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  #1  
Old 11-30-2004, 08:27 AM
Studio Dweller Studio Dweller is offline
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Default Music video sync issue

Hi,

I'm working on some audio and video from a (low budget) music video shoot. During the shoot, the playback was handled by a portable CD player plugged into AC to which the band lip-synch'ed. I'm aware that this is far from being an optimal set-up, but it's all that was available. Video was shot on a Canon XL-1s. I'm now trying to sync shots from the video to the WAV file that was used to burn the playback CD, but I'm having sync issues. All I've done so far is sample-rate-convert the WAV file to 48KHz before importing it into Final Cut Pro HD. I'm doing this as a favor for a band and I don't do post work so I'm not sure if I need to apply pull-up or pull-down to sync things up. Any help would be greatly appreciated.

Thanks!
-Larry
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  #2  
Old 11-30-2004, 09:15 AM
Frank Kruse Frank Kruse is offline
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Default Re: Music video sync issue

what kind of sync issues? drift, everything late, everything early, everything too fast/slow etc. etc. etc. etc. what video-system PAL/NTSC?
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  #3  
Old 11-30-2004, 09:19 AM
cmaynes cmaynes is offline
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Default Re: Music video sync issue

Hi Larry-

It sounds like the shoot was done to video, so Pull Down should not be an issue-

In the material losing sync, It would be helpful to further detail what is happening-

A couple things to investigate are-

How did the Music make it to the camera- was it directly inserted via a line input?

If this is the case, and you loaded analog to whatever rate you are working at, all should still be OK.

Also- With the video file, was it loaded on to the computer? is it conformed to the sessions timecode rate? You should check that out- Most of the time, I think it wise to work in 29.97 Non Drop, however certain things require Drop Frame timecode to be used. These all need to be checked.

cheers!

charles maynes
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  #4  
Old 11-30-2004, 09:33 AM
Studio Dweller Studio Dweller is offline
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Default Re: Music video sync issue

Quote:
what kind of sync issues? drift, everything late, everything early, everything too fast/slow etc. etc. etc. etc. what video-system PAL/NTSC?
It's NTSC. I added a 2-bar click countoff at the beginning of the song for the playback at the shoot and I have the audio from the camera mic to use as reference. When I line up the clicks from the camera audio to the studio WAV file, it's in sync for a while, but it doesn't too long for the audio to become out of sync. I was working on this late last night and at the moment, I can't remember if the audio was late or early, but I will check tonight and post here. Most of the cuts will be very short so I think that I'll be able to nudge things into position, but I'm just wondering in this situation if there was a standard practice that should be taken with the audio (or the video).

Thanks very much for the help.
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  #5  
Old 11-30-2004, 09:47 AM
Studio Dweller Studio Dweller is offline
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Default Re: Music video sync issue

Quote:
Hi Larry-

It sounds like the shoot was done to video, so Pull Down should not be an issue-

In the material losing sync, It would be helpful to further detail what is happening-

A couple things to investigate are-

How did the Music make it to the camera- was it directly inserted via a line input?

If this is the case, and you loaded analog to whatever rate you are working at, all should still be OK.

Also- With the video file, was it loaded on to the computer? is it conformed to the sessions timecode rate? You should check that out- Most of the time, I think it wise to work in 29.97 Non Drop, however certain things require Drop Frame timecode to be used. These all need to be checked.

cheers!

charles maynes
Charles,

The only audio captured by the camera was from the camera-mounted microphone. I foolishly thought that if I had the camera mic capture the 2-bar click countoff from the CD playback through the PA system, I could easily line things up later with the studio produced WAV file of the song.

Quote:
With the video file, was it loaded on to the computer? is it conformed to the sessions timecode rate?
I apologize for my lack of post knowledge, but could you elaborate on conforming? The video was captured via Firewire into Final Cut Pro. I also went into Pro Tools to the session where I added the 2-bar countoff for the playback CD and sample-rate converted to 48KHz. I imported that 48KHz file into Final Cut Pro and that's when I discovered the sync problems. I have to check tonight to see if the audio was late or early and I'll post here when I do.

Thanks for all the help!
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  #6  
Old 11-30-2004, 10:40 AM
The Cobbler The Cobbler is offline
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Default Re: Music video sync issue

I've tried something similar with a couple of commercial CD players. I found that not all of them play CD's at the same speed. Their speed can be off by 1% or more.
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  #7  
Old 11-30-2004, 11:11 AM
David Sandwisch David Sandwisch is offline
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Default Re: Music video sync issue

How far out of sync are we talking? Does the video progressively get more out of sync the furthur down the timeline you go? In theory what you did should work just fine if you recorded the music via a line input on the camera from the CD player. The only problem I see is that you recorded the music through the camera's microphone which was pointed at a PA. The distance the camera was from the PA will affect how insync the sound appears to be. For example if the distance between the camera's mic and the PA was 100 feet, the sound of the music you recorded in-camera vs the CD track would have a delay equal to the time it took the sound to travel the 100 feet to the microphone. Sound doesn't move very fast compared to light. That's why delay speakers at concerts need to have the audio that is sent to them electronically delayed so people don't hear two sounds out of sync. If the camera was constantly changing distances between itself and the PA over the course of your shoot, the delay in audio would be constantly shifting to reflect the different distances from shot to shot. Does that make sense? It would probably be differences of milliseconds or at most a frame or two but if you are off by seconds then I'm stumpted.
In the future you should always connect the CD player directly to the camera via a line input. There won't be a delay because the signal will travel down the cable at the speed of light.
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  #8  
Old 11-30-2004, 12:07 PM
Studio Dweller Studio Dweller is offline
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Default Re: Music video sync issue

Quote:
How far out of sync are we talking? Does the video progressively get more out of sync the furthur down the timeline you go? In theory what you did should work just fine if you recorded the music via a line input on the camera from the CD player. The only problem I see is that you recorded the music through the camera's microphone which was pointed at a PA. The distance the camera was from the PA will affect how insync the sound appears to be. For example if the distance between the camera's mic and the PA was 100 feet, the sound of the music you recorded in-camera vs the CD track would have a delay equal to the time it took the sound to travel the 100 feet to the microphone. Sound doesn't move very fast compared to light. That's why delay speakers at concerts need to have the audio that is sent to them electronically delayed so people don't hear two sounds out of sync. If the camera was constantly changing distances between itself and the PA over the course of your shoot, the delay in audio would be constantly shifting to reflect the different distances from shot to shot. Does that make sense? It would probably be differences of milliseconds or at most a frame or two but if you are off by seconds then I'm stumpted.
In the future you should always connect the CD player directly to the camera via a line input. There won't be a delay because the signal will travel down the cable at the speed of light.
The sync progressively got worse further down the timeline and I'd say it was about a second off by the end. I appreciate what you're saying about running the audio to the line in on the camera, but many of the shots were on a long moving jib arm which made it difficult to run cables all the way to the separate room where the mixer and amps were. I also didn't want to go through a less than stellar A/D conversion for the final audio by relying on the camera's on-board audio. My goal is to use the original WAV file and I had no intention of using the mic audio for anything but a potential sync reference at the beginning of the song.

I also appreciate the issue of time delay and yes, if the camera was an appreciable distance from the PA at the time of the clicks, that would account for a sync discrepancy, but then the newly placed audio (the original studio recording) should be off by a constant amount unless the playback speed varied during the shoot. This was shot in a rehearsal studio and the guys in the band were a fixed distance from the PA cabinet. The singer was only about four or five feet from it so the delay wouldn't be significant and since the distance didn't vary, whatever delay was there would be constant. The bottom line is that even if I try to sync by a visual reference only (ie: a drum hit), the sync still gets progressively worse further down the timeline. I'll check to see how much it's off and post what I find later.

Thanks again.
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  #9  
Old 11-30-2004, 08:24 PM
Studio Dweller Studio Dweller is offline
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Default Re: Music video sync issue

OK, I checked it out and if I sync the click countoff on the WAV file to the clicks on the camera audio so the first beat of the song is in sync, the WAV file is 26 frames late by the end of the 3:11 song and about 13 frames late at the mid point. So does this look like the it was probably just a matter of the CD player that was used for playback during the shoot being a little fast? Any suggestons on what the best approach would be to remedy this?

Once again, thanks for the help with this.
-Larry
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  #10  
Old 11-30-2004, 09:42 PM
sleadley sleadley is offline
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Default Re: Music video sync issue

I have also seen the problem with CD Players playing off speed. That is the most likely scenario. For any critical playback we always use a sync locked source and to a sync test before shoot.
Now to help you in this case I think you are going to have to get the video editor to cut out the frames and keep the sync.
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