Beginning Sound Mixer needs TIMECODE advice.

[Niko]

Hi there,
I've been working as a Production Sound Mixer for over 3 years now. My equipment and package was mostly intended for the independent filmmaker. I have a TASCAM DA-P1 DAT Recorder and am now ready to make the jump to a TIMECODE Recorder. But before I do this, I need some advice from some professional top dogs.

Ok, so I understand the basic theory of TIMECODE. It was talked about very lightly in school. From my understanding, the Sound Department provides TIMECODE and a Smart slate. But what I don't understand is how exactly this all works, and more importantly...it's overall purpose.

Out of all the TIMECODE Recorders out there, (AATON Cantar-X, Fostex PD 4M DAT, Fostex PD6 DVD-RAM, HHB portadrive recorder, HHB PDR1000, Sonosax Stelladat II DAT, Sound Devices 744T, Zaxcom DEVA-V recorder, Nagra IV-STC recorder, etc...) I'm not quite sure which to get.

I learned TIMECODE as being something of a marker, or something that helps sync sound in a much quicker way then having to match wave files to a clapper. I know the recorder is generating numbers, and the smart slate is reading them. But what I really don't know is what the numbers mean, or how they work exactly.

Is timecode being recorded on the DAT, or on the digital recorder, so that in post all the audio has timecode already there? (Example: If I recorded everything on a Fostex PD4 or on a DIVA, then transferred everything onto my ProTools Digi002 rig, will the timecode transfer as well? Will ProTool read the timecode?)
Is there a special way to transfer TIMECODE audio? (Firewire, XLR’s, etc…)
What if there are 2 or 3 cameras involved…do I need 3 smart slates?
When using a recorder that allows multiple tracks to be recorded, (i.e.: Aaton Cantar, Zaxcom DIVA, HHD Portadrive), is timecode laid out on each individual track.
How are having a timecode recorder and a smart slate beneficially to making a film and in post production?
Do we NEED timecode?
Would it be unprofessional if I didn’t provide it, and spend my money on something else like a state of the art wireless system or on ENG mixers and field production mixers?

When I was at school, we recorded a lot of audio on 2 inch tape (24 tracks). We would use a timecode generator and recorded timecode on track 24. It took up the entire track and even had a sound (a digitized computerized sound pulsating randomly). We did this so that machines would talk to each other, and so that everything stayed in sync.

Does this technique apply to Production Sound as well?
I hope some of this stuff makes sense to someone. Any information about this topic would greatly be appreciated. I might just be way over my head and I have a feeling it’s much easier then I thought, but for the amount of money I’m about to spend…I would like to know what I’m getting myself into.

Thanks a lot.

[Charles Dayton]

I can understand why people have not responded to this right away, It's a huge topic, not often well understood even by "professionals". Here is my take. Timecode is a positional refrence. Many people confuse it with sync, that is not its purpose. Sync is a function of motor speed, which is governed by blackburst(also called "house sync", or "video black"). On set sync between nagra and camera is acheaved by crystal sync. In video shoots its black burst. Both are based on the same principle. They both create a 60 cycle signal that tells the camera motor/ nagra motor/ digital recorder/DAW/and video camera, how fast to run. The idea being, if you started them all at the same time, they would run in sync, and stay in sync. Timecode allows us to pick a spot, say 3 minutes 32 seconds and 5 frames into a reel, and have video and sound start at the same place. Remember, the timecode is not syncing these machines after we start running, the 60 cycle signal is. The timecode is mearly telling us where to start and where we are.
Timecode in post is vital. It is what syncs up the start point of all our tracks. The DAW will refer to the time code to make sure all elements are at the same place positionally in time, while the blackburst is controlling speed.
This is the basic, I mean basic explanation of Timecode. Books have been written on the subject. The important thing here to understand is, the better your knowledge of this topic, the less headaches you personally will cause for post.

[jayrose]

Well, the principles are right even if some details aren't.

Timecode -can- be used for speed control, and still is in analog multitrack setups. A typical audio post edit/mix suite for TV from the early 1980s until digital multitracks and DAWs would put TC (in the form of LTC) on the center track of stereo tapes and track 24 of the multi. The synchronizer box would use that code to cue/slew those tapes to sync with a master, and then would use the code to keep the tapes at the same speed as the master. The mechanical analog decks were sluggish enough that any momentary instability in the code would be smoothed over so there wouldn't be flutter.

(In that same kind of setup, an edit controller would often dictate precise offsets to the various decks and issue record in- and out- commands, based on timecode and keyboard commands.)

Timecode isn't stable enough even for analog video, so the first TC-controlled video edit systems would use code to locate and cue the VTRs, but the decks would drop to house sync for speed control.

Digital audio requires even better stability than analog video, so the same system is used there: timecode for location and rec in- or out- commands, and either house video sync or word clock for speed control.

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Crystal sync isn't. If the camera and digital recorder (and slate, and MDM, etc) have separate crystals, precise sync is a matter of luck. Today we're very lucky: the high-stability crystals in pro equipment can be good for as little as one frame error in a half day's shooting. The crystals in prosumer equipment figure at about one frame in 40 minutes (I did the math once). If the camera and recorder have different crystals, there's always the chance that they'll drift in different directions, so the error becomes one frame in 20 minutes. However, I've had correspondents tell me that in some prosumer situations they've seen a frame drift after 6 minutes.

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House sync, video sync, blackburst and similar in the video world, and word clock in the digital audio world, are heartbeats distributed to every piece of equipment at the shoot or in the post facility. They really are sync: every device looks to the same signal, locking the tape/file speed to it. Timecode may be used for cueing and slewing - or it may not even be available, if you're using 'wild' recorders or most miniDV and a slapped slate.

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Analog Nagras of the N-IV generation used three different sync methods, all of which printed a special sync signal to the tape during record and interpreted it during play, so both mechanical speed variations and slip or stretch would be compensated.

Mono recorders used a 60 Hz pilot, from a crystal in the recorder (most common configuration), a generator in the camera (common in N-III days) or stepped-down wall current. It was recorded in two narrow tracks on the tape, 180 degrees out of phase with each other. A flipped-phase playback head would read this signal, but it would cancel itself out on a proper full track audio play head. Badly-trained audio posties would play production tapes on stereo or half-track mono decks, hear the 60 Hz pilot, assume there was hum and blame the mixer. (Well-trained ones would sum the tracks from a stereo deck to get audio, and flip one track to get pilot.)

Stereo pilot recorders would put the 60 Hz signal in a special track down the center of the tape. IIRC, it was FM on a carrier.

Timecode recorders would write LTC on the track previously used for stereo pilot.

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Digital audio recorders, like analog and digital video recorders, have a control track. This is used to precisely regulate speed and mark frame boundaries, which is essential even in non-sync situations. The control track does not have to carry location information; in the case of analog video, timecode is carried on a different track.

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Pilot is based on a 60 Hz tick. House sync is (roughly) 59.97 Hz. Timecode can be 24, 25, 29.97, or 30 FPS depending on application.

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As I said, these are details. The basic workflow previously described is correct.

The best timecode handbook for a production mixer is Wolf Seeberg's (available from pro film sound shops). It's got detailed workflow, specific settings, hidden menu commands, and practical on-set philosophy.

[Charles Dayton]

:oops: Thanks Jay,
I always learn somthing new from your posts.

[Niko]

Wow guys,

I really appriciate all the information. I have Wolf's book already in the mail. Who knew TIMECODE was such an advancement and a headache at the same time.

Thanks again.

Niko

[Carl Warner]

Why all this conversation about TC? Providing TC during origional production sound is now becomming passe. The trend now is to add TC in post, much more accurate than production TC and it is unsally included in audio post services anyway. Is there really any advantage to producing two seperate TC signals?