Verifying my understanding of the pulldown...

Blade Borge

Blade Borge

Well-known member
Okay so I already did a search but don't think the answer is around here yet,

So a camera that shoots 24p with pulldown puts the 24 or 23.978 frames into a NTSC 29.97 friendly wrapper right? This is so it plays friendly with NTSC systems and what not, but don't dvd players and tv's automatically add this pulldown anyways? If so, why is the camera 'helping' me?

Also, if the 24p footage is pulled down to 29.97 frames, why does it still look so film-like?

So I think I heard that the only difference between watching true 24p footage and 24 pulled down footage is that the pulled down footage has a more slight blur to it right?

Another thing I hear is, you gotta pulldown if you're putting that on the web, at least I thought I heard that, if so why? Okay thanks for your responses.
 
It's the other way around, 24p/24pa is recorded at 29.97 and is pulled down to 23.976 when you edit or play it off a DVD player.

I don't have any charts handy, but yes, every fourth frame in regular 24p will actually not be progressive which is what gives that footage the slight blur, due to the way it packed 23.976 frames into 29.97. This isn't really noticeable on standard definition televisions, but is noticeable on a progressive display when you're losing half your vertical resolution six times a second.

24PA is a more sophisticated and involved process for getting all twenty four progressive frames into that 29.97 wrapper. This is what you want for progressive displays (computer monitors, plasma screens), or film transfers, etc.

And yes, when it comes to the web, you shoot in 24 frames per second, you present in 24 frames per second. There's no NTSC bull you should be dealing with on the web because frankly, you don't have to. That's why you pull down on the web.
 
Last edited:
I see so putting the footage into a 29.978 wrapper isn't a pulldown, but the taking away of the wrapper itself is the pulldown.

So DVD players play 23.98 but then the television adds the wrapper again so that it plays on screen?

But I can still put 29.97 on the web right? The reason I wouldn't want to if I didn't have to is because of the slight blur as mention before right? Thanks for the clarity.
 
Blade,

I'm not sure where Shauntron gets his info, but it's mostly wrong. Your initial post is mostly correct.

Blade Borge said:
So a camera that shoots 24p with pulldown puts the 24 or 23.978 frames into a NTSC 29.97 friendly wrapper right? This is so it plays friendly with NTSC systems and what not, but don't dvd players and tv's automatically add this pulldown anyways? If so, why is the camera 'helping' me?
Click to expand...

Because there is no format for recording native 24p onto tape. The tape mechanisms are all designed for 29.97, so the camera MUST add the pulldown to put the images to tape. It's just a fact of life.

Some of the solid state cameras that record to flash memory and hard drives skip the pulldown, because they don't have to worry about tape formats.

Also, if the 24p footage is pulled down to 29.97 frames, why does it still look so film-like?
Click to expand...

When you watch a film on DVD, does it still look film-like? Yes. That is essentially 24p material (film frames) pulled down to 29.97. The pattern is the same on the DVX or a film on DVD.

So I think I heard that the only difference between watching true 24p footage and 24 pulled down footage is that the pulled down footage has a more slight blur to it right?
Click to expand...

No blur involved, but there is a "feel" to the motion. The pulldown pattern is 2:3, so you see even frames for a longer period of time than even frames. It's a "judder" or "stutter," a cadence unique to watching films or 24p material played back on 29.97 tubes.

Another thing I hear is, you gotta pulldown if you're putting that on the web, at least I thought I heard that, if so why?
Click to expand...

I'd say it's quite the opposite. You need to remove the extra pulldown fields (a process called inverse telecine), so you get back to your original 24 progressive frames. If you fail to do this, you'll get interlacing artifacts on your web videos, and it's nasty.
 
I see, so what about the deinterlace option that comes with NLE systems, would that get rid of interlaced artifacts for 29.97 footage, thus allowing it to be played on the web okay?
 
If you're talking about footage you shot as 60i -- as in, you didn't shoot as 24p, 24pA, or 30p, yes. But you don't want to use a deinterlace filter or process on 24p, 24pA, or 30p footage. 30p doesn't need it, and with 24p, you'll end up with a really big mess.

Pulldown removal means you're taking away the 12 extra fields per second which are created to fit the 24 progressive frames into the 60-field stream of conventional video (like you see on TV). Each field is half a frame, so you can split each 24p frame into two fields, but that only gives you 48. You need another 12 to make 60 fields per second -- and those 12 extra fields ARE the pulldown.

So, you don't deinterlace -- you get rid of those extra fields, and then you take the 48 fields and put them back together as 24 frames. The footage was only ever interlaced because that's how it had to be recorded, for technical reasons. Otherwise, it wouldn't have been done that way.

Deinterlacing is what you can do to inherently interlaced footage, like 60i (standard video), because it was always interlaced. But you lose vertical resolution that way (which is another reason you don't want to try it with progressive footage).
 
Blade Borge said:
So a camera that shoots 24p with pulldown puts the 24 or 23.978 frames into a NTSC 29.97 friendly wrapper right? This is so it plays friendly with NTSC systems and what not, but don't dvd players and tv's automatically add this pulldown anyways?
Click to expand...

Just to reinforce Joshua, yes, this is correct.

And to clarify a little bit, a DVD player will add the pulldown if it's reading a 24p file and playing to a standard NTSC TV. It won't add any pulldown if it's reading a 29.97 file, which could be 24p with pulldown already added (nobody does it that way anymore; all Hollywood films are on DVD as straight 24p).
 
Speaking of pulldown problems, I've had a couple of my own, but I think I've finally gotten an answer. As I've stated before, my NLEs (Adobe Premiere Elements 1.0 and 3.0) do not have the capability to edit in 23.97 and I have to edit on a 29.97 timeline. Until recently, I was shooting everything on 24pA and editing on the 29.97 timeline. I had no problems doing this and burned DVDs for my projects, which played perfectly on my home DVD players, which were older models, and displayed perfectly on my interlaced, CRT TVs.

But my university recently bought new DVD player/projectors and when I tried to play those same DVDs at school for my class projects, they would not play; the DVD players would either not recognize the DVD in the player, would say it was a corrupted disc or a dirty disk. Then, when I would try a project shot on 24p, they would play without a hitch. So, I began shooting all my class work on 24p and the problem went away.

I recently purchased a new widescreen, progressive only 720p TV and a new Philips DVD player with progressive scan and DVD upscaling. Guess what? If the DVD player is set to progressive scan, none of my 24pA stuff would play, but all of the 24p DVDs work fine. The 24pA stuff will play fine if sent directly to the TV from the camera and it will play the DVDs when the player is set to interlace but the DVDs of the same footage will not play if the player is set to progressive. So, I wrote to Philips and this is what I was told:

When I was using an interlaced CRT TV, the DVD players were also automatically using interlace to send the images to the TV at 60 fields per second. Under these conditions, the type of pulldown used for shooting does not matter because the DVD player is not incorporating any pulldown detection/removal protocols and is sending the data as is in separate fields, one after the other, as in any other interlaced video.

But the new players/projectors at the university are all progressive scan players, as is my new TV/DVD player setup. According to the tech guy at Philips, a progressive scan DVD player uses pulldown detection/removal protocols to remove 2:3 pulldown and display the video at 24fps. So, if footage is shot at 24p and edited on 29.97 then burned to a DVD, when the player reads the data on the DVD and detects the 2:3 pulldown, it removes the pulldown to display the video at 24fps. But the pulldown detection/removal protocols of most players are programmed to deal only with the industry standard 2:3 pulldown, not the newer 2:3:3:2 pulldown of 24pA. So, according to the Philips tech, they read the 24pA disc as corrupted or damaged, if at all.

To get the 24pA DVDs to play on my new TV, the progressive scan mode of the player must be turned off.

The same players deal with a disc burned from a 23.97 timeline in one of two ways: If being sent to a progressive scan TV, then nothing is done; the data is sent as is to the TV (although each frame is actually displayed twice to give an actual frame rate of 48fps to reduce flicker, the same way theatrical projectors project each frame of a film twice). If it is being sent to an interlaced CRT TV, then the standard 2:3 pulldown is added and the data is sent interlaced.

So, like these guys on here have been saying, if your NLE has 23.97 editing capablity, then 24pA is the way to go. But if you're like me and cannot afford the more pricy NLEs and yours can only deal with 29.97, then definitely shoot 24p. 24p (2:3) is still the industry standard in NTSC land and you'll avoid the problems I've had trying to get 24pA to work with players expecting to see 24p.
 
Last edited:
Yes, 24pA is an "acquisition" format, not a "distribution" format. Capture and edit ONLY. It's not suitable to directly project 24pA or encode it to DVD.
 
You must log in or register to reply here.
Back
Top