What Does 1080p Actually Mean?

1080p is two pieces of information joined together, and most people only ever use the first. The number is a count of pixel rows: 1,080 of them, stacked from top to bottom, almost always 1,920 wide. The letter is the part that gets ignored.

The p is not for pixels

It stands for progressive. Every frame is a complete picture, drawn in one go. The alternative, written with an i, is interlaced: each pass draws every other row, and two passes alternate to build a full picture.

Interlacing was an ingenious solution to a real problem. Broadcast bandwidth was scarce, and drawing half the rows twice as often gave the appearance of smooth motion for half the data. On the cathode ray televisions it was designed for, it worked well. On any modern display, which draws whole frames, interlaced material has to be converted back, and that conversion is never perfect. The comb-like artefacts on horizontal motion in old footage are the fingerprint of interlacing being undone imperfectly.

Full HD and its relatives

1920 x 1080 is commonly called Full HD, distinguishing it from the 1280 x 720 that arrived first and was simply called HD. Both are 16:9, the widescreen shape that replaced the older 4:3.

1,920 by 1,080 works out at 2,073,600 pixels, a little over two megapixels per frame. Put next to a modern phone camera taking twelve megapixel stills, that is a reminder that video resolution has always trailed photography, for the straightforward reason that video needs thirty of them a second.

Why a 1080p video can still look bad

This is the part the label hides. Resolution describes the grid, not what is drawn on it. A 1080p file compressed to a very low bitrate has 1,080 rows of increasingly approximate pixels: blocky, smeared on motion, banded in the sky. It is genuinely 1080p and it looks worse than a well-encoded 720p file.

The same applies to the source. Upscaling 480p footage to 1080p produces a file that is 1080p by the numbers and carries no more detail than it started with. The label is honest about the grid and silent about everything that matters.

Vertical 1080

1080 x 1920 is Full HD rotated: 1,080 across and 1,920 down. It has exactly the same pixel count and is often loosely called 1080p as well, which is imprecise but rarely causes confusion in context.

Is 1080p still enough?

For most viewing, yes. On a phone at normal distance, most people cannot reliably distinguish it from 4K on ordinary footage. On a large screen close up the difference is visible. Given a fixed file size, a well-encoded 1080p file will usually look better than a 4K one, because the bits are not being stretched across four times the pixels.