1080i

1080i is a standardized video signal for HD television. The image consists of 1080 vertical lines with 1920 pixels in each line.

The ‘i’ in 1080i stands for ‘interlaced’, which implies that with each image refresh cycle either the odd or the even lines will be updated. Although 1080i has more vertical lines than 720p, effectively 1080i only rewrites half of it’s number of lines within each refresh cycle. (see the enlarged illustration). As a consequence the real difference in image quality between 1080i and 720p is rather small. On the other hand the advantage of interlaced is that this format demands significantly less bandwidth in comparison to the so called progressive signal.

720p and 1080i currently are the most popular formats for HDTV.

An interesting article to read maybe 720 > 1080