The defination of 1080p and 720p?
720p, made by SMPT Society of Motion Picture and Television Engineers,
is a format standard for high-grade HDTV . It refers to a progressive HDTV signal with 720 horizontal lines and an aspect ratio of 16:9 .
Each frame is displayed in its entirety on screen for 1/30th of a second.
This is know as progressive scan (hence the 'p').
A 1080i signal comprises 1080 horizontal lines but all the lines are not displayed on
screen simultaneously. Instead, they are interlaced (hence the 'i'), ie. every other lines is displayed
for 1/60th of a second and then the alternate lines are displayed for 1/60th of a second.