What is the difference between 1080i and 1080p?

by Anonymous

When I connect my blu ray player to my lcd tv it shows me I am getting 1080p. When I watch something through my HD cable box it tells me that it is 1080i.

I thought both of these were supposed to be high definition - so why the difference?

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What is the difference between 1080i and 1080p?

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by: Paul - The Home Cinema Guide

Hello Anonymous!

Firstly, these are both high-definition signals, so there's no need to worry about that, the difference is just down to how they are displayed on your TV.

The 1080p signal from your Blu-ray player is a progressive signal (hence the 'p' at the end), which means the image is drawn on your TV screen line by line - or line 1 through to line 1080.

The 1080i signal from your cable box is an interlaced image (hence the 'i' at the end). This also has 1080 vertical lines of information, but the difference is this image is drawn in two passes down your TV screen - first the odd lines (line 1 to line 1079) and then the even lines (line 2 to line 1080).

The downside of an interlaced image is this method of drawing the image in two passes can make the picture appear to flicker or lack sharpness - although it can be hard to tell the difference.

Most TV companies send their HD images in 1080i as it takes less bandwidth to send this type of signal.

Anyway, all that is explained in a bit more detail (with pretty pictures!) in this article about 1080i, 1080p and 720p.

All the best

Paul