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Discussion Starter · #1 ·
I have been bothered by the fact that my Sony W900 seems to show 1080i HDTV signals

(presented as RGB from an RCA DTC100 and Telemann HiPix card) as 1920x540. Basically

the alternate 60hz fields (two halves of the interlaced picture) display right on top of

each other rather than staggered as they should be.


540 vertical lines is actually enough that many people on many computer monitors

wouldn't really notice that they weren't seeing the full 1080. Many monitors don't have a

small enough "spot beam" for you to tell easily. But with the W900 the "gap" was wide

enough (between scan lines) that I couldn't ignore it.


There have been some topics on the Home Theater Forum about this:
http://www.avsforum.com/ubb/Forum12/HTML/013718.html
http://www.avsforum.com/ubb/Forum12/HTML/011833.html

and I thought those topics really should have been started over here in "HDTV

hardware", so I am starting this topic here to solicit more responses.


Some questions I have:

1> Is there a way to "fix" this on the Sony W900 series?

2> Does the FW900 do a better job with 1080i interlaced signals?

(The Sony specs for the W900 and FW900 only show non-interlaced resolutions as

"supported presets")


There have been reports that very many computer monitors

have this "interlaced fields don't stagger" problem. Is there a "list" anywhere?
 

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Now that you have pointed this out to me. I've check five (19'-21') monitors. And am thinking most computer monitors do put the alternate fields right on top of each other, instead of stagered 1080i output when connected to a hdtv source. Making it look 540p (ish)


It is just harder to noticed on smaller monitors then on the 24 inch w900's.


If i get real close, within a foot I can see the problem on the monitors I've checked quite esaily, and on the 21 inch plus monitors, now that I know what to look for It can be seen as far away as a few feet.


I really wonder if the fw900 doesn't do this too but people are not looking closely enough. Two people have reported in other threads they thought it outputed correctly.


It would be nice if fw900's did work tho as I need a large screen monitor and would like one that can handle hdtv.


I'd be interested if some other people who have fw900's would check very closely to see if their monitor interlaced properly when hooked to an hdtv source.


-tony

[This message has been edited by tonyb100 (edited 09-02-2001).]


[This message has been edited by tonyb100 (edited 09-02-2001).]
 

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This is one of those subjects that I seem to think I know a lot about and yet questions come up that baffel me.


So let me ask a question:


Do you believe there is a difference between 1920x1080i and 1920x540P?


Me personally...I don't. I believe that are one in the same. They both have the same Hort. Scanning frequency (33.75 kHz). The only difference is one shows 540 scan lines in 1/60/sec while the other shows 1080 scan lines in 1/30/sec.


The 1920 stays the same for both being the Hortizontial resolution. The scan lines represent the vertical resolution.


Do you believe that if you could get your Monitor to show 1920x1080i versus 1920x540P that you will see a better image?


Lee
 

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ok I've heard that too. that 540p is basisly 1080i


But do you have any idea then why our computer monitors are showing spaces / that look like -- scan lines when useing hdtv cards outputting 1080i.


People have used power strip to have their (non hdtv) video cards output 1920 540p to the desktop, they get the spaces / scan line effect on the desktop we are seeing useing our hdtv cards. So this is what makes me think there is some sort of a difference in the way the two outputs are handled.


any ideas are greatly appeciated.
 

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Tony,


I will take "a stab" at answering your question with the disclaimer that though I consider myself knowledgable...I am not an expert.


There is a definite difference between Static images and Dynamic (moving) images on a PC Monitor.


A PC monitor is designed with Static images in mind. They use very small apeture plates and numbers like .19 and .21mm dot pitches are common even on large 19 to 21" monitors. They are designed to show text very clearly.


The reason for this is that your eyes are probably two feet or less from the screen. They can go with these super low dot pitches which greatly reduce the amout of light eminating from the screen due to the closeness of the viewer.


HDTV is a Television Format. It was designed from the beginning (1975) as a Television format. You are taking a format that was designed to be on 40"+ screens primarily using 3 gun CRT PJ's which have no dot pitch or apeture plates.


Television is all about "life" in motion be it real or fiction. PC's are about text and graphics which are designed with the PC in mind. Ever try to use a Television set as a PC monitor...text just doen't look anywheres near as good. And it shouldn't because the dot pitch of the average TV set is around .80mm or higher. There are now on the market "special" Direct View 16x9 HDTV sets that have a dot pitch of .50mm yet will deliver a very bright image.


Sony makes a professional line of broadcast montiors for the Broadcast industry. Their largest is 19" and it sells for $25,000.


When people use PC monitors, especially in the larger variety like 19" or 21" these monitors were designed from the get go to do high resolution graphics like CAD/CAM and such. They were never designed to do HDTV. They can do HDTV but that is not their primary design.


Personally, I believe it is the motion in the image that is causing you to see the faults in the monitor.


There is more to a montior than just dot pitch or frequency response. There is also something called retrace time. How fast can the electron beam light up each line of pixels or scan lines. The higher the frequency the faster that electron beam has to work. This is one of the limiting factors to the Hortizontial resolution and why some $30,000 FPTV PJ's can't create the entire 1920x1080i. Yet they are rated at 2500x2000...but this rating is for a static image.


Did I help or just confuse you more?


If anyone has another reason or "the correct" reason why...PLEASE jump in.


Lee

 

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Discussion Starter · #6 ·
Tony & Lee,

I think you are a little bit off the mark on some of

your details and assumptions. Not that I am a real expert

either, but I think I can make some corrections to some of

your statements:


1920x1080i is *NOT* the same as 1920x540p.


Yes, they share the same scan rate, and offer the same

number of pixels per second sent to the display.

The difference is subtle - when the 1080i signal finishes

with the first 540lines and comes back for the second

pass it is supposed to send a slighly different signal

that is _supposed_ to tell the display to offset the

second field down a small bit so that it "interlaces" the

second field between the gaps in the first.

Where interlacing sort of "chokes" is with side to side

motion. You can see a "tearing" in the images with

the alternate fields being mismatched. Various comb filter

devices and deinterlacing hardware attempt to correct

this shortcoming. So in some ways seeing 1920x1080i as

1920x540p actually offers some improvement (less visible

"tearing" during side to side motion), but the visible

gaps on sharp resolution displays can be very distracting.

Also, some of the vertical resoltion detail is lost because

your eye is blending the two fields.


--


Yes, Sony makes professional broadcast monitors but

they do make larger ones (e.g. 30"+) for HDTV. The professional

monitors tend to have much smaller dot pitches than

the consumer versions. The professional monitors

are much more expensive for alot of reasons but some

of those include:

* More exotic higher quality phosphors that produce

more "true" colors

* Much more hand tuning at the factory to get things

just right

------------

I agree to some degree that computer monitors were

designed with different goals than live video displays,

but I have long since learned that computer monitors

can make a very good live video display.


I prefer my computer monitor / home theater PC

with dScaler software for watching TV over regular

interlaced consumer TVs, and I prefer computer

software DVD playback over my standalone DVD player

with component outputs connected to a consumer

interlaced TV.


I watch most TV at 1600x1200 progressive (upconverted

by dScaler software)

and most DVDs on a RadeonLE equipped PC

at 1920x1080 progressive. (OAR anamorphic DVDs)


Even with the "interlace problem" (lack of interlace)

the HDTV image on my W900 still looks awesome. I

just wish it staggered the fields properly so that

I had the best possible image and didn't have to notice

the vertical scan lines so much.


One reason why a computer monitor has an "advantage" over

a consumer TV is that it doesn't need a built in

tuner, PIP hardware, Closed captioning, V-chip, speakers, etc.

If you already have an NTSC/ATSC tuner (e.g. HiPix card),

and an audio system (e.g. external dolby digital amp)

then it makes sense to not pay for those components

again as part of your display.


[This message has been edited by PVR (edited 09-02-2001).]
 

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PVR,


You stated that "side to side motion" is a problem. This can be attributed to Retrace times. The Electron beam is running side to side at high speed and it does reach a point where it can't keep up with the signal it is sent.


In 1998 a study was done to see which displays could do the full 1920x1080. Companies like Sony, Barco, Ampro Electrhome and Vidkron were looked at. It was found the though all the PJ's in question has the "specs" to do 2500x2000 only one could actually do it...The Vidikron Vision One. Simply because of the retrace time.


You are taking a display that was specifically designed to show a progressive signal and feeding it an interlace signal instead. You may be seeing some of the inherient problems with the whole interlace TV system because your montior has such a fine pitch.


Have you tried to attach an HD STB like an RCA DTC100 or a DISH 6000 or someother specificially designed for the TV marketplace HD decoder? I would try one just to see if the problem went away or if it remains.


I do know that many FPTV PJ owners have experimented with the kind of source equipment that you have and found that there is a law of diminishing returns when it comes to resolution. Many have found that an 800x600P image looks better and "crisper" then a 1280x720P which takes on a softer image.


Lee

 

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obviously I'am just learning and was trying to figure out what was goiing following the various posts and from my observations.


I must be slow today. I still think 540p isn't equally to 1080i.


even tho I've heard that 540p is 1080i, it still seems wrong to me. I must not understand how progressive works.


I thought a progressive scan was the display device darwing all the lines of an imagine in one pass, and interlaced was drawing half the lines on one pass and the other have on a second pass and this makes progressive look alittle more solid.


i was thinking 1080i has much more information/detail in the picture then 540p.


which i still think is true because a dtv 480p broadcast doesn't have anywere near the detail of 1080i broadcast, and if 540p was basicly the same as 1080i then there would not be much diffence in teh standard dtv 480p broadcast and the 1080i broadcast, which is obviously not the case.


I think the problem; with some, most,-- who knows, of the computer monitors is they don't hold the interlace/or alline it correctly and instead of staggering the two passes, they over lap them or maybe placed them on each other. Leaveing a blank space in between lines which robs some of the resolution


I guess it is beyond me.. how this stuff works


just kind wierd these monitors (w900) have a hdtv perset that is listed as interlaced in the manual but they can't do it correctly; tho people say some computer monitors do.


I know someone posted a pic in the htpc forum that had a correct interlaced picture on a 21 mits computer monitor from a hdtv source. It did look better then what I get-- oh well just wish my 24 inch monitor looked similar.


thanks for teh info guys.


-tony
 

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Tony,


A quick lesson:


The quality of an image is based on three differnt parameters:


1. Hortizontial resolution - how many pixels make up each scanning line.


2. Vertical resolution - how many scanning lines are used to create the omage itself.


3. The Frame Rate - also called "refresh rate" - how quickly is the entire image created.


Now there are two differernt ways to create the entire image; Progressive and Interlace.


Progressive - the entire image is created in 1/60 of a sec.


Interlace - half of the image (the odd scanning lines) is created in 1/60 of a second, then the other half (the even scan lines) are created in 1/60 of a second creating the entire image in 1/30 of a second.


As you can see the porgressive method creates the entire image twice as fast as the interlaced method. The faster you create the entire image the harder it is to see the scanning lines.


You are only comparing the vertical resolutiion in your comparison...540P versus 480P but that is not the whole equation. you must state the full H & V resolutions to compare apples with apples:


1920x540P versus 640x480P


480P is nothing more than our NTSC system which is 640x480i with the frame rate doubled. There is no increase in H. Resolution.


There is 3x more H resolution in HDTV than there is in 480P.


Just look at the number of pixels that make up the entire frame: 345,000 versus 1,036,000. Remember both use the same frame rate...1/60th of a sec. If you use the 1920x1080i specs which produce 2,0736,000 pixels but it does it in 1/30th of a second so you have to divide it by two to make them equal.


There is another HDTV Format called 720P it's specs are 1280x720P and is Progressive in nature. It produces 921,600 pixels per frame.


People that have seen 720P along side of 1080i say they are primarily equal to each other in picture quality. And as you can see the 540P HD format has only 10% more pixels than the 720P format which the eye would have a bit of difficulty seeing. The advantage of 720P is for sports because you have a 30% more scanning lines creating the image which will handle motion better than an interlaced system.


PVR:


You should really try to get a hold of a STB that can produce 720P. i know my Dish 6000 gives me the ability to convert 1080i to 720P and pass 720P native or convert 720P to 1080i and pass 1080i native.


Hope this explaniation helps you understand the different formats; 480P, 720P and 1080i/540P


Lee
 

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the reason I only used vertical resolutions in my comparesions is because vertical resolution is where the loss in picture quility I'm having is coming from. I'm not loseing horizal resolution.


i was saying that 480p vertical resolution looks much worse then 1080i vertical hdtv resolution, so I could not see how 540p VR could equal 1080i vertical resolution as it doesn't contain much more vertial resolution the 480p


I guess i'll take your word that 540p is the same as 1080i in terms of pq/resolution.


tho I don't see how a image with a resolution of 540p drawn in one pass, can have equal PQ/resoplution of a 1080i image made of two interlaced passes of 540 resolution, even if the the pogressive is twice as fast. To me 1080i contains twice as much picture information.



anyway I won't waste any more of the forums bandwidth on this I guess it is just counter intuitve to me.


thanks for your help


ps as to people not seeing much difference in 720p and 1080i i think this is because many display devices can not show the entire 1920 1080i imagine resolution. many come closer to only being able to display the 1280 720p resolutions. -- or just a small amount better.



[This message has been edited by tonyb100 (edited 09-02-2001).]
 

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Tony,


here is your statement:


"i was thinking 1080i has much more information/detail in the picture then 540p.


which i still think is true because a dtv 480p broadcast doesn't have anywere near the detail of 1080i broadcast, and if 540p was basicly the same as 1080i then there would not be much diffence in teh standard dtv 480p broadcast and the 1080i broadcast, which is obviously not the case."


Tony, do you see by your statement that your are comparing 640x480P to 1920x540P. You even say that the DTV 480P image is nowheres near the 1080i/540P...and it shouldn't be.


NOWWWWWWWWW...I am going to throw a wrench into the whole equation....There is another 540P format!


Most of the current HD STB's offer the option of viewing normal NTSC TV from satellite/OTA in either two ways; First is through the S-Video/Composite which produces 640x480i (NTSC). The second is to view satellite/OTA through the VGA/RGB or Hi Band Component outputs. These outputs produce a signal of 640x540P because 540P and 1080i have the same hortizontial Scanning rate...33.75khz.


In essence it acts like a line doubler (or a line doubler and then some). This type of 540P would lokk very much like 480P because the difference is only 60 scanning lines in the vertical resolution. The H. res (640) stays the same for both...a marginal improvement if any.


720P is the best HDTV for sports where there is fast movement. It is supported by Panasonic and 720P equipment is more expensive than 1080i equipment because the H. Scanning rate is 45 kHz so the electronics cost more.


This is a last version of HDTV and this is currently being used in the commericial industry for shooting movies and TV shows. It is called 1080P and it's spec is 1920x1080p @ 24 frames/sec and has over 2,000,000 pixels in each frame...all at once...no Interlace. it has twice the resolution of 1080i/540P.


You say you are trying to see the difference between 540P and 480P in the vertical mode. How can you do that? Your eye is seeing the entire frame.


640x540P will look very close to 640x480P: These formats are called Enhanced definition TV or EDTV


1920x1080i will look very close to 1280x720P: These formats along with 1080P are HDTV.


Comparing EDTV to HDTV...HDTV should look head and shoulders better than EDTV.


Lee

 

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i didn't mean to compare the total resolution of hdtv to dtv. only the number of vertical lines of resolution.


I understood you to belive an 1920 540p image has the same vertical resolution of 1920 1080i image.


I should have been more specific in asking my question and making my compasions.


since I understood you to say 1920 540p and 1920 1080i are the same.


I should have asked why is there so much better vertical resolution on hdtv then dtv, since dtv sd is 480p vertical resolution which is almost 540p vertical resolution, which you say is the same as 1080i vertical hdtv resolution? if that were true I would expect less of a difference in vertical resolutions between hdtv and dtv.


maybe you think me crazy but i can look at vertical resolution and not whole frame I just look at the resolution/ lines up and down the screen.


To me a vertical line made up of 540 elements has less pixels then a line of the same sized made up of 1080 elements. Making the 1080 line have less space between between pixels and therefore more resolution.


someone could use power strip if they have a htpc, to have their video card output 1920 540p to the desktop and then 1920 1080i to the desktop, and tell me which one appears to have more space between lines or if they look exactly the same.


thanks again


-tony.


ps if 1920 540p is as good as 1920 1080i why did they bother with 1920 1080i. Is it cheaper?



[This message has been edited by tonyb100 (edited 09-02-2001).]
 

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I have to support PVR's conclusions above that there is at least a slight difference between 540p and 1080i signals, at least when being sent to a CRT.


While the timings are almost the same we are ignoring the timings in the vertical blanking interval. 1080i actually is supposed to send 1125 lines, where the extra lines are in the invisible vertical overscan area. Turning this into 540p means each field needs 562.5 lines and it is that extra .5 invisible line that should change the timing enough that the even and odd fields are equally spaced vertically.


I guess if the extra .5 line delay is not present, or ignored, then the two fields might lay on top of each other.


- Tom





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Discussion Starter · #14 ·
Thanks trbarry - this thread was really starting to drift off topic.


What you say describes my point -

From what I can see ~my~ W900 seems to ignore that

offset delay and the fields incorrectly display right

on top of each other.


=====================================================


In response to other posts:


LeeAntin wrote:


>> You stated that "side to side motion" is a problem. This can be attributed to Retrace times.


Lee - I think you are a little "hung up" on retrace times

as being a huge factor in all of this.


In my opinion the "side to side" motion issue is the

downside of interlacing for the following reason:


If you have an image like this:


......

.####.

.####.

.####.

.####.

......


and you move it across (side to side) on a progressive display then

the whole block jumps over on the next screen update.

(which is good for your object to stay in one piece!)


If you are using an interlaced display then the block does

this:

......

..####

.####.

..####

.####.

......

Notice how the alternate lines moved to the right but

the others did not. This "even waiting for odd to catch

up" system causes a "tearing" effect in the image during

side to side motion.


Now there are various ways displays are designed to help

avoid this inherent shortcoming with interlaced video:

1> Multi line Comb filter

2> Digital deinterlace circuit (e.g. dScaler or iscan)

3> Long persistence phosphor

4> Large dot pitch

Unfortunately all of these tend to blur the image

to help "blend away" the interlace tearing artifacts.


LeeAntin wrote:

>> Have you tried to attach an HD STB like an RCA DTC100 or a DISH 6000 or someother

>> specificially designed for the TV marketplace HD decoder?

>> I would try one just to see if

>> the problem went away or if it remains.


I think I said this already - I tried two HiPix cards

and a DTC-100 box and all of them show the 1080i signal

with only 540 _DISTINCT_ vertical lines visible on my W900.


LeeAntin wrote:

>> People that have seen 720P along side of 1080i say they are primarily equal to each other in picture quality.


This is very debatable. I have stated in other topics

that I think so many people thought 720p looked as good

as 1080i because the display devices weren't cable of

showing much detail beyond 1280x720 resolution.


==================

tonyb100 wrote all sorts of stuff including:

>> I thought a progressive scan was the display device darwing all the lines of an imagine

>> in one pass, and interlaced was drawing half the lines on one pass and the other have

>> on a second pass and this makes progressive look alittle more solid.

>>

>>

>> I think the problem; with some, most,-- who knows, of

>> the computer monitors is they

>> don't hold the interlace/or alline it correctly and >> instead of staggering the two passes,

>> they over lap them or maybe placed them on each other. >> Leaveing a blank space in

>> between lines which robs some of the resolution


That seems correct and in sync with my understanding.

I don't think you need to be "humble" about posting in

this topic. It sounds to me like you understand this

as well as the rest of us posting in here.


I think LeeAntin is sort of dragging us off in tangents

that aren't very important to my original point.


I still plan to do the following tests soon:


PowerStrip 1920x1080i (interlaced!) output from

my Radeon card to see if the W900 interlaces it better.


Drag my HTPC over to a shop with an FW900 to scruitinze

_it_ more carefully to see if it interlaces better than

the W900.


========================================================

Now something else I should mention which I didn't think

was important but I should say just in case:


My "W900" is actually not a Sony labeled monitor.

It is a Sun X7124A display which (as far as I know)

is the exact Sony W900 hardware with a Sun brand

printed on it. Externally it has the same controls

and layout, same menus, etc. The only real difference

that I know of is a Sun standard monitor interface

on the back instead of 5 BNCs. It does have a VGA style

input for the 2nd input and I have tried both inputs with

the same results.
http://cgi.ebay.com/aw-cgi/eBayISAPI...tem=1270799489


The W900 was also OEMed and sold by Compaq and Dell under

their own part numbers.
 

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Discussion Starter · #15 ·
..AND...


My HiPix card has some different output modes

including 720p. So I tried 720p mode on this monitor

and I can see that it has a bit more scan lines showing

(720 instead of 540) and less "scan line gap", but I

am not happy running at 720p because:


1> 99% of the source material I have is 1080i format

(PBS recordings, etc) and the image suffers some

"scaler artifacts" if you force the HiPix to convert

it to a different output resolution.

2> 1280 horizontal pixels just doesn't show as much

detail. Even with my monitor "limping" along at 1920x540

I can see more detail in the image than running at 1280x720

3> I really want to get this thing to display the full

1920x1080 since the "dot pitch" is fine enough to support

it. Running at 1280x720 would be "crying uncle",

"throwing in the towel" and basically giving up on the

goal I had in mind when I bought this monitor.
 

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Discussion Starter · #16 ·
OK - now I have discovered something _VERY_ interesting.


While playing with the W900 monitor settings I found

that if I shrink the horizontal size about 80% of the

width of the screen suddently the interlacing pops on!


So if I shrink the vertical and horizontal picture size

about 20% overall (leaving about a 1/2" black border all

around my HDTV image) I get properly interlaced 1080i

and it looks wonderful.


As I play with the horizontal size control and stretch

the image to fill the screen, there is a very specific

horizontal size at which point it just pops out of

interlace and I see the 540lines instead of 1080.


It is particularly apparent when using the controls because

the onscreen menu is up (showing a sliding bar indicating

how much width setting is selected). The fonts in the

menu look very different when it is doing interlacing

versus "semi-progressive" (overlayed fields).


Now I don't know why this happens. Maybe the "1035i" HDTV

spec that my monitor supports is somewhat incompatible

with the 1080i signals I am sending and somehow shrinking

the displayed area kicks the interlace circuit back in???


I don't know... But in any case I am reasonable happy with

the image I now have (even though it doesn't quite fill

the screen). Sitting about 2 feet from the monitor it

still pretty much fills my field of vision.


If other people are trying out 1080i on computer monitors

and suspect 540 lines are showing, then try playing with

the image size controls and see if it helps!
 

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If the signal was coming from a computer video card with custom timings you could leave the monitor controls shrunk but then decrease the horizontal front and back porches in PowerStrip or whatever to adjust the image size seen on the screen.


But I have no idea how to do that with either a DTC100 or a HiPix card.


- Tom


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i want to say thanks everyone for the help.


lee, I thought about it and I understand what you were saying. thanks for your help, I should have slept on your first post and I would have saved alot of time, i was obviously to tired to think.


pvr thanks for the tip that makes the monitor interlace. I got it today from my rental office it was delivered friday but i was not home.


tony burney


[This message has been edited by tonyb100 (edited 09-02-2001).]
 

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I just moved up from a Hitachi 17" display to a

ViewSonic p225f 21" display. In both cases I use the

Panny HUDS-20 STB. With the ViewSonic I was also able to

move up from a VGA cable to 5 x RG6 cables with BNC connectors.


With either display and the STB set to native mode, I have been able to see native 480p,720p,1080i. Few computer

monitors will show 480i because their lowest horizontal

sweep frequency is 30 KHz, and 480i needs 15 KHz. I am sure

that I am seeing true 1080i interlaced properly. I do not

have to shrink the horizontal size. I do shrink the vertical

size in order to approach the 16 x 9 aspect ratio. This then

requires some tweaking of the geometry adjustments, but not

much in the case of the ViewSonic.


The ViewSonic HD picture is fantastic. For those of us

willing to accept the limited size, I believe the picture is better than any large screen technology under $10 grand.

The PBS demo material, particularly the Italian travel stuff,

has tremendous detail that is really lacking in the $3K to

$4K sets I see at the video stores. I realize the color of

these store sets is usually not properly adjusted, but I believe the resolution they show, when displaying the same PBS OTA material, is similar to what I would see at home.
 

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I believe Lee is incorrect in saying that 1080p at 24 frames a second has twice the resolution of 1080i. I believe 1080i is really 1920 x 1080 x 59.94i which means you are getting 29.97 frames a second vs 24 frames a second (of course the interlacing reduces the actual useful resolution when there is motion but that is another subject entirely).


Milton Henry
 
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