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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old July 24th, 2007, 11:33 PM   #1
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Can someone make sense of this email?

This is an email I just received from a TV guy on the project.

"I forget. Can your cameras receive SMPTE time code like the XL-H1? This will be critical for sync'ing up to the audio track.

I just checked the XL-H1 and the 60i will play back as 29.97DF in SMPTE speak. There is no provision for 24FPS in SMPTE. Sorry. When they do a 24 frame project on film and telecine it, it gets converted to SMPTE Drop Frame (29.97) with a 3:2 pulldown."

First off I have the XH-A1 and we are shooting a music video.
Can someone explain the email to me.. I'm not a techie kind of shooter.

I was wanting to use 24p with 5-6 cameras mix of XH-A1's and XL-H1's. The Audio is being captured separately. Is there something I should be knowing or asking?

(This is a follow-up post from my previous thread).. thanks!
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Old July 25th, 2007, 12:51 AM   #2
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This may be helpful:

http://dvinfo.net/canonxl2/articles/article11.php
Chris did a great article on how to fake the time code and sync things up... I believe the A1 will do the same thing as the H1 but in a different way....

That 'may' help with the first part but I couldn't tell you about the 2nd part...
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Old July 25th, 2007, 04:07 AM   #3
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Quote:
Originally Posted by Michael Padilla View Post
This is an email I just received from a TV guy on the project.

"I forget. Can your cameras receive SMPTE time code like the XL-H1? This will be critical for sync'ing up to the audio track.

I just checked the XL-H1 and the 60i will play back as 29.97DF in SMPTE speak. There is no provision for 24FPS in SMPTE. Sorry. When they do a 24 frame project on film and telecine it, it gets converted to SMPTE Drop Frame (29.97) with a 3:2 pulldown."

First off I have the XH-A1 and we are shooting a music video.
Can someone explain the email to me.. I'm not a techie kind of shooter.

I was wanting to use 24p with 5-6 cameras mix of XH-A1's and XL-H1's. The Audio is being captured separately. Is there something I should be knowing or asking?

(This is a follow-up post from my previous thread).. thanks!

While everything this guy is saying is true, not much of it applies to you. When shooting DV for concerts or music videos, remember a couple things:

1-DV (or HDV) cameras all run off of a very accurate crystal clock. Anything recent, and especially recent and of the same make/manu are virtually guaranteed too stay in sync with each other. If you get them into the computer and something is out of sync, then it is your software playing things offspeed, or has dropped frames upon capture or playback.

2-If you record your audio digitally, and with even slightly modern digital gear, your audio will not drift either.

Ok, so now that you know that your cameras and audio recorder are recording the same material at the same speed...there's the issue of synchronization.

Old school super-pros will tell you you need to genlock the cameras (which keeps the cameras making frames in lock-step), and you need to feed them timecode for syncing with audio. I'll address each in order:

1-Genlock was necessary (and still is, sometimes) for live switching cameras. When genlocked, all cameras make a picture at the exact same instant, and the signals from each camera were all "synced". For post editing purposes, this is not really necessary, because the most one camera could ever be off from another would be one half-frame if they were not genlocked. Half a frame of error is not really noticeable.

2-Timecode feed for syncing purposes is a post-speed issue. Even when I cut my first concert ever with 5 cameras, and I was painfully slow at getting the camera takes lined up in sync on the timeline, I bet it didn't take me more than an hour.

So if you don't feed timecode, you'll have to sync up the cameras by hand on your timeline, using audio from each camera mike. I'll start by putting one camera on the timeline, and then lay a second on another track, with audio as well. You can then fine tune their sync pretty easily by listening to the amount of echo between the two tracks, and then moving one of them frame by frame in the right direction until the audio "echo" disappears. When they're in sync, there will be no echo. Lay another camera (and it's audio) on top of these two, and repeat.

This method relies on each camera's onboard mic, so make sure the ops have them working and levels usable.

There once was a time before NLEs when syncing multiple camera tapes without timecode would have been a nightmare. I do it now for 8 camera concerts in about 20 minutes.

For the 24fps/timecode/etc comment he has above, it doesn't apply to you. You'll be cutting on a 23.98 timeline most likely, something old-guard broadcast folks never do (or very, very rarely).
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Old July 25th, 2007, 08:29 AM   #4
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It's embarrassing to follow up on Nate's excellent post with such a brief reply, but here goes: Can your cameras receive SMPTE time code like the XL-H1? No. The XH A1 cannot receive SMPTE time code from an external source like the XL H1. However the XH G1 can. Hope this helps,
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Old July 25th, 2007, 08:52 AM   #5
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An alternative way to sync multiple cameras is to line up by a single image action seen by all, such as a flash.

It gets harder if the different cameras have random stops/starts rather than continuous footage.

When using sound to sync cameras, keep in mind that the speed of sound is roughly 1120 feet per second. So a camera that is 37 feet further from the sound source will "hear" it a frame later. Usually not an issue for cuts to different camera angles, views.
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Old July 25th, 2007, 10:16 AM   #6
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I still use a clapboard for syncing multiple cameras that don't have genlock, because generally I'm doing double system sound in those cases. However, lots of people use a still camera flash. With single system sound, this is probably better, actually. The flash will be one frame in duration, and all you have to do is line up each camera's footage on the timeline.

Roll all cameras, wait a few seconds to be sure everybody's running, then pop the flash where all cameras can see it. If one camera is stopped, you have to do it again, so it only works when all cameras roll continuously.

If your time code on all cameras is set to free run, that can help too, and you can get the tc of each one started fairly close.
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Old July 25th, 2007, 10:18 AM   #7
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Oops, I just saw the link to Chris's article about syncing with free run. That's even better, since you can start all the time codes together with the remote.
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Old July 25th, 2007, 04:51 PM   #8
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Quote:
Originally Posted by Don Palomacki
An alternative way to sync multiple cameras is to line up by a single image action seen by all, such as a flash.
Quote:
Originally Posted by Bill Pryor View Post
Roll all cameras, wait a few seconds to be sure everybody's running, then pop the flash where all cameras can see it.
Don, Bill,

When shooting 24p or 30p with 1/48th or 1/60th shutter, some cameras will miss the flash in the vertical interval. There's a 50% chance the camera will not photograph it.

I've learned this the hard way.
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Old July 25th, 2007, 05:03 PM   #9
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Good point! Never thought about it.

Back to the trusty clapboard.
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Old July 26th, 2007, 08:34 AM   #10
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Typical electronic flash duration (usable light output) is on the order of a millisecond, and maybe much shorter if the flash is "quenched" by an auto exposure system, and that can be a problem is the exposure duration is less than the effective field capture rate.

The good old flash bulbs (remember them) had flash durations on the order of 1/30 or so.

Maybe use a flash light or other conventional lamp and sync on the light being turned ON or OFF.
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