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1080I, True HD, Plasma & Lies
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Spliceman
Suspended due to non-functional email address
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23. July 2004 @ 08:45 |
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Recently I have been very shocked to learn that even the most expensive plasma displays only have resolutions of 1366 x 768. In my mind this means that the closest standard that these monitors can reproduce is 720(i or p). So when you feed a 1080i signal into one of these monitors what is actually happening? And, when they say their monitor can handle 1080i how can this be? Finally, are there any plasma displays that actually have resolutions of 1920 x 1080? Thanks?
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fklentz
Newbie
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2. August 2004 @ 21:31 |
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A HD signal of 1080I only needs 540 horizontal lines, The I (interlacing) means that it is alternating the image displayed 540 lines at a time. A display that has 720P is capable of displaying an image at 1440I. There are a lot of deceptions out there on plasmas, when you see one that only has 480P but it says HD compatable the image signal is down converted and not in true HD resolution of 1080I.
This message has been edited since posting. Last time this message was edited on 2. August 2004 @ 21:32
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zarlaan
Newbie
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2. August 2004 @ 21:56 |
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The lines of resolution ie. 720p 1080i and the number of pixels ie. 1920x1080 are two different things.
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Spliceman
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3. August 2004 @ 05:03 |
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That is interesting... So what you are saying is a 720p image is throwing 720 lines on the screen all at once when a 1080i image is only displaying 540 lines at a time. That makes sense because I could never figure out why a 720p DVD would be better than the 1080i that comes in on my local network HD feeds. Thanks...
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Staff Member
2 product reviews
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3. August 2004 @ 11:01 |
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It's true that a 1080i signal only uses 540 lines at a time, but each field only uses every other line. 1080 does refer to the total number of lines used by the picture. Interlaced video has 2 fields, top and bottom, with the top field starting on the top line and using every other line below that (ie lines 0,2,4,6,8,etc,...). The bottom field starts on the next line down and also uses every other line (ie lines 1,3,5,7,9,etc,...). Since each field is 540 lines, the total required is 1080 lines.
This message has been edited since posting. Last time this message was edited on 3. August 2004 @ 11:03
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Spliceman
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3. August 2004 @ 12:45 |
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So that brings me back to my original question. Does a monitor need to be capable of 1920 x 1080 pixels to reproduce 1080i in all of its glory? Or, am I missing something when it comes to the difference between dots & lines. I'll believe anything at this point... Thanks for your response, Vurbal.
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Staff Member
2 product reviews
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3. August 2004 @ 13:03 |
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Basically what it means is that 1080i will be down-converted to the resolution of the screen. So no, you won't get full quality 1080i from a screen with fewer than 1080 lines.
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sdifox
Member
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18. August 2004 @ 07:19 |
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The basic confusion is the ordering of numbers. In computer world we say 1024x768. But in TV land, they talk about 720p, this number is the second number in computerland. And since we are talking 16:9, 720p is actually 1280x720NI in computerland. Progressive=Non-interlaced. 1080i=1920x1080 interlaced. That should clear things up.
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Spliceman
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18. August 2004 @ 10:43 |
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Thanks for your response. I agree that the confusion lies there. Its like, when a monitor says its 1024 x 1024, you think, great it will do 720 but really in 16 x 9 it can only do 1024 x 576 max. Now this is where I get a little confused - because I haven't heard of a 576(i or p) standard does that mean that everything gets scaled back to 420?
Also, I was reading an article about Mitsubishi's 82" LCoS RPTV and saw that true 1920 x 1080 only costs $21,000. Has anyone found 1920 x 1080 native resolution on any other (large screen) monitors. Here is a link to the Mits. review...
http://www.soundandvisionmag.com/article.asp?section_id=3&article_id=513&page_number=1&preview=
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sdifox
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18. August 2004 @ 17:55 |
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Spliceman
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19. August 2004 @ 05:14 |
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I was kind of hoping to go the other direction... True 1080i in the $8,000 to $10,000 range... But thanks for the suggestion I hadn't seen those before.
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sdifox
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19. August 2004 @ 06:31 |
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true 1080 projectors would be 1080p, not likely 1080i since everything is going digital. Think about this, 1080p projector and a htpc scaling all your dvds to 1080p...drool...
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Spliceman
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19. August 2004 @ 06:39 |
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Yes, and a fiberoptic OC-3 to every house... I'm going to have to change clothes...
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sdifox
Member
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19. August 2004 @ 06:45 |
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why would you need a oc-3 to your house? 3mbps should be sufficient for most people. The key is the bandwidth and horsepower of the file servers :)
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Spliceman
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19. August 2004 @ 07:53 |
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This may be a discussion for another thread but here goes. This is the way I understand it? Please correct my errors? How many bits of color description are needed per pixel 24? Lets just say 16 bit color? 1920 x 1080 is one frame and with Progressive were throwing up 30(?) frames per second. So for uncompressed video that?s 1920 x 1080 x 16 x 30 bits per second. That number was too big for my calculator and it doesn?t include multi-channel audio and obviously compression is a big factor. I admit I do probably not understand something integral when it comes to broadcasting a 1080p image. But there?s got to be some reason you don?t hear everybody yammering on about 1080P yet? Check out this article on HDMI interface cables - http://www.hometoys.com/htinews/apr04/articles/weizer/hdmi.htm
This cable is capable of passing uncompressed video & multi-channel audio & will utilize 5Gigabits / second to do it? Even with compression 1080P seems like a whole different animal? I am still drooling though.
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sdifox
Member
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19. August 2004 @ 09:29 |
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but why would you want to stream everything over internet? That is a complete waste of bandwidth! Say you set up a ppv service and stream movies over internet. Everytime someone requests the movie you are going to stream the whole thing. That is just not sensible. Just buy the damn disc (be it blue ray or hd-dvd). Progressive is 60Hz in NTSC world and that is a joke compared to what we do on computer display.
also, you do not send the full frame everytime. You just send the difference. MPEG is very important for digital transmission of video contents.
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FlatEric
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28. September 2004 @ 10:37 |
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Could someone please clear up one last thing regarding this issue.
I now understand that 1080i only actually needs device resolution of 540 lines due to interlacing.
How do we get to the 1920 figure ??
As pointed out, even the best plasma displays only go to 1366 x 768, which is fine in the vertical (768 > 540). Does the horizontal resolution also get interlaced !?!?
Please bare with me if I appear to be asking questions with apparently obvious answers.
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Staff Member
2 product reviews
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28. September 2004 @ 10:46 |
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Quote:
I now understand that 1080i only actually needs device resolution of 540 lines due to interlacing.
No, it needs 1080 lines. The 540 is just for a single field, which consists of every other line, or half the vertical resolution. interlaced video is only drawn one field at a time, but both fields are on the screen simultaneously. In other words, the top field (the even numbered lines only) is drawn, and it stays visible while the bottom field (the odd numbered lines only) is drawn.
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FlatEric
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28. September 2004 @ 10:53 |
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OK,
so where does 1920 fit in ??
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Staff Member
2 product reviews
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28. September 2004 @ 10:58 |
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1920 is the horizontal resolution.
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FlatEric
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28. September 2004 @ 10:59 |
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I know that, but how does a 1366 horiozontal resolution display end up with 1920.
As I asked, is this also interlaced ?
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Spliceman
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28. September 2004 @ 11:04 |
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Many monitors will scale the 1080i information down to a resolution that is viewable on that monitor. That is why the monitor says it can accept a 1080i signal. But in order to view a 16x9 image in 1080i (and see every line) you need a monitor capable of 1920 x 1080. Even if only 1/2 of the lines come on at a time...
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FlatEric
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28. September 2004 @ 11:07 |
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So it is interlaced in the horizontal dimension also ?
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Spliceman
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28. September 2004 @ 11:21 |
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You mentioned 1366. 1366 would be the number of verticle lines your display has. Divide that by 16 and multiply the result by 9 and you get 768. So your monitor immediately scales the 1080 lines to 768 lines. This is still a very sharp image but not as sharp as 1080... Then because the image is interlaced the monitor then outputs 1/2 of the lines (384) on the even numbered lines, each of these lines is made up of 1366 dots. In the next frame it outputs the odd numbered lines, all 1366 dots in each line...Both frames happen so quickly your eye can't detect the fact that it only saw half the lines. This is happening at 30 or so frames per second. I Progressive all 768 lines are being outputted with every frame. So I think the answer to your question is no the verticle lines are not "interlaced", but the whole image is being scaled down...
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FlatEric
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28. September 2004 @ 11:29 |
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Hmm..
If it is scaled down (1366/1920 = approx 70%) then you're saying I'm losing 30% of the image. I wouldn't consider this good value :o)
I know that it's still far superior to normal PAL/NTSC resolution but I would still feel a little cheated watching my shiny new plasma knowing that it's disposing of 30% of my clarity....
Oh well, I suppose I'll have to invest in a decent projector now... SWMBO will not ba happy.. :o)
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