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A colorful full-page HDTV ad in Monday's New York Times business section caught my attention. This ad 'blended' with some discussion in this recent thread, 30 MHZ video bandwidth good enough? , about component switch requirements. The Times ad is for Samsung's wide-screen 24-in. SyncMaster 240T. . This LCD model, with certain graphics cards, claims 1920 X 1200 resolution. There's discussion here and elsewhere, though, whether the 240T, which boasts an all-digital DVI interface option, can resolve such detail.


But is 1920X1080-pixel detail available from HDTV programs in homes? Such a HDTV format starts with 2200 pixels X 1125 lines (1920 active or visible pixels X 1080 lines) from a TV camera or telecine film scanner and diminishes to a potential ~1700 pixels X ~800 lines on superior displays. More likely, it's considerably less detailed unless high-resolution monitors are used. Screens on consumer direct-view-CRT sets don't provide 1080 scan lines or full horizontal resolution. These resolution numbers all refer to stationary B&W test patterns. That 2200X1125 resolution for 1080i HDTV involves extra pixels for both horizontal and vertical retrace, as Greg Rogers detailed here (about halfway down).


Engineer jhue in his component-switch ( 12/10 post ) explains that cameras must digitally sample scenes or film at twice the HDTV scan-format frequencies, or 74.125 MHz. Then, before a 1920X1080i signal is compressed with MPEG-2 encoding, it's filtered. This anti-aliasing filtering, though, blocks more than half the original frequency (37.125 MHz) to eliminate higher sampling frequencies that spoil images.


Jhue stressed three factors (underlined) that especially weaken camera-to-home higher frequencies and image details: Anti-alias filters; MPEG-2 compression; post digital/analog filtering; video switching in an A/V receiver or outboard switcher; video circuitry in the TV; ability of the CRTs to resolve fine detail.


Higher-frequency details are created by the higher-contrast B&W (luminance) portion of the two-part HDTV signal. Our eyes are more sensitive to luminance. Color signals 'paint in' additional pixel details. Here's how resolutions of both luminance and color measured in HDTV approval tests (my 8/22 post) for the FCC:
Code:
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[B]Measured resolutions of the ATSC 1080iX1920 HDTV system[/B]
           
Scan format         
1080 vertical lines
1920 horizontal pixels

                                     Vertical       Horizontal        
Measured B&W Static Resolution       800            1638
Measured B&W Dynamic Resolution      400            1780^
Measured Color Static Resolution     280            890
Measured Color Dynamic Resolution    200            481


[B]Measured resolutions of the ATSC 720pX1280 HDTV system[/B]
           
Scan format         
720 vertical lines
1280 horizontal pixels
                                     Vertical       Horizontal         
Measured B&W Static Resolution       550            1139
Measured B&W Dynamic Resolution      420            1068
Measured Color Static Resolution     360            641
Measured Color Dynamic Resolution    320            605
The test for B&W static 1080iX1920 horizontal resolution was 1638 pixels (full screen width). That's close to the 1536 pixels anticipated with 20% filtering of horizontal resolution. It's also close to the 1707-pixel estimate in this luminance horizontal resolution chart (halfway down) for most U.S. video sources. Surprisingly, for a moving test pattern, the mid-1990s test for the FCC showed a 1780-pixel horizontal resolution--only ~7% down from 1920 instead of ~20%. Measured resolutions for color test patterns are also shown.


Vertical resolution involves scan-format lines for CRTs and tiny fixed-pixel elements such as LCDs. These are constant, even with no signal. But vertical-signal components are filtered to prevent image flicker; they're 'smeared', contributing to the ~800 measured lines above instead of 1080 for a static B&W pattern. Vertical resolution drops still further, to 400 (down 63%), for a moving B&W test pattern. With movement, the Kell factor plays an even greater resolution reducing role. (As cameras scan objects, scan lines may skip over or straddle more details).


So, what happens when a 1920X1200 Samsung 240T displays a 1080i HDTV signal produced by a Sony HDCAM? Sony's system deliberately filters pixels beyond 1400 horizontal resolution for recording. And how would that compare to a 'window-effect' live broadcast from a system using a 'full' HDTV 1080i signal? Finally, how much of the potential 20% horizontal resolution filtering takes place within the 240T, and how much filtering occurs before the HDTV signal reaches the LCD display? -- John
 

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Thats alot to swallow in one posting!

(even though much of it is rehash).


Keep in mind that the Samsung 240T is a

digital display device so it has an

_ACTUAL_ 1920x1200 individual picture

elements so we pretty well know its

resolution potential.


On the other hand, direct view CRTS have

various factors to do with shadow mask size,

gun deflection, spot beam size, (etc) that

give an approximate max resolution.


The first thing most people would notice about

the Samsung 240t is that it is darn small for

an HDTV display. 24" diagnol looks puny next

to a 50" rear projector.


Another thing people will notice is that it has

a high price. $5000+ for something only 24"

is going to keep the market small.


LCDs also have issues (when compared to direct

view CRTs) with viewing angles. It is possible

that the colors would look weird if you view

it from an extreme angle (e.g.: looking at it

from the side).


Yet another LCD issue is with "blown pixels".

With 1920x1200 "elements" I would guess that

some of those displays will have a couple of

pixels that don't function properly, so depending

on the material being viewed (for instance a

solid white image) you may notice some "spots"

on the display.


Going back to an old argument - I don't think

we should give up on 1920x1080 as a true target

because the source materials (e.g.: cameras

and telecine devices) may evolve over time to

better maximize resolution (within the ATSC spec)

so we may shoot ourselves in the foot if we

were to say that 1600x900 (for instance) was

"good enough" for a top line 1080i display.
 

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This Samsung is also a "dream" computer monitor -- Really big 24" size that fits in places where only a 19" monitor fits, and razor sharp 1920x1200.


This will look rather good on a desktop...


A question to ask is about persistence specifications -- since LCD's are not as suitable as CRT's for gaming and video (also depends on personal preference as well).
 

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I want one of these new Samsung monitors but I can't find anyone who sells them yet.

Anybody got one of these things?


Frank
 

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It's not for TV or HDTV it's for business. I can't wait to show this baby to the design department.

Of course, since it can show HDTV I might have to.............


Thanks for the links. Not in stock anywhere I guess..


Frank
 

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Discussion Starter · #8 ·
Thanks for the replies. Certainly agree about rehashing, pvr.:) It's sort of a HDTV newbie intro; that helps focus stuff for me, and usually uncovers new HDTV tidbits as I go along. And corrections by experts to properly align the little gray cells always help.


The main point, and the reason for not posting in the hardware forum, was, here's a 1920X1200 display. But are 1920X1080 HDTV program sources (not hardware test patterns) available in homes after all the processing and filtering steps? Be delighted to learn otherwise, but it appears ~1700 X 800 (actual viewing) is about maximum with top-grade gear.


To revisit Samsung's 240T briefly, I found Guy Kuo's comments, near the end of the thread I cited, intriguing. He's using the 240T's predecessor, and stresses the key role of the digital-visual-interface (DVI) feature. Kuo describes the modulation transfer function (MTF) as being very sharp (square-wave-like) with DVI. I pictured the MTF graph for analog 240T inputs, at each LCD pixel, as looking like Hershey's Kisses (sloped sides). Result: smeared resolution. But non-analog DVI inputs, like narrow Tootsie Roll segments, create crisp images. (Sorry, I blame a recent TV show about Hershey, Pa.:))


But what about digital cinema? Theater hardware/software, of course, isn't restricted by 6-Mhz TV-channel bandwidth. Lots of favorable comments here about its fidelity on really giant screens. They may exist someplace, but haven't seen any on-screen resolution test reports. Such displays must use anti-aliasing filters, too. With vastly expanded bandwidth for hard-disc-stored digital compression, though, most of HDTV's high-resolution detail doesn't have to be discarded for TV transmission. And JVC is readying 3840 X 2160 resolution with its Q-HDTV , based on reflective-LCD D-ILA technnology (link requires Acrobat).


Also, perhaps HDTV programming for the home will bypass 6-Mhz TV channels one of these days. This article on broadband fiber optics, for example, outlines how Sorrento Networks offers hardware for sending up to 128 wavelengths along fibers, delivering 1.28 trillion bits per second. My local Time Warner Cable now squeezes two 19.39-million-bits-per-second HDTV channels into a 6-MHz cable slot (in a 860-MHz+ fiber-upgraded system). Cable-supplier Scientific Atlanta offers such wavelength-multiplexing equipment, too.


Finally, perhaps we'll soon see less-compressed HDTV on fluorescent multilayer discs ( FMD ) based on standard red lasers. According to a nice summary in December's Widescreen Review, the developers have 25-gigabyte (GB) 8-layer FMDs (the FMD-25) suitable for international HDTV standard's minimum 20-24 Mbps. Illustrated in a graph is a hypothetical 300-GB 100-layer FMD (equal to 469 CDs in storage capacity). -- John
 

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Flat-panel imaging technology is already capable of outrunning the actual resolution of the typical HDTV broadcast.


John has correctly identified the bottlenecks (the biggest of which is bandwidth) in the way of showing true 1920x1080 HD broadcasts.


Texas Instruments several years back hand-made some 1920x1080 Digital Micromirror Devices for testing of HDTV playback. Their current resolution is capped at 1280x1024 pixels, but they can go higher.


JVC's highest-resolution Digital Image Light Amplifier (another name for their homeotropic liquid crystal on silicon technology) is 2048x1536 pixels, as implemented in the DLA-QX1 high light output front projector.


The Samsung panel does indeed have 1920x1200 pixel elements using TFT liquid crystal. It was designed to display two A4 sized documents at the same time. HDTV was not a primary goal of this display.


Panasonic showed a 1920x1080 prototype plasma display panel a few years back at NAB, but it never came to market. Too difficult and expensive to manufacture.


Given all this things in the signal transport chain that degrade the resolution of a 1920x1080 HD signal (and let's not forget that the HDCAM format compresses 11:1 as opposed to Panasonic's D5 format, which compresses 5:1), it appears that manufacturers believe 16x9 flat-panel devices with 720 to 768 vertical pixel resolution are all that's needed for showing either HD format. That would include 1280x720 DMDs, 1366x768 LCDs, and 1280/1365/1366x768 plasma.


Pete
 

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>> To revisit Samsung's 240T briefly, I found Guy Kuo's comments, near the end of the thread I cited, intriguing. He's using the 240T's predecessor, and stresses the key role of the all-digital DVI interface.


I think he was referring to the 170T

(the 240Ts "little brother").


It really isn't a "predecessor", rather it

is a less expensive, smaller, lower resolution

display using similar technology.


Unfortunately there are some shortcomings to

the DVI input on the 240T that (apparently)

prevent anyone from using it to display

1920x1080 HDTV.


Also, very few HDTV output devices have DVI

output yet.


When Telemann was getting set to demo their

card with the 240T is was all to be done via

the analog cables.


...still waiting for 1920x1080 Plasma, dILA, LCD and DLP... overkill is a good thing for display devices.
 

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Discussion Starter · #13 ·
Let's see. If you double 1080i resolution (vert. and horiz.) and display it on the IBM, what happens when you use a laptop projector? Could projection lenses resolve it? Suspect, with LCDs meant for graphics, video would be a mess. -- John
 
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