Pro Tools audio off by 2-frames by end of 20 min.

[BradG]

I got an OMF file with accompanying video (.mov) for a 20 minute film.

Everything lines up nicely at the top but the audio in my Pro Tools session is off by exactly 2 frames by the end of the film.

Is there a way that I can shift all the audio regions (relatively) by making them Tic-based tracks? Like, can I compress the whole session by 2-frames, without actually time compressing the individual audio files?

The video is 25fps PAL, if that makes a difference, but I'm pretty sure I set up everything properly.

[Slutpuppy]

Did you make sure that the pt session is set to 25? Is there a pull up/down on the audio? Double check all of you session set up info before doing anything else. I usually find that thats where the problem lies...

[Jonkr]

Im not really a post guy but if its PAL shouldn't you be set to 25fps non-drop?

[hummer]

uhhhh, there's no such thing as 25 fps drop frame, so... that's certainly not the problem. (probably best not to give advice on a topic with which you're unfamiliar, Jonkr)

2 frames over the course of 20 minutes is not indicative of any run-of-the-mill frame rate issues, pull downs, etc.

sounds like there's just some nudging/offsets happening, which could be the result of a variety of things, probably from the picture editing. part of your job is to check and adjust sync as necessary, so just adjust it until you're happy.

unless what you're saying is that you've delivered the mix and the editor is telling you that the mix is 2 frames off at the end? that would be different, but unlikely.

[sailor]

I'd strongly recommend troubleshooting the cause rather than trying to compensate with any kind of timesqueeze or shifting right out of the gate. The latter would only address the symptom as you see it, and when you deliver back to the editor it may be YOUR mix that's deemed to be "out."

Your video playback setup may be a culprit. I/O boxes like the older Canopus sometimes drift during an extended playback, things like Avid Mojo tend to be more stable. If it's just a QuickTime in a video window....should be OK but ya never know.

If you START playback near the end, what happens? Is it in sync? If so, then you have a playback speed issue of some sort. If not, then somehow your clips have some kind of offset happening. If the audio is out by two frames at the end, is it out by one frame at the midpoint of the show?

Did you import the audio from the video file you got? Put it up against your tracks and see how and where it starts to drift.

Like Hummer said though, if it were a pulldown or TC mismatch, you'd probably see more drift than just two frames after 20 minutes.

Given the opportunity, I like to ask video editors to put a beep at the beginning and at the end of the OMF, with corresponding flash frames of text in the QT which show those exact TC addresses. Then you know whether you're at least starting off on the right foot.

[Jonkr]

Originally Posted by hummer

uhhhh, there's no such thing as 25 fps drop frame, so... that's certainly not the problem. (probably best not to give advice on a topic with which you're unfamiliar, Jonkr)

You're right, my mistake. Wasn't giving advice though... just trying to suggest something he might have looked past.

[BradG]

Originally Posted by sailor

I'd strongly recommend troubleshooting the cause rather than trying to compensate with any kind of timesqueeze or shifting right out of the gate. The latter would only address the symptom as you see it, and when you deliver back to the editor it may be YOUR mix that's deemed to be "out."

Yeah, that's what I'm afraid of.

If you START playback near the end, what happens? Is it in sync? If so, then you have a playback speed issue of some sort. If not, then somehow your clips have some kind of offset happening. If the audio is out by two frames at the end, is it out by one frame at the midpoint of the show?

It's 2 frames off at the end. I can hear the delay when I unmute the movie's audio track and I can see it in the waveform. Yes, it is one frame off in the middle.

Did you import the audio from the video file you got? Put it up against your tracks and see how and where it starts to drift.

See above.

Given the opportunity, I like to ask video editors to put a beep at the beginning and at the end of the OMF, with corresponding flash frames of text in the QT which show those exact TC addresses. Then you know whether you're at least starting off on the right foot.

I agree except it was obvious where the end of the session was as the last audio file ends exactly two frames after the end of the movie file.

[BradG]

I've been snooping some post forums for answers and haven't found any but I did find a reference to a variation of 48kHz (48.0xx something, I don't remember). Could that somehow be the culprit? If the editor is working in a slightly different sampling rate?

I'm going to try and get her to output another OMF for me. I know she works in Final Cut which isn't going to help.

[minister]

Originally Posted by BradG

I've been snooping some post forums for answers and haven't found any ...

Eesh!

Originally Posted by BradG

...I did find a reference to a variation of 48kHz (48.0xx something, I don't remember).

That refers to 48.048kHz which is .1% away from 48kHz. Won't help you. The difference is 1:05 over 20 minutes.

Originally Posted by BradG

I'm going to try and get her to output another OMF for me. I know she works in Final Cut which isn't going to help.

Why not?
I think it would help a lot. It will also tell you if the audio clip sync is off from the video clip.

It really just sounds like something got slid 2 frames somewhere and it affected everything else down stream. As was suggested above, listen to the audio imported from the QT against the OMF. No plug-ins. You could also put the guide track in the left and the OMF in the right and hit the mono button. You'll instantly know the moment it goes out. Mark that moment and look at the OMF. Fix it. Or call the editor to discuss.

[Andrew Mottl]

Haven't had time to read all the answers, but I would check this:

Is it one continuous clip? Or a "real" OMF session with edits?

Check to see where the edits in the audio line up with the picture cuts. I would also suspect that something was nudged in the video room without noticing that the audio hadn't moved. Then you should be able to find the cut where it all goes out of sync.

Hope it helps!

[PoxyMusic]

I'd listen to the reference audio along with the OMF, and see if the drift is linear. That is, is it .5 frame off at 5 minutes, 1 frame off at 10 minutes etc.

One sure way to check sync against reference is to pan the reference left, and OMF dialogue right. Any sync discrepancy will be obvious right away.

That would be a clue…as to what I'm not sure since as mentioned above, 2 frames after 20 minutes doesn't fit any sync problem profile that I know of.

Andrew's hypothesis is the most likely, IMO.

[charles maynes]

anybody check the tail pop?

[Rick Sanchez]

Originally Posted by charles maynes

anybody check the tail pop?

Sound to me like it might be one of those "we don't need no stinkin tail pop" projects.

Lessons learned.

[gsilbers]

Originally Posted by Andrew Mottl

Haven't had time to read all the answers, but I would check this:

Is it one continuous clip? Or a "real" OMF session with edits?

Check to see where the edits in the audio line up with the picture cuts. I would also suspect that something was nudged in the video room without noticing that the audio hadn't moved. Then you should be able to find the cut where it all goes out of sync.

Hope it helps!

+1


you might be under the impression that the video guys know 100% what they are doing.

so, besides the audio being 2 frames longer then the video, is it actually out of sync? does the P's and T's of dialog seem off? hard production effects which u can jog?

one of my jobs is to sync up shows and movies audio to picture cause sometimes the video editors just dont care, dont realize it or know the audio guys will fix it. it depends on the project and editors.
so jog around the program material and see if there is a jump or place where the editors might of moved the audio by accident. see that eveything is in sync , specially video and production.

2 frames also sounds like they applied or rendered an effect and pushed the video 2 frames out of place.
but ive only seen this twice and not in this context but in picture corrections. so not likley but something to look at. fixing it is just conforming the audio to picture.

[TVPostSound]

Have you checked the sync against picture??

Might the audio extracted from the QT be wrong??

Some things are just not worth the effort, and time to figure out.
It's 2 frames across 36,000 frames.

Shift the audio 1/4 frame at 8 points across the 20 minutes, be done with it.










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[PoxyMusic]

Originally Posted by TVPostSound

Shift the audio 1/4 frame at 8 points across the 20 minutes, be done with it.

That advice only works if the drift is linear throughout the film, which it probably isn't. Your advice will ensure that the entire film has soft sync…instead of the most likely scenario, which is that only a clip or two (and probably everything to the right of it) have slipped.

All he has to do is play reference and the OMF at the same time, tab quickly through the cuts and where you hear a 60 ms delay, there's your problem.

10 minutes tops to find and fix the problem providing the sync of the reference track is good.

[Andrew Mottl]

One wee thing - he is stating it is a PAL project, so wouldn't it be 80ms, not 60ms?

[georgia]

He said it was linear across the project. I'm guessing a simple video/audio export or video codex problem if it's only 1/10 of a frame / minute.


Have the video guys drop a visual 2 pop and a visual tail pop into their time line and re-export the video. have them add an audio 2 pop and tial pop as well in ALL tracks at the same timecpode points.... Get the actual timecode frame point of each from them and check it in your session before continuing.


cheers
geo

[BradG]

My mistake!

Looks like it was not a steady drift across the whole project as I first thought. In fact, for some bizarre reason, there were two extra frames inserted in the audio, at 1:28 into the project. I did a time-cut of two frames, across all the audio tracks, right at that point and now everything lines up perfect.

This isn't the first time that I've had trouble with this editor...

[Henchman]

Originally Posted by BradG

My mistake!

Looks like it was not a steady drift across the whole project as I first thought. In fact, for some bizarre reason, there were two extra frames inserted in the audio, at 1:28 into the project. I did a time-cut of two frames, across all the audio tracks, right at that point and now everything lines up perfect.

This isn't the first time that I've had trouble with this editor...

Yeah, sound sliek the old:
Audio Guy: "are you sure you didn't change anything"
Picture editor:"nope, nothing changed"
Audio Guy: "You're sure"
Picture Editor: 'Yep. Sure"
Audio Guy "So nothing changed"
Picture editor: "Nope.... Well nothing that changed audio. Just a visual change".

Right.....

[kk@jamsync.com]

Originally Posted by Henchman

Yeah, sound sliek the old:
Audio Guy: "are you sure you didn't change anything"
Picture editor:"nope, nothing changed"
Audio Guy: "You're sure"
Picture Editor: 'Yep. Sure"
Audio Guy "So nothing changed"
Picture editor: "Nope.... Well nothing that changed audio. Just a visual change".

Right.....

Ha!

[philper]

Originally Posted by Henchman

Yeah, sound sliek the old:
Audio Guy: "are you sure you didn't change anything"
Picture editor:"nope, nothing changed"
Audio Guy: "You're sure"
Picture Editor: 'Yep. Sure"
Audio Guy "So nothing changed"
Picture editor: "Nope.... Well nothing that changed audio. Just a visual change".

Right.....

Thank you. "Just a picture change--doesn't affect you."

Philip Perkins

[Sonsey@mac.com]

Originally Posted by Henchman

Yeah, sound sliek the old:
Audio Guy: "are you sure you didn't change anything"
Picture editor:"nope, nothing changed"
Audio Guy: "You're sure"
Picture Editor: 'Yep. Sure"
Audio Guy "So nothing changed"
Picture editor: "Nope.... Well nothing that changed audio. Just a visual change".

Right.....

That would be even more laughable if I hadn't had that conversation on one of the last shows I did. After sending the mixes back to the editor, the transfer house called and said the audio was all out of sync. I checked my version and everything was okey dokey. Call the editor...

Me: "I hear the audio is out of sync?"
Editor:"Ya."
Me: "Well my version is in sync here. Did anything change?"
Editor:"I didn't touch the audio."
Me: "Yes, but did anything change?"
Editor:"No, we didn't cut the audio."
Me: "I understand that, did you change the video at all?"
Editor:"Well ya, I had to change a bunch of shots, but I didn't touch the audio!"

[mbvoxx]

Originally Posted by Sonsey@mac.com

That would be even more laughable if I hadn't had that conversation on one of the last shows I did. After sending the mixes back to the editor, the transfer house called and said the audio was all out of sync. I checked my version and everything was okey dokey. Call the editor...

Me: "I hear the audio is out of sync?"
Editor:"Ya."
Me: "Well my version is in sync here. Did anything change?"
Editor:"I didn't touch the audio."
Me: "Yes, but did anything change?"
Editor:"No, we didn't cut the audio."
Me: "I understand that, did you change the video at all?"
Editor:"Well ya, I had to change a bunch of shots, but I didn't touch the audio!"

sounds like a possible scenario; LOL it's happened here before.
in your case the editor may have made a 2 fr cut and forgot to turn on the audio channels during the cut. I would first try finding a point midway where the sync starts to shift and snip 2 fr out of the audio and shuffle the audio tracks into sync. If you find the right spot you have have it licked. Sometimes the easiest approach is the best fix. Just a thought.

[ggegan]

If you are syncing up multiple Pro Tools they can lock up out of sync on some passes, always a delay in my experience. Also, there is a degree of latency with some plug ins that can account for things being out of sync, even if you are working entirely within one Pro Tools system. Individually these things may not account for a full frame during a single take, but if you stack them up and first record the final and then use the final to create the print master, it can easily add up to a frame. I just had this situation occur on a print master where LT/RT versions that were laid down simultaneously were offset from each other and both were different from the 5.1, which was created from the same session and same tracks. I have often seen situations where Satellite Link occasionally locks up different sessions two or more frames out of sync. Haven't you ever noticed that when you carefully sync up foley to top production, it is slightly different on every pass?

The sync resolution is not as high as it should be. It is, however, no worse than mag systems were due to the displacement caused by the motion filters on the recorders and reproducers.

These things can drive you crazy. On most good sized mixing stages the sound is already 1/2 to 3/4 of a frame late to begin with just because of the fact that each foot of distance accounts for approximately 1 millisecond of delay, so things are never what they seem. In the end you just have to eyeball it and make a judgement as to whether it's within acceptable tolerances based on feel. It's never going to be 100% accurate.

[kk@jamsync.com]

Originally Posted by ggegan

These things can drive you crazy. On most good sized mixing stages the sound is already 1/2 to 3/4 of a frame late to begin with just because of the fact that each foot of distance accounts for approximately 1 millisecond of delay, so things are never what they seem. In the end you just have to eyeball it and make a judgement as to whether it's within acceptable tolerances based on feel. It's never going to be 100% accurate.

Good point and yet another reason why mixing for theatrical playback in a small room is fraught with danger, as is the reverse situation.

[ggegan]

Originally Posted by kk@jamsync.com

Good point and yet another reason why mixing for theatrical playback in a small room is fraught with danger, as is the reverse situation.

I think the saying goes something like, "If you're not worried, you aren't paying attention"

When you start really dissecting things like sync, it really opens a can of worms. You have to do it, but at the same time, you have to accept the limitations of an imperfect system and the fact that it may not even be possible to determine whether something is in or out of sync.

Even when it is possible to absolutely determine correct technical sync, sometimes it still just looks wrong because of an actor's way of shaping words. Sometimes things just work better when sync is cheated.

But more often than not it is impossible to vouch for the absolute sync at every frame, be it because of human error, internal processing latencies, imperfect syncroniser resolution, etc. The variables can be so numerous that getting too distracted by the issue can take away from the time and concentration you need to invest in the creative process and result in an inferior mix.

In the end you do the best you can and it either works or it doesn't.