Originally Posted by npras42
Is this entirely correct?? I've never entirely understood...
Is this all correct?
You have things mixed up a little. First off, http://en.wikipedia.org/wiki/High-definition_television
1080i = 1080x1920x60hz (interlaced)
1080p = 1080x1920x30hz (progressive)
So, for 1080p, the image will be drawn line by line from 1 to 1080, 30 times a second. For simplicity we will say you get 1080 lines drawn once every 30th of a second.
For 1080i, the image will be drawn first by filling in all the odd numbered lines from 1 to 1079, then going back and filling in all the even lines 2 to 1080. As well for simplicity we will say you get 540 lines drawn once every 60th of a second.
If you do your math, you will notice that both methods have the exact same bandwidth requirements, and that if you had a memory buffer that could hold a single frame of data, it would be simply to convert from one into the other. In the case of going from interlaced to progressive, hold on to the first set of 540lines and then drawn them progressively when you get the second set, but it would half your refresh rate. In the case of progressive, if you hold onto the second set of 540 lines and draw then after, which would increase your refresh rate.