for an HDTV to be 1080 by 1920. In order to be called HDTV the image has to be at least 720P or 1080i. There was no requirement that the horizontal resolution be 1920. It could be 1080i with a horizontal resolution of, say 1200. As long as the verticle resolution was 1080i the manufacturer is allowed to call it HDTV. 1080x1920 is just the maxximum resolution within the ATSC format. (you will see higher resolution TVs eventually that scale this resolution higher but the signal will max at 1080x1920)

This was more for the CRT TVs. Now that everything is fixxed pixel we usually assume a 1080p TV is 1920H and a 720p is 1366H or so.

Incedentally none of the current TVs are interlaced. All LCDs, Plasmas, and fixxed pixel projectors are progressive. If you see a 1080i rating on one they are misleading you by using the maximum allowable input signal. These TVs then downscale to 720P or whatever their maximum native resolution is.

Answer 3

To make it easier obivousally

Answer 4

Our terms for resolution are influenced by the legacy of our original TV's technology. In that legacy, an electron gun was used to scan horizontally across a series of phosphoric dots arranged in a line across the face of a glass screen. Because this scanning occurs horizontally, we have always referred to resolution as (vertical) lines of resolution. The horizontal resolution was never needed because the aspect ratio fixes the horizontal resolution as a ratio tied to the vertical resolution (i.e 4:3 or 16:9). Specifying only the vertical resolution, therefore, becomes a short hand nomenclature for the complete resolution (i.e. 1080p = 1920 x 1080 with 16:9 aspect ratio).