1080i, 50 & 1080i 60

I'm having trouble understanding the difference between 1080i 24 & 30 vs 1080i 50 & 60. I've worked in both, but I still don't seem to quite get it.

Thanks!

John

Lengthy discussion here.

[www.lafcpug.org]



www.strypesinpost.com

Where to begin.

There's no such thing as "1080i24" or "1080i30." Those might've been typos on your part or something, but just in case, understand that those formats don't exist.

Generally it breaks down this way:

1080i60: NTSC-standard high-definition. Used in any NTSC country, which is mostly the Americas and a few other places. Used as a broadcast format for everything, and an acquisition format for sports, TV news, some reality television and occasionally a few other types of programming.

1080i50: PAL-standard high-definition. Used just like 1080i60, only in PAL countries.

1080p24: The universal format for acquisition. Almost all television is shot this way, whether it be on actual high-definition video cameras or on film. Film that's meant for TV broadcast is converted to 1080p24 through a process called telecine. Footage in 1080p24 can be trivially converted either to 1080i60 for NTSC delivery or 1080i50 for PAL delivery.

In general, the rule for televised content is "acquire in 1080p24, deliver in 1080i60 or 1080i50 depending on what region you're sending to." There are exceptions, but this is true most of the time.

1080i60 is the horizontal lines of resolution (1080) and the FIELD RATE (60 - NTSC)
1080i50 is the horizontal lines of resolution (1080) and the FIELD RATE (50 - PAL)

The EBU (European Broadcasting Union) uses the FRAME RATE instead of the FIELD RATE separated by a slash - hence 1080i/30 & 1080i/25... so yes, there is such a thing as 1080i/30.

When life gives you dilemmas...make dilemmanade.

p- stands for progressive, where the full frame is scanned at the same time. Variation to this notation would be in cameras where p24/pA24 means that a pulldown is added to make it 29.97, since most tape formats require footage to be either 29.97 or 30 frames a second. There is also "psF", which is a way to send a progressive signal through an interlaced system.

i- stands for interlaced. Where alternate lines (fields) are scanned at a rate of twice a frame, so when both fields are displayed at the same time, you would see a combing effect on moving objects. In practice, most broadcast streams are interlaced, which means the fields are refreshed at 1/50th or 1/60th of a second, and in the case of LCD HDTVs, where the TV is unable to display an interlaced signal, each field may be duplicated so they tend to display at p50 or p60.

Between 24, 25, 50 and 60, these usually refer to the refresh rate (in hz). However, as Joey mentioned, EBU uses frame rates.

As a general rule, at 24 frames a second, the format is always progressive. At 25 frames per second, it is either (25p) progressive or (50i) interlaced, with the exception of the 720p format, which is always a progressive format, and is notated at frame rate. At 30, it usually refers to 29.97 (except in the case of some still cameras which shoots video at this frame rate. Canon, I'm talking about the 5D), and is usually interlaced (60i), but it can be progressive (30p).



www.strypesinpost.com

Thanks for the info. My only remaining confusion is between 30 & 60. Whether in 1080 or 720, should I choose 30 or 60? Will I see a difference? Obviously, my timeline should be set to match, right? I did one project set in 60 and my transition length changed, ie a 30 frame dissolve seemed too fast. Maybe I'm missing something.

> I did one project set in 60 and my transition length changed, ie a 30 frame dissolve seemed too
>fast.

A 30 frame dissolve in a 60 frame per second sequence means your transition lasts for half a second. A 30 frame dissolve in a 29.97 frame per second sequence means your transition lasts for about a second.


>Whether in 1080 or 720, should I choose 30 or 60?

720p is a progressive only format, and broadcasts at 50 or 60 frames a second (depending on your region). At a resolution of 1080, you cannot squeeze enough data through the bandwidth to support 50 or 60 progressive frames a second, so 1080i60 is essentially the same as 1080i29.97 (depending on whether you are using SMPTE or EBU notation), and 1080p30 refers to 30 progressive frames a second. For 1080p30, we tend to avoid it, because it tries to mimick the film look (24 progressive frames a second), but the movement and motion blur is very different, making it look like a half baked film look.

What format you choose depends on (a) delivery requirements, (b) which medium will display the final video, and (c) the type of content- eg. if you're shooting a fast action basketball game, you'd shoot at either 720p60 or 1080i60, and if you're going for that single cam drama/film look, you tend to shoot at 1080p24.



www.strypesinpost.com

An interesting thread.

What would be the best way to convert 1080i25 to 1080p24?

...or would converting to 1080i60 be a better option for a Blu-ray project for it to play seamlessly on European and US BD players?

All HDTVs and Blu-ray players should follow the ATSC standards and therefore it doesn't matter at all what format you write your Blu-ray to. All our HDTVs (on both sides of the pond) can handle it as can the Blu-ray players. It is only when broadcasting that you may want to look at the specs.

By the way PAL & NTSC are SD formats only.

There is no such thing as PAL-HD or NTSC-HD.

That is A. confusing and B. some marketing schmucks poor understanding of terminology. So C. try not to use it!

More simply put:

There are flavours of HD that better downconvert to either PAL or NTSC as their framerate and fields are matched. Those are [50i/25p] and [59.94i/29.97p/23.976p (aka 23.98p)] respectively.



For instant answers to more than one hundred common FCP questions, check out the LAFCPUG FAQ Wiki here : [www.lafcpug.org]

There is 1080i 60Hz for the USA and 1080i 50Hz for PAL machines - can you advise how I can make my content playable on both machines?

I was under the impression that USA Blu-ray players cannot handle HD content at 25fps?

US players should be able handle 1080i50 so any 25fps/50i or 25p on 50i should playback. All Euro BRPs (Blu-ray Players) can handle 1080i60.

I am not sure about true 25p though.



For instant answers to more than one hundred common FCP questions, check out the LAFCPUG FAQ Wiki here : [www.lafcpug.org]

I would have said the same as Jeff Harrell: "There's no such thing as '1080i24' or '1080i30'. Those might've been typos..." and I would have been similarly corrected by grafixjoe who points out the EBU notations '1080i/30' and '1080i/25'.

The EBU terminology is horrible terminology for those shooting or editing video. 1080i/30 means 30 frames per second only indirectly, in the sense that there are enough fields per second to construct 30 frames. There are really no frames captured in 1080i/30 video. There are 60 incomplete images captured per second.

The EBU terminology is primarily useful for engineers coding or transmitting video. In a 1080 line digital video file all 1080 lines are written sequentially. If the video is interlaced, half these lines represent a different time than the other half do. If the video is progressive, all the lines represent the same time. The file doesn't show which is the case except, perhaps, in its header. File structure isn't video structure.

As people shooting and editing video I think we should avoid the EBU terminology and stick with the sane terminology 50i, 60i, 24p, 50p, etc. The number says how many images are recorded per second. The letter says whether the images are half empty (i) or complete (p).

Luckily there's no risk of ambiguity between the two terminologies. For example, 30i would be completely different video from i/30 (which is 60i), but 30i video is never made. Another example, 60i would be completely different video from i/60 (which is 120i), but 120i video is never made. So far as I know, only 50i and 60i are made, and hopefully interlaced video will end with those two.

Dennis Couzin
Berlin, Germany

Agreed on the EBU terminology being poor....

Graeme

I've been reading more into this and it would appear that it is in fact some US TVs that cannot handle 1080i50.

Also, take a look here:

[www.avsforum.com]

Any thoughts?