1080i = 540p??

[NYClubKid55]

Ok I'm not trying to start a thread where people list the reasons why they think that 1080i or 720p is better. I'm just asking if my math is correct and therefore assume that 1080i = 540p.

In 1080i, 540 odd number lines are drawn in 1/60th second. Then, 540 even number lines are drawn in 1/60th second.

In 540p, all 540 lines are drawn sequentially but in 1/60th second.

Now, there are less overall lines (1080 vs. 540) but the full picture is being drawn in different times. Doesn't that mean they would display the same number of lines in 1/60th second?

If my math is wrong, please correct me.

[keith1229]

you are correct that there are 540 lines on the screen at a time in 1080i, but that doesn't make it 540p. if each line was a "picture" of it's section of the picture, than in 1080i there are 1080 of those pictures total. with 540p, you'd only have 540 total "pictures" for the image. yes they both display 540 lines at any given moment, but that doesn't make them the same thing. (did you leave this same post on avsforum?)

[NYClubKid55]

No it was not me on avsforum. I'm not even registered there.

I see your point there about 540 total lines making up a picture in 540p while 540 lines only make up half the picture in 1080i. Thanks for clearing that up.

So let's say in 2/60th second, you get 1 full picture with 1080i but you'll get 2 full pictures with 540p. Does this make any visual difference? How about in terms of clarity?

Thanks again for the reply.

[57U]

Interestingly, I believe most people with Toshiba and Hitachi RPTVs can compare a 540P picture with a 1080i picture when fed a good signal like a DVD for example. When you switch between the two display modes, you'll likely see very little difference...

Now, this is not the same as a true 1080i HD picture, but it is an interesting experiment in "virtual HD"...

[keving]

Does 540P actually paint all it's lines in 1/60th of a second? If that's the case, why can't the same TV in interlaced mode paint half of it's lines in 1/120th of a second?

I think that they both end up displaying the same amount of picture in the same amount of time (interlaced, 1/2 picture in two 1/60th passes = 30fps, progressive, 1 picture in 1 1/30th pass = 30fps), but I could be off.

[NYClubKid55]

Yes that would be interesting to try. But your right....With an actual HD source (instead of the DVD source) the 1080i would blow 540p away since 540p would not be able to display all 1080 lines that make up the picture. It would have to reduce it to 540 lines.

[urbansouljah]

540p is nowhere near 1080i. Not even with a DVD source. Like they said with 1080i you actually get 1080 lines just not at the same time. 720p is also only slightly better than 1080i. Not enough a difference to really matter which HD resolution you need unless you play video games which in that case 1080i (Dragon's Lair 3d) actually looks better than the games in 720p. I know it's not supposed to but it does but that is only one game in 1080i.

[57U]

Originally posted by urbansouljah 540p is nowhere near 1080i. Not even with a DVD source. Have you ever compared the two display modes back to back on the same CRT-based RPTV?

[urbansouljah]

Yes I have and nothing so far comes close to what I have seen from HDNET except for DVHS movies which are even better.

[57U]

US, you did not answer my question. I was talking about comparing 540P and 1080i display modes, using a 480i or 480P input.

I was not talking about 540P vs a 1080i HD signal.

Perhaps you misunderstood what I wrote in my previous posts.

[urbansouljah]

Oh sorry 57U. I did misunderstand you a little. Kind of got caught up in what the original poster wrote.
- Jose'

[J in OP]

Doesn't frame rate play a role here too?

At 30 fps, it seems to me that an interlaced set that refreshes 60 times per second should be essentially the same as progressive scan. At 60 frames per second, this would not be the case.

So a 720p at 60fps should refrest faster that a 1080i, but still have fewer lines. At 30 fps, it would seem that there should be no practical difference between the progressive scan and interlaces if the 1080i refreshes 60 times per second.

Do I have it right? Wouldn't the source frame rate play a role in this discussion?