1080i on 32" HDTV's with 1366x768 res. ??? how?

[snadge]

This has been bugging me for Months and I cant seem to work it out or find an answer...

Now on the understanding that the terms 720p/i & 1080p/i (P=Progressive / I=Interlaced) are explaining the amount of resolution... for e.g.

HDTV's with 42" (some 37") or more have a 1080 resolution (1080x1920) to enable true HD on large HDTVs
and 37" and smaller have 720 resolution (720x1280 or 768x1366) - HD for that size HDTV...

HOW can a 32" HDTV with a resolution of 768x1366 display 1080i ?????

Ive been into Currys and everywhere and they just look at me with a dumb glare and dont have a clue...

everywhere i read that 1080 is the number of lines on the screen (resoution) but nearly all 32" HDTV's can display 1080i..... is this a farce to lull people into thinking there HDTV is better than it really is?

Somebody please explain hehe?

[jagabo]

HOW can a 32" HDTV with a resolution of 768x1366 display 1080i ?????

They deinterlace then downsize the image.

[politiken]

The TV will deinterlace or inverse telecine 1080i to 1080p and then downscale to 1366x768 for display.

Look to: https://forum.videohelp.com/topic338208.html#1760727

Pol

[JohnnyMalaria]

Some cheap ones discard one field and upscale the resulting 1920 x 540 image. Homework is required!

Bear in mind that for the most part, displays capable of native 1080 (i or p) are overkill. With perfect eyesight, you can resolve an object of about 1mm from a distance of 10 feet (nice mix of metric and imperial!) Unless you have very large displays and/or sit very close to them, you'll be hard pushed to see the difference between 1080 and 720 displays (though psychologically you may because of the extra money spent).

[snadge]

Thanks

SO - it IS a farce then? this is a trick used by hardware manufacturers to LULL buyers into thinking theyre TV's are better than they actually are?
having a selling point like 1080i!!! is wrong if it just gets downscaled to 720p

How can companys get away with this and isnt there anything that can be done?

My friend bought a 32" HDTV and was bragging about the 1080i.. imnagine his disgust when ive just explained to him that his TV doesnt really display 1080lines and that the guy in shop lied to you, infact he doesnt believe me and is convinced his 32" 768x1366 resolution monitor can display 1080i or p..hehehehehe ive shown him this site to prove otherwise

[slukaczyk]

everywhere i read that 1080 is the number of lines on the screen (resoution) but nearly all 32" HDTV's can display 1080i..... is this a farce to lull people into thinking there HDTV is better than it really is?

I don't understand the question - if you have a vertical resolution of 768 and you only display 540 lines at a time (frame, that's what 1080i or interlaced means) then you still have 228 lines left over per frame. Switch to 720p and you display 720 lines at once (that's what progressive means) and you still have 48 lines left over. You must be confused about 1080p, in other words how can a screen with only 768 lines display all 1080 lines at once, or 1080p. Looks like that has been answered by others here though. Unless you have an HD DVD or Blu-Ray player 1080p is a moot point because 1080i is the max broadcast spec for HDTV. By the way, both 1080i and 720p are stunning compared to SDTV. Hope this helps, Steve
[/quote]

[snadge]

no im not confused
so 1080i is 540p...? thats what Iam asking for clarification on?
if you read the advice from others above they explain that 1080i is de-interlaced then downscaled to 720 cos the 768x1366 tv CANT display 1080i

AND

If what you say is right... 720p is BETTER than 1080i yet companys use 1080i as a better selling point than 720p

What Iam Trying to say is:
Isnt it WRONG to sell TVs saying they can display 1080i when infact they cant cos they get downscaled???
can anybody see my point here?

[jagabo]

no im not confused
so 1080i is 540p...? thats what Iam asking for clarification on?

Each interlaced frame contains two half pictures, called fields. One field is in all the even numbered scanlines, one in all the odd numbered scanlines. One simple way of deinterlacing is to simply throw away one field. With a 1920x1080i source this leaves you with a 1920x540p picture. That will get scaled to the HDTV's native resolution.

If what you say is right... 720p is BETTER than 1080i yet companys use 1080i as a better selling point than 720p

There are many better ways of deinterlacing than the above mentioned "drop field". Note that Johnny Malaria said "Some cheap ones discard one field and upscale..."

What Iam Trying to say is:
Isnt it WRONG to sell TVs saying they can display 1080i when infact they cant cos they get downscaled???

Well, if you're told that a 720p HDTV can display every detail of a 1080i/p picture, it's wrong. On the other hand, 1280x720 is a lot higher definition than 720x480 or 720x576.

[slukaczyk]

no im not confused
so 1080i is 540p...? thats what Iam asking for clarification on?
if you read the advice from others above they explain that 1080i is de-interlaced then downscaled to 720 cos the 768x1366 tv CANT display 1080i

As someone said a 1080i picture FRAME is composed of 2 FIELDS each containing 540 scan lines. Each field of 540 lines is displayed by itself, eg even field first then the odd field a split second later iter-woven or "interlaced" between the even fields. Your eye's simply see one picture because it's so fast. Take a standard def TV. Same thing. Would you say consumers have been cheated since day 1 by the TV marketeer's because we have been told we are getting a 720x480 picture? We are getting that - 240 lines in the even field and 240 lines in the odd field for a total picture FRAME of what appears to the eye as 480 lines. 32" Hi Def TV's with an X by 768 resolution have no problem with 1080i - it' the 1080p that would need some digital trickery to display properly. Steve

[jagabo]

32" Hi Def TV's with an X by 768 resolution have no problem with 1080i - it' the 1080p that would need some digital trickery to display properly.

Any progressive display has to use some "digital trickery" to display an interlaced signal. Any TV that is displaying a frame that doesn't match its native resolution will be using some "digital trickery" to display that frame.

[slukaczyk]

32" Hi Def TV's with an X by 768 resolution have no problem with 1080i - it' the 1080p that would need some digital trickery to display properly.

Any progressive display has to use some "digital trickery" to display an interlaced signal. Any TV that is displaying a frame that doesn't match its native resolution will be using some "digital trickery" to display that frame.

Agreed 100%.

[snadge]

Its been explained in this thread that 1080i on x768 sets are de-interlaced to progressive then downscaled to 720p OR is it how you say...1080i is displayed through two fields which fit on a 768 set (2x540 fields interlaced)..?

its seems Iam being given 2 answers

(Interlaced images, because they are interlaced (the way Iam being explained) wouldnt that mean that Progressive is better picture quality as interlaced frames would be moving up/down 1 line as they are displayed, Im aware as its so fast its a blur creating one image but in theory P is better yes?)

Its all very complicated but Ive got the jist of it now and understand how 1080i works.. if its the latter (2 fields inter-woven (2x540) then it would make 1080i infrerior to 720p as 720 has more lines and can therefore display more as its a higher resolution to 540 in 2 fields)

My friends DVD HD Recorder displays 1080i or 720p on his 32" Sharp HDTV and BOTH Images are same ratio/clarity leading me to believe that the 1080i input is downscaled to 720p on the TV....

Thanks for explaining guys

[slukaczyk]

My friends DVD HD Recorder displays 1080i or 720p on his 32" Sharp HDTV and BOTH Images are same ratio/clarity leading me to believe that the 1080i input is downscaled to 720p on the TV....

I think you've hit the nail on the head. Being a new owner of a 32" LCD HDTV I could not agree more. Either format blows away SDTV and to persue a set capable of native 1080p might be overkill IMHO.

[snadge]

i agree about 1080p ... if you have a small living room and/or sit close and even more so if you dont watch HD feeds through it....

1080p sets should be used for LARGE living rooms that will have SKY HD and/or HD DVD or Blu-Ray...

I was surprised to see a 37" 1080p set the other day...

Some people say its like being in the pictures (with regards to sitting close) but Ive been instore and put myself infront of a 42" with HD movie on and I was mesmerised and thought I would be sitting inspecting the quality all the time instead of enjoying the film hehe)

[dun4cheap]

I could be wrong here, but it is my understanding the max res. is VGA/DV resolution. The HD TV's such as my Vizio 47" can display 1920x1080P 30/60 which is different than the VGA/DV timings. I can achieve 1920x1080 HD resolutions from my PC as well but it requires me to select HDTV Settings.

Anyhow, this is my understanding on all of this. When I go through different modes my TV reports the output, 1080i, 1080p, and if you go to the info screen it reports the resolution.

[jagabo]

Its all very complicated but Ive got the jist of it now and understand how 1080i works.. if its the latter (2 fields inter-woven (2x540) then it would make 1080i infrerior to 720p as 720 has more lines and can therefore display more as its a higher resolution to 540 in 2 fields)

I'm not sure you fully understand it yet.

First note that fields do not overlap. That is, if a still scene is displayed, one field contains half the picture and the other contains the other half. The two can simply be woven together to restore the full 1920x1080 resolution. It's when things are moving that processing gets tricky.

When film sources are interlaced for broadcast they are telecined into fields in a 3:2 pulldown pattern and sent to the TV. A 1080i TV (limited mostly to CRT) will display each 1920x540 field in sequence and in the correct location on the screen. This indeed causes flickering and bouncing of sharp horizontal edges. A progressive TV can take pairs of fields, weave them together to restore the original 1920x1080 film frames (inverse telecine), and display that (resized if necessary). Most HDTV's can now do this pretty well, both 720p and 1080p.

With true interlaced sources the processing is more complicated. As was mentioned earlier one of the cheapest methods of converting interlaced frames into progressive frames is to simply throw out one of the fields. When you do this you are indeed throwing away half the vertical resolution. But better progressive displays use smart algorithms that attempt to retain the full vertical resolution in non-moving parts of the frame. They can even use motion adaptive techniques to maintain vertical resolution in many parts of the frame are moving. This type of deinterlacing is getting better and better with each new generation of HDTV.

[edDV]

Maybe we should step back to the basics.

A 1366x768 progressive LCD-TV converts everything to 1366x768 progressive. Are we clear with that? The methods used to convert 1080p/1080i/720p/576p/576i/540p/480p/480i to 1366x768 progressive are the next topic.

When the store salesman says 1080i, he means the 1366x768 set will accept a 1080i input. If he says it will display 1080i resolution he is lying.

[dun4cheap]

The clarity still beats our old CRT TVs that displayed a whopping 200-240 vertical scan lines.

[edDV]

Another basic point, due to kell factor* 720p and 1080i display similar vertical resolution to the human eye. 1080i has potential for greater horizontal resloution. This will only be noticed on larger screens at normal viewing distances (e.g. over >42". at ~6 ft. viewing distance). Some human tests show no difference for 52" screens at 6ft.

*http://en.wikipedia.org/wiki/Kell_factor

[edDV]

The clarity still beats our old CRT TVs that displayed a whopping 200-240 vertical scan lines.

The negative differences you see will be deinterlacing errors in areas with motion. CRT sets display native interlace so don't have these issues. The differences between a good and bad progressive televisions center on the quality of the deinterlacer/cinema processing and the ability to display a true black rather than dark gray. Motion smear used to be an issue but LCD-TV displays have recently improved refresh rate. Avoid old models.

[snadge]

Maybe we should step back to the basics.

A 1366x768 progressive LCD-TV converts everything to 1366x768 progressive. Are we clear with that? The methods used to convert 1080p/1080i/720p/576p/576i/540p/480p/480i to 1366x768 progressive are the next topic.

When the store salesman says 1080i, he means the 1366x768 set will accept a 1080i input. If he says it will display 1080i resolution he is lying.

Thank You.... While that is exactly want i wanted to know - I'AM Interested in learning how Interlacing works.

Somebody was saying earlier that 1080i is actually displayed on a 1366x768 screen in two fields of 540 which leaves over 228 lines on screen...??? this doesnt sound right to me... Ive been told several times now that 1080i on a x768 32" HDTV is De-Interlaced to Progressive then downscaled to 720 (which isnt 2 fields of 540 on screen leaving over 228 lines)

[turk690]

snadge's original bewilderment was over how a physical 1366x768 display can show a 1080i signal fed to it, not on whether 720p looks better than 1080i on any given HD-capable display. Or not. As edDV said, we should step back to basics. A 1366x768 display will ALWAYS display 1366x768; it can't help it: it's a fixed-pixel display. A much more important question, IMHO, should be, how capable are the internal scaler circuitry of that display in accepting the gamut of resolutions out there, SD & HD, i & p, thrown to it and neatly scaling and resolving all of them to 1366x768 without adding artifacts of any sort?? Highly-rated scaler circuitry is not cheap, like those made by Faroudja; they are among what makes Sony Bravia LCDs at least twice as expensive as the next no-name brand for the same screen size. Other manufacturers, like JVC will have their own schemes. The bottom line when buying a fixed-pixel display that is not either 1080 or 720 vertically (like our wretched 768) is to observe it as it's fed different resolutions with material familiar to you and see what fazes it. I have a 1280x720 Panasonic PT-900AE projector that manages to produce awesome images, whether the signal is 1080ip or 720p, 480/576ip. Does that mean its scaler circuitry is superior? Could be.

[snadge]

well said turk690... this brings another point to notion... Upscaling DVD Players... If your HD-TV upscales Standard Def DVD anyway...why the need for Upscaling DVD Players?

[jagabo]

Somebody was saying earlier that 1080i is actually displayed on a 1366x768 screen in two fields of 540 which leaves over 228 lines on screen...???

What was meant that the 1080i frames are separated into two two 1920x540 images. Then each image is resized to the LCD's native resolution for display. This is called a "bob" deinterlace.

[snadge]

Somebody was saying earlier that 1080i is actually displayed on a 1366x768 screen in two fields of 540 which leaves over 228 lines on screen...???

What was meant that the 1080i frames are separated into two two 1920x540 images. Then each image is resized to the LCD's native resolution for display. This is called a "bob" deinterlace.

Ahh Right... Amazing what they can do these days - newbie! hehe

[JohnnyMalaria]

Somebody was saying earlier that 1080i is actually displayed on a 1366x768 screen in two fields of 540 which leaves over 228 lines on screen...???

What was meant that the 1080i frames are separated into two two 1920x540 images. Then each image is resized to the LCD's native resolution for display. This is called a "bob" deinterlace.

Is there a resource that lists which current 720p HDTVs use which deinterlacing method? I really don't want to end up with a plain ol' bob set.

[edDV]

Maybe we should step back to the basics.

A 1366x768 progressive LCD-TV converts everything to 1366x768 progressive. Are we clear with that? The methods used to convert 1080p/1080i/720p/576p/576i/540p/480p/480i to 1366x768 progressive are the next topic.

When the store salesman says 1080i, he means the 1366x768 set will accept a 1080i input. If he says it will display 1080i resolution he is lying.

Thank You.... While that is exactly want i wanted to know - I'AM Interested in learning how Interlacing works.

Somebody was saying earlier that 1080i is actually displayed on a 1366x768 screen in two fields of 540 which leaves over 228 lines on screen...??? this doesn't sound right to me... Ive been told several times now that 1080i on a x768 32" HDTV is De-Interlaced to Progressive then downscaled to 720 (which isn't 2 fields of 540 on screen leaving over 228 lines)

CRT tubes display fields sequentially. They draw odd lines followed by even lines. The complete image is constructed in your brain which follows the 50Hz field sequence for motion and combines fields into a full image for slower scenes. In other words, the human brain is part of an interlace display.

Progressive display of interlace material (720x576i or 1920x1080i) requires the complete image to be built in the display buffer every 1/50th sec. Deinterlacing requires combining two fields that are offset in time by 1/50th second into a complete image every 1/50th second*. When there is motion, simple addition (aka weave) results in odd/even line displacement.



The deinterlace processor will use complex algorithms to convert 50 field/sec interlace to 25 frame/s progressive. This processing leaves artifacts. The eye is drawn to sharp moving edges and flashing pixels

Cheap processing relies on blend deinterlace which just blurs the picture until you don't see the split lines. The more the motion, the greater the blur. High end deinterlacing will identify and process moving objects while leaving non moving areas at high resolution.

As a general rule the deinterlace processor quality tracks price because the better techniques require royalty payment. Generic TV processing chips get better each generation so a current generation LCD-TV will usually look better than the discounted last year model.


*I'm describing live video here such as sports or news. Film source is processed somewhat differently especially in the NTSC market. PAL LCD-TV sets identify progressive film source and process with 2:2 pulldown instead of deinterlace.

[TBoneit]

Thanks

SO - it IS a farce then? this is a trick used by hardware manufacturers to LULL buyers into thinking theyre TV's are better than they actually are?
having a selling point like 1080i!!! is wrong if it just gets downscaled to 720p

How can companys get away with this and isnt there anything that can be done?

My friend bought a 32" HDTV and was bragging about the 1080i.. imnagine his disgust when ive just explained to him that his TV doesnt really display 1080lines and that the guy in shop lied to you, infact he doesnt believe me and is convinced his 32" 768x1366 resolution monitor can display 1080i or p..hehehehehe ive shown him this site to prove otherwise

And it can display 1080i by scaling it to its native resolution which is most likely 1366 by 768.

Why worry about it? It'll look good and if you can find a 32" HD LCD that has a 19xx by 1080 it'll cost a fortune compared to what he has. I'm using a 32" 1366 by 768 LCD and it looks good. Before I'd have spent a ton of money to get a better native resolution I'd have gone to a bigger screen.

[snadge]

WOW Thanks for that edDV... I understand much more now, it seems that its one of the most important factors when buying a LCD TV then... Its Interlacing Processor am i right?

I thought that lower Response Time and higher Contrast Ratio meant for better image clarity but suppose that means nothing if it has poor interlacing...Iam goin to inspect my cheapo BUSH 32" HDTV, We bought 12months ago for £399 and the 1st model ended up getting a line of pixels go dark down the screen so got it swapped for another one... Now you can get a half decent brand for that price....

What Brands use high-end technology>?

[edDV]

Somebody was saying earlier that 1080i is actually displayed on a 1366x768 screen in two fields of 540 which leaves over 228 lines on screen...???

What was meant that the 1080i frames are separated into two two 1920x540 images. Then each image is resized to the LCD's native resolution for display. This is called a "bob" deinterlace.

Is there a resource that lists which current 720p HDTVs use which deinterlacing method? I really don't want to end up with a plain ol' bob set.

Most current HDTV chip sets are more sophisticated than a simple Bob. Motion detection is used to isolate objects and backgrounds by relative motion and then each section is processed based on relative motion. Fast moving objects may get a blend or field decimate, bob will be used for slower motion areas and weave will be used for still objects. The better techniques require frame memory and royalty payment so are reserved for higher priced models. For example, the Faroudja DCDi chip can be licensed for use with no memory at a lower payment than when frame memory is used.

Remember that 1080p LCD-TV sets also need the same processing for 1080i, 576i or 480i sources.