FORUMS: list search recent posts

Sync Drift problem??? screen capture included

COW Forums : Audio Professionals

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
Al Bergstein
Sync Drift problem??? screen capture included
on May 3, 2017 at 10:47:17 pm

Hi guys. I was working on a project today, did a sync of three cameras and an audio track from a Tascam DR680 prosumer deck that my field sound guy has used for a couple of years now. We have never experienced this problem before, and after looking at it I would have to say that I wonder if this is a sync problem associated with the timing chip? Take a look and see what you think. Thanks in advance.



Al


Return to posts index

Al Bergstein
Re: Sync Drift problem??? screen capture included
on May 3, 2017 at 10:55:02 pm

By the way, I meant to mention that the track is recorded at 48kHz just like it always is. All cameras are synced to
Image Size: 1920 x 1080
Frame Rate: 29.97
Source Audio Format: 48000 Hz - compressed - Stereo
Project Audio Format: 48000 Hz - 32 bit floating point - Stereo
Total Duration: 00:04:31:15
Pixel Aspect Ratio: 1.0
VR Projection: None

Just so the obvious questions are answered.
We've worked with this footage and this recorder for 47 videos now and this is the first time we've seen this.

Al


Return to posts index

Bouke Vahl
Re: Sync Drift problem??? screen capture included
on May 4, 2017 at 10:08:01 am

I'm with Richard.
If you can tell exactly how many frames it drifts over how much time, we can do math to see if it's a 'logical' pull-up/down problem or alike.
(That's typically a 0.1% drift, so get out your calculator.)

hth,

Bouke
http://www.videotoolshed.com


Return to posts index


Richard Crowley
Re: Sync Drift problem??? screen capture included
on May 3, 2017 at 11:58:22 pm

Can you identify which track is which?
Did all four pieces of gear (3 cameras, one audio recorder) go together or randomly.
Most of the clues one would need for troubleshooting are not included in your question.

Are you saying that it STARTED out-of-sync and then drifted into sync?
Can you put some numbers on this? Drift of a few frames in 10-20 minutes is rather common IME for prosumer gear that is not locked together.

---------------------------------------------------------------------------------
Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.


Return to posts index

Al Bergstein
Re: Sync Drift problem??? screen capture included
on May 4, 2017 at 2:24:30 am

Thanks. The bottom green track is the audio recorder and the upper tracks are the audio for the video. All ended in sync and in the past 43 videos we've shot on this project, never have I seen any drift at all.

There was no professional sync of the cameras and audio. I usually use a clap or a slate.

It started out of sync and drifted into sync, as these additional shots show.

The timeline shows about 20 seconds of the issue. It didn't drift *out* of sync, it drifted *into* sync.

These are far more than a few frames, as they are a couple of seconds out of sync to start.

Used two different scales here.. Click on the photos to expand them and see the timeline at the top.

Luckily, because it is at the beginning, I have a fix for it to cover the video with titles, etc. If it were farther in the shoot would have been a lost cause.





I'm buying a much more pro level sound recorder and telling my audio guy he'll have to use it. The new equipment will have jam time code so I'm hoping it will help.

Hope this helps! and I hope this is useful to others who face the issue of what kind of gear to buy/rent. Again, buy the best, though everything can fail.

Al


Return to posts index

Richard Crowley
Re: Sync Drift problem??? screen capture included
on May 4, 2017 at 3:03:01 am
Last Edited By Richard Crowley on May 4, 2017 at 3:03:59 am

Time code won't do anything for drift. It will only document the drift. If you really want guaranteed lock, then you need to use genlock.

For the gear to go that far out of sync so quickly, and after working OK in previous productions, something must be dramatically wrong. It would appear that something broke.

You said you have three cameras, but you show only one. What about the other two? Do they track with the first camera or with the audio recorder? That will help you discover whether it is the camera or the recorder which broke.

---------------------------------------------------------------------------------
Recording audio without metering and monitoring is exactly like framing and focusing without looking at the viewfinder.


Return to posts index


Al Bergstein
Re: Sync Drift problem??? screen capture included
on May 4, 2017 at 1:16:22 pm

Hi Richard if you look carefully there are actual multiple audio tracks above the one on the bottom that show all three cameras audio tracks. But the short answer is that all three cameras synced perfectly using Adobe's audio sync capabilities The only track with any problems at all came from the tascam on the bottom. I recognize that genlock wasn't used, and I've never used it and never had this problem as before. I've never even encountered audio drift in any of my productions prior to this except one that was shot with an older SD video camera that used tape . I certainly recognize it could've happened but it never has.

I'm not going to bother with calculating the percentage as asked because it starts out quite far out and then slips into sink within 20 seconds, and the rest of the four minutes or so of the video is totally in sync on all tracks. That doesn't seem to point to a typical audio drift issue where's something starts out in sync and then drifts out of sync as time progresses
Or at least that's how I have always understood it to be defined

I'll leave it up to my sound engineer to investigate his equipment and figure out what the heck is actually going wrong, but I appreciate the feedback it's been helpful to think about that .

Al


Return to posts index

Ty Ford
Re: Sync Drift problem??? screen capture included
on May 4, 2017 at 6:28:20 pm

Hey Al,

You said it all worked before, but now you're using new cameras, right?

Different cameras, different clocks, different timing.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


Return to posts index

Al Bergstein
Re: Sync Drift problem??? screen capture included
on May 5, 2017 at 4:31:04 am

No sorry Ty. The cameras are all the same. If you look at the screen captures you will see that the drift is ONLY in the lower track which is the Tascam recorder. All three cameras were fine. Not sure how I can be clearer about this.

Al


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]