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Syncing offspeed Cameras


Joe Riggs
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We are working with a RED Monstro and a BlackMagic PCC, timecode is being jammed to both,.
This is not to sync audio but to sync the two cameras together.

Both have project/base frame rate of 23.976, and our shooting rate is 29.976, to give a slight
gliding/slow mo feel.

When sycning both via timecode in Resolve, the cams have been off everyday so far, sometimes by 6 frames, sometimes 2 seconds and it drifts throughout the day.

I was wondering if we're doing there's anyway to get TC spot on for both or if it's impossible because of the off speed shooting rate, and

therefore it will always be off regardless that both cams have the exact same settings:
23.976 project/base, 29.97 shooting rate

Thanks

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Check your TC devices, do you have a way to check sync? Can you plug your TC devices into another device and check sync? 6 frames sounds like faulty gear but not sure. 

 

I use an old Ambient slate and it works great. 

 

2.2.3 External TC framerate identification

Press BLUE button to display the Generator framerate and next to it the external TC framerate. A single bar to left of the framerate indicates the eventual error in the following ways:

0 1/4 1/2 1 1-1/4 1-1/2 1-3/4 2> if external TC

frames error ext fps slate fps 2.2.4 EXT TC error check

Bar full left indicates an error of 0 frames or less the 1⁄4 frames . 4 bars from left 1 fps error.
Full right indicates 2 or more frames error.

2.2.5 Framerate identification

The ACD slate display shows the various framerates in the following way:

 

Display

24

25

23

29

2d

30

3d

Framerate

24

25

23.98

29.97

29.97 Drop Frame

30

30 Drop Frame

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The problem is you’re shooting slow-mo, so the cameras will not continuously run TC.  TC will only run when you are recording.  So if you have a TC box on the camera and the camera is in its base/project frame rate(shooting real time), you will see the TC running and jammed to the TC box, but as soon as you switch the camera to off-speed shooting(any frame rate besides the base/project), TC in the camera will stop running at that moment(and not accept external jam)and will only run when recording.  And thus the TC mismatch.

 

It’s not a frame rate mismatch, per se, it’s just how the cameras work.  You’ll never be able to jam them, because they do not run free run TC during off-speed shooting, which is required to “jam” everything together.

 

The simplest solution is to shoot 29.97 base/project frame rate in-camera, jam the cameras(TC) at 29.97(either DF or NDF, just make sure every device is the same) and do the slow-down in post/drop into a 23.98 timeline.

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Ambient Lockit Box is what is being used but it is not on the camera the entire time.

From my understanding they'll jam it, then remove it, then jam it later in the day, and so forth.  

 

So who is correct Dalton or Run and Gun? 

 

My first instinct was that it wouldn't work due to the offspeed but Dalton says it is possible. 

 

Thanks again you guys, very informative. 

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Needs to be left on the camera all day. Continuously jamming camera. 

 

Think of it this way, three cars driving down the road or 1 car towing 2 cars. 

 

Older ambient stuff is capable of cross-jam, newer units are not. 

 

What they are doing is exactly why you are having your problem. 

 

 

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I shoot a lot of sports and go into and out of over-cranking(slow-mo) and real-time on any given shoot many, many times.  I have a TC box on the camera that keeps it jammed when shooting in real time(project/base frame rate) to be able to sync it with sound, radio calls, etc. if I’m shooting someone in real time.  The moment I go into overcranking(slow-mo), TC in the camera stops running, because the camera cannot run TC in free-run mode while over/under-cranking.  TC is then held at that moment I switched modes.  When I start rolling, it will start running from that last static TC value, but at the accelerated frame rate I’m shooting.  When I stop rolling, TC will stop(at whatever value corresponds to the duration of my roll at the given real frame rate).  Then when I switch back into “real time”(the original base/project frame rate), the camera will re-jam and lock back onto the TC coming from the sync box(which will obviously differ from the value when I stopped rolling during the off-speed roll), because it can run in free-run TC mode, again.  
 

I agree that the TC/sync boxes should be left on the cameras, that’s just “best practice”, but it doesn’t matter if it supports cross-jamming of frame rates or not, it’s not going to solve the problem in this instance, because the cameras can not run TC in free run while in over/under-cranking mode, and thus cannot be synced/jammed. (it’s not a situation of one camera shooting 23.98 and another shooting 29.97, both cameras are shooting slow-mo[29.97 over 23.98]).

 

Again, in my opinion, the simplest and most fool-proof solution for this situation is to just shoot real-time/base frame-rate of 29.97, which will allow you to easily jam and maintain sync across both cameras and then slow it down in post/drop the footage into a 23.98 timeline.

 

Or, I suppose they could line them up visually with a traditional slate, too...  29.97 real-time, just seems the easiest way, though.

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18 hours ago, Joe Riggs said:

So who is correct Dalton or Run and Gun? 

 

Run and Gun is correct. I have a feeling that Dalton didn’t notice the part where you mentioned slow-mo. 
 

I always leave the sync box on the camera, too, and my experience matches that of Run and  Gun. There’s no SMPTE TC for off speeds, the TC box won’t support and the camera won‘t either - even though theoretically it could be done, of course. 
 

Indeed, make extra sure to slate the take and I recommend a start and end-board, which can sometimes help to align the audio

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I totally don't get this.
This is NOT shooting slomo with an off speed, this is a speed change in post with a 1:1 frame relation.
(And yes, that results in a 'slomo', since the frame duration is stretched, but I consider this 'pull down', as 29,97 is NOT an 'off' speed.)

 

Are both set to drop / non drop alike? If not, that's your problem.

Then, depending on how smart Post is, how is the new TC calculation done? If they are in sync in 29,97, they also should be in 23,976

 

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11 hours ago, Bouke said:

I totally don't get this.
This is NOT shooting slomo with an off speed, this is a speed change in post with a 1:1 frame relation.
(And yes, that results in a 'slomo', since the frame duration is stretched, but I consider this 'pull down', as 29,97 is NOT an 'off' speed.)

 

Are both set to drop / non drop alike? If not, that's your problem.

Then, depending on how smart Post is, how is the new TC calculation done? If they are in sync in 29,97, they also should be in 23,976

 

 

Regardless of 29.97(30) being a normal frame rate, in this context, it is considered off speed.  They are not shooting regular 29.97.  They are shooting with the cameras set to a base/project frame rate of 23.98.  23.98 is the "real time" frame rate and they are then shooting 30(29.97) frames over top of that, which creates (slight) slow motion.  The camera recorded files/footage plays back automatically in slow motion.  It's not a post effect. 

 

This has nothing to do with a frame rate or drop/non-drop mismatch.  It's a simple fact of how the cameras operate, regarding time code, when over or under cranking.

 

It's simple.  A camera MUST be running TC in Free Run to be able to be jammed to an external TC source.  When over/under cranking/shooting off-speed(meaning shooting any frame rate above or below the base/project frame rate) the cameras TC will only operate in Record Run.  That means that the time code is static UNTIL the camera starts recording.  Then it runs/counts up from that last held static TC value.  It does not matter if there is a TC/Sync box attached feeding it TC of any frame rate (DF or NDF), the camera cannot accept external TC in this mode.  Therefore, they cannot be jammed via external TC and synced via the recorded TC, because the TC will never match(except out of shear dumb luck).  Now, if you had some type of electronic trigger you could attach to all cameras to SIMULTANEOUSLY start them recording at the exact same moment,  then you could manually set all cameras to the same TC before rolling and get the shot synced.  But the easiest way for them to do it, would be to either 1) shoot the cameras at 29.97 real time(base/project frame rate), jam them with 29.97 TC(DF or NDF, as long as its the same for everything), sync them in post and slow it down in post or 2) If they still want to shoot slow-mo in-camera, use a slate and line them up visually with that in post.

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Yes, it is shooting slo-mo, as the cameras have a project (base) frame rate different from the actual recording frame rate. As already mentioned, most cameras can only jam sync in their set project frame rate, otherwise they work in record run and cannot be synced. For this example, it might be beneficial to set the project frame rate (and the Timecode boxes and the audio recorder) to 29.97 and slow it down in post to 23.97

 

For cross-jamming, the Timecode Box makes no difference. Timecode is always unidirectional, so only the receiver has to be capable of cross-jamming. The Timecode Box just outputs a timecode signal in the selected frame rate.

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Ah, my bad. I've overlooked this:

15 hours ago, matthiasp said:

as the cameras have a project (base) frame rate d

 

But then the solution seems simple enough, set the cams to regular 29,97, and have post interpret as 23,976 (read, 1:1 frame relation.), as RunAndGun mentioned.
Any half decent NLE can do this.
Or am I still missing something?

 

Having said this, if you can manage to put 23.976 LTC on an audio track, my LTC_convert can probably set 'correct' TC's on the files.
(And if not, send me testclips and I'll make it work...)

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1 hour ago, Bouke said:

Ah, my bad. I've overlooked this:

 

But then the solution seems simple enough, set the cams to regular 29,97, and have post interpret as 23,976 (read, 1:1 frame relation.), as RunAndGun mentioned.
Any half decent NLE can do this.
Or am I still missing something?

 

Having said this, if you can manage to put 23.976 LTC on an audio track, my LTC_convert can probably set 'correct' TC's on the files.
(And if not, send me testclips and I'll make it work...)

I like the way you think, but most cameras do not record audio internally when over/under cranking.  It’s cracked me up for years that my ~$1000 iPhone can shoot 240fps AND record matching audio simultaneously, but my dedicated, purpose-built $30K-$40K+ “cine” cameras can’t*.

 

*I believe some RED’s can actually record audio while shooting slow-mo, but it’s a separate file and of course, it’s TC does not match up with the video files TC, with probably the exception of the first frame.  But I don’t know enough about it to speak authoritatively on it.

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 For Mp4 / Mov, only the start frame is written as 'tc', as a frame number. The rest is  calculated based on the frame rate. (And yes, you can specify a different framerate for the TC if you like, but it 'should' not be an issue, it's just math...)
You don't know me, but I'm a coder, not a sound guy. (I used to be a video editor, but have seen little off speed files.)

 

 

 

 

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