Long-form multi-camera problem at DVinfo.net

Jon Fairhurst · June 26th, 2007, 01:02 PM

A group that I work with would like to do a multi-camera production with long takes. I know from experience that we will have audio sync problems if we free-run.

Option 1: Get some Canon XL-H1s or XH-G1s and genlock 'em. Record to tape. Assemble in post. The problem: the cameras are out of budget, and the group wants the capability long-term, so they don't want to rent.

Option 2: Use DV cams. Run 'em into a switcher through time-base-correctors. Record the output. Problem: can't fix a bad cut easily. We'd rather assemble in post.

Option 3: Buy some used SD camcorders with genlock. Any recommendations?

I'm interested in any and all suggestions.

Thanks!

Richard Alvarez · June 26th, 2007, 01:20 PM

Well, with the XL2's you can start the lot of them simultaneously with 'free run'... and they'll still have the same timecodes. Just set them down together on a tabletop, aim the remote controller at them, and start the time codes running.

Jon Fairhurst · June 26th, 2007, 03:06 PM

Quote:

Originally Posted by Richard Alvarez

Well, with the XL2's you can start the lot of them simultaneously with 'free run'... and they'll still have the same timecodes. Just set them down together on a tabletop, aim the remote controller at them, and start the time codes running.

But after 30 minutes or so, won't they drift apart in time?

I tried something similar a few years ago with a number of DV cams. We sync'd them with a still camera flash, so I could get things aligned on the timeline, but it didn't take long before they drifted apart drastically.

The project is a product evaluation where a user is asked to do various tasks. One camera might look at their face, another at the keyboard, another at a computer screen and so on, depending on the product. If the video drifts you don't know it until things stop making sense, and its hard to know if a given source is early or late - it all looks kinda the same.

The XL2 method works fine for short takes, but our takes will be from one end of the tape to the other.

Thanks for the suggestion though!

Any others?

Ron Evans · June 26th, 2007, 03:13 PM

We frequently do multicam with an FX1, TRV50, GS500 and a PD150 most except the PD150 at DV LP!!! to get the run time for a show that is going to be close to 90 mins. I do the editing and do not have a problem with sync most of the time. I also record to a ZOOm H4 set at front of theatre. I use Edius PRO3 to do the video editing and have little problem syncing up the cameras using the audio waveform. Sound mixing is done in Vegas 7 that is able to stretch and match audio perfectly from all cameras if needed( I output audio from timeline in Edius and import into Vegas so they are close in sync anyway). Vegas has the advantage of releasing audio from video frame sync to audio clock rate.
Just start all cameras at beginning and let them run till they need a tape change. Make sure only one camera at a time does a tape change and you will have no problem resyncing. The most important thing is do not start and stop individual cameras to save tape!!!! Let them run as long as possible.
Bottom line any reasonable set of DV cameras can be used, discipline in recording is important ( don't stop the cameras), learn to sync in your NLE and I have to recommend Vegas for the audio editing because of its ability to really sync up audio to a reference audio.

Ron Evans

Nate Weaver · June 26th, 2007, 03:42 PM

Jon, I've done a zillion multicam shows with DVXs. Some up to 9 cameras. Most around 7 cameras.

Drift is not an issue. If it is, then something is not working correctly in FCP.

All we've ever done is just make sure every op keeps rolling the entire show, no stopping. If they have to change rolls, then fine. I don't even try to schedule a common roll signal...if you let every op decide on their own, then they all roll out at different times and it gets naturally staggered.

Genlock is not necessary if you're doing a post edit. The most a camera could ever be off without genlock is a half-frame.

If your experience in the past gave you audio sync issues, then something was wrong, most likely with your NLE or how your audio was imported (or recorded).

Tom Wills · June 26th, 2007, 04:35 PM

When I did a multicam show, I was running with such an oddball setup that it wasn't even remotely possible to genlock, not to mention the size of the space we were in. We had my Panasonic DVC60 in the back of the room getting XLR feeds from the soundboard, and a Canon XL2 in the front right, using its shotgun for audio and getting closeups, and we had a "backup" at the front left, which was a Canon ZR60. So, what I had my crew do was change tapes every time they ran out, and I changed tapes after 40 minutes. That way, it was impossible for there to be no camera rolling. That way, in Final Cut, I just would put down and sync based upon picture camera 1 to camera 2, then sync camera 3 to camera 2, then when camera 1 cut, I'd then re-sync it to camera 2, and then when camera 2 cut, I'd then re-sync it to camera 1, and so on and so forth. Certainly not the easiest edit I've ever done, but not that bad.

Jon Fairhurst · June 26th, 2007, 05:08 PM

Quote:

Originally Posted by Nate Weaver

Genlock is not necessary if you're doing a post edit. The most a camera could ever be off without genlock is a half-frame.

If your experience in the past gave you audio sync issues, then something was wrong, most likely with your NLE or how your audio was imported (or recorded).

Hi Nate,

I think the problem we had was poor camera quality. Seriously, the drift was terrible. There were no dropped frames during capture. (Vegas.) We used a consumer DV cam, a security cam (eye in the sky with remote control) and an old VX1000. It probably came down to a really cheap clock circuit (who needs a crystal?) in one or more of the cameras.

Good to hear that pro-sumer cams should be up to the task - and that the DVX can start recording synchronously.

Richard Alvarez · June 26th, 2007, 05:25 PM

Jon,

I'm in agreement with everyone else, any decent Prosumer cams running concurrently should allow you to cut without ANY drifting in synch.

The 'free run' tip I gave in my post, will insure that REGARDLESS of stopping and starting the cams, they will have the EXACT SAME timecode for the exact same moments. Making synching even easier than using a flash or slate. It's a tip, but not necessary.

Frank Simpson · June 26th, 2007, 05:49 PM

I recently did a 3 camera shoot with 2 Canon GL2s and a GL1. Fortunately each session was just under an hour, so running out of tape wasn't an issue. I did use a slate for sync each session, but I was anticipating some drift in post.

Much to my delight, when I brought everything into FCP it was extremely easy to sync, and there was no drift at all in over 16 hours of captured footage!

June 26th, 2007, 01:02 PM	#1
Jon Fairhurst Inner Circle Join Date: May 2006 Location: Camas, WA, USA Posts: 5,513	Long-form multi-camera problem A group that I work with would like to do a multi-camera production with long takes. I know from experience that we will have audio sync problems if we free-run. Option 1: Get some Canon XL-H1s or XH-G1s and genlock 'em. Record to tape. Assemble in post. The problem: the cameras are out of budget, and the group wants the capability long-term, so they don't want to rent. Option 2: Use DV cams. Run 'em into a switcher through time-base-correctors. Record the output. Problem: can't fix a bad cut easily. We'd rather assemble in post. Option 3: Buy some used SD camcorders with genlock. Any recommendations? I'm interested in any and all suggestions. Thanks! __________________ Jon Fairhurst

June 26th, 2007, 03:42 PM	#5
Nate Weaver Wrangler Join Date: Oct 2002 Location: Los Angeles, CA Posts: 2,100	Jon, I've done a zillion multicam shows with DVXs. Some up to 9 cameras. Most around 7 cameras. Drift is not an issue. If it is, then something is not working correctly in FCP. All we've ever done is just make sure every op keeps rolling the entire show, no stopping. If they have to change rolls, then fine. I don't even try to schedule a common roll signal...if you let every op decide on their own, then they all roll out at different times and it gets naturally staggered. Genlock is not necessary if you're doing a post edit. The most a camera could ever be off without genlock is a half-frame. If your experience in the past gave you audio sync issues, then something was wrong, most likely with your NLE or how your audio was imported (or recorded). __________________ My Work: nateweaver.net

June 26th, 2007, 01:20 PM	#2
Richard Alvarez Inner Circle Join Date: Sep 2002 Location: San Mateo, CA Posts: 3,840	Well, with the XL2's you can start the lot of them simultaneously with 'free run'... and they'll still have the same timecodes. Just set them down together on a tabletop, aim the remote controller at them, and start the time codes running.

June 26th, 2007, 03:13 PM	#4
Ron Evans Inner Circle Join Date: Mar 2003 Location: Ottawa, Ontario, Canada Posts: 4,222	We frequently do multicam with an FX1, TRV50, GS500 and a PD150 most except the PD150 at DV LP!!! to get the run time for a show that is going to be close to 90 mins. I do the editing and do not have a problem with sync most of the time. I also record to a ZOOm H4 set at front of theatre. I use Edius PRO3 to do the video editing and have little problem syncing up the cameras using the audio waveform. Sound mixing is done in Vegas 7 that is able to stretch and match audio perfectly from all cameras if needed( I output audio from timeline in Edius and import into Vegas so they are close in sync anyway). Vegas has the advantage of releasing audio from video frame sync to audio clock rate. Just start all cameras at beginning and let them run till they need a tape change. Make sure only one camera at a time does a tape change and you will have no problem resyncing. The most important thing is do not start and stop individual cameras to save tape!!!! Let them run as long as possible. Bottom line any reasonable set of DV cameras can be used, discipline in recording is important ( don't stop the cameras), learn to sync in your NLE and I have to recommend Vegas for the audio editing because of its ability to really sync up audio to a reference audio. Ron Evans

June 26th, 2007, 04:35 PM	#6
Tom Wills Major Player Join Date: May 2005 Location: Philadelphia, PA Posts: 326	When I did a multicam show, I was running with such an oddball setup that it wasn't even remotely possible to genlock, not to mention the size of the space we were in. We had my Panasonic DVC60 in the back of the room getting XLR feeds from the soundboard, and a Canon XL2 in the front right, using its shotgun for audio and getting closeups, and we had a "backup" at the front left, which was a Canon ZR60. So, what I had my crew do was change tapes every time they ran out, and I changed tapes after 40 minutes. That way, it was impossible for there to be no camera rolling. That way, in Final Cut, I just would put down and sync based upon picture camera 1 to camera 2, then sync camera 3 to camera 2, then when camera 1 cut, I'd then re-sync it to camera 2, and then when camera 2 cut, I'd then re-sync it to camera 1, and so on and so forth. Certainly not the easiest edit I've ever done, but not that bad.

June 26th, 2007, 05:25 PM	#8
Richard Alvarez Inner Circle Join Date: Sep 2002 Location: San Mateo, CA Posts: 3,840	Jon, I'm in agreement with everyone else, any decent Prosumer cams running concurrently should allow you to cut without ANY drifting in synch. The 'free run' tip I gave in my post, will insure that REGARDLESS of stopping and starting the cams, they will have the EXACT SAME timecode for the exact same moments. Making synching even easier than using a flash or slate. It's a tip, but not necessary.

June 26th, 2007, 05:49 PM	#9
Frank Simpson Major Player Join Date: Jun 2007 Location: Bozeman, MT Posts: 217	I recently did a 3 camera shoot with 2 Canon GL2s and a GL1. Fortunately each session was just under an hour, so running out of tape wasn't an issue. I did use a slate for sync each session, but I was anticipating some drift in post. Much to my delight, when I brought everything into FCP it was extremely easy to sync, and there was no drift at all in over 16 hours of captured footage!