3:2 Pulldown for 24p

[John Hewat]

Now that I will finally own a camera that records 24p (with 3:2 pulldown apparently) I suppose I had better figure out exactly what 3:2 pulldown is.

I've read a few threads that dabble in it but it seems as if knowledge of the process is assumed in most discussions. I have NO IDEA about it and would love some light shed on what it is and how it works if anyone would care to help out.

I'd also like to know whether when I edit (in CS3) I need to tell Premiere that the footage "has" pulldown or something like that...

Much appreciated,

-- John.

[Theodore McNeil]

Try these as a primer...

http://www.dvdfile.com/news/special_...2_pulldown.htm

http://en.wikipedia.org/wiki/24p

[Serena Steuart]

Originally Posted by John Hewat

Now that I will finally own a camera that records 24p (with 3:2 pulldown apparently) I suppose I had better figure out exactly what 3:2 pulldown is.

I've read a few threads that dabble in it but it seems as if knowledge of the process is assumed in most discussions. I have NO IDEA about it and would love some light shed on what it is and how it works if anyone would care to help out.

I'd also like to know whether when I edit (in CS3) I need to tell Premiere that the footage "has" pulldown or something like that...

Much appreciated,

-- John.

The camera is native 23.98P and records with 3:2 pull down in SP mode (1440 x 1080). One day I must open up Premiere to see what it does, but you'd have all the options in Vegas Pro 8.

[John Hewat]

Originally Posted by Serena Steuart

The camera is native 23.98P and records with 3:2 pull down in SP mode (1440 x 1080). One day I must open up Premiere to see what it does, but you'd have all the options in Vegas Pro 8.

That's what I thought until the Roadshow, where the guy said to me "It's not native 24p unfortunately."

[Serena Steuart]

Originally Posted by John Hewat

That's what I thought until the Roadshow, where the guy said to me "It's not native 24p unfortunately."

Well, I guess 23.98 isn't 24, but putting aside that sort of junky response the camera is specified as 23.98P native recording. That is the essential matter. Everywhere that is stated it is accompanied by "in 1440 x 1080/23.98P mode the images are handled as 23.98P and recorded as 59.94i signal through 2-3 pull down". The reasonable interpretation is that in HD mode the signals are recorded as progressive. However it isn't important because your NLE will restore it to progressive. In my case I'll be running clips through HDLink which has the facility to remove the 3-2 pull down at the same time as converting to the digital intermediate.
So it's not important. But it would be interesting to have it cleared up.

[John Hewat]

Originally Posted by Serena Steuart

I'll be running clips through HDLink which has the facility to remove the 3-2 pull down at the same time as converting to the digital intermediate.
So it's not important. But it would be interesting to have it cleared up.

I suspect I will too, for Prospect HD in CS3, but I imagine that if you tell HDLink to remove 3:2 pulldown that isn't there then you'll be compromising your footage.

Does anyone know for sure? I figured the Sony guy at the roadshow would be a reliable source but perhaps not in this matter.

If it does reecord with 3:2 pulldown, is that not as good quality?

[Serena Steuart]

No, the quality isn't affected. The inserted frames are discarded and the fields combined back into a progressive frame. It's all artifice, a rearrangement of the data. Yes, if you have progressive 23.98P and tell the software otherwise then problems may arise (unless the software is clever enough to know you're wrong). The format is coded into the data, so detecting the format is pretty straight forward.
All will be known, soon enough.

[David Heath]

Originally Posted by John Hewat

Now that I will finally own a camera that records 24p (with 3:2 pulldown apparently) I suppose I had better figure out exactly what 3:2 pulldown is.

John - I note you live in Australia, so 50Hz standards and PAL Standard Definition TV. As such, I wonder if you really want to be shooting 24p, or whether 25p may be more appropiate?

The two main reasons for shooting 24p are for compatability with 60Hz TV systems such as NTSC (and hence the whole 3:2 pulldown issue) and/or when the eventual finished product is destined for film printing.

Even if you intend going the second route, it may be worth considering shooting 25p and accepting a 4% slowing down on film projection - the opposite to what normally happens when films are telecined in 50Hz countries.

That said, a good general link to the whole subject is http://en.wikipedia.org/wiki/Telecine . That the signal is "handled as 23.98P and recorded as 59.94i signal through 2-3 pull down" is known as psf - Progressive segmented Frame - see: http://en.wikipedia.org/wiki/Progres...egmented_Frame . Fundamentally, it's a way of maintaining a true progressive image through an interlace chain.

When Serena says quality isn't affected, that is true in so far as the progressive image isn't altered, duplicate frames are just added to "pad out" the signal. However this can mean that either storage is wasted on storing these duplicates, or for a given bandwidth the overall compression is higher. None of that is an issue with 25p(25psf) which also avoids the need to use drop frame timecode.

[Serena Steuart]

David, well put. Yes, 25P is certainly the way to go here. If one is going to filmout there is a strong argument for 24 (4% is noticeable in audio). If storing the camera data files it would be very undesirable to compress them further.

[David Heath]

Originally Posted by Serena Steuart

If one is going to filmout there is a strong argument for 24 (4% is noticeable in audio).

True enough, but I suspect that nowadays it's difficult to say that any project will only be shown solely on either projected film or electronically, (projected or on a screen) - let alone the possibility that the film print may end up telecined!!

Hence, in a 50Hz country, it's quite conceivable that even if you went for 24, the project may well still be shown at 25fps on a number of occasions, and so we're back to being 4% out - just now speeding up, not slowing down!

I believe it is possible to utilise pitch changers to counteract the worst of the speed difference effects for audio?

It all really depends on where John sees his prime market being. Just worth being aware that 24p is far more significant if you live in a 60 Hz area than a 50Hz one.

[David Heath]

Originally Posted by Serena Steuart

If storing the camera data files it would be very undesirable to compress them further.

The compression issue affects the original capture, assuming a fixed bitrate. Say you have a nominal 100Mbs I-frame only stream to store your signal, then with 25p or psf that's effectively 4Mb/frame.

Now go to 24psf and you are spreading the 100Mb over 30 recorded frames per sec, of which 6 (20%) are redundant - hence only 80Mbs is actually being used to store non redundant information, so here only 80/24= 3.33Mb/frame.

[Thomas Smet]

Originally Posted by Serena Steuart

David, well put. Yes, 25P is certainly the way to go here. If one is going to filmout there is a strong argument for 24 (4% is noticeable in audio). If storing the camera data files it would be very undesirable to compress them further.

No you would still edit as 25p so you use the raw material from the cards no more compression is needed. The only time you would shift from 25p to 24p is during the film out process. Even you master on tape should stay as 25p.

Like David said it really is best to to work in 25p. That way if you have any I/O hardware to view the material you will have no problems. Also if you need to make tapes for dailies you are all set to go even to run off SD copies to share with people to check out. David also made a great point that until you get a film otu deal chances are you will be delivering as some sort of tape or disc format to try to get your project sold or to share with people.

Most film out places I believe will just take your 25p master and shift the audio for you with time compression.

You guys don't know how lucky you are to have 25p. 24p is a pain in the rear.

[Serena Steuart]

Originally Posted by Thomas Smet

No you would still edit as 25p so you use the raw material from the cards no more compression is needed. The only time you would shift from 25p to 24p is during the film out process. Even you master on tape should stay as 25p.

You guys don't know how lucky you are to have 25p. 24p is a pain in the rear.

Yes we do! Pitch shifting to compensate for the 4% is readily done. But there are plenty of people who argue that 30 fps is better (smoother motion). Others like the cadence of 24 (or 25fps) and argue that to be superior. I'm afraid I don't see what they see. To me film is all about analogue images, roughly equivalent to 12 to 22 bits of Y and 4:4:4. Guess I've grown up with film and don't see anything magical about 24fps. Hoping that the EX is another step in the direction of film.

[David Heath]

Originally Posted by Thomas Smet

You guys don't know how lucky you are to have 25p. 24p is a pain in the rear.

To go off topic, some may find an EBU article about the history behind all of this useful in terms of putting everything in context. See http://www.ebu.ch/en/technical/trev/trev_home.html , then click on "HDTV in Europe", then article 311 - "The development of HDTV in Europe — a tale of three cities: Dublin, Dubrovnik and Geneva"

Did you know of the proposals for a single, global HDTV standard in 1982, for example? Analogue and interlaced, with a frame rate of 40Hz, it could have led later to a global 1080p/40 standard if adopted. Legacy issues are a terrible thing.........