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Long takes, no lockits


Richard Thomas

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So a real world question. If shooting scripted drama on 2 Red cameras (takes max at maybe 4 or 5 minutes), Do you need more than TC? I own 2 SB-3 boxes. Initially bought for jamming a RED on a single camera job, but I have used them for 2 camera shoots, and I know that camera never hooked up anything to the WC output. Should that work fine, or is post just not sending me an angry email and fixing it? I follow that the TC should make it so each clip starts "on time", but at what point does it require something more extensive (WC, or upgrades to a SB-T).

I would have jammed the SB-3 with a Zaxcom Fusion.

When I work on multi-cam reality, they never use more than just TC ports on sync boxes. Those takes can be a full camera load (tape, disc, card whatever). Does their post just deal with it?

Sorry for what may be noob questions. I don't do post. I've never been able to find really good reads to explain all of this and how it works in modern camera/sound hardware.

Lower range recorders will tend to have drift issues and will require WordClock. One of the ways to keep the price down is to use lower quality clocking. Usually you are still alright for few minute takes. Top end recorders will not need WC unless your are chaining them together with digital ins and outs for some reason.

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There's some interesting theories in this discussion.

"thesoundguy" is maintaing that you can't get wordclock from timecode.

jamming timecode or a constant time code connection will. not. help your word clock.

Lets try it this way.

They are 2 different types of streams. Timecode is a data stream with the 1's and 0's (on,off) that is then red by your recorder.

wordclock is simply a stream of 1's and 0's that signal when to take a sample of audio. at 48k, a on and off mode are repeated 48,000 times in a second. the 1 signal is the cue for the sample.

one cannot be read by the other.

Phil Perkins takes the view that professional recorders can use external imecode as a sync source for their word clocks.

...But TC as a signal stream contains clocking information as field-rate. A professional recorder can use this information as an external clock for its sample rate. Sound Devices recorders do this automatically, an HDP2 can be made to do this via its menus, as can various computer audio interfaces....

Timecode was fundamentally developed in the late 1960's and early1970's as both a time address and sync source. Although it's only a slow rate of 2400 baud, there is a sync start to a frame in that stream of 1's and 0's.

Assuming the timecode source is accurate and stable, it's possible to compare the timebase of an external timecode against a recorders internal timecode timebase and use the difference to slew the recorders wordclock so that it's effectively the same speed as the incoming timecode.

An example of this was the now obsolete Rosendhal Wif / Nuendo TimeLock Pro. The internal wordclock generator is resolved to incoming LTC or VITC.

I'm not aware of any Sound Devices recorder that can sync it's wordclock to incoming timecode. I re-read my 788T & 744T manuals and there's no reference to this feature anywhere. Just in case it's an undocumented feature, I reference tuned my 788T and a Lockit with a Master Controller and hooked up the wordclock outputs to a dual trace oscilloscope. Both wordclock signals were stable against each other. I then detuned the Lockit by 4ppm. The 788T was set to external timecode from the Lockit and I left them to run for 2 hours. The wordclock signals never stabilised into sync, which IMHO, disproves Phil Perkins comments regarding the SD recorders ability to "automatically" sync wordclock to incoming timecode.

However, the Tascam HD-P2 can sync it's wordclock to the incoming timecode (owners manual P21).

Does anyone know of any other recorders that can sync their internal wordclock to external timecode?

David M

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As I read the HD-P2 manual, in the "Clock Source" menu, the user selects the source of clock which includes the "timecode" option. This would imply that a signal such as WC going into the BNC would not be used. The external clock capability of the HD-P2 would appear to be the amongst the most flexible available. As with the Fostex PD606 and SD 788T it takes composite and Tri-Level sync in addition to word clock.

Regardless - best engineering practice for use of external timecode with cameras or audio recorders is to use common sourced word clock or genlock. Timecode only is 2nd best.

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So a real world question. If shooting scripted drama on 2 Red cameras (takes max at maybe 4 or 5 minutes), Do you need more than TC? I own 2 SB-3 boxes. Initially bought for jamming a RED on a single camera job, but I have used them for 2 camera shoots, and I know that camera never hooked up anything to the WC output. Should that work fine, or is post just not sending me an angry email and fixing it? I follow that the TC should make it so each clip starts "on time", but at what point does it require something more extensive (WC, or upgrades to a SB-T).

I would have jammed the SB-3 with a Zaxcom Fusion.

When I work on multi-cam reality, they never use more than just TC ports on sync boxes. Those takes can be a full camera load (tape, disc, card whatever). Does their post just deal with it?

Sorry for what may be noob questions. I don't do post. I've never been able to find really good reads to explain all of this and how it works in modern camera/sound hardware.

I think this is a very good question. Even Jeff mentioned in his reply to you that he sent TC only to two Red cameras, but no WC signal. So who is actually using WC (genlock), and when?

Charlie from Denecke touches on this topic lightly toward the end of this http://www.youtube.com/watch?v=ANcXY9I7w4A. I'd love to hear from Charlie or anyone else in-the-know on the technical side of things about when WC becomes critical vs. optional.

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" Lower range recorders will tend to have drift issues and will require WordClock. "

I suspect it is even more complex while being more simple!! :mellow:

That is, SMPTE signals are a stable and accurate reference as an ongoing signal, but not all equipment is locked (resolving) to the TC signal it may be receiving, it is just recording TC, or time-stamping from it.

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" Lower range recorders will tend to have drift issues and will require WordClock. "

I suspect it is even more complex while being more simple!! :mellow:

That is, SMPTE signals are a stable and accurate reference as an ongoing signal, but not all equipment is locked (resolving) to the TC signal it may be receiving, it is just recording TC, or time-stamping from it.

THESE PRETZELS ARE MAKING ME THIRSTY

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I just found this on the Sound Devices FAQ section, in response to someone who asked if they could have the SD722 slave to Canon XL2 camera using a Horita timecode generator. The Horita takes a composite video signal and derives TC from it.

A: Word clock and time code are related, but you will need a word clock signal for the 722 to accept it and lock its sampling rate to it. Our understanding of the XL-2 camera is that it does not have a genlock input nor a time code input. It uses its internal sync generator. That means that sound and picture will be running independently. For most applications, that is sufficient and marrying them in post will work well. However, for takes longer than ~15 minutes, there may be drift as each device will be clocked independently. Sample rate lock is not essential, but helpful. As long as each device holds its sync, you will be able to mate them in post. The tried and true method of using a slate (clap board) are still very relevant. I am not familiar with a device that generates word clock from a video signal. With such a device, you could clock the 722 from the composite output of the XL-2 camera.

Seems like Phil P. and thesoundguy are both right.

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No, that makes it sound like I'm right. They are saying there is nothing that can sync timecode and that you cannot sync wordclock.

They are saying that you have to sync the old fashioned way and that the camera internal clock is not good and that it will drift.

Which is what I have been saying the whole time.

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Wow, wish I had been paying closer attention to this thread.

It seems there are some misconceptions about what is going on with timecode and SD recorders. A timecode input will not drive a 7 Series recorder in the same way that a word clock signal does.

When a 7 Series jams to incoming timecode, the internal timecode generator jams to the external code right at the top of the second. This has the effect of putting the internal generator in near-perfect phase with any word clock or Bi/Tri-Level sync that is associated with the timecode signal. Since the temperature compensated crystal oscillator in the 7 series machines is extremely accurate, it will maintain this phase relationship over a long period of time.

This works very well in conjunction with an Ambient or Denecke timecode box which generates code in near-perfect alignment with its sync signal. Especially with the Ambient Lockit, which can be tuned to match the 7 Series TCXO, you have a very stable timecode/sync relationship over (relatively) long periods of time.

So the timecode doesn't drive the 7 Series Word Clock, it is more like the 7 Series generator aligns itself to the external code, which has essentially the same effect.

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