Dual System Sound/timecode sync

R

ric8138

Active member
I am shooting indie shorts, often with very small and green crews. On my next project I will be using my new Black Magic Ursa Mini Pro 4.6, shooting DNG Raw 3:1. We would like to record dual system sound, probably with a Zoom F4 and a combination of lav & boom mics. Most of this project will be interiors, without a ton of camera motion, so I am considering just using a 50' camera snake, dual XLR and single BNC, feeding the mix from the F4's Main Outs to the audio in on the camera, and connecting the timecode out from the F4 to Reference In on the cam via BNC with it's reference set to external.
For any dolly shots or the few exteriors where the snake would be a hindrance, I would jam sync the camera to the F4, disconnect the snake and just stick a shot gun on the camera for some wild sound to reference if needed. Has anyone done a setup like this? Comments appreciated.
 
Unless your takes are longer than 10 minutes, you would probably be fine jams syncing the camera to the F4 at the beginning of a setup and letting both free run so clock times match when recording.
 
Yes, That would probably be the more conventional way of working, but the BM cameras are notorious for unreliable sync after being disconnected from the source. That, in addition to the fact that I am DP'ing and would rather not deal with any technical questions with non-pro crew, means I am looking for an almost foolproof method that will take as little input from me to keep things synced up and happy.
 
I agree and just put a clapper board marker on the front to ident and keep track and a sync point between camera mic and recorder.
 
The snake will be a PITA, especially with a green crew.

First, ask yourself if TC sync is even necessary. Does your post workflow account for its use, or understand how to use it? Most of the time, especially on low-budget stuff, a dumb slate is plenty to get the job done. If the slate is properly maintained, there’s technically no need for any sound to be recorded to camera. But, as a failsafe, an on-camera mic for scratch sound will be enough.

If you’re still bound and determined to use TC, Tentacle Sync is an affordable system for maintaining wireless sync. Grab a couple of BNC sync cables (sold separately) and you’ll have a solid system to keep everything jammed on set. You can use the system itself as the master clock, but typically the sound recorder is used as the master clock (also easy to do with the Tentacle Sync system). And unless you have a smart slate jammed as well, I’d still recommend you use a dumb slate.

If you’re bound and determined to use TC sync, and you absolutely must have a reference track from the mixer recorded in-cam, add a wireless channel to send one of the mixer’s outputs to one of the camera’s inputs (and use an on-cam mic on the other camera channel as a failsafe).

But really, a dumb slate and a camera mic are all you really need. This is the most foolproof system because it is the simplest and least technical.
 
I would also recommend really thinking through from the end backward. TC is not really something you probably want to use with a "green" crew, or at least depend on since it has a lot more ways to screw up than just using a guide track.

So things to think about.
Depending on positions syncing to a guide track may be better than TC. If you are all pretty close not a big deal but if the camera is noticeably farther away than the mic then the recorder is picking up the sound sooner than the camera position would "hear" it. Light travels a LOT faster than sound. On more distant shots it can sound "wrong" if the sync is tighter than your brain would expect it to be based on distance. Using a guide track syncs your sound to the timing of the camera position.

There are a number of flavors of TC and everyone needs to have all their settings the same or you just end up with a mess. If you are the only one on the crew who knows anything about TC then they won't even notice if things are off.

An umbilical is a PITA. People trip over it and it gets unplugged or yanked and a camera goes flying (or sound gear). If you are not locked down you need a wrangler to keep it untangled, etc.
I have done with and with out and with out is a LOT simpler. We have gone with generally with a ENG type shoot where the camera audio is the hero track and the recorder is backup.

There used to be the argument that it took too long to sync to a guide track, but these days many NLE's have the ability built in and for those that don't PluralEyes can do it almost with out user help. So it's about the same speed by guide track or by TC and both have a good track record of doing a reliable job.

Slate. You need to slate every shot either way. Some folks get it into their head that TC is a magic bulet that solves everything but even with full reliable TC you need to slate your tracks. Having tracks with nothing to identify them but TC is a disaster waiting to happen. And that means visual AND audio slate. Trust me no mater how well you remember every detail of XYZ if you end up with a drive full of files that have no slates it will takes weeks of sorting out what is what. If everything is slated then you can have one of those green crew members sit down and rename files based on the slates and your life in post will be so much better.

Nothing against TC, it can be a godsend on the right shoot, but any single thing you can do to simplify the shoot eliminates about ten ways things can screw up on shoot day.
 
If using time code is an option I would use it. The easiest way if the setting is available is to set camera and recorder to time of day reference and let them free run with the clocks jam synced between setups. Any time code devices that are not positively locked to the same master clock reference will drift apart over time. It is unavoidable. But that typically won't be more than a few frames per hour if the TC formats match and the clocks are synchronized to start with.
It still saves a lot of time in post as shots can be automatically synced to code in the NLE and the necessary minor offsets can be quickly dialed in with a slate. If you can rent a digital slate that can serve as master clock reference for jam sync, so much the better.
My Digital Bolex records double system sound internally. Video shots all start with a shot number + 00.00.00.00 timecode. Audio is a separate internal board, a discrete PCM recorder with its own clock. It records shot number plus time of day reference at the beginning of a shot in BWF format.
I set up Resolve to use the audio time code as start reference and shots are automatically synced at the head of first frame. This works flawlessly. Takes longer than 11 minutes or so may show a frame or two of drift.
If you record an audio format that doesn't support time code, there is no guarantee of frame lock between audio and video.
 
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Razz16mm said:
If using time code is an option I would use it. The easiest way if the setting is available is to set camera and recorder to time of day reference and let them free run with the clocks jam synced between setups. Any time code devices that are not positively locked to the same master clock reference will drift apart over time. It is unavoidable. But that typically won't be more than a few frames per hour if the TC formats match and the clocks are synchronized to start with.
It still saves a lot of time in post as shots can be automatically synced to code in the NLE and the necessary minor offsets can be quickly dialed in with a slate. If you can rent a digital slate that can serve as master clock reference for jam sync, so much the better.
My Digital Bolex records double system sound internally. Video shots all start with a shot number + 00.00.00.00 timecode. Audio is a separate internal board, a discrete PCM recorder with its own clock. It records shot number plus time of day reference at the beginning of a shot in BWF format.
I set up Resolve to use the audio time code as start reference and shots are automatically synced at the head of first frame. This works flawlessly. Takes longer than 11 minutes or so may show a frame or two of drift.
If you record an audio format that doesn't support time code, there is no guarantee of frame lock between audio and video.
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Some of this is a bit out dated, I think we may be close to the same vintage...

The last line in particular does not apply to digital audio. While with analog it was possible to slave the deck to TC, TC is no where close to accurate enough to slave a digital signal to. If you are actually slaving you need word clock for the timing and TC for positional, big PITA.

And digital files don't use continuous TC anyway. They read the TC at the start and put a time stamp in the header. Some may check back every once in awhile so they can throw an alert if the clocks have drifted but most don't seem to do that. So TC only gets you a start reference. Or to put it a different way it's just a slate the computer can read, it doesn't help with sync at all.

But the good news is that the drift issues are generally a thing of the past. A frame in an hour is actually a lot these days. If you re jam between takes pretty much any recorder on the market will drift no more than a few samples over a normal take.
Even a cheap handheld will hold better than a frame an hour usually. They need to to keep all the digits working properly, you start having your timing drift and you get glitching and even the metal head listening to MP3's gets upset by that.

Wave form sync is also built into resolve and will get you subframe sync with out TC.

Everything you said used to be true and certainly it still works but some of it is from the days of crystal sync and devices today are just so much more stable than they used to be that drift is not the demon it used to be.

On the down side it was actually fun watching decks chase TC sync.
 
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I am old enough to remember flying Q-lock Eclipse and even Maglink!

"I love the smell of oxide in the morning to me it smells like Victory"
 
Thanks all for input. I do plan on slating everything, and the Ursa Mini Pro has a great internal slate that stamps Reel. Scene, Shot & Take with auto increments into metadata as well. I was really thinking that the TC would be most helpful to organize and merge large numbers of clips over the course of each reel in post using Resolve so I can then generate proxies to hand to the director/editor. I jury rigged cables today and the camera simply syncs to the TC generated from the F4 when the BNC cable is connected from F4 TC Out, to Cam TC In. Disconnect, and the two machines stay together for as long as I could test today. Reconnect and they sync up again (if off). I also want to run the mix into my camera so I can listen to what the sound person is doing to help with their technique as well. The sound recorder/boom op may or may not know what the hell they are doing either. Thx again.
 
GaryNattrass said:
I am old enough to remember flying Q-lock Eclipse and even Maglink!

"I love the smell of oxide in the morning to me it smells like Victory"
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Ah, I had forgotten the smell of fresh pancake. I still have 4-5 pancakes of 1/4" in the basement.

Never heard of Maglink. We used to use FSK which kept things at the same speed but no positional info so... Then TC with a resolver which was pretty fun. But a machine room full of dubbers cranking up to speed chasing a 35mm print is hard to beat.
 
I have the sound of a roomful of dubbers winding up to speed in a short I made. Unfortunately, I have a song running under it so I can't post it.
 
Darn. The last film I did at the Ranch we were in the machine room and realized we had never recorded it and now it was very quiet with the digital dubbers. We were always so buisy and nobody thought to record them in their glory. Well except I guess you!
 
TC is an amazing asset to a production, which massively will make life easier in post for them. Especially as it has never been cheaper and easier to do than it is now! We're spoiled for choices. However it seems most people in this forum, still don't practice effective use of TC on a daily basis on set like I would. But then again I'm a sound recordist, so is one of the core parts of my department.

As for your non-technical newbie recordist, I'd suggest you spend a training day with him, then put your trust in him that he is getting it "ok". (as trying to monitor all tracks mixed together via your camera, is just a hassle with limited benefits that will greatly distract you from your own job at hand)

But do check in with him during the shoot that he is doing ok and give him direction (even people with a little on set experience, still often need to be told where to put their boom exactly. Especially as they have no idea whatsoever as how to estimate the frame line). Then do a quick check over his recordings at lunch break.


ric8138 said:
We would like to record dual system sound, probably with a Zoom F4 and a combination of lav & boom mics.
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Good! Dual system is the way to go if you care about sound. And the Zoom F4 is the beautiful sweet spot right now for a low budget recorder. (I even own one myself)

ric8138 said:
Most of this project will be interiors, without a ton of camera motion, so I am considering just using a 50' camera snake, dual XLR and single BNC, feeding the mix from the F4's Main Outs to the audio in on the camera, and connecting the timecode out from the F4 to Reference In on the cam via BNC with it's reference set to external.
For any dolly shots or the few exteriors where the snake would be a hindrance, I would jam sync the camera to the F4, disconnect the snake and just stick a shot gun on the camera for some wild sound to reference if needed. Has anyone done a setup like this? Comments appreciated.
Click to expand...

If you have a lot of motion, then you're setting yourself up for a world of hassle to use a snake. Usually the only place where I'd recommend a snake these days is for long sit down interviews. (though I've used it a few other times too, when the client requests it, but isn't something I'd recommend unprompted otherwise)

And I'd always keep a shotgun on the UMP no matter what, as a safety net back up for syncing.

Razz16mm said:
Unless your takes are longer than 10 minutes, you would probably be fine jams syncing the camera to the F4 at the beginning of a setup and letting both free run so clock times match when recording.
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I would never ever ever recommend this (not unless you're some super broke student shoot, then it is better than "nothing". Maybe... perhaps).

Tried this out of curiousity a while back with the C300mk2 (which likely implements TC better than BMD does), and it was just utterly useless.

What happens when the camera goes off speed? Changes media slots? Does a battery swap? Or any of a million other setting changes. Even without all that, how long until the camera drifts a frame out, half an hour, five hours? Who knows.

You're just begging for trouble by trying this approach. You'd have to baby sit the camera, which isn't your job as the sound recordist. That is the camera department, you've got a million other things to worry about instead (especially if the OP is using someone non-technical for sound, which it sounds like).

ric8138 said:
Yes, That would probably be the more conventional way of working, but the BM cameras are notorious for unreliable sync after being disconnected from the source. That, in addition to the fact that I am DP'ing and would rather not deal with any technical questions with non-pro crew, means I am looking for an almost foolproof method that will take as little input from me to keep things synced up and happy.
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Give your boom up the F4 with an external battery supply, and tell him to never ever ever turn off the recorder! (you can turn it off at lunch, then rejam before you start the 2nd half of the day's shoot)

Have a scratch mic on the URSA Mini as well.

Put a Tentacle or Ultrasync on the URSA Mini as well, and if budget allows a camera hop too.
 
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IronFilm said:
TC is an amazing asset to a production, which massively will make life easier in post for them.
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This is the only part I have a bit of dispute over. Since I do post mostly I would be one of the people that TC would make my life "massively" easier. And well not really. Assuming a narrative style shoot with one camera it is not particularly faster or easier to sync with TC than with a guide track. For sound post it can sometimes be of use but only IF the film department has been keeping up the "book" and there are really good sound logs. Neither of those have I ever seen in a non big budget film. I did a lot of work at a couple of large film post studios and one didn't even own a TC deck. They would now because as you pointed out it is a lot more common and affordable now. And film was still on film so TC was not the counting system of choice.

The point being that TC is not a bad thing, but it is not going to make a huge difference in post. The danger with TC is that you get people using it that think that is all they need to do and you hit post with a mess of files with nothing to indicate what they are. It's also good to point out that unlike the old days where you had continuous TC and you could chop it however you wanted and the TC would stay with the bits, TC on files is just a stamp in the metadata and is thus a bit fragile. Altering or damaging TC with continuous code was difficult at worst damaging or altering TC is just a few key clicks or a dodgy file transfer away these days.

If I get TC in post and it makes sense I will use it, but I hardly ever see useful TC in post and I don't really worry about it.
 
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