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JonG

Digital-analog sync sound

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JonG   

I have a film coming up and production wants to record on film and tape. I intend on using my analog mixer, take the direct outs and record the ISOs into my 788T, and send the mix to the Nagra, and back into the 788T. The idea being that everything is already there, even though the tape mix will have a delay, it'll have the slate, and the actual tape would have TC on it. 

 

I guess my question is this: should I record everything at 24fps, 23.976, or something funky like 48048?

 

I know that normally we would ask post, however post has not been lined up yet, and likely will not until after we've shot the film. So if anyone has ever done something like this, please chime in :)

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Are they shooting film?  What fps?  If the Nagra is just there to give them an analog sound on your prod mix then I'd consider doing 60Hz pilotone with a clap and voice slates.  The TC-on-analog-tape thing isn't well understood by anyone doing data management anymore, so I wouldn't go near 48.048 unless someone signs in blood.  Your 788 is 1:1 in transfer, a 1/4 tape with 60 Hz can be the same .  If they are doing film and USA telecine with pulldown I think I'd still do this.  

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JonG   

Yes they are shooting on film. So the 788 should stay at 23.976, and the nagra should just run on Pilotone huh?

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On 9/6/2017 at 9:44 PM, JonG said:

Yes they are shooting on film. So the 788 should stay at 23.976, and the nagra should just run on Pilotone huh?

 

In my experience it really depends on the workflow. are they planning for a full 24fps workflow for cinema release and convert at 23.976 at the end for video release? or are they running everything at 23.976 and if a DCP needs to be made convert this at the end?

 

in the first case a possible workflow would be:

camera rolls at 24fps

sound rolls at 24fps 48Khz

telecine transfers at 24fps

editing and mastering done in 24fps (for cinema release)

final conversion to 23.976 (for video release)

 

in the second, if the camera can roll at 23.976 then:

camera rolls at 23.976fps

sound rolls at 23.976fps 48Khz

telecine transfers at 23.976fps

editing and mastering done in 23.976fps (for video release)

final conversion to 24fps (for cinema release)

 

or if the camera only can run at 24fps but post needs to be done at 23.976, then you'll have a mismatch. one solution would be:

camera rolls at 24fps

sound rolls at 23.976fps (but usually 48.048)

telecine transfers at 23.976fps

*edit*: sound needs to be slowed down 1000/1001

editing and mastering done in 23.976fps

final conversion to 24fps

 

since in this last case the picture has been slowed down 1000/1001 on telecine compared to the "real-world-time" when sound was recorded, sound needs to be slowed down as well. this will be the equivalent to resampling the audio to 48.048Khz, thus usually it's preferably to record at this sample rate to start with and not introduce any resampling artefacts. 

 

I hope I haven't made any stupid errors in the options above (or if I did, somebody please correct me)

chris 

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Your last set up isn't  completely correct, if the camera rolls at 24 and then transfers to 23.97 and audio is rolled at 23.97, 48K, they won't sync unless audio is recorded at 48.048 and then played back at 48.00, then everything will sync together. That's the reason for the increased sample rate. This is why they need to make a decision now so when it gets to edit, everyone is on the same page.

 

Scott

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JonG   

@Marc Wielage, you seem to know all when it comes to, well, all. Any thoughts? My director just spoke with the house that's going to digitize the film. They say shoot at 24, digitize at 24, sync at 24. But of course didn't go into detail. So then do I do 24fps at 48048? I'm getting so many mixed messages, and we don't have a post sup on board yet, so I guess we need to develop a game plan and stick to it without boning anyone down the line. What did y'all shoot at when you were recording files and they were still shooting film?

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8 hours ago, carbonhobbit said:

Your last set up isn't  completely correct, if the camera rolls at 24 and then transfers to 23.97 and audio is rolled at 23.97, 48K, they won't sync unless audio is recorded at 48.048 and then played back at 48.00, then everything will sync together. That's the reason for the increased sample rate. This is why they need to make a decision now so when it gets to edit, everyone is on the same page.

 

thanks for the correction/clarification, that's basically what I meant. But I thought that theoretically you could synch them up by resampling the audio 1001/1000, only this is not very desirable, hence the 48.048

 

8 hours ago, JonG said:

They say shoot at 24, digitize at 24, sync at 24. But of course didn't go into detail. So then do I do 24fps at 48048? I'm getting so many mixed messages, and we don't have a post sup on board yet, so I guess we need to develop a game plan and stick to it without boning anyone down the line. 

 

that would be case one in my three examples and IMO the best one.

23.976 was important when files had to be transferred to NTSC and editors worked mostly in 29.97.

 

case two is also pretty good if the camera can roll at 23.976 because you basically treat it like a normal video shoot.

 

case 3 is asking for trouble if you don't plan things well.

 

 

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Anyone from production or camera that says the word "24" to me immediately gets asked the question "do you mean 23.98"?  The answer is "yes" 99.9% of the time but you have to ask.   If they shoot film @ 23.98 then the telecine is 1:1, 788 @ 48k and Nagra @ 60 Hz are the important numbers, because the audio file TC can be whatever you want it to be and be changed later if someone wants it different.  If they have to have TC on the Nagra and no one from post (esp audio post) is around to cast a vote then I'd go 23.98 or 29.97 fps.  And warn the production that post needs to do a workflow test before they crank up the machine, so to speak.

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JonG   

Thanks for your input. Still gathering information, but I think you're right @Philip Perkins the TC on the audio files doesn't matter all that much since it can change. 

 

Since the scanning house says 24 in a question about 24 or 23.98, I'm going to guess that we will have a 24fps workflow and the editor can convert to 23.98 upon exporting the project. As soon as we line up a post team I'll verify that, but there's a chance that it won't happen until the film has been shot. 

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I'm in a bit late in this discussion, but up to the last series I shot on  24fps film, we ran 30fps TC and 24bit 48K. The lab took care of all the rest. Since workflow is so different now (that was about 2012, or 2013), that may not be the right way to do it now...so no help really, just a bit of history.

Please let us know how it all works out, Jon G.

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