Auto match off by 1 frame often. Anyone else?

[Nate Clapp]

I have been doing some sync tests and love the auto sync function except that I find that either it is in sync or audio is one frame early. This is even with camera jammed by ambient clock it box and with "sync" also jammed. It appears as if it is not an auto sync error as much as the timecode of the audio does a actually seem to be one frame early but not consistantly. I even rendered footage and and then put in fcp and brought audio in and one frame offset. It has happened during testing and on a shoot with different audio equipment so I think it is the camera or the way redcine assigns timecode to the video portion of the clip. Running epic beta 1.7xx software. Perhaps that is it. Anyone else have a similar problem?

 

[David Ibbitson]

Timecode by itself isn't phase accurate so you can have slate, recorder, and camera be out of phase in different directions.
That could push it plus/minus one frame of error between the three.

David

 

[Nate Clapp]

In my case I was using a dumb slate, for what it's worth, and my final test I got the clock it box to Jim both TC and Sync (as displayed on LCD) thinking that would fix any offset that might be incurred by the camera. That didn't work either. Is there some way to bring things into being phase accurate? While I never did the syncing myself on docs I worked on back in the day but I never heard any problems with Aaton code- camera would be jammed and then cam and sound could roll and never use slates as timcecode "matched".

Id have to look at which cable we connected the breakout cable to, but choices are TC, shutter, genlock I think. Perhaps if I got camera to genlock off clock it box? Or do I need to make the clock it box generate tri level sync? It's a sound guys box so I a) don't have it in front of me b) don't know it very well.

 

[Nate Clapp]

I had connected to the green bnc which is the genlock I think (in addition to the yellow one which is TC) So I would have thought that would have been enough to get them in phase.

 

[Deanan]

I had connected to the green bnc which is the genlock I think (in addition to the yellow one which is TC) So I would have thought that would have been enough to get them in phase.

I could be settings on the clock it also.

 

[Nate Clapp]

Sounds like more testing is in order. Looks like I'm buying another Soundman's lunch

 

[Marc Wielage]

If it's consistently one frame off, don't sweat it. Tell the assistant editor to bump the track of every shot 1 frame when the offline footage is imported into the timeline. Not a big deal -- happens all the time.

Bear in mind there is often a 1-frame delay in certain flat-screen monitors. You might want to run some tests to see if that's the case.

If you're really concerned about it, either have the sound mixer try a 1-frame offset in his or her recorder, or run a delay line going into the camera (assuming sound is early rather than late). If sound is late, you'll have to fix it manually.

 

[Nate Clapp]

Unfortunately it is not consistent. That would be too easy. I am watching on laptop and freeze framing on clapsticks so not a lag on the screen.

 

[Marc Wielage]

In that case, I would genlock the camera to an external timecode box like the Denecke SB-T, and run the camera on external timecode and reference. Assuming you're running a separate audio recorder, have the audio recorder jam to that at least twice a day. Use a timecode slate and make sure it's also jammed twice a day.

Bear in mind that if the slate sticks are still blurred, the sticks are not yet closed and you should not year the clap. Typical rule of thumb is to sync up the clap on the first non-blurred frame. My opinion is that it's better if sync is a half a frame late than early, but I've worked with assistant editors who feel exactly the opposite.

My belief is also, this is the assistant editor's job: tweak every single take and double-check sync all the way through each day's material. If you don't have an assistant editor, get one. And also bear in mind the 1-frame delay in many monitors.

 

[Nate Clapp]

I am not an editor, nor do I want to be. I am merely trying to test workflows to advise clients on how to handle audio in the field. The auto sync feature is great, in theory. I am testing exactly the theory you suggest, genlock the camera via a tc/genlock box (in this case an Ambient clockit box) and an external sound devices audio recorder. And I am getting the 1 frame slip occasionally. While I am not an editor, I have logged many, many hours on a Steenbeck 20 years ago back in school so I am familiar with the whole "which frame is "THE" frame" thing. The slip does not seem to be related to it. I currently suspect I need to test the TC generator and make sure it is providing tri level sync and/or dip switches are dialed in. One reason I got a Soundman to spend time with me dicking around is that he had just bought the ambient box and wanted to try it out. Perhaps there is operator error. Anyway, further testing is in order before I make any further assessment. If I can get it to consistently get auto sync to work w no slipping that would be awesome. I could tell clients that they could do double system with no tethering to camera. Until the pro in/out module comes out sound guys look at RED with a gimlet eye

 

[Marc Wielage]

My solution, again, is just to hire an assistant editor and have them check sync on every single clap on the edit system, before the dailies are shown, and before the editor begins editing the material. Literally, a $10/hour assistant can check 100 takes in an hour, if they're fast.