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Karl Lee

A Few Questions about TC Slates & TC Editing Workflows

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I was curious if anyone might be able to help with a few questions I have about production workflows that use a TC slate for sync sound.  While I understand that an external TC generator is used to sync both the TC slate and TC-capable audio recording device, my questions are specifically about how TC on the audio recording device translates to the editing workflow.  My understanding is that there are a couple of ways to handle audio TC in double system recording.  

One method, which seems to be the most widely discussed, is that the TC-synced audio recorder adds a timecode “stamp” to each file to note the exact time at which the recording started.  From what I’ve read, .bwf seems to be the most popular file format for TC-stamped audio recordings.

Secondly, while this method may not be widely used, another option, on a multi-track recording, would be to record SMPTE timecode (from an external TC generator synced to the slate) on one audio track, thus providing TC reference for the recorded clip by virtue of the SMPTE recorded on a spare audio track.

Being mindful of present-day NLE workflows, are both of these TC methods practical, or is one typically preferable over the other?  And, for the latter workflow, can most NLEs decode SMPTE timecode from an audio track, or would this need to be done in a third-party program or utility?  In particular, I’d be interested to know how these two workflows would translate specifically to DaVinci Resolve or Avid Media Composer | First.

It would seem that the second method I mentioned might be a little more helpful in spot checking sync throughout a longer clip, as this method would have a running TC reference for the duration of the audio clip as opposed to a single time stamp that was marked at the beginning of the recording.

Any thoughts or information would be appreciated.  Thanks!

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I've never "adjusted" timecode settings in a camera or audio recorder. Generally, I plug in my master clock, hit the "sync lock" button and that's it! I keep checking it every 6 hours to insure they don't drift and that's it.

With film cameras, you need a special programmer and a timecode reader on the scanner, but the file will have TC like a digital file. 

In post production, when you import the media, you simply right click on the media in DaVinci and "sync to timecode" and it magically takes the picture media and adds the new soundtrack. In Avid, you create syncing bins and right click on all the media and it will auto sync into subclips. Both Avid and DaVinci syncing is nearly instantaneous and you're ready to edit right away. 

Without timecode, you're screwed because I don't know of any program that does waveform syncing well at all. They all have issues with it. 

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In my experience method one is the preferred and it's how most professional cameras are set up. The second method is useful when working with cameras that don't natively support TC (Sony FS5, Fuji XT3)

Most devices can hold time code longer than any single clip so I wouldn't be so worried about drift in a take unless there's a frame rate issue. 

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I should have specified this in my original post, but I'm primarily interested in how this relates to production workflows where the camera itself isn't synced (such as when using a film camera not equipped with Aatoncode / Arricode), in which case the TC slate captured visually on film and the TC-synced audio recorder are the only two reference points for synchronization.

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All of the approaches you mention have been used. I've personally written software that will read timecode out of an audio track and create a new wave file with the BWF headers so that it can be used with any BWF-compatible software. My impression is that isn't very common, though. It would usually only be used with audio recorders that don't have timecode facilities, and to do that you'd need a timecode source permanently connected to the audio recorder. The cost of a timecode source like that is reasonably high and the cost of a timecode-compatible audio recorder is lower than it ever has been. An Ambient Lockit box costs UK£750 or so, and you can buy a Zoom F4 recorder, with inbuilt timecode facilities, for almost half that. I suspect you can probably get cheaper timecode sources than from Ambient, I haven't looked, but as you see this is not necessarily a very sensible approach.

As such it doesn't make much sense to deliberately set up for that sort of workflow. It may possibly make sense if you are extremely desperate to leverage existing equipment.

P

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5 hours ago, Karl Lee said:

I should have specified this in my original post, but I'm primarily interested in how this relates to production workflows where the camera itself isn't synced (such as when using a film camera not equipped with Aatoncode / Arricode), in which case the TC slate captured visually on film and the TC-synced audio recorder are the only two reference points for synchronization.

Working at home with consumer software, I'm unaware of any tools that can sync based on "image" timecode. Camera timecode is the only way to "auto" sync at home. Either file based timecode OR analog audio timecode like Phil said above. 

For film, Cintel has an automated syncing system that reads the slate, but it's not 100% accurate. You still have to do manual alignment of things when the slate isn't perfectly in the same position on every scene. 

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Right...I can't imagine that there are any systems that can (accurately and consistently) visually resolve TC from a TC slate in a video clip.  Rather, I'd imagine that if the TC slate was the primary visual reference, TC would need to be set manually in the NLE for each slated take.

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I've never heard of anyone writing code to do optical character recognition on a slate, but it's certainly been talked about. The visible numbers are a backup; in modern practice, the camera will have marked the file because the camera is itself jammed to the audio recorder. Assuming this system works, as it almost always does, it is generally not necessary to slate at all. I have worked on productions which didn't slate, though, and perceived a certain breakdown in discipline and procedure. That's clearly an issue of training and habituation, but that doesn't make it not a real problem, and if you don't slate, you have no backup if things do break.

What tends to break things is operator error and poor recordkeeping. Many workflows use the first three sets of user bits to indicate the date, with the last indicating roll number; that's often all that separates 10am on Tuesday from 10am on Wednesday in the mind of the computer. Often the scene and take numbers are only set for human readability, but some software may make note of those, too. If any of this is not done correctly, material may have out-of-sync or even completely wrong audio, from some other day or take.

Anyway, all of these things we've discussed are plausible ways to implement a timecoded workflow without really needing any special equipment. You can type in the timecode numbers by hand, you can feed timecode to a scratch track on almost any camera, right down to a DSLR, and have software work that out later; you can feed timecode to a spare track on an audio recorder. Many approaches are (at least theoretically) possible.

P

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