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-   -   Tone for syncing that cannot be heard (http://www.dvinfo.net/forum/all-things-audio/494260-tone-syncing-cannot-heard.html)

Vince Pachiano April 7th, 2011 02:21 PM

Tone for syncing that cannot be heard
OK, I'm still a novice, but I video-tape my daughter's dance recital with 2 DV camera's
Currently to synch the audio, I have one of those "dog clickers" that are used to train dogs.
I snap it between the two microphones as a poor-man's clap-board just before she performs.
During post, I can "see" the click on the two audio waveforms, and easily synch the two camera's

Looking forward to this year, I'm wondering if there is a quick-sharp tone (either high pitched, or low pitched)
that I can embed in my daughter's audio CD that will be captured onto DV and clearly show-up on the waveform, but not be audible to the audience?

Rick Reineke April 7th, 2011 04:06 PM

Re: Tone for syncing that cannot be heard
It's possible, but it would require a direct feed from the CD player on one track of both cameras. Above or below the frequency range of the PA/playback system. A blip around 40-50Hz may not be audible if there is no sub-woofer. On the other end of the scale, a blip around 15KHz may also be inaudible or at least unnoticed but would clearly be visible on the timeline audio waveform. If.. your cameras audio chain components go that high. This would require some testing but should be 'doable'.

Evan Donn April 7th, 2011 05:48 PM

Re: Tone for syncing that cannot be heard
Not sure what you're editing with, but Pluraleyes would be great for this... as long as the cameras are both recording similar audio it should be able to sync them automatically.

Stan Harkleroad April 7th, 2011 07:58 PM

Re: Tone for syncing that cannot be heard
I don't know about putting a signal in the audio coming from the mixer. I always sync manually using the waveforms in Vegas and it's not that hard when you know what you're doing.

A tip for the 2 cams though, if people are taking photos you can use a camera flash to sync the video. The flash will take up exactly 1 frame of video and makes it nice and easy to sync. I do it for weddings, beauty pageants, and high school graduations I film.

Christian Brown April 8th, 2011 09:01 AM

Re: Tone for syncing that cannot be heard

Originally Posted by Rick Reineke (Post 1636572)
...A blip around 40-50Hz may not be audible if there is no sub-woofer. On the other end of the scale, a blip around 15KHz may also be inaudible or at least unnoticed but would clearly be visible on the timeline audio waveform...

If the PA is capable of playing those, they WILL be heard by most people in attendance.

To the OP, I really like you solution of using the dog "clicker". Personally, I've never needed to lay down any sort of sync for event videos. If all the cameras are recording the same musical/theatrical performance, it is pretty easy to see where they line up. Just use a snare-hit, a downbeat, a yelp, a doorslam, etc instead of a deliberate click.

Basically, I wouldn't worry about sticking any sort of tone on the CD. The way it lines up should be obvious.

Good luck!

Greg Miller April 8th, 2011 09:28 AM

Re: Tone for syncing that cannot be heard
Interesting question. Which suggests two more questions to my mind:

1.) Are both cameras the same distance from the stage?

2.) What's the purpose of being in sync? To have the action in sync, or to have the audio in sync?

Remember, sync at the back of a large auditorium is different from sync in the first row, since sound (1,100 feet/sec) is much slower than light (186,000 mi/sec). If the cameras are a different distance from the stage, then unless the clicker is exactly the same distance from both cameras, audio sync will be different from video sync.

So if the cameras are different distances from the stage, and you want to have the action in sync, then Stan's suggestion to sync on a strobe flash is probably the best. I never would have thought of that (being an audio guy) but it is elegant in its simplicity.

If you want to stick with an audio sync solution, and you don't want to stand up with your clicker, you could make up a similar track on a CD... maybe a sequence of five clicks, with different time intervals between them. Play it back on the house system, loud enough to be audible over the mumble of the crowd before the show starts. (Sure, it would be audible, but it wouldn't be objectionable... I'd guess that most people wouldn't even notice it.) And if one of the clicks were covered at one camera (because of a nearby cough or whatever) having different lengths of time between different clicks would make it possible to identify which was click #2 and which was click #3 (for example) when the time comes to sync up the tracks.

Vince Pachiano April 10th, 2011 05:46 PM

Re: Tone for syncing that cannot be heard
Well, I guess I should have fully described my workflow before asking you kind people for solutions

1. Camera A - Tight shot that follows the action; Camera B - Static wide shot, the cameras are located next to each other
2. The recital has about 60 numbers, I start/stop the tape(s) between each number so that each number is in its own "scene" during Post
3. Just before the crowd hoots-and-hollers I "click" right between the two cameras which puts a sharp spike onto the Audio waveform

During Post, I import both tapes
4. So now I have Scene 1A and Scene 1B (camera A&B)
5. I locate the click on both audio tracks, I then Mark In to delete everything before the click
6. I output Scene 1A to an AVI file (lets call it Scene 1C)
7. I copy the audio track from 1A onto the audio track of 1B
8. I output Scene 1B to an AVI file (lets call it Scene 1D)

I now have two AVI files that are perfectly synched, and have the same audio track.
Now, you are asking WHY do I do this? I am self-taught on Pinnacle Studio 12, and
ff both AVI's are synched, I can easily mix them on the timeline.

So my original question was could I embed a tone in the music CD that is played for the audience that would be picked-up by the camera mic, but not disturb the audience. There would need to be several during say the first 10 seconds since I never know when people quit hooting-and-hollering

Some issues with previous suggestions:
1. Camera B is wide, so it is sometimes hard to visually sync, say a Dancer lifting their shoe, etc.
2. No flash photography is allowed, so I cannot sync on a flash. I do own some Photographic strobes with a wireless transmitter that I could trip at the start of each scene (he-he), but I'm afraid that would invite other people to think they can also use flash photography.

Adam Gold April 10th, 2011 06:08 PM

Re: Tone for syncing that cannot be heard
We have a similar workflow, but we use four cams and just use the waveforms to sync. And we never stop recording once we start (except for intermission). Then we only need to sync once at the beginning of each show. After everything is edited, we delete the parts between the dances/songs we don't want.

No click. No flash. No problem.

Not sure why you need to re-encode and output and re-import, but then I don't know Pinnacle. We mix down the sound from our four cams plus a Zoom and output a final mixed track, but you could also just use one track and mute all the others. And for a dance recital you should be importing the audio from the original CD and not using camera audio at all (except for tap and audience applause).

As has been mentioned before in this thread, if you don't want even that much effort, Plural Eyes is for you. But you'd need to switch to an editor they support. It's easier to edit with an NLE that has a real multicam function anyway -- does Pinnacle have this?

Edit: I just did some reading on how you can do multicam with Pinnacle 12. I have to tell you I'd kill myself if I had to work that way. If you're just shooting DV (not HDV or HD of any kind) then download and try the free trial of Premiere CS5 and check out the multicam editing feature. It will blow you away by comparison.

I know how frustrating it can be when you ask one question and people answer another different one in an attempt to be helpful. So no, I don't think the type of tone you want is possible, because if the PA can play it and the cam can hear it, I think many in the audience will as well, and this type of thing 50 or 60 times per show would make them stampede up the aisles and kill you. I think the very clever method you are currently doing is probably the best way if you want to stick to your current workflow.

Greg Miller April 10th, 2011 10:15 PM

Re: Tone for syncing that cannot be heard

No, there is nothing you can embed within the recital music track that you can reliably sync to without being audible to the audience (unless all the audience members have badly defective hearing). This is especially true because of the unknown quality of the sound system, reverberation/echo within the auditorium, unknown background noise, etc. Abandon that idea.

Therefore, I will answer a different question (just to fit in with the overall scheme of things)...

Are your cameras located where they would be distracting/annoying to the audience, or are you fairly unobtrusive? You could easily rig some sort of flashing light that would be quite inconspicuous. It wouldn't have to be a bright photographic strobe. It could just be a small LED mounted on a black plastic box, which you hold up within sight of both cameras... the visual half of a clap board. It wouldn't even need to be in focus; focus won't affect the time when the light goes on or the time when it goes off. The whole thing might cost $10 for parts at Radio Shack.

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