Does 1080i really exist??

mrmrbungle

I'm confused, i've been searching round the net for ages and i cant find a proper answer. My tv is hd ready, which means it can display images at 1366 x 768 max coz thats how many pixels it has. What's the point of having inputs of 1920 x 1080 if it's going to be scaled anyway? and how can my tv display more pixels than my screen has?

Any help is appreciated

Captain Chaos

mrmrbungle wrote: »

I'm confused, i've been searching round the net for ages and i cant find a proper answer. My tv is hd ready, which means it can display images at 1366 x 768 max coz thats how many pixels it has. What's the point of having inputs of 1920 x 1080 if it's going to be scaled anyway? and how can my tv display more pixels than my screen has?

Any help is appreciated

Thats actually a 720p screen you have which can also do 1080i.
If your screen was 1920x1080 then its a 1080p screen.

The HD ready term can be used for screens as low a spec as 480p.

mrmrbungle

so does that mean that there's actually screens out there that are 1920x1080 resolution that can't display 1080p? can you display 2 million pixels on a 1 million pixel screen?

Captain Chaos

No, if a screen has a resolution of 1920 x 1080 it can do 1080p max. It will not do 1080p if the signal going to it is of a lower standard unless you have something that can upscale the images. Like what a PS3 can do for standard DVDs.

Captain Chaos

A screen can only display an image up to the max amount of pixels it has.
If you tried to put a 2mp image on to a 1mp screen it will get resized to what the screen can do.

mrmrbungle

Captain Chaos wrote: »

No, if a screen has a resolution of 1920 x 1080 it can do 1080p max. It will not do 1080p if the signal going to it is of a lower standard unless you have something that can upscale the images. Like what a PS3 can do for standard DVDs.

i don't think you understand the question, 2 million pixels will not fit on a 1 million pixel screen. i want to know why they say hd ready can display 1080i when it clearly cant and i thought someone might have an in-depth knowledge of such things including scaling

stevenmu

The clue is in the i and p letters which stand for interlaced and progressive. A TV picture is made up of rows of pixels, in the case of 720 it's 720 rows, for 1080 it's 1080 rows. When the picture being shown is progressive scan, e.g. 720p, all rows in the picture are shown at once. But when the picture is interlaced e.g. 1080i, first all the odd numbered rows are shown, e.g. rows 1,3,5 ... etc, then all the even numbered rows are shown, e.g. rows 2,4,6 ... etc (it's actually a little more complicated because obviously 1080 != 720 * 2, but that's the rough idea). This means each physical pixel on your TV shows more than one pixel from the signal image.

pH

mrmrbungle wrote: »

i don't think you understand the question, 2 million pixels will not fit on a 1 million pixel screen. i want to know why they say hd ready can display 1080i when it clearly cant and i thought someone might have an in-depth knowledge of such things including scaling

At this stage you're just arguing semantics, clearly when you connect a 1080i source to the TV you can see a picture, so it can display a picture.

HD Ready was a logo/mark agreed by the industry to have a particular meaning.

In the USA, "HD Ready" refers to any display that is capable of accepting and displaying a high-definition signal at either 720p, 1080i or 1080p using a component video or digital input, and does not have a built-in HD-capable tuner.

There are also some connector requirements to be allowed display the HD ready logo (see wiki page linked above)

jmal

This might simplify things.

I think what you missed is that a screen marked as HD Ready means it can display a HD content which can be up to 1080p.

What basically happens is your HD Ready Screen may only have a resolution of 1366 x 768 but when the 1080p signal is recieved by the TV ,it then descales the signal (content) to match the resolution of your screen (1366 X 768). A screen that is not HD Ready may not be able to descale 1080p or 720p content to its current resolution (800 X 600) so it may not be able to process the picture.

Hence you will normally see something like this in the specifications for a flat panel or projector explaining what content resolution a screen can handle.

" 525 (480)/60i, 525 (480)/60p, 625 (576)/50i, 625 (576)/50p, 750 (720)/
50p, 750 (720)/60p, 1125 (1080)/50i, 1125 (1080)/60i"


This descaling process is what makes the difference between a good screen and a cheap screen, and is usually the reason why some flat screens can look poor when displaying SD content (Standard NTL) etc.

Its alot easier to descale down from (E.g. 1080 to 720) than it is to descale up from (480 to 720) and only the top manufactures can do this well.

Hope i've explained this correctly.

stevenmu

If you just say scale instead of descale it becomes a bit clearer

Also not all HD Ready TV's can scale down and image from 1080p, many will just refuse to show a picture. I don't think there's any requirements on them to do this.

mathias

I'm confused, i've been searching round the net for ages and i cant find a proper answer. My tv is hd ready, which means it can display images at 1366 x 768 max coz thats how many pixels it has. What's the point of having inputs of 1920 x 1080 if it's going to be scaled anyway? and how can my tv display more pixels than my screen has?

I'll sum it all up in a few lines because theres a lot here thats incorrect ,

first , HD ready ,

For a TV to be hd ready it has to have a vertical resolution of at least 700 pixels/lines , amongst other things , but thats probably the most important bit.
http://en.wikipedia.org/wiki/HD_ready

There are two main HD resolutions on most HD content available at the moment. They are 1280 x 720 , and 1920 x 1080 , 1080 can come in interlaced ( 1080i ) or progressive ( 1080p)

The most common TV set resolution for 720 is not really 720 but 1366 x 768 , which is a resolution that is easy for the manufacturers but is not consistent with either of the two main HD content resolutions so a TV like this must scale ( shrink or enlarge the picture ) to fit the screen. and it will do so with everything thats fed to it.

The next most common is so called " full HD " or 1920 x 1080 , a screen like this does not have to do any scaling on any 1920 x 1080 content , regardless of whether its 1080i or 1080p.

Most HDTV sets with a resolution of 1366 x 768 will accept input up to 1080i and will scale this to fit the screen. If the set takes 1080i maximum , then you cant feed a 1080p signal to it as it wont show it , but most content players will allow you to turn the output to a format it will take , so there shouldnt really be any content you cant watch. ( for instance the PS3 can be set to output everything in 1080p , 1080i , or 720p etc., it will interrogate your TV over the HDMI and suggest the best setting for you.)

Currently the best sets to buy , but also the most expensive is a set with a resolution of 1920 x 1080 , they are the best because they dont have to scale 1080 content , such as most blu ray movies , Sky HD etc.

norrie rugger

mathias wrote: »

Sky HD etc.

going ever so slightly off topic.

I thought that Sky HD was 768?

pH

norrie rugger wrote: »

going ever so slightly off topic.

I thought that Sky HD was 768?

The Sky HD box can handle either 720p or 1080i - all channels broadcasting HD on sky have opted for 1080i, though you can force the box to output 720p (if the sky box does a better job of scaling/deinterlacing than your panel)

There was some debate about whether fast moving sports would be better served by 720p but I think mainly due to the availability of cameras Sky opted for 1080i for sports too.