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Hello,

I am a bit confused by this issue. I am working on a MacPro with two graphic cards and Nuendo as main Software. So I have three displays attached, one of which I use for the video. I always assume that sync problems are only important when trying to synchronise an external source, but not within a system. But I am getting reports that the sound that I am exporting is collectively out of sync. Strangely enough that does not seem to be the case for every export. Now I came across a Synccheck devise on the internet that apparently measures the offset of audio and video.

Does anyone have experience with this? Is there an offset within one computer system? If so are there any cheaper ways of measuring it other than Synccheck, since that device seems to be quite expensive.

Many thanks,

Nico

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Perhaps expand on a couple of points. Who is reporting the sync problem and what are they doing/using. Is it an editor importing your audio to their timeline? Also how out of sync is it, and does this value stay constant? –  Mark Durham Dec 4 '12 at 13:26
    
The editor is reporting that the sound files don't start where they should start. Up to 4 frames out of sync. And at screenings in cinemas the sound suddenly seems out of sync. I always assumed that it is the fault of the editor or the cinema, as it all looks very sync on my system. But then this sync check made me think that maybe there is something wrong with my system. Although then it should probably consistently occur in all projects. I also had the case that the sound was slowly running out of sync, but that seems to be due to a bug in FCP. –  Sound1844 Dec 4 '12 at 18:15

3 Answers 3

The path to solving such problems lies in having systems in place so you can backtrack to find where the error/s are occurring.... A friend wrote a post for me about using the SyncCheck device, you should have a read of it as it will verify the offset you should be using with your system:

http://www.musicofsound.co.nz/blog/calibration-2-sync

But you should also have procedures in place to verify sync as the project is transferred between picture editorial and you, and then back again. With every turnover of a new picture cut, the Quicktime should have a correct frame rate SMPTE leader with a visual and audio head pop, and a tail leader on the end of each video with a tail pop. You should also receive a list from the editor of the FFOA and LFOA - first frame of action and last frame of action. If you do not do this and there is a problem then you wont easily be able to verify the source of the problem and resolve it.

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Thanks very much, that is good advise. Will definitely insist on beeps in the future. –  Sound1844 Dec 6 '12 at 1:05

Within a DAW, as far as i know, delays of up to a few frames can be caused by processor-heavy plug ins. I'm not sure if Nuendo has a delay compensation feature, or a way to measure the delay in your chain, but maybe someone else can help there.

Different monitor outputs can bring delays with them too, although if you're plugging the monitor straight into your computer (as opposed to using a Canopus box or something, which converts the signal to component), the delay shouldn't be huge. Play a pip (without any plug ins in the chain), accompanied by a flash, and watch. Does it seem out of sync to you? One trick i use, in lieu of a sync checking device, is to do this and watch the flash in my peripheral vision. Just relax; don't be in sync-checking mode, just be aware. If you focus too hard on sync, your brain can artificially impose it. If you do have a big delay in your monitor, this will make you cut your FX in earlier than necessary, and you will need to offset your video (again, i'm not sure if Nuendo has this feature).

Finally, what kind of sync problems are they reporting? Does it slowly drift out of sync, a few frames every few minutes? More? Lately, i've had some clients report sync drift issues, although the majority have been totally fine. I haven't figured out why yet, but i think it might be the picture editing software assigning a frame rate to my audio and adjusting the speed while importing. Ask for a pip at the head and tail of the program in future. This way, they can tell you whether they line up, and if not, how many frames you're out by.

  • If sync starts out ok, and drifts out by about 18 frames every 10 minutes, then you can try pulling your audio up/down by .01%.

  • If you're a few frames late from the start, then it's a processing delay in your system. Although if they line up your front pip with theirs, it should be in sync.

That's all i can think of pre-coffee. Hope it helps.

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Thanks. No Nuendo has always had delay compensation. That cannot be it. But I will try to check the sync with a beep. –  Sound1844 Dec 4 '12 at 18:19
    
@Sound1844 All of Tim's advice will go a long way towards solving the issue. There's also the possibility that they've changed something in the edit without telling you. That would explain things suddenly going out of sync. You can check that by asking them to re-export their audio only (without your mix) for you; then line it up with your mix and check it. –  Roger Middenway Dec 5 '12 at 16:59
    
Thanks, I had that once actually.But these issues are normally very obvious, as it goes out of sync at a specific timcode. –  Sound1844 Dec 6 '12 at 1:07

If the offset is not rather small and constant you'll need to answer Mark's questions. ;)

In generell: Any kind of display (flat screen/projector) will add latency. Latency that your system is not aware of. Also different video codecs will add different latencies. This is why you can adjust the video sync offset in ProTools eg. (not sure how it works in Nuendo, but there should be some option.)

Nevertheless: if you put a beep on the leader and this beep looks good, then the rest should look just as good. Because you can allign the beep by timecode (mind proper frame grid) you can use it to check the sync of your material. But this is not as precise as a synccheck.

Maybe try to find a studio close to you where you can rent a synccheck to determine your system's delay for a few common codecs and then you should be fine for a while.

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Thanks, I didn't know that screens add latency. That might be a source for the problem. But know that you say it, it seems to occur in projects where the editor is not supplying a beep, but is syncing up to another sync point, mostly the In point in his edit, which of course is also the first frame of my video. But with a beep, even if there was a delay in my system it should not make a difference, as long as everything is consistently sync on my system. –  Sound1844 Dec 4 '12 at 18:25
    
If you get picture from the editor without start and tail beep/peep/pop (or whatever you want to call it) in picture and sound, just send it back and ask for proper material! It does not matter where your file starts (except for certain DCP-deliveries, but usually they are able to deal with longer files as well). The only things that matters is that the sync beep is aligned so sound and picture match. If things are slowly running out of sync it might be a framerate issue. –  user891 Dec 5 '12 at 10:25
    
Yeah, will definitely insist on a beep in the future, thanks. –  Sound1844 Dec 6 '12 at 1:08

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