1080i

May 15, 2006

It might be a silly question. But how can a camera go 25P (Progressive) in 1080i (interlaced). :blink:

Phil Rhodes · May 15, 2006

Hi,

I'm not entirely clear what you're talking about here. It's entirely possible to have a progressive stream which is marked as interlaced - this is how all film transferred to PAL (and indeed NTSC, with other factors) works - it just means both fields were captured at once. Sony call this "segmented frame", but it's been a standard technique for decades at least.

What circumstances are you talking about, specifically?

Phil

May 15, 2006

I've just been looking at the new Panasonic HVX-200, which you can set to 1080i/25P - this puzzled me. Then I was asked what the specs for Sony 750 was. Of course you can set the camera to Progressive or Interlaced and the signal from the HD-SDI is 1080i, when the camera is set to 25P, but why not 1080P?

cheers

July 12, 2006

It might be a silly question. But how can a camera go 25P (Progressive) in 1080i (interlaced). :blink:

Hi, not sure what you mean either, but to be clear...

The P or i relates to how the CCDs are scanned/captured, not to how it is recorded.

Progressive means the entire image is captured in one pass in 1/50second at 25fps (assuming 1/50 shutter europe.)

Interlaced means two captures in the same time of 1/50th each (no shutter, 1/25second in total)

The signal is recorded in the same way for each method, ie two fields in 1/25 second.

On a CRT the image is displayed as an interlaced image, whether shot P or i.

hope this helps.

David Mullen ASC · July 12, 2006

The simple thing would be to take 25P capture and split it into two fields for storage as 50i/1080. It's a little more complicated if it has to be recorded to 60i/1080.

It's the same thing as a PAL DVX100 shooting 25P and storing as 50i.

Phil Rhodes · July 12, 2006

Hi,

Yes, they're just talking about segmented frame. Most recording devices, even HD ones which should frankly know better, expect to get all the odd lines followed by all the even lines. Therefore that's how things tend to be sent, allowing manufacturers to set the 50i flag in the data stream while everyone knows it's 25p footage.

Phil

JA Tadena · September 10, 2006

Hi, not sure what you mean either, but to be clear...

The P or i relates to how the CCDs are scanned/captured, not to how it is recorded.

Progressive means the entire image is captured in one pass in 1/50second at 25fps (assuming 1/50 shutter europe.)

Interlaced means two captures in the same time of 1/50th each (no shutter, 1/25second in total)

The signal is recorded in the same way for each method, ie two fields in 1/25 second.

On a CRT the image is displayed as an interlaced image, whether shot P or i.

hope this helps.

Yes I also wanted to clear this. I just shot something with the HVX-200 this morning on blue screen. We also had a pc setup so we could capture the video afterwards. We set the camera on 1080i/24P. When we played back the video in the PC we saw interlaced frames on some images. I thought when you set it at 24P then your scanning each frame entirely for all the 24 frames. I guess I was wrong and thought the same as Mr. focus71. We should have just set it at 720P/24P if we wanted a true progressive scan since the HVX-200 doesnt have a 1080P. So how come I get interlaced frames with a 24P/1080i? Thanks

Edited September 10, 2006 by jatadena

David Mullen ASC · September 10, 2006

So how come I get interlaced frames with a 24P/1080i? Thanks

Do you mean you recorded 24P to 60i/1080? Or 24P/1080? (I don't think the HVX records 24P/1080 but I could be wrong.)

There is no such thing as 24P/1080i -- either it's 1080i or 1080P.

If the camera records 24P to 1080i, then it's adding a pulldown to convert 24 frames to 60 fields.

JA Tadena · September 10, 2006

Do you mean you recorded 24P to 60i/1080? Or 24P/1080? (I don't think the HVX records 24P/1080 but I could be wrong.)

There is no such thing as 24P/1080i -- either it's 1080i or 1080P.

If the camera records 24P to 1080i, then it's adding a pulldown to convert 24 frames to 60 fields.

Yeah i recorded at 24P/1080i.

The recording format options are: 1080i/60i, 1080i/30P, 1080i/24P, 1080i/24PA, 720P/60P, 720P/30P, 720P/24P, 720P/30PN, 720P/24PN, 480i/60i, 480i/30P, 480i/24P, 480i/24PA. The factory default option is 720P/60P. (http://www.jkor.com/peter/hvx200.html)

so i guess 24P/1080i is interlaced then. Then HVX-200's 720P/is the only true progressive. Should this be right? thanks

If the camera records 24P to 1080i, then it's adding a pulldown to convert 24 frames to 60 fields.

BTW, david how did you find out that there is a pull down when you say 24P/1080i? thanks

David Mullen ASC · September 10, 2006

There is no such thing as 24P/1080i. 1080i HDTV is either 60i or 50i, so if the capture was at 24P, and you need to record to 1080i, then it has to be converted to 50i or 60i (usually 60i/1080 since that is a common HDTV broadcast format here in the U.S.)

There is the 24PsF/1080 recording format... but I don't know if the camera has that option.

Looking at the list of options, I guess when the manual says "24P" versus "24PA" for 1080i, they mean both are getting pulldown to convert to 60i, but you have the option of using the "advanced" pulldown rather than standard 3:2 pulldown.

You can record 24P to interlaced formats (just the the DVX100 does) but you have to know how to restore it to true progressive frames in your NLE system.

JA Tadena · September 10, 2006

There is no such thing as 24P/1080i. 1080i HDTV is either 60i or 50i, so if the capture was at 24P, and you need to record to 1080i, then it has to be converted to 50i or 60i (usually 60i/1080 since that is a common HDTV broadcast format here in the U.S.)

There is the 24PsF/1080 recording format... but I don't know if the camera has that option.

Looking at the list of options, I guess when the manual says "24P" versus "24PA" for 1080i, they mean both are getting pulldown to convert to 60i, but you have the option of using the "advanced" pulldown rather than standard 3:2 pulldown.

You can record 24P to interlaced formats (just the the DVX100 does) but you have to know how to restore it to true progressive frames in your NLE system.

Ok. I havent checked the HVX manual yet. Your'e right I guess the 24P/1080i must be some HVX term for the pull down your saying or something else. But that weird format is really in the recording format option menu of the HVX-200. I'll look into that as soon as I can.

Thomas James · September 10, 2006

When you record 1080i24p and view on a progressive monitor some of the frames will be interlaced in the sense that the fields will be derived from different frames so you will be able to see temporal displacements when these fields are assembled as one frame. To avoid this if you shoot 1080i30p all of the progressively segmented interlaced frames will be reassembled as 30 complete photographs per second with no interlace artifacts. Each photograph will then be displayed twice so that a total of 60 frames per second will be displayed. If you insist on shooting 1080i24p you can do a reverse pulldown with software. What this does is convert the 1080i stream into a 1080p60 stream that consists of 24 complete photographs with each photograph repeated twice and then three times.