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Is it still 1920x1080 if it's widescreen?


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10 replies to this topic

#1 of 11 Ken Burkstrum

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Posted November 22 2005 - 12:12 AM

I'm curious about the relation between aspect ratio and pixel count. I'm not sure if pixel counts are just pixel counts or if they really do have a native resolution. Basing on computers, am I correct in thinking 1600x1200 is a 4:3 pixel count, 1920x1080 is a 16:9 pixel count and 1920x1200 is a 16:10 pixel count? I know TVs can scale this up or down but how come TVs don't know how to take something like widescreen and stretch it to fill a whole 4:3 screen? On my 1920x1200 computer monitor for instance, I can use Divx to take 4:3 or 16:9 material and change it to a 16:10 so I can full screen it, I know there's something not right about that method but hey, the picture doesn't look weird to me.

I'm kind of confused how it all works. If you have a 1920x1080 resolution, is it any aspect the filmmaker wants it to be, 16:9, 2.35:1 etc, or is it native to one aspect and TVs scale up/down to fit it. I've seen these videos online that are supposed to be 1920x1080p but according to their properties they are only 1920x816p because of 2.35:1 aspect ratio. Why would you call a 2.35:1 video 1920x1080 if it's not really 1920x1080?

#2 of 11 Ken Burkstrum

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Posted November 22 2005 - 12:26 AM

oops, I meant to put this in Display Devices, admins if you'd be so kind.

#3 of 11 Roger_R

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Posted November 22 2005 - 12:41 AM

Quote:
I've seen these videos online that are supposed to be 1920x1080p but according to their properties they are only 1920x816p because of 2.35:1 aspect ratio. Why would you call a 2.35:1 video 1920x1080 if it's not really 1920x1080?
HDTVs and the forthcoming HD-DVD/Blu-ray players are set to work with specific resolutions, one of them being 1920x1080. When a movie's in 2.35:1, there's black bars added to the top and bottom when it's encoded into a 16:9 area like 1920x1080.

The reason why those so-called 1080p trailers you download on the net not always are in 1920x1080 is because a PC can display a video of any resolution. Encoding a trailer intended to be shown on PC in 1920x1080 if it's in 2.35:1 would therefore be a waste of harddrive space since you'd have black pixels on the top and bottom. However, the same trailer would have to be encoded in 1920x1080 if it's put on a HD-DVD or Blu-ray because of the limitations I mentioned earlier.

#4 of 11 Ken Burkstrum

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Posted November 22 2005 - 01:26 AM

Wait, so with HD-DVDs and Blu-rays they are wasting some of the 1080 scan lines with top and bottom bars or do they scrunch it so the 2.35:1 so the source picture is 1920x1080? Or better yet, all DVDs are 720x480 right? Are they 720x480 in 4:3, 16:10, 16:9 and 2.35:1, or are some scan lines wasted on black bars? If that were so, 16:9 TVs wouldn't actually be watchin 480p and I dont think that's correct.

#5 of 11 Roger_R

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Posted November 22 2005 - 01:39 AM

Yeah, in effect there are some lines wasted when watching movies not in 16:9 with HDTV. Same goes for movies in 4:3 on HDTV where there's black bars on the sides of the image.

Quote:
Are they 720x480 in 4:3, 16:10, 16:9 and 2.35:1, or are some scan lines wasted on black bars?
With movies in 4:3, all the lines are used. When it comes to movies in 16:9, all the lines are used if it is anamorphically enhanced which means that the picture is stretched vertically to avoid having any black pixels. With movies wider than 16:9, there are black bars added to the top and bottom. Also, movies wider than 16:9 can be anamorphically enhanced, but there will still be black bars.
On a 16:9 TV, anamorphically enhanced movies are simply stretched horizontally so that they appear as intended and on a 4:3 TV, the DVD player squeezes the picture back to its original shape and adds black bars to the top and bottom.

#6 of 11 Ken Burkstrum

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Posted November 22 2005 - 02:21 AM

So, 1920x1080 doesn't mean 16:9 right? It CAN be shrunken and stretched any which way? the whole 1080p can be in smushed into all aspects? I notice when I open videos on my computer that not only does it assume an aspect ratio, it'll fit itself relative to my screen. Like I have 1920x1200 so if it's 1920x1080, when I open it up it'll stretch from end to end, and leave alittle room on the top and bottom. See thats what bothers me though, you did say computers work different. When I opened this supposed 1920x1080 it didn't assume the 1920x1080 aspect with little black bars on top and bottom, it assumed 1920x816, with big black bars. Computers don't smush the resolution in the aspect right? So I was looking at 1920x816 on 1920x816 not 1920x1080 smushed into 1920x816, right?

So on computers, videos have a fixed aspect ratio until you tamper with them, so that does prove that every resolution has a native aspect, but unlike TVs, on computers you can manually tamper with them. Am I right on this?

#7 of 11 Roger_R

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Posted November 22 2005 - 02:35 AM

Quote:
So, 1920x1080 doesn't mean 16:9 right? It CAN be shrunken and stretched any which way?
No, on a HDTV, 1920x1080 will always be 1920x1080 and the aspect ratio will be 16:9 as all the pixels are square. However, how many of those pixels are actually used depends on what is being shown. For all the pixels to be used, what's being shown has to be in 16:9. If something in 4:3 is being shown, the pixels on the sides will simply be black.

On rare occasions, you can get videos where the pixels aren't square, like with 720x480. If you divide 720 on 480, you'll notice that the result isn't 1.33. HDTV tries to eliminate that by always having square pixels and having them shown at all times, no matter if they're used or not.

Quote:
Computers don't smush the resolution in the aspect right? So I was looking at 1920x816 on 1920x816 not 1920x1080 smushed into 1920x816, right?
Yeah. I guess the site's been a bit misleading. See, a computer can accept a video file in 1920x816, but an HDTV will only accept one that's in 1920x1080. So when the video's made for HDTV, they'll add black bars on the top and the bottom to the video image itself so it is in 1920x1080. This means that more pixels have to be stored and the resulting file will take more space. However, the part of the image itself will have just as much pixels no matter if it's in 1920x816 or 1920x1080 as the extra pixels are just black. When they put up videos intended for computers, they remove those black pixels to make the files smaller. I think that's why they call it 1080p even though it's technically not.

Quote:
So on computers, videos have a fixed aspect ratio until you tamper with them, so that does prove that every resolution has a native aspect, but unlike TVs, on computers you can manually tamper with them.
Yeah, with editing software and some players too you can stretch the video all you want on computers. It'll look weird though if you deviate from the original aspect ratio. Posted Image

#8 of 11 Ken Burkstrum

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Posted November 22 2005 - 03:39 AM

So unless a video has 1920 pixels on each line, I'm watching video that has been scaled on account of it's ratio? Like 1440x816 isn't going to be as tall as 1920x816 right? Or would it only scale one way and stretch 1440 pixels into 1920 and leave the 816 alone?

Finally, do any 1920x1200 videos exist? Posted Image

#9 of 11 Roger_R

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Posted November 22 2005 - 03:46 AM

Quote:
Like 1440x816 isn't going to be as tall as 1920x816 right?
The first number is width, the second number is how tall it is. 1440x816 would give you an image with an aspect ratio of about 1.7647:1 (close to 16:9 which is 1.78:1) and 1920x816 2.35:1.
Quote:
Finally, do any 1920x1200 videos exist?
That'd be something with an aspect ratio of 1.6:1. The closest film format is 1.66:1. I have no idea where they came up with 16:10, but I've seen a lot of monitors in that format.

#10 of 11 Ken Burkstrum

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Posted November 22 2005 - 04:15 AM

So one more time, 1280x720 is 16:9, you watch it on a 1280x720 16:9 TV. If the HD-DVD your watching is 2.35:1 it won't squeeze 1280x720 into 2.35:1, it'll take the image and fill out the viewable area with what is it, 1024x464? So instead of watching 1280x720 in a 1024x464 screen are, your watching 1280x720 that was scaled down to 1024x464 and viewed in a 1024x464 area? Or is it one in the same, it's so confusing to me. Wow high definition is a loose term. I know when you scale up from say 1280x720 to a 1920x1080 screen, it takes 1280x720 source stretches it and fills in the rest of pixels the best it can, it's scaling down that's got my mind in knots.

#11 of 11 Ken Chan

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Posted November 22 2005 - 07:59 AM

DVD uses 720x480 pixels for either a 4:3 frame or a 16:9 frame; in neither case are the pixels square. HD uses 1920x1080 or 1280x720 for 16:9 only; the pixels are always square. For either format, if the image does not match the frame, you have black pixels to fill the frame.

Quote:
If the HD-DVD your watching is 2.35:1 it won't squeeze 1280x720 into 2.35:1, it'll take the image and fill out the viewable area with what is it, 1024x464?
When filling the frame, it always fills in just one dimension (because that's easier and less wasteful), so the image would be 1280x544. Those pixels would be displayed 1-for-1 on a 1280x720 display.

Quote:
So unless a video has 1920 pixels on each line, I'm watching video that has been scaled on account of it's ratio?
Any HD content that claims to be 1080, 1080i, or 1080p always uses a 1920x1080 frame with square pixels. If the content is shorter/wider (same thing) than 16:9, then it will always be 1920 pixels across and less than 1080 pixels high. If it is taller/narrower than 16:9, then it will always be 1080 pixels high, and less than 1920 across.

Quote:
do any 1920x1200 videos exist?
That may not be the question you really wanted to ask. I don't know of any standard video formats that uses that frame size. (To confuse things though, widescreen LCD computer monitors in the 24" range are that size. You might think of such a screen as being capable of displaying a full 1920x1080 frame, pixel-for-pixel, with an extra strip for controls on the top/bottom.) But of course you can take any video and crop/scale/fill it to any pixel frame/shape.


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