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1080i vs. 720p


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#1 of 15 OFFLINE   Adam Krogul

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Posted March 03 2003 - 12:54 PM

ive been out of the loop for a little while and did a search trying to explain the diferences but came up with no luck. (i didnt look to hard) at anyrate, i wanted to know what displays a better picture and why? my first thought was 1080i but for some reason im second guessing myself... any thoughts would be greatly appreciated.

l8rz,
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#2 of 15 OFFLINE   Erik_C

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Posted March 03 2003 - 02:20 PM

I prefer 1080i. The greatest comparison was between the Super Bowl (720p) and the week's prior playoff games on CBS (1080i). The 1080i had more detail, seemed crisper, and just more realistic. Still, if I'm stuck with 720p, I'm not going to complain. It's excellent.
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#3 of 15 OFFLINE   Allan Jayne

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Posted March 04 2003 - 09:15 AM

1080i gives a more detailed picture of stationary subjects, 720p looks more crisp for moving subjects. For moving objects, very thin details are more likely to want to be reproduced by an odd scan line when the even scan lines are being drawn, or vice versa, we get added flicker or even omission of these small details.

720p is more sensitive to shortcomings in the electronics, horizontal resolution suffers first. 720p has 1280 pixels all the way across, 1080i has 1920. Both require a "bandwidth" of 37 MHz.

If the bandwidth of the equipment happens to be half of that required (19 rather than 37 MHz) which is not unusual, the horizontal resolution is halved. 1080i still has about 1000 dots across but 720 has now been cut to 640 dots across (a dot comes out no smaller than 1/640'th the screen width)
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#4 of 15 OFFLINE   Adam Krogul

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Posted March 04 2003 - 11:21 AM

thanks guys... thats what i thought
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#5 of 15 OFFLINE   Dean Wette

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Posted March 04 2003 - 11:59 PM

Check out this article. It explains why ABC chose to use 720P for their broadcasts.

Good HDTV: It's More Than a Numbers Game

Dean
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#6 of 15 OFFLINE   RandyMathis

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Posted March 05 2003 - 04:04 AM

Nice article. Thank you!

#7 of 15 OFFLINE   MichaelFusick

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Posted March 05 2003 - 11:51 AM

http://www.hometheat....hreadid=119696

Read this thread

Quote:

In theory, 1080i should provide a superior image in terms of detail, since 1080ix1920 contains more "active" pixel elements than 720pX1280 does.

Even if you look at a field of video and not a frame, (two interlaced fields make a frame)1080i on paper looks better.

One field of 1080i is- 540 lines by 1920 pixels for total of 1,036,800 pixel elements. (right?)

One field of 720px1280 is 921,600 (720x1280)

Now, since our eyes can be fooled into thinking we see all 1080i of the interlaced lines at once... 1080i does indeed contain more picture elements than 720p does. Also, the first 540 lines don't have to be exactly the same as the second set of 540 lines, where 720p this is the case.

Now for reality,

There is not really any 1080ix1920 signals available. As posted earlier, due to current limitations from certain brands of HDTV recorders, cameras, and broadcast station links to local networks really the most you get is about 1080ix1454 or so.

Now try the math out again...

One field of 1080i now give you 540x1440 = 777,600

While, 720px1280 still gives you 921,600.

Take into acount that 1080i has more interlaced artifacts and picture noise, and 720p seems superior.

Particuarly if you extend this to a full frame of video, where as much as 30% (according to Mr. Kane) of the interlaced resolution can be lost in the conversions from progressive to interlaced to minimize the visibiity of interlaced artifacts, which 720p again does not suffer from.

If you take the full frame (two fields) 720p looks alot better because now you have 1280x720x2=1,843,200 active picture elements and resolution in both horizontal and vertical directions remains constant over time, where 1080x1440 (540x1440x2) only gives you 1,231,200 active picture elements.

1,843,200 minus 1,231,200 = 612,200 more active elements of the picture in 720p, along with the absence of interlaced artifacts.

I think Joe Kane was trying to show us that for now, 720p is really better in reality than 1080i, while in theory or the future perhaps 1080i can be better... perhaps even 1080p someday....




#8 of 15 OFFLINE   MichaelFusick

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Posted June 25 2003 - 10:36 AM

Anyone try the new D-VHS in 720p?

How does it look?

Anyone compare it to 1080i?


#9 of 15 OFFLINE   Michael TLV

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Posted June 26 2003 - 01:39 AM

Greetings

Mike, your math is flawed on the 720P calculation. It is always shown one frame at a time. It is always 921,600. Never double.

1,231,200 form 1080i is still higher based on your reasoning.

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#10 of 15 OFFLINE   MichaelFusick

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Posted July 02 2003 - 12:14 AM

I was looking at the "time" of 1 field, not one frame, for which 720p contains more information.

For 1 frame- 1080i in theory could provide more picture elements, but after the interlaced artifacts- probably won't look as good unless it's a still image.

Too bad most HDTV is 1080i and most TV's do 1080i and not 720p- which for most ordinary people with TV's makes the whole point a non-issue because their tv supports only one scan rate, and most of the programing is in that scan rate anyways.

Now for front projection, and D-VHS of HDTV-DVD sources.... I am sure 720p holds many advantages, not only in compression and realstate on disc, but in lack of interlaced and motion artifacts and color.

Progressive scan typically has better color and contrast I have found... than interlaced.


#11 of 15 OFFLINE   Michael TLV

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Posted July 02 2003 - 01:37 AM

Greetings

What good is 1 field if the eye simply puts two half fields together to form one complete frame of information? It's called temporal resolution ... and its always been that. If you interlace two half fields fast enough ... the eye can't tell anyway.

It's kinda the same concept as why DVD's are encoded in the 480i format and not 480p.

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#12 of 15 OFFLINE   MichaelFusick

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Posted July 03 2003 - 01:46 AM

True- but Progressive scan still promotes or provides better contrast, color, lower noise foor, lower interlaced artifacts, and takes less room on a DVD, Tape, or to broadcast.

720p is also better for sports, movement, or fast motion.


#13 of 15 OFFLINE   Michael TLV

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Posted July 03 2003 - 02:29 AM

Greetings

Where did you get the idea that progressive scan takes up less space?

Both formats have their proponents and detractors ... so ultimately ... what is your point? Are you trying to convince us that an orange is better than an apple?

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#14 of 15 OFFLINE   MikeMcNertney

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Posted July 03 2003 - 08:33 AM

Michael, you mention that a single frame of 720p has less information than a single frame of 1080i, even at the reduced horizontal resolution. However, isn't it true that in the same time 1080i shows a single frame (ie, two fields), the 720p shows two full frames (hence the doubling)? So in fact if you are calculating the number of pixels displayed in a certain amount of time the 720p would come out on top (assuming 1080i has a reduced horizontal resolution as mentioned).

Or are the two 720p frames just duplicates or something?

#15 of 15 OFFLINE   Michael TLV

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Posted July 03 2003 - 08:56 AM

Greetings

The point of interlacing an image is that if you do it fast enough, the eye only sees one complete frame and not a field. This way you can save space since the end result is the same thing. The person sees the same thing. This is why it is called temporal resolution.

Ideally, we'd all like 1080P ...

Extra resolution is good if you can see it. If the human eye cannot see it, then the benefit of the extra resolution is lost.

It's not too different from the DTS / DD arguments that persist ... one uses 12:1 compression and the other ... 3:1 ... though now 6:1 ...

DD's argument has been that most people cannot hear the difference between music compression rates like these ... so if that is the case, why not save space and use 12:1 instead.

Ditto for JPEG formats versus TIFF and RAW. If a Fine JPEG compression yields a image virtually indistinguishable from an uncompressed TIFF image, but only takes up 1.5 MB rather than 7 MB ... isn't the JPEG more efficient in terms of space?

If it's optimal quality with no limitations ... then I want 1080p ...

Note that I am not anti-720P ... I just want the argument presented properly ...

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Michael @ The Laser Video Experience
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