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time code genlock and syncing audio

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Craig Alan
time code genlock and syncing audio
on Nov 25, 2013 at 10:19:00 pm

I want to shoot a music video with three AG-HPX250 camcorders.

We do not have an audio mixer/recorder yet.

Each camcorder has two channels for external mikes.

My plan is to connect 2 mikes each to 3 Sound Devices mixers which are connected to the 3 250s.

Thus each mike of the 6 is being recorded to its own channel but to three different camcorders.

Thus the camcorders need to be kept in sync.

IAccording to the manual vol 2 on page 67 it is possible to genlock with timecode more than 2 250 camcorders.



Can anyone help with the exact workflow to accomplish this?

I get connecting time code in with time code out and the menu settings.

Is video out to genlock in the SDI out to genlock in?

And once you do this do you need to start the recording on the master first and leave both devices recording?

How would you get the third camcorder in sync with the first two?
video out the slave 1 to genlock in on slave 2? How would timecode get sent to the third camcorder?

Panasonic support had me talk to a tech that had never done this before. He did suggest that once you make the connection that as long as you don't turn off the units that you have set the clock to be in sync and you can unhook the sdi cables and even record and pause as you wish on all camcorders and they would be in sync but might drift over time which of course defeats the purpose.

Its not the visual I'm worried about - I can sync that in post. Its the music I care about keeping in perfect sync. The audio techs tell me even a fraction of a frame difference will screw up music.

I understand there are third party tools designed to do this but I'm trying to get by until I can buy an audio recorder with 6-8 channels. Once all sound is being recorded to a single recorder then I need only use a clapper to sync up my camcorders.

Mac Pro, macbook pro, Imacs (i7); Camcorders: Panasonic AG-HPX170/AG-HPX250P, Canon HV30/40, Sony Z7U, VX2000, PD170; FCP 6 certified; write professionally for a variety of media; teach video production in L.A.


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Steve Eisen
Re: time code genlock and syncing audio
on Nov 26, 2013 at 1:45:36 am

Keep it simple. Use Free Run Timecode. To jam sync the time code, all you need to do is set camera 1. Connect a BNC cable to that camera's Timecode out to Camera 2's Timecode In. Disconnect cable from Camera 2 and connect Camera 3 Timecode In. Disconnect all cables and you are set. The only time you need Genlock is if you are recording a Live event with multiple cameras connected to a switcher.

You only need to connect 1 mic to 1 camera for a clean audio feed. The only way for your audio to go out of sync is if one of your cameras frame rate is different. You will get good enough audio from the on camera mics.

Steve Eisen
Eisen Video Productions
Vice President
Chicago Creative Pro Users Group


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Craig Alan
Re: time code genlock and syncing audio
on Nov 26, 2013 at 2:12:33 am

Thanks,

That certainly would give each cam operator a bit more freedom.

but I want to use 6 mikes to 6 channels so we can mix them independently in post. Will the jam sync as you described keep all three cams in sync enough so each of the six mikes going to the 6 channels on the three cameras remains perfectly synced?

If I just wanted to record sound to one camera I would simply use a clapper. I want 6 channels of audio recorded using external mikes. This is a live performance not prerecorded where all I'm doing is matching visuals to the music.

Mac Pro, macbook pro, Imacs (i7); Camcorders: Panasonic AG-HPX170/AG-HPX250P, Canon HV30/40, Sony Z7U, VX2000, PD170; FCP 6 certified; write professionally for a variety of media; teach video production in L.A.


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Steve Eisen
Re: time code genlock and syncing audio
on Nov 26, 2013 at 1:18:46 pm

Again, keep it simple.

[Craig Alan] "I want to use 6 mikes to 6 channels so we can mix them independently in post."

This is not the correct workflow. You will need to record to a multichannel recorder if you want to record independent tracks. You will also need an audio engineer control the levels during the recording. Recording to the cameras is not the way to go. I do not know who told you about sync drift, but I have NEVER had an issue with sync drift with any video camera. The ONLY way that audio sync would be off is if you set your cameras to a 24p frame rate and your separate audio recorder was set to 29.97 or 59.94. Audio and Video stay in perfect sync when you record to the camera.

Steve Eisen
Eisen Video Productions
Vice President
Chicago Creative Pro Users Group


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Craig Alan
Re: time code genlock and syncing audio
on Nov 26, 2013 at 3:22:39 pm

Thanks again Steve,

Yes a 6-8 mixer/recorder is on my wish list and when funding becomes available, it is a priority. This is a HS video production program and I have no standing budget. I'm trying to accomplish this given the equipment I have now.

Each mike will be going to a 302 mixer with an audio tech to ride gain. Each camera has two channels, thus two mikes to each 302 with one set to the left and one to the right channel.

So three 302s with two mikes each. Three audio techs. Three cameras. One live music performance. 6 channels of audio. Obviously not the best work flow; but if the 3 camera's were perfectly in sync, why would this not work?

I was told by panasonic tech support that using the built-in timecode generator of the 250, if you were to jam sync, that there might be some drift. But he had no experience doing this. I have also read on-line that a jam sync from a 250 could drift over time but would be fine for dialog. Audio techs tell me that any drift, even a fraction of a frame, for music is unacceptable. Although inconvenient, I'm told it is more accurate if the slave remains tethered with hd sdi cables or if each camera had a cordless receiver designed to be jam synced. Somewhere in the $500 per camera range.

In my situation I do not anticipate a shoot lasting more than an hour or an hour at one session and would start with fresh batteries. I would use all the same size cables for my mikes and the cameras are pretty much the same distant from the talent, just different angles.

So do you know for certain that jam syncing the two slaves will give perfect audio sync? If keeping the cameras connected works better, we can use two mikes each to two cameras and leave the sdi cables connected. The cameras have xlr cables running to them from the mixers anyway. The third camera could be left completely cordless and just use the on-board mike as a reference to sync the visual. For that we could use a clapper.

Mac Pro, macbook pro, Imacs (i7); Camcorders: Panasonic AG-HPX170/AG-HPX250P, Canon HV30/40, Sony Z7U, VX2000, PD170; FCP 6 certified; write professionally for a variety of media; teach video production in L.A.


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Mark Bogart
Re: time code genlock and syncing audio
on Jun 18, 2014 at 7:55:36 pm

I have seen drift in some situations.
Get an embedder (muxer) and embed 8 channels on one machine.


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