Re: Anyway to get a 1080p signal from fios?
KenAF
Specialist - Level 2

@SamRay wrote:

@KenAF wrote:

What you've stated above is a common misconception.  While a 1080p60 signal represents twice as much information, and would therefore require roughly twice as much bandwidth, the same is not true of 1080p24.


Thank you for your extensive detailed explanation, but I expect that most of us won't understand and most of this is not currently relevant to most of us.

I think most of us are interested in 1080p24i and 1080p24p. Oh, and first, perhaps you should explain the difference between 1080p60 and 1080p24. I am not sure, but perhaps 1080p60 has 60 frames per second and 1080p24 has 24 frames per second. If so, then it really helps to mention that, since most people are not familiar with that. If I am wrong, then I think it is even more importatn to explain the difference. I do know that i is interlaced and p is progressive. So on the subject of 1080p24, what is the difference between interlaced and progressive? As far as I know, they both have the same data, except interlaced does not send the data sequentially and progressive does. If that is true, however, then I don't understand the advantage of using interlaced instead of progressive. Isn't interlaced only for support of older CRTs?


You're right, 60p (or p60) refers to 60 progressive frames per second and 24p (or p24) refers to 24 progressive frames per second.

 

Every consumer 1080p TV outputs to its screen at 60 frames per second, or 1080p60.  But there is no source of 1080p60 content.  There's no 1080p60 content on TV, none in the theater, and none on any form of high-definition disk.  There are very few cameras that can acquire in 1080p60, and they cost $$$$$, so nobody uses them.

 

If there is no 60p material, what do we display on our TVs?  We display 24p content and high-definition video.

 

Movies and series are "filmed" at 24 frames per second using traditional film or a high-definition camera running in 24p mode.  Film-sources are telecined -- i.e. converted -- to digital at 1080p24 resolution.  Blu-ray disks store this 1080p24 source directly on the disk.  To display this 24p material on your TV at 60 frames per second, the first frame is repeated twice, the next frame is repeated three times, the next frame is repeated twice, the next frame is repeated three times, and so on and so forth.  Repeating some frames more than others produces an effect called judder; as Americans, we are accustomed to this because we've had it for the last 50 years with NTSC.

 

High-definition video on CBS and NBC -- such as news broadcasts and live sporting events -- is acquired in native 1080i60.  This is not the same as 30 frames per second, nor is it the same as 60 frames per second.  It is 60 unique interlaced 1920x540 fields each acquired 1/60th of a second apart.  A field is not a full frame; it's  every other line of a frame.  If there is no movement whatsoever in the picture, these 60 fields fit together to form a perfect 1080p30 image; unfortunately, there is almost always some movement in the picture, so the fields do not fit together.

 

The first 1080p TVs on the market created 60p output from the interlaced signal through a process called "bobbing."  They essentially created a frame from a 1920x540 interlaced field, then it created the next frame from the next 1920x540 field, and so on.  These TVs weren't providing 1920x1080p resolution at 60 frames per second, they were providing 1920x540p resolution at 60 frames per second.  At some point, you may have heard someone refer to 1080i as 540p; that's where it came from.

 

Over the years, interlace -> progressive algorithms have become far more sophisticated.  Now, most consumer 1080p displays do something called motion-adaptive video deinterlace.  They compare multiple sequential interlaced fields and look for places where they align (i.e. where there was no movement in the image in the last 1/60th second).  They match up the parts of the picture that align, and they interpolate (i.e. average) the parts of the picture that do not.  The result is a 1080p60 signal, which offers excellent detail in the parts of the image that did not move, and less detail in the parts of the image that did move.  Displays with better video processors do a better job at finding the parts the image that align, so less interpolation (averaging) is necessary.  The result is that some displays provide more detail (less blurriness) in the parts of the picture with movement.

 

Back to the subject of 24p...As I noted in the prior post, to send 24p content in a 1080i60 signal, broadcasters split each of the 24 progressive frames into two interlaced fields.  The fields are displayed in a repeating 2/3 sequence...two interlaced fields for one frame, then three interlaced fields (with a repeat) for the next frame, then two interlaced fields for the next frame, then three interlaced fields of the next frame (with a repeat)...in order to create a 1080i60 signal from 48 unique interlaced fields.  The extra twelve interlaced fields (60 vs 48) are aren't actually sent down the cable, they are created by the STB/DVR's decoder in response to a bit that tells it to repeat certain fields.  Displays that perform 24p detection do it by looking for these repeated / duplicated fields (otherwise known as 2/3 cadence detection).

 

On a typical 1080p display without 24p detection, this content is treated just like the native 1080i60 video mentioned earlier; it's treated as if it were 60 unique fields per second rather than 48 halves to 24 frames.  The display uses motion-adaptive deinterlace to align parts of the the fields with no motion, and the rest is interpolated (averaged).  Since there are two repeated fields of one frame, followed by three fields of the next frame, the fields don't line up.  The result is that the display interpolates a lot of the motion.

If you think about it, interpolation (averaging) of the motion areas should be unnecessary, because all the information from the original 24 progressive frames is still present in the signal, just not in the correct order.  True 24p detection (described in the previous post) eliminates the duplicate fields, so the 48 fields line up in the correct order, and you get the full resolution of the original source not just in the areas without motion, but in the areas with motion too.  After the 48 interlaced fields are combined to recreate the original 24 progressive frames, these frames are repeated in a 2/3 sequence to provide a 60p signal for the TV.

Message Edited by KenAF on 03-23-2009 10:07 PM
Re: Anyway to get a 1080p signal from fios?
SamRay
Enthusiast - Level 2

Note that in spite of that very lenghty and detailed explanation, there is not an answer to my question. You said nothing about the difference between interlaced and progressive when the resolution and frames per second are the same. Or if you did it is lost among all the other details.

As you indicate, the 60 frames technology is irrelevant. The fact that video is occasionally created using 60 frames is not relevant to anything I can do differently.

Most people don't care about the details of how all that is done. I would be impressed if you could explain the affect it has on me in a manner that helps me to understand what I can do.

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Re: Anyway to get a 1080p signal from fios?
KenAF
Specialist - Level 2

@SamRay wrote:

Note that in spite of that very lenghty and detailed explanation, there is not an answer to my question. You said nothing about the difference between interlaced and progressive when the resolution and frames per second are the same. Or if you did it is lost among all the other details.

As you indicate, the 60 frames technology is irrelevant. The fact that video is occasionally created using 60 frames is not relevant to anything I can do differently.

Most people don't care about the details of how all that is done. I would be impressed if you could explain the affect it has on me in a manner that helps me to understand what I can do.


Perhaps the answer was lost in the details.  Perhaps a picture would help.

 

A frame is a full image -- as seen in the merged image below.  An interlaced field is essentially half an image, although it's not the top or bottom half, but every alternating line -- as seen in the unmerged images below.

 

A 1080p24 film source consists of 24 frames like the merged image above; a 1080p60 signal is created by repeating those 24 frames in a 2/3 sequence.  The same 1080p24 film source can be sent as a 1080i48 signal with 48 fields, like the unmerged images above; a 1080i60 signal is created by repeating the 48 interlaced fields in a 2/3 sequence -- this is what CBS, NBC, and HBO do on their series and movies.

 

A native 1080i60 video source (like NCAA basketball on CBS) doesn't have fields that "line up" or "fit together" as shown above; a native 1080i60 video signal is a stream of 60 interlaced fields (like the unmerged images above), all acquired at different moments in time.  Creating full video frames when none existed in the first place is one of the things that digital displays do through video processing.  How that is done by your particular TV -- i.e. the details --- has a significant impact on the quality you perceive on the screen.

 

If you already own a 1080p TV, and/or aren't looking to buy something new to get the best possible 1080p picture from the signal FiOS provides, then nothing I have described should be relevant to you (unless you're interested in how you get a 1080p image from FiOS).  It probably is relevant if you are shopping for a new TV and care about picture quality.

Message Edited by KenAF on 03-24-2009 12:21 AM
Re: Anyway to get a 1080p signal from fios?
SamRay
Enthusiast - Level 2

KenAF, if you want people to listen to you, you need to learn how to listen. Try to understand the following.

Assuming the resolution (such as 1080) is the same, is it true that the (uncompressed) size of the data for a 24-frame interlaced image the same as for a 24-frame progressive image? The details of why or how is not part of the question, and is just confusing. Is it true or false? Yes or no? If my question's terminology is not perfect, then I hope you understand what I mean and you don't correct my terminology for it's inaccuracy. Please try to understand what I am trying to ask and answer that.

You will get more attention if your comments are more concise by limiting them to whatever is relevant to your audience.

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Re: Anyway to get a 1080p signal from fios?
KenAF
Specialist - Level 2

@SamRay wrote:

Assuming the resolution (such as 1080) is the same, is it true that the (uncompressed) size of the data for a 24-frame interlaced image the same as for a 24-frame progressive image? The details of why or how is not part of the question, and is just confusing. Is it true or false? Yes or no? If my question's terminology is not perfect, then I hope you understand what I mean and you don't correct my terminology for it's inaccuracy. Please try to understand what I am trying to ask and answer that.


That's what I've been trying to do.

You keep asking for a comparison of frames, but there are no frames in an interlaced signal.

 

Progressive transmission uses frames.  Interlaced transmission uses fields.  That's the difference between progressive and interlace.

 

One progressive frame takes about the same bandwidth as two interlaced fields.   Hence, a 24p signal takes about the same bandwidth as a 48 field (48i) interlaced signal.

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Re: Anyway to get a 1080p signal from fios?
SamRay
Enthusiast - Level 2
Earlier you said "A field is not a full frame; it's  every other line of a frame.". You used the terms frame and full frame to describe interlaced images, now you are saying the terms are incorrect in that context.
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Re: Anyway to get a 1080p signal from fios?
KenAF
Specialist - Level 2
The full quote:

@KenAF wrote:
High-definition video on CBS and NBC -- such as news broadcasts and live sporting events -- is acquired in native 1080i60.  This is not the same as 30 frames per second, nor is it the same as 60 frames per second.  It is 60 unique interlaced 1920x540 fields each acquired 1/60th of a second apart.  A field is not a full frame; it's  every other line of a frame.  If there is no movement whatsoever in the picture, these 60 fields fit together to form a perfect 1080p30 image; unfortunately, there is almost always some movement in the picture, so the fields do not fit together.

I described a field (as compared to a frame) without the benefit of a picture, because I thought it would help you understand the difference.  If that comment caused confusion, then my apologies.

Message Edited by KenAF on 03-24-2009 11:18 AM
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Re: Anyway to get a 1080p signal from fios?
jmcohen231
Contributor - Level 3

okay, so the short answer is, "No"

and it does not seem likely that Verizon (or anyone else for that matter) will start anytime soon.

However, here is a response I got from someone at http://www.highdefforum.com

"With most OTA/Cable/Sat HD Channels they are 1080i, so your display will just deinterlace those channels and you have your 1080p output"

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Re: Anyway to get a 1080p signal from fios?
cvarner
Newbie

KenAF, I certainly appreciate the effort you put into your answers. I think I get most of it -- and found it to be very interesting.

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Re: Anyway to get a 1080p signal from fios?
Deluxe
Newbie

KenAf, I also appreciate your time and answers, although they leave me a little confused. When you say blurring, do you mean artifacts/pixilation? I get artifacts (blocks) during fast moving, panned scenes when watching Fios Hi def. Only get them sometimes in background crowd scenes during sports. I do not get them when watching a DVD (regular of Blueray). Verizon said this is a result of the source (networks, HBO ,etc).

I own a Panasonic th-58pz800u plasma. I can also see it sometimes on an old standard def Toshiba. Below is there Panasonic review:

In terms of resolution, the TH-58PZ800U performed as expected, resolving every line of 1080-resolution signals and properly deinterlacing video-based sources, although it failed the test for film-based deinterlacing. We counted between 800 and 900 lines of motion resolution on this set, which is about what we expected on a plasma TV, although not quite a high as either the LG or the Pioneer. As usual, we couldn't tell any difference between the TVs' resolutions in our side-by-side comparisons. 

Any thoughts?

Thanks. 

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