Audio Drift for long concert

Report · Oct 05, 2019

I have the following file structure from a 2.5 hour continuous performance. Cam A (multiple .mov files),
Cam B (multiple .mov files)

Cam C (multiple .mov files)

Cam D (single mp4 file)

Audio (single file from the mixing board)

I try to create a multiple camera sequence, and things seem to all line up, but the audio from the board starts to drift as the concert goes on. Specifically by the end, the audio from the board is faster. I’d also like to say that I’d like to keep the audio at 100% volume and cam D’s audio at about 25% volume as it has audience reactions (all other audio will be muted). I’ve tried changing frequency rates and bit rates, I can’t seem to get the audio from the board to sync. Any thoughts?

I should meniton that if i don't throw the audio from the board in there, it all seems to sync up.

EDIT:

Cams A, B, and C, and D have their audio at 48khz 16 bit. The audio from the board was at 96khz and 24bit. I did try boucning it in Logic Pro X to match 48khz 16bit, but the issue was still there.

Thanks,
jas

Report · Oct 05, 2019

What is the frequency of the separate audio against the camera audio files? I've known of situations where changing the frequency was a fix.

But a couple times, it was a simple time-change for one audio file that fixed things.

Neil

Report · Oct 06, 2019

Hi Neil,

Cams A, B, and C, and D have their audio at 48khz 16 bit.

The audio from the board was at 96khz and 24bit. I did try boucning it in Logic Pro X to match 48khz 16bit, but the issue was still there. How did you do the simple time change that might help? Any other ideas?

thanks,

jas

Report · Oct 06, 2019

Unless sync locked all cameras and audio recorders will drift over time, how far are your tracks out at the end of the recording?

Report · Oct 06, 2019

Hi Richard,

I'm not sure how to measure that. Just a guess by watching it would be like half a second off.

thanks,

jas

Report · Oct 07, 2019

gotta say I've been working with multiple cameras and a separate digital audio recorder that were not synch locked for many years without any noticeable synch drift issues in programs well over an hour. How was the audio from the board recorded? if the sampling rate is 44.1, I'd resample to 48k to match the video cameras (assuming you were using video cameras that record 48k).

Sounds like it's probably caused by how the audio board was recorded. I once had a multicamera shoot with separate audio recorded professionally and the audio would not synch up. Turns out the audio engineer and added timecode the the wave file that was causing the problem... Anyway, you can change the duration of the audio file to match the camera audio without changing the pitch... Audition will do a much better job than doing it within premiere (at least in my experience). If you need help figuring out the speed adjustment, post back... I've figured out a few tricks...

Report · Oct 07, 2019

Hi mgrenadier, Cams A, B, and C, and D have their audio at 48khz 16 bit. The audio from the board was at 96khz and 24bit. I did try boucning it in Logic Pro X to match 48khz 16bit, but the issue was still there. Id love to get your tricks. I tried using the stretch tool in audition, but didn't have much luck.

Report · Oct 07, 2019

hmm. sounds odd. OK, line up the audio at the beginning of the video. Go down to near the end and find a place to synch for example the first sound of applause often works. I put markers on both the timeline and the video and audio clips. Keep adjusting the speed of the audio clip using the speed duration option in the clip menu (or select the clip in the timeline and hit command-j (at least on the mac) and make sure maintain audio pitch is checked until the markers at the end line up. As I said, if you've got the full cc suite, sending to audition will more than likely do a better job. You might also be able to use logic to do the speed change. It's been years since I worked in logic...

Report · Oct 08, 2019

hi, thank you for the help. i do have the full suite. I'll try in audition and see if that works out and follow up back here. It might be a few days.

Report · Oct 14, 2019

hi, sorry for the delay in reply but I wasn't able to test this out until tonight. so what I did try was to open the premiere project in audition, and then use the stretch tool. I picked a final hit on the drum to line up between the board track and the cam d track. That seemed to work, when I spot checked the end of the recording, it was all in sync. I was happy. But then I checked the beginning of the recording and now that is out of sync. So it seems like the problem just moved around. Any other suggestions?

Report · Oct 16, 2019

Ok, here is where i'm at with this. I broke the 2.5 hour concert audio file form the board down into 5 min clips. I then created a multicam sequence, with the board audio, and cam's a, b, c, and d. I dragged the 5 min clips up all on to one audio track, deleted the audio from all teh cameras except camera d. i open the premiere project in audition. i start at the end (last 5 min clip) and zoom in real close and align it (checking the beginning, middle, and end of the 5 min clip). so far i haven't done any stretching, but i do notice that when zoomed in real tight, there are tiny gaps between the 5 min clips. This seems to be working, i've only done a few so far and working my way forward. I'll let you all know the progress