Resolution and frame rate confusion

[sweatytim]

I think I understand resolution and frame rate from what I've read on this forum but my understanding is leaving one big question in my head so Im missing something. Could someone confirm my interpretation below:

1920 x 1080i = 1920 pixels displayed horizontally on 1080 lines which alternate at 540 lines.

1280 x 720p = 1280 pixels displayed horizontally on 720 lines at once.

If this is true then how can a TV with 1280 x 720 upconvert to 1080i?

Sorry for such a noobie question, Im trying to get this stuff straight in order to make better informed purchasing decisions. : to learn!

 

[berck]

If this is true then how can a TV with 1280 x 720 upconvert to 1080i?

Well, for every 1.5 pixels horizontal on a 1920 line, will create 1 pixel on a 1280 line. I'm not sure how they really do it in hardware, but its wouldn't be too difficult to create the process of that type of conversion. Its possible to take 3 pixels from the 1920 to have 2 pixels on the 1280 line. It could be as easy as taking 2 and then ignoring the third pixel. Since many manufacturers may empliment things differently, it wouldn't suprise me this is done. Another way can be to take the first two pixels from 1920 and average them to create the first pixel for 1280. Then take pixel two and three from 1920 and apply the same process to create pixel two for 1280.

On the 1080i lines and 720p, I can only assume that they use the 540 active lines to create 720 lines. Every 1 pixel line on the 540 active lines in 1080i is equivalent to 0.75 pixels on the 720p. Enessence, for three vertical pixels, they need to create four vertical pixels in the 720p scheme. The simplist approach would be to blank out every fourth line, but I believe that would be too easy to notice. They probably implement something similiar to what I suggest earlier with the horizontal pixels, only in reverse. They take the three pixels and use a process to create four.

 

[sweatytim]

Ok, I think I've got it. At least enough to know that it can be done. The day will come when I can upgrade my set to 1920 x 1080p and not worry about it anymore. Thanks for answering my question.