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"True" 24 fps


Jeff Wexler
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Some DCP houses make a deal out of many projectors out there in theatres being ONLY able to play 24 fps DCPs, while others can play several frame rates (29.97 even).  So the DCP makers always seem to lean on the filmmakers to deliver 24fps projects.

 

Most of the deliverables contracts I see in post are very specific about 24.00fps DCPs. But every post house in town routinely deals with 23.98 picture and sound, and then at the very end of the project, they shift the speed up .1% to 24.00 for the DCP delivery. It is true that the latest DCI projectors can handle lots of different speeds, but the distributors generally prefer only sending out 24.00fps, because that's the only speed that's guaranteed to play on 100% of all DCI-compliant projectors out there. The choice of acquisition format doesn't really matter.

 

 

and, BTW, I would agree that the DIT was a bit brusque, and will probably be surprised when s/he learns of JW's level of experience and competence.

 

I'm always amazed when people from other departments are rude or disrespectful on sets. They seem unaware that we're all fighting the same war. My take in a situation like this is that some of these guys are 1) in way over their heads, and 2) very insecure about what they're doing. All you can do is shrug, keep your head down, and move on.

 

I've worked with DIT's where, at the end of the shoot, I hand them the sound files and they frown and say, "what am I supposed to do with this?" I generally stop myself from saying well, you could shove it up your ass, but I smile and say, "I think the editor would prefer getting both picture and sound for the edit." There is much dissent, even at local 600 and from DPs, about the long-term prospects for DIT's, plus the problem of Data Wranglers (aka "Data Monkeys") who call themselves "DITs" but in reality have little or know understanding of the process. 

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Here in Finland Alexa and 24fps is a very common format for feature films. I've been through more than one of those films, both location sound and post production, and there has never been any issues working with 24fps code.

Sound was 48kHz from the beginning to end.

 

It's been 24fps / 48kHz all the way to the DCP, totally without problems.

 

 

Tuomas

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  • 5 weeks later...

The projectors will run anything...23.9,24,25,29.9 etc.

 

A friend of mine (whose wife runs a neighbourhood art house film theatre) is operating a small scale DCP mastering service. A lot of his work is actually quality control and standards compliance monitoring.

 

I am not 100% sure, but I am under the impression that audio and video files stay as separate file structures all the way to the actual playback and projection. If the video file is 23.98 instead of 24.00 and you want to play back the package at 24 fps, I think that the DCP server can be instructed to "auto-conform" the audio files on the fly by re-interpreting the audio at a different sample rate, if needed.

 

Anyways, 24.00 fps is indeed a standards-compliant frame rate for DCP packages.. 23.98 fps is not.

 

As Tuomas mentioned, 24.00 fps / 48 kHz is a tried and true workflow for theatrical release films here in Europe.

 

As a side note, I had a strange 23.98/24.00 issue with a PIX240. Even if the PIX240 was set to 24.00 timecode (freerun), it would drop into 23.98 TC mode if the SDI signal from the camera dropped (during battery changes). Luckily I found out about the issue during tests before the actual shoot.

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A picture editor friend and I tested a DCP file with audio at 23.976, picture at 24.00 and they noticeably drifted apart very quickly. We then converted everything to 24.00 and all was well.

 

For features destined for DCP theaters it makes sense to shoot and edit in 24.00. Everything is on integers and there is no confusion about pull up/down (until you go to make 23.976 versions).

 

Mark O.

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For features destined for DCP theaters it makes sense to shoot and edit in 24.00. Everything is on integers and there is no confusion about pull up/down (until you go to make 23.976 versions).

 

I respectfully disagree. All you need to do is keep the entire project at 23.98 until delivery. When you make the final sound and picture files to deliver to the DCP facility, then you do a .1% pull-up to 24.00fps. And make sure you label all the files and provide paperwork and so on. There is absolutely no need to shoot and edit at 24.00fps just to deliver a DCP at some point. 

 

This is a trivial process that costs no time and money and has zero effect on picture or sound quality.

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I respectfully disagree. All you need to do is keep the entire project at 23.98 until delivery. When you make the final sound and picture files to deliver to the DCP facility, then you do a .1% pull-up to 24.00fps. And make sure you label all the files and provide paperwork and so on. There is absolutely no need to shoot and edit at 24.00fps just to deliver a DCP at some point. 

 

This is a trivial process that costs no time and money and has zero effect on picture or sound quality.

Yes please.

 

p

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A friend of mine (whose wife runs a neighbourhood art house film theatre) is operating a small scale DCP mastering service. A lot of his work is actually quality control and standards compliance monitoring.

 

If the video file is 23.98 instead of 24.00 and you want to play back the package at 24 fps, I think that the DCP server can be instructed to "auto-conform" the audio files on the fly by re-interpreting the audio at a different sample rate, if needed.

 

Just to clarify, I asked about this and I found out that it is not possible to conform the audio file from 23,976 to 24,000 on the fly while the DCP package is being projected. Changes to picture aspect ratio and playback volume are the only adjustments available at that stage… at least with their projector. So, as far as I understand it, the .1% pull-up during mastering is mandatory if the source material is 23,976 and the film is destined for 24,00 fps DCP projection. I am not sure if such a thing exists as 23,976 fps DCP projection.

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Just to clarify, I asked about this and I found out that it is not possible to conform the audio file from 23,976 to 24,000 on the fly while the DCP package is being projected. 

 

That is correct. You have to pull up the sound before the DCP is made. I thought this was obvious. The digital projector doesn't do anything except spit out the files you hand it -- it doesn't sync or change the speed of anything.

 

This is one reason why I always tell my clients to hire a company that specializes in DCP creation, rather than trying to do it themselves. In LA & NY, there are companies that will take the 23.98 picture and sound, pull it up to 24.00fps, and create a DCP for maybe $100 a minute (under a grand for a 90-minute feature). I think this is very cheap and affordable, especially when you compare it to Ye Olden Days of maybe 7-8 years ago where you'd have to get an Answer Print and an optical negative track for about $30K. 

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Marc, you might want to check your math for a typo.

 

Whoops, I dashed that out too fast: $10/minute. There's a whole slew of people who will do DCPs for anywhere from $500 to $1500 in LA. $1000 is a reasonable middle ground: 5.1 surround, XYZ color space, all checked and double-checked. But you still have to book a screening in a DCI-compliant theater to make sure it's all in sync and looks correct. Things can go horribly wrong inbetween the computer and the theater. Too many people just push the button and "assume" it'll wind up OK. 

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  • 2 weeks later...
  • 6 years later...

Raising this from the dead.

Here's the article that has been posted here before, from 2013 (?): https://www.trewaudio.com/articles/48048-khz/

 

I'm mixing a Netflix movie next week. Just had the Dailies call and they want to shoot true 24.000 fps on Alexa Mini LF's but they have 48kHz listed as the audio sample rate, which was probably just a holdover from their template. I don't believe they have any post-sound positions hired yet. I will not be sending audio to the camera. I have never shot true 24 or 48048 before. I will reach out to the post supervisor but before I open that can of worms:

 

My questions are:

-Do I need to record at 48.048kHz if we're rolling at 24.000?

-Is the article above still relevant or is it outdated?

 

Thanks!

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such a good question. Let us know what you find out, if you're not then too busy! I'm inclined to think they really mean it. This is Netflix, not a cable channel with Must-Carry rules. I'd be more interested in Netflix' content intake/upload criteria. That could help you anticipate your answer or leverage your expert practices (if you see an opportunity or benefit to dictate the terms. typically for liability, most of us would not opt to be the decision maker on this matter, but in this case the decision could make the workflow easier for a lot of people, and your input is worth something.)

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59 minutes ago, cstauffer said:

If it helps, I did a Netflix shoot a while back at 24 and we were told to still run straight 48 and there were no issues as far as I know.

Good to know, thanks!

 

25 minutes ago, James Louis said:

such a good question. Let us know what you find out, if you're not then too busy! I'm inclined to think they really mean it. This is Netflix, not a cable channel with Must-Carry rules. I'd be more interested in Netflix' content intake/upload criteria. That could help you anticipate your answer or leverage your expert practices (if you see an opportunity or benefit to dictate the terms. typically for liability, most of us would not opt to be the decision maker on this matter, but in this case the decision could make the workflow easier for a lot of people, and your input is worth something.)

Just reached out to Post. I'll let you guys know what they say. We're doing all sorts of interesting things like shooting 2:1 but protecting 16x9 and screwing sound in the process! They even skipped the whole sound page in the meeting which I had to remind them about. Good times.

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I did a series last year where the DP wanted to shoot at  true 24FPS because of worries concerning potential LED flicker.

Post wanted to work at 23.976.

 

Julian Daboll at Technicolor is the guy I like to talk to regarding these issues. The solution decided on for sound is  24/48.048 on the recorder , then

they pull down later to 23.976 and 48K. Time code on the recorder, slates, and sync boxes was 24fps

It just depends on what they will do post at. If they will continue at a true 24, then we would have done 24/48 on sound.

 

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42 minutes ago, Jim Rillie said:

I did a series last year where the DP wanted to shoot at  true 24FPS because of worries concerning potential LED flicker.

Post wanted to work at 23.976.

 

Julian Daboll at Technicolor is the guy I like to talk to regarding these issues. The solution decided on for sound is  24/48.048 on the recorder , then

they pull down later to 23.976 and 48K. Time code on the recorder, slates, and sync boxes was 24fps

It just depends on what they will do post at. If they will continue at a true 24, then we would have done 24/48 on sound.

 

That all makes perfect sense, thank you. Did they end up finishing at 23.976 by the way?

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Did a movie at April for theatrical and Netflix combo (not as sound mixer), both was 24/48. No issues as far I know. Only issue was 1 Tentacle which for no reason decided to change from 24 to 30 for 2 takes. 

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Thanks all. Post got back to me. The Sup and the AE didn't really know what I was talking about. I explained it and sent them the article so they checked with Netflix who said there will be no pulldown and so 24.000 and 48kHz is good to go.

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Have a good show, Ben. And in retrospect, so long as you reported your concern up the chain, it still holds true that the answer they instructed, rather than the one where you or I dictate, is still the choice that best protects you.

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On 5/20/2021 at 9:43 PM, BAB414 said:

Thanks all. Post got back to me. The Sup and the AE didn't really know what I was talking about. I explained it and sent them the article so they checked with Netflix who said there will be no pulldown and so 24.000 and 48kHz is good to go.

I wish it was always that simple!

 

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