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Old September 3rd, 2010, 10:06 AM   #1
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Slate mic and tone -- advice needed

Was reading up on the Sound Devices 302 (don't own it yet) and noticed that it has a tone and slate mic. The idea, if I understand it correctly, is to generate a tone to all outputs and allows for recording of a description (i.e., what take it is, etc) via the onboard mic.

I was thinking about how this might be used to sync up audio with video on a DSLR. (Am trying to avoid slating since a lot of what I am doing is documentary-style work and slating is both inconvenient and, more importantly, messes up the ability to film "incognito")

If I ran an outupt to both a digital recorder and to the DSLR, could I then use the tone from the mixer to sync up? I wouldn't have a visual in the video but would have the tone in the audio part of the video.

Any advice on whether this would work?

Thanks.
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Old September 3rd, 2010, 10:43 AM   #2
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Of course, the primary purpose of the tone is to coordinate sound levels between the mixer and the destination devices (recorders, camcorders, etc.)

But a quick burst of tone certainly seems like a usable method of syncing the on-camera track with whatever double-system audio recorders you are also using.
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Old September 3rd, 2010, 11:40 AM   #3
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Tone would work, but would be terribly annoying while wearing headphones at a normal volume for monitoring field sound.
I'd be more likely to use the slate mic, unless you're also booming and operating the mixer at the same time. That would just end up being one more time you'd have to take one hand off the boom and flip the slate mic to on. Since you said incognito, I assume you aren't booming though.
I've debated getting one of those clickers they sell at the checkout counters of pet stores. Cheap, small, noticeably distinct "click".
Simply say out loud "sync" and then click it, or have the talent click it if wearing radio mics and then slip it into their pocket.
Honestly, unless one device is just using onboard mics as a reference track, simplying saying out loud "sync" (or any other distinct code word) is enough since the same signal is carried with equal quality to all your devices that are fed by the mixer. You only need something really noticeable if one device is using onboard mics that may not pick up as well as your main mics.
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Old September 3rd, 2010, 11:50 AM   #4
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The slate mic switch on the SD mxers is a momentary contact 'push-and-hold' switch. If you 'flip' it it will turn off as soon as you take your finger off it. Its intended use is to allow the production mixer to verbally identify the take information right after he rolls recording. The tone might be usable for sync but I doubt you'll find it precise enough. Usually you want something that is a very short impact sound, not something stretched out over many frames like a few seconds of tone would be. You need to be able to match up as nearly instantaneous as possible a pulse with the precise frame during which it occurs. Even one frame of imprecision is too much.
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Old September 3rd, 2010, 03:16 PM   #5
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Quote:
Originally Posted by Jay Massengill View Post
Honestly, unless one device is just using onboard mics as a reference track, simplying saying out loud "sync" (or any other distinct code word) is enough since the same signal is carried with equal quality to all your devices that are fed by the mixer. You only need something really noticeable if one device is using onboard mics that may not pick up as well as your main mics.

As of now, one device is using just onboard mics (the DSLR).

I've tried the new plural eyes for Windows, but it's not working on my computer (their tech support is working on the problem but no solution found yet after a few weeks of trying).

A somewhat related question: Any advantage to using a timecoded slate without timecode on the camera, vs just using a slate without time code?
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Old September 3rd, 2010, 03:26 PM   #6
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The slate mic switch on the SD mxers is a momentary contact 'push-and-hold' switch. If you 'flip' it it will turn off as soon as you take your finger off it. Its intended use is to allow the production mixer to verbally identify the take information right after he rolls recording. The tone might be usable for sync but I doubt you'll find it precise enough. Usually you want something that is a very short impact sound, not something stretched out over many frames like a few seconds of tone would be. You need to be able to match up as nearly instantaneous as possible a pulse with the precise frame during which it occurs. Even one frame of imprecision is too much.
Makes sense. Sounds like it won't work.
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Old September 3rd, 2010, 04:25 PM   #7
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..
A somewhat related question: Any advantage to using a timecoded slate without timecode on the camera, vs just using a slate without time code?
How are you recording the audio? Are you recording to a timecode-aware external recorder? Timecode slates were pioneered with film where there is no timecode possible with the camera. Sound is recorded on a timecode capable recorder and the slate is sync'ed with the recorder so that both devices' clocks have indentical code. When the slate is photographed, the timecode numbers visible in the image correspond exactly to the timecode recorded with the audio at the same instant. You import picture into your NLE and slide the timeline so its timecode matches the numbers in the image. Then you drop in the audio, setting the editor so it positions the audio such that its recorded timecode head-of-file timestamp is automatically aligned to the matching timecode in the timeline. Since the timeline code matches the numbers in the picture and the audio is positioned in the project based on the timeline code, audio and video will fall into sync.

Note that in a file-based workflow, timecode only establishes a single POSITION reference, aligning the video and audio at one point. It does nothing for a SPEED reference and won't prevent 'drift' if the audio and video clocks in the original recording devices aren't running at exactly the same rate. In order to make sure that which is put in sync at the start of the scene is still in sync at the end, you need to have the camera and the audio share the same timebase clock, and there are various ways of doing that, none of which are really possible with consumer cameras and/or recorders. The better professional audio recorders have good enough clocks that sync drift is less of a problem but with the popular consumer recorders, how long a scene can run before sync drifts off to unacceptable amount is a crap-shoot.
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Old September 3rd, 2010, 04:30 PM   #8
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Thanks Steve. That's incredibly helpful!

Don't have a timecode recorder yet (have been using H4n): that's one of my decision points -- is it worth getting a timecode recorder?

Also, do you happen to know if Adobe Premiere can do what you describe? (I can't seem to find anywhere if Premiere can even read timecode in audio).

Thanks.
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Old September 3rd, 2010, 07:56 PM   #9
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Originally Posted by Steve House View Post
The slate mic switch on the SD mxers is a momentary contact 'push-and-hold' switch. If you 'flip' it it will turn off as soon as you take your finger off it. Its intended use is to allow the production mixer to verbally identify the take information right after he rolls recording. The tone might be usable for sync but I doubt you'll find it precise enough. Usually you want something that is a very short impact sound, not something stretched out over many frames like a few seconds of tone would be. You need to be able to match up as nearly instantaneous as possible a pulse with the precise frame during which it occurs. Even one frame of imprecision is too much.
Doesn't matter how long the tone is. You can line up the beginning or the end of the tone (editor's choice). I know this from first-hand experience.
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Old September 3rd, 2010, 08:31 PM   #10
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Doesn't matter how long the tone is. You can line up the beginning or the end of the tone (editor's choice). I know this from first-hand experience.
Great! Do you use the slate mic to sync up separate audio with video (including audio)?
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Old September 3rd, 2010, 08:34 PM   #11
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The "slate tone" has other uses, normally its a lower freq. & lower level than line up tone.
The slate tone looks like a square block on a wave form display and easy for the editor to identify the various takes... and in analogue days you could hear the takes as they were spooling through on the tape machine as a BIP or BEEP.
If your mixer has the option, use "Tone +Mic" rather than "Tone" or "Mic"

The tone or slate from a mixer can NEVER be used to sync up the video and audio as there is NO video reference....
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Old September 3rd, 2010, 08:46 PM   #12
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Great! Do you use the slate mic to sync up separate audio with video (including audio)?
No, because the slate mic is typically too far away to effectively "hear" anything the camera can see.

REMEMBER: We are NOT recording to a separate sound recorder because the video camcorder sound track is out of sync. In fact, in virtually all cases, the camcorder/DSLR sound track is in BETTER sync than what we are using to record separate sound.

We are recording separate sound because the QUALITY of the camcorder audio track sucks, NOT because of its synchronicity. Because the low-quality track on the camcorder/DSLR is still in sync, it is perfectly capable of being a reliable sync reference when joining the video and separate audio tracks back together in post-production editing.
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Old September 3rd, 2010, 08:48 PM   #13
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The tone or slate from a mixer can NEVER be used to sync up the video and audio as there is NO video reference....
Right. So it would be useless for traditional dual-system productions that used cine cameras with no sound track. But in the modern era, we are using video cameras (even DSLRs) that record SOME kind of synchronous sound track. No matter how poor they are, they are at least good enough to record the sync signal. Whether that is a traditional clapstick, or a tone pulse from the mixer. It is a different paradigm.

Now SLATING is a different matter. Doing it properly means that someone holds up a slate with the scene and take numbers written so that the camera can record it, while the sound mixer speaks the scene and take numbers into the slate mic (before the sync reference). Traditionally, the slate was combined with clapsticks and that made slate/sync an efficient, single action. When you start getting lots of nearly-identical takes of a scene, there is no substitute for proper slating, no matter how you are recording audio (or even running MOS).
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Old September 3rd, 2010, 10:19 PM   #14
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No, because the slate mic is typically too far away to effectively "hear" anything the camera can see.

REMEMBER: We are NOT recording to a separate sound recorder because the video camcorder sound track is out of sync. In fact, in virtually all cases, the camcorder/DSLR sound track is in BETTER sync than what we are using to record separate sound.

We are recording separate sound because the QUALITY of the camcorder audio track sucks, NOT because of its synchronicity. Because the low-quality track on the camcorder/DSLR is still in sync, it is perfectly capable of being a reliable sync reference when joining the video and separate audio tracks back together in post-production editing.
Thanks. What I was thinking was running the tone from the mixer to both the off-camera recorder and to the audio recorded on the camera. This way, there would be a tone to both audio recordings. Then I'd speak into the mixer mic to give info on the take (could even give the file name of the DSLR). In post, there would then be a tone to line up from both the DLSR and the off-camera recorder, without having to do a slate.

Would that work?
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Old September 3rd, 2010, 10:49 PM   #15
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Yes, the whole discussion was based on the assumption that you were sending the same audio signal (with the slate mic and the tone) to BOTH the camcorder/DSLR AND to the separate sound recorder.

It is still pretty nice to have the visual slate at the head of the picture clip so you don't have to listen to the track to find out what scene and take number you are looking at. It was very convenient a few weeks ago when I was editing our team's 48-Hour film. :-) The 48 Hour Film Project
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