a maybe-stupid question about 1080i

[daWsOn_s]

Hello,
I always wondered this: in the US with ATSC 1080i broadcasting during shows shot in 24p,60hz with pulldown is used .
If I do the inverse telecine I can get the original 24p progressive frames, so if I do the math correctly broadcasting in this way isn't like if it was 1080p24? My guess would be NO, but how could they not do that? is there another type of pulldown that actually interlace frames giving a real 1080i?

What about Europe that use 1080i50hz with 25p material? I always see movies and series broadcast in this way and analyzing the stream is totally progressive, so this would real 1080p again? is it possible here to give a real 1080i? Do broadcaster know that they're airing in FULL HD with 1080i bitrates?

Could someone explain ?

[Guest]

You're confusing the content of the stream with how it is presented to a display device.

[daWsOn_s]

what do you mean?

[Guest]

The output to the display is 1080i29.97, i.e., 59.94 fields per second. That field stream can have pure video with a new temporal moment at each field. Or it can have a 3:2 pulled down film stream. Either way, the field rate to the display is the same.

[daWsOn_s]

OK but I wanna know is that if for the second option (3:2 pulldown) is like having 1080p24 when removed

[Guest]

OK but I wanna know is that if for the second option (3:2 pulldown) is like having 1080p24 when removed If you have a 3:2 pulled down progressive source and you apply IVTC, obviously you then have the progressive source frames at film rate again. That's what IVTC is all about.

[daWsOn_s]

so if I had that and a real 1080p24 there would be no difference in quality?

[Guest]

a real 1080p24 You're making no sense, I'm afraid.

[daWsOn_s]

Am I? :) mmm let's try this

If there a difference in quality (details/resolution) between:

1) 1080i source with 3:2 pulldown removed
2) 1080p24 source, like Blu-Ray

[Guest]

If they are arbitrarily different source material, how can that be answered?

If they are the same source material, then doing soft pulldown followed by removal of that pulldown is a no-op.

Doing hard pulldown and then removing that heuristically (as must be the case) may result in some field matching errors.

[daWsOn_s]

I'm talking about a same source. What about PAL HD with 25fps material? Is that a true 1080p even if the stream is flagged as 1080i? It seems so to me

[Guest]

Progressive content can be coded as interlaced, and vice versa. What makes something progressive *content* is whether or not there is new information at the field rate or not.

You need to distinuish these things:

the content itself
the encoding of the content
the tranport of the decoded content to the display device (the interface)

[daWsOn_s]

I have samples during movies from HDTV, if i analyze them with dgindex or megui tool it says that the content is progressive (just as 576i streams) , so in Europe every 1080i broadcaster during 25p content delivers a true 1080p, that's what I found out during tests. Could that be real?

[Guest]

every 1080i broadcaster during 25p content delivers a true 1080p, that's what I found out during tests. Could that be real? Wow, you just don't get it, even when I keep repeating myself.

25P content can be encoded as interlaced.

true 1080p Just as senseless as the first time you mentioned this.

[daWsOn_s]

FINE I get it, so why don't they just say it? Like directv offering 1080p recently, if everyone has been doing that all along with interlaced 1080.



I'm feeling I said something wrong again.

[Guest]

You are failing to distinguish between 1080P at 30 fps versus 1080P at 60 fps.

Progressive content in 1080I at 60 fields per second can be thought of as 1080P 30 fps. But there is also 1080P 60 fps, although I don't know if that is what DirecTV is offering.

[daWsOn_s]

No i totally got that, what I don't get is that why people dispute between 1080i vs 1080p in TV broadcasting if they actually broadcast progressive content (if the source is progressive) with interlaced streams, except live events

[Guest]

Maybe the dispute is all in your head? :)

I only say that because I have no idea what you are talking about.

Where and what is this "dispute" you are referring to?

[daWsOn_s]

just google it :devil:

anyway thanks for the explanations :thanks:

[Guest]

You want me to read random uninformed trash on the internet?

Forgive me if I decline.

[daWsOn_s]

I forgive you :p

[dylmaster]

Let me see if I can help!
There are only two official HD broadcast standards in Europe, normally known as 720p and 1080i. 720p is 1280x720 pixels frame size sent as a progressive frame 50 times a second. 1080i is 1920x1080 pixels sent as an interlaced frame at 25 times a second. The equivalent rates in USA are 59.94 and 29.97 times a second. Arguments rage as to which is best but certainly in Europe, 1080i has 'won' the day.

Technically, 1080p or a progressive 1920x1080 at 50 frames per second would be best but this would require too much 'bandwidth' and is not supported. There are currently very few broadcast cameras capable of shooting this format.

Which leads us of course to exactly what is 1080/25p (or in US 1080/29.97p)? Well it is basically a progressive image shot at 25fps (29.97) to get a film style motion rendering, that is rather stuttery. Some folks actually like this and think it clearly separates the result from studio style 'soap' type drama look. Having shot it at 25fps, it is then interlaced onto the 50i 'carrier' for broadcast.

Which finally leads us to what is 1080/24p? Well this is basically what you get from movie film but there is no (current) broadcast format to directly support it. In USA it is normal practice to run it at 23.98fps and then perform a '3:2 pulldown' to render it to 59.94i. Effectively then each frame of the movie gets repeated either 3 or 2 times (alternately). There is no easy equivalent ratio in Europe so the practice has been to run the film 4% fast at 25fps and then treat it as per progressive scan video.

Exactly what subsequently happens on a consumer TV becomes very complex, since modern TVs have 'Pixel Engines' to process the broadcast signals and effectively construct a 1080/50p (or 100 or even 200p) signal to display to the viewer.

hope this helps a little