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Author Topic: Video at front, audio at back....timing issues?  (Read 6925 times)

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Offline Ringside

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Video at front, audio at back....timing issues?
« on: January 04, 2014, 01:25:40 PM »
Hello all,

First let me say I only record in bars or the smallest of clubs. I use a camcorder and record a separate audio source from a recorder that I have mounted on a DIY bracket, screwed into the camera.

In some clubs when I want to record up close, I can't always do it as I lose vocals from poorly placed PA speakers, so I was thinking of leaving the audio recording further back then I'd get a better mix.

In a small bar would timing be an issue when syncing? I would expect a problem in an arena but I'm not sure about a small place.

Thanks!

Offline achalsey

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Re: Video at front, audio at back....timing issues?
« Reply #1 on: January 04, 2014, 02:18:20 PM »
Yep.  No two recorders will ever record at the exact same time unless actively synced together at the time of the recording.  That said, in a small club it will most likely be a relatively minimal difference.  You might be able to get away with it if its less than 30' or so, but in my experience even then you start to get a slight discrepancy between stage and back of the room.

Do start a new recording for each song or just keep it rolling through the set?  If you just keep it rolling and your recording is in relative sync with your video even at the exact same spot after an hour or so you are very lucky.

Sound travels at roughly 10' per .01 seconds.  In my experience, once you get off by even a couple hundredths of a second between AUDIO sources it becomes noticeable.  Video might be a little more forgiving, but not positive.  For the sake of accuracy, I will always manually line up two different sources.

Offline stantheman1976

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Re: Video at front, audio at back....timing issues?
« Reply #2 on: January 04, 2014, 05:24:24 PM »
Between different devices yes, there will always be some time drift. If you are using digital recording devices the drift will be constant and can be adjusted easily. I use Vegas Pro to edit which can easily stretch or shrink a clip on the time line.

Offline Ringside

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Re: Video at front, audio at back....timing issues?
« Reply #3 on: January 06, 2014, 12:33:10 PM »
Thanks for the replies.

So far I've been using a camcorder with a seperate audio source then mixing them in Vegas. Once the initial synching is done, I have never noticed any loss as the show progresses but keep in mind I only really go to see punk bands playing 20 - 45 minute sets. I'm sure if maybe I'd got a 2hr show I could detect something.

I'm hoping that due to the short set times and small bars I'm taping in, there wouldn't be too much of an issue in recording audio from further back.

Offline ScoobieKW

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Re: Video at front, audio at back....timing issues?
« Reply #4 on: January 06, 2014, 03:00:34 PM »
Thanks for the replies.

So far I've been using a camcorder with a seperate audio source then mixing them in Vegas. Once the initial synching is done, I have never noticed any loss as the show progresses but keep in mind I only really go to see punk bands playing 20 - 45 minute sets. I'm sure if maybe I'd got a 2hr show I could detect something.

I'm hoping that due to the short set times and small bars I'm taping in, there wouldn't be too much of an issue in recording audio from further back.

Two types of sync issues to consider.
First, is clock drift between the two recorders, sounds like you're used to this one.
Second is placement. The recorder in the back of the room will be several milliseconds behind the upfront recording due to the speed of sound. Find a loud drum kick, and slide the two sources until they match.
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Offline Teen Wolf Blitzer

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Re: Video at front, audio at back....timing issues?
« Reply #5 on: January 06, 2014, 04:08:10 PM »
Plurel Eyes.  I waved it off at first but it is AWESOME.  :facepalm:

Offline willndmb

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Re: Video at front, audio at back....timing issues?
« Reply #6 on: January 06, 2014, 11:19:08 PM »
Plurel Eyes.  I waved it off at first but it is AWESOME.  :facepalm:
have you used it for long videos and checked for drift?
It used to be that it synced the start but that was it
IMO it's basically only good for multi cam and that's questionable too
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Offline Ringside

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Re: Video at front, audio at back....timing issues?
« Reply #7 on: January 07, 2014, 08:16:08 AM »
I've got Plural Eyes and I found it fine up until a while ago, For some reason my last 2 recordings failed to sync. I have no explanation why. I just manually set it.

Offline ScoobieKW

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Re: Video at front, audio at back....timing issues?
« Reply #8 on: January 07, 2014, 10:39:21 AM »
short answer Ringside?

Yes time alignment will be an issue. But it will be the same issue that you have with the camera and recorder in the same location.

Syncing two sources. This time there will be a few milliseconds more gap between the two.

The difference in timing between hitting record on the two devices will be larger than the time arrival difference.

Enjoy.
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Offline guitard

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Re: Video at front, audio at back....timing issues?
« Reply #9 on: January 12, 2014, 11:19:24 AM »
I have found on a fairly consistent basis that a distant shot in an arena will be three or maybe four frames off (NTSC 30 frames/sec) - or roughly a tenth of a second off.  Which is very noticeable, i.e., you hear the drum beat but the drummer is holding the stick straight up.

In a small club, the difference is so negligible, I don't even bother checking for it.  It will certainly be less than one frame, and for 99% of the people who will ever see something like that - they will never notice.  Really, the only way you'd be able to notice would be if you had a really clear shot of the drums or possibly a closeup of a keyboard.

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Offline Ringside

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Re: Video at front, audio at back....timing issues?
« Reply #10 on: January 21, 2014, 08:22:25 AM »
Thanks for all of the replies everyone. I'm pretty much done with my project now. It was a 2 cam shoot, one at the front of the stage, and one at the back of the room by the sound desk. The audio recording was also captured from the rear.

I used Vegas to mix all three sources and found that maybe 30 mins in, the audio and front cam had gone out, just enough to notice on close ups of singing. It wasn't a great deal at all but I corrected it while I could. Had I not noticed and completed the project, burned the DVD and THEN found out, I wouldn't have even gone back as it was very minimal.

Thanks again people.

Offline Tom McCreadie

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Re: Video at front, audio at back....timing issues?
« Reply #11 on: February 01, 2014, 04:26:55 AM »
In everyday life, it's completely _natural_ to encounter a time difference between the arriving sound and the arriving picture. For instance, if we see someone 50 yards distant in the arena car park slamming his car door, the picture event precedes the audio event - like a mini lightning/thunder.  :-)

So for perfection in a video recording that contains a mix of wide-angle and close-up shots, we should ideally arrange to have a tighter sound/picture synchronization when we zoom in close...and a slightly bigger synch disparity when we pan out wide.

Offline guitard

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Re: Video at front, audio at back....timing issues?
« Reply #12 on: February 01, 2014, 02:31:36 PM »
In everyday life, it's completely _natural_ to encounter a time difference between the arriving sound and the arriving picture. For instance, if we see someone 50 yards distant in the arena car park slamming his car door, the picture event precedes the audio event - like a mini lightning/thunder.  :-)

So for perfection in a video recording that contains a mix of wide-angle and close-up shots, we should ideally arrange to have a tighter sound/picture synchronization when we zoom in close...and a slightly bigger synch disparity when we pan out wide.

Are you saying it would be best to leave the distant angle out of sync, because that's how it naturally occurs?
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Offline Tom McCreadie

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Re: Video at front, audio at back....timing issues?
« Reply #13 on: February 01, 2014, 04:32:01 PM »
So for perfection in a video recording that contains a mix of wide-angle and close-up shots, we should ideally arrange to have a tighter sound/picture synchronization when we zoom in close...and a slightly bigger synch disparity when we pan out wide.

Are you saying it would be best to leave the distant angle out of sync, because that's how it naturally occurs?

Ach, my comments were rather theoretical in character and I don't think you'll have too many concerns in a small bar situation. If your mic/camera is, say, 10 yards distant, the sound emerging from a vocalist's lips will arrive (directly) 27 msec later at your mic. But there again, it could well be a shorter interval  if the singer uses the house  PA, whose speakers happen to be sited close to your rig. And longer too, of course,  for any reflected, ambient sounds.

 I would just leave that distant mic recording unadjusted, but scrutinize any video material containing extreme head & shoulders close-up shots of a singer or a concert-compere, to check if anything appears unnatural - i.e. "'too early lips". People tend to be more sensitive to oddities with singing faces than with guitar strums or drum whacks.  [With luck, the lips may be hidden behind a big mic...or, in an arena context, too far away to be noticed, anyway - unless it's Mick Jagger.   :-)]  If you later implement an extra mic up close, consider delaying it to match your distant mic.

Offline guitard

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Re: Video at front, audio at back....timing issues?
« Reply #14 on: February 01, 2014, 06:16:24 PM »
So for perfection in a video recording that contains a mix of wide-angle and close-up shots, we should ideally arrange to have a tighter sound/picture synchronization when we zoom in close...and a slightly bigger synch disparity when we pan out wide.

Are you saying it would be best to leave the distant angle out of sync, because that's how it naturally occurs?

Ach, my comments were rather theoretical in character and I don't think you'll have too many concerns in a small bar situation. If your mic/camera is, say, 10 yards distant, the sound emerging from a vocalist's lips will arrive (directly) 27 msec later at your mic. But there again, it could well be a shorter interval  if the singer uses the house  PA, whose speakers happen to be sited close to your rig. And longer too, of course,  for any reflected, ambient sounds.

 I would just leave that distant mic recording unadjusted, but scrutinize any video material containing extreme head & shoulders close-up shots of a singer or a concert-compere, to check if anything appears unnatural - i.e. "'too early lips". People tend to be more sensitive to oddities with singing faces than with guitar strums or drum whacks.  [With luck, the lips may be hidden behind a big mic...or, in an arena context, too far away to be noticed, anyway - unless it's Mick Jagger.   :-)]  If you later implement an extra mic up close, consider delaying it to match your distant mic.

I've authored several hundred multi-cam DVDs, and of course, many of them included a distant angle (or two or three).  I can say from experience that the best thing is to simply get everything in sync.  Once you get experienced at it - it's not that hard to do.

Keep in mind - in a big arena, the distance is going to create enough of a delay for people in the cheap seats that when the drummer's sticks are straight up the air - you are just then hearing the drum beat.  And these days almost all arena acts have a large video screen as a backdrop to the stage (probably so they can justify making people in the 'cheap' seats pay $100 - but that's a story for another thread).

I almost always use the drummer's drumsticks to get things synched up.  Typically, I get one angle synched rock solid - and then I use that angle to synch other angles by lowering the opacity of the new angle and comparing the movements with the angle that's locked in.  There are other tricks to the trade for synching - that's just one.

Occasionally, however, you will run across the odd situation where the big screen isn't in synch with the performers on the stage (that monstrosity that U2 had a few years ago was often times not in synch with the guys on the stage).  In situations like this - it's a judgement call:  which is the lesser of two evils?  Having the big screen synched with the other angles -- or -- having the performers on stage in synch with the other angles?
Mics: Schoeps MK41s & MK41Vs >:D
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Video: Canon HF G70 (4K), Sony FDR AX100 (4K), Pany ZS100 (4K)
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