1080p > 1080i... why?

Author
Discussion

Nuclearsquash

Original Poster:

1,329 posts

263 months

Monday 26th January 2009
quotequote all
Why is 1080p considered better than 1080i?

My tv at home is capable of max 180i, bought before the wide availability of 1080p, when viewing blu rays through my PS3 i've noticed that the picture is "better" for want of a better word @ 720p than if i view it at 1080i, to me it seems less pixelated, and sharper, but surely the resolution is that much higher again at 1080i that it should be better.

Hope that makes sense.

randlemarcus

13,530 posts

232 months

Monday 26th January 2009
quotequote all
refresh of picture (hopefully less artefacts, fuzzy motion etc).
1080i is interlaced, so only half the screen refreshes every pass.

dtmpower

3,972 posts

246 months

Monday 26th January 2009
quotequote all
Because i means interlaced - which basically means you get the fuzzy half screen refreshes.

Interlaced is where lines 1,3,5,7,9 change in one cycle , and in the next cycle 2,4,6,8,10 lines etc do....

Mr_Yogi

3,279 posts

256 months

Monday 26th January 2009
quotequote all
Your TV isn't really a 1080i set, there are no LCD or Plasma 1080i panels (well maybe some ALI/ ALS? plasmas from years ago?).

Both these types of panel are progressive which means they change the whole picture with each refresh, as opposed to CRT TV's which are traditionally interlaced, meaning they scan (display) the even lines, then as these are decaying scan the odd lines, etc.

Any interlaced signal means it has two fields (odd and even lines), If you simply add these together you get artifacs because they are from different 'times'.

For example if you had a black square moving accros a white screen, left to right, the leading edge of the square wouldn't be straight but instead would look like saw blade or combe, as every odd line would be ahead of the even lines. The faster the square moves the bigger the distance between the odd and even lines.

The other way of displaying the image on a progressive dispaly would be to just take 1 field (odd lines) and double each line, then display the next field (even lines). This obviously reduces the verticle resolution of the image by ½!

There are some instances (movies for example) where the original 1080p progressive image can be reconstructed from the 1080i signal, but for anything recorded using video (broadcast TV - news, live shows, sports incl. Sky SportsHD, etc.) displaying an interlaced signal on a progressive panel is a pain.

That's why more expensive TV's are generally better, as they have the power processing power to deal with these sintuations much better, decided when best to use each of the above techniques and even blending a number of frames together.

Your panel will likely be 1366x768 (ish) resolution and as thats much closer to the res the games are rendered in you'll get less artifacts anyway.

Also when you get the PS3 to downscalling blurays from 1080p to 720p that's not a hard job then the TV upscaling from 720p to 768x1366, keeps everything progressive. As opposed to the PS3 interlacing 1080p to 1080i, then you TV de-interlacing (and possibly throwing away ½ the verticle resolution) and downscalling (and possibly upscalling yikes) the image to 768x1366.

Edited by Mr_Yogi on Monday 26th January 17:29

Plotloss

67,280 posts

271 months

Monday 26th January 2009
quotequote all
On televisions its a moot point anyway, 95% of people arent sat close enough to notice the difference.

Projectors a different matter...

Nuclearsquash

Original Poster:

1,329 posts

263 months

Monday 26th January 2009
quotequote all
i don't have the ability to compare to 1080p, but to my eye, the 720p picture is distinctly better than 1080i, i very much noticed this the other day when watching hellboy 2, i'd been messing with the settings and put it on 1080i, it looked positively nasty, then on 720p most pleasing.

Maybe my tv will have an accident so i can get that proper 1080p experience wink

Plotloss

67,280 posts

271 months

Monday 26th January 2009
quotequote all
The difference between 720p/1080i on two equally capable properly setup systems is imperceptible essentially.

What you're seeing is processing/scaling issues probably.