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"tuning"Lockits to House Clock


nickreich

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Hi All,

I do mainly live performance shoots with multiple cameras all Receiving Timecode and Genlock from Lockits, and a Lockit feeding TC and Word Clock to ProTools (or a SD recorder with it's internal TC).

I have a shoot coming up where we are splitting MADI Audio from the House System, thus our truck and ProTools will sync from house clock (sourced from an Apogee master clock). As we have 6 REDs shooting 90 minute continuous takes, I'm thinking we should try and tune the Lockits to the house master clock so the audio session timecode doesn't drift over long takes. While I'm familiar with the Lockits, I'm not with the Clockit master controller. Does anyone have any experience or tips to do with firstly tuning the Clockit to the house clock, then tuning the Lockits to that. Once done, should they stay tuned over the week? Also, the Ambient documentation is unclear as to whether the function to tune the Clockit master controller to incoming sync rather than incoming TC is active yet. The local importer thinks it is but haven't done it ever.

cheers

nick

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Hi Nick,

I have retuned Master Controllers on many occasions. You will need a timecode source clocked from the Apogee to do the Tune. The wordclock sync tune has not been implemented on the Master Controller though my one will tune to PAL video.

Assuming you have the ACC501 Controller, go into the "TUNE" menu and first select "2 Tune Intern". Keep a record of the 'dac value" on the screen if you want to reset the Controller back to it's current value at a later date. Then select "4 LTC" and it will retune the Controller to incoming timecode which should be sourced from your Apogee wordclock.

If the timecode is stable and has low jitter, the Controller will sample the timecode for 60". If not, the Controller will sample the timecode for 10 minutes. Once the Controller is retuned, it will go back and do a 2nd sample. You may have to do this a few times to get it down to 0.1ppm.

Sync over a week or even a day depends primarily on how stable the Apogee unit is. The Apogee is possibly more of a music grade product than a 1ppm or better broadcast grade sync source. You could use a Lockit or Master Controller to clock the Apogee.

David M

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Hi Phil and David,

Thanks for the info. Phil - ProTools will be running for between 90 and 120 mins per start, 4 starts in a 10 hour shooting day. Cameras will be doing random number of official takes, and RED-related restarts, battery changes and so on during each audio 'block'.

David - thanks for the comprehensive instructions, much appreciated. I'll give it a go off the ProTools Sync I/O timecode out and see how it goes.

nick

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The durations you mention are fine, although I'm sure you understand that the real issue is time between jam syncs of the camera-connected Lockits and the master sync gen. The first issue is always to make sure that the master clock (the one driving your audio rig) is REALLY stable. The next is to jam the remote boxes as close to the start time of the show as you can get away with for max. accuracy. In truth, the editors will end up nudging the sync around even if your sync is always numerically perfect, just to get the shots to look+feel right (esp on long-lens shots from cameras far from the stage).

phil p

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Phil, ProTools will still be getting it's timecode from another Lockit, just not it's clock - so even though we'll probably only jam all the lockits (6 camera and one for the audio truck) once or twice a day, the audio TC will be right each time we initiate record on PT - thus 'jamming' it's start time. The issue as I see it is PT drifting against the genlocked cameras over the 2 hours PT is running, effectively freewheeling. Sure with multiple takes and angles from different days, Post will need and be able to nudge sync.

nick

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Phil, ProTools will still be getting it's timecode from another Lockit, just not it's clock - so even though we'll probably only jam all the lockits (6 camera and one for the audio truck) once or twice a day, the audio TC will be right each time we initiate record on PT - thus 'jamming' it's start time. The issue as I see it is PT drifting against the genlocked cameras over the 2 hours PT is running, effectively freewheeling. Sure with multiple takes and angles from different days, Post will need and be able to nudge sync.

nick

I'd strongly suggest you use the clock out from the Lockit (word clock or AES black) to drive your PT rig. That will make your audio rock solid, so any drift in the system will be due to cameras (which should take the TriLevel sync output of their Lockits). The TC input to your PT rig only indicates a position, the word clock will force the system sample rate to stay in dead frame-edge sync with the TC--this is good. Depending on what interface you are using, you might be able to derive word clock from incoming TC as well.

phil p

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Hi phil,

totally agree that would be best, and is normally how I work if doing analog splits - the problem is all our inputs are 108 channels of MADI splits from an existing house sound system on a running show that is not interested in changing their clocking arrangements for a recording - therefore the console and ProTools rig in the truck have to clock from the wordclock embedded in the incoming MADI stream. Trying to clock PT separately won't work. Hence the original question about tuning the kit of lockits that are supplying TOD TC to ProTools, and TriLevel sync to the cameras, as close a possible to the house clock in the hope of reducing drift.

cheers,

nick

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Phil

Nick will probably have clocking issues with the incoming MADI steam if he uses the Lockit wordclock with the Protools rig. It's the Apogee that really needs to be clocked from a Lockit and that Lockit's timecode fed to the Protools rig for a really stable setup. Logistics might be problem though.

David

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Hi phil,

totally agree that would be best, and is normally how I work if doing analog splits - the problem is all our inputs are 108 channels of MADI splits from an existing house sound system on a running show that is not interested in changing their clocking arrangements for a recording - therefore the console and ProTools rig in the truck have to clock from the wordclock embedded in the incoming MADI stream. Trying to clock PT separately won't work. Hence the original question about tuning the kit of lockits that are supplying TOD TC to ProTools, and TriLevel sync to the cameras, as close a possible to the house clock in the hope of reducing drift.

cheers,

nick

What is clocking the house system then? A digital console? An outboard sync generator? How stable is it? If the PT system is being driven by the house clock on MADI, and the house clock is pretty good (ie not a cheaper Yamaha digital board etc), and your durations are what you say then you should be good to go without tuning if the Lockits are in good shape and you can jam them to

TC being generated by the PT rig, yes. If the house clock isn't great then there isn't much you can do to--at least the cameras will stay synced together (those on Lockits) even if the audio drifts off a bit. You could consider recording an extra track of LTC from a jammed Lockit (as jammed with the cameras) so you could compare the metadata TC to the Lockit TC in post, but my guess is that it will all be well within "cuttable" range anyhow, esp since they will end up nudging sync on every edit in post in any case.

phil p

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