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Conformed original BWAVs are out of sync by up to a frame compared to the AAF


Matthias Richter

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You're right, Peter. I think my misunderstanding was in part due to so many people trying to state the same thing over and over and over again that I felt sure they must be saying something new or why would they be regurgitating the same points if it's already been said?

(Please consider the foregoing as a very tongue-in-cheek comment.)

I was wondering the same thing. I presume the tongue-in-cheek refers to the "in part" bit, when actually that was all?
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If the solution to this issue caused any extra work for us then I may agree with you. However, all the aforementioned solutions don't impact our workflow at all, but would save a lot of time in post and produce more accurate results for our sound tracks. I don't see the need to fight against post on this particular issue. I would hope they would do the same for us if the situation was reversed - i.e. They do something simple like click a box and solve a huge time-consuming hassle for us.

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In post production does a sync error when picture edit material does not line up with imported BWavs (comb filter effect or echo) make it much harder for the sound editor to do her/his job without first correcting the error or can they just ignore it and work on anyway?

 

Sound editors (in my experience) are professional enough to understand the job and know that the inherent granularity of sound sync is going to require them to slip and slide tracks. I've run into cases where specific actors looked out of sync in relation to everything else, just because of their head and mouth movements. You gotta go with what looks and sounds right, not what is technically right. 

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Sound editors (in my experience) are professional enough to understand the job and know that the inherent granularity of sound sync is going to require them to slip and slide tracks. I've run into cases where specific actors looked out of sync in relation to everything else, just because of their head and mouth movements. You gotta go with what looks and sounds right, not what is technically right. 

Thank you thank you thank you.

 

Sync is in the eye of the beholder.

 

philp

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I just read through this thread. I don't mean to "revive" it now that it seems to finally be at rest, as I think the most relevant information have been said many times over. I just thought I'd respond to a question a ways back and mention that Final Cut Pro 7 and X do support subframe editing of audio (up to 1/100 of a frame), though I don't know if this has any relevance when the files are imported, or only after.

 

Does anyone have information about or experience with working on a program other than Avid, and do they have the same issue? Is this only a problem with Avid?

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  • 2 months later...

I just found this thread yesterday and have been looking for these answers for quite sometime. Unfortunately I was looking on the ProTools side of things and not the Avid side, so I did not have much luck, but now that I have found this, most of my questions have been answered. I do have one question, but maybe it is not for this forum, but I will ask just in case.

 

When the Avid gets files that do not start on a frame edge, what exactly does it do? Does it move it to the closest frame edge? How does it decide which frame edge to move it towards? I saw someone said something about appending audio at the end of the clip. Why would it do that? Is it to keep the out point the same as the original file? Is it actually stretching the entire clip, thus only slightly altering sync but creating a very subtle drift?

 

If the file moves to the nearest frame edge, then wouldn't the entire audio portion of the AVID edit be out of sync by up to 1 frame? If so, then any AVID AAF/OMF Sound post has used since file based workflows began have been out of sync, whereas we (post sound) assumed they were perfectly in sync and should be considered GOD as far as sync is concerned. If all this is true, the next questions is, if post sound receives an AAF, and the field recorder workflow is used to reassemble the production sound dailies, would the sound dailies then actually be back in sync in comparison to the AAF, or are they off by the opposite amount that the file was moved in the AVID?

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I just read through this thread. I don't mean to "revive" it now that it seems to finally be at rest, as I think the most relevant information have been said many times over. I just thought I'd respond to a question a ways back and mention that Final Cut Pro 7 and X do support subframe editing of audio (up to 1/100 of a frame), though I don't know if this has any relevance when the files are imported, or only after.

 

The problem with this is when the OMF is exported for Pro Tools later on, as far as I know it can only deal with timecode in whole frame increments, so it still needs to be "hand tweaked" if it's half a frame or less. But that's essentially the dialogue editor's job (part of it, anyway). 

 

 

When the Avid gets files that do not start on a frame edge, what exactly does it do? Does it move it to the closest frame edge? How does it decide which frame edge to move it towards? 

 

I believe John Purcell deals with a lot of this in his book Dialogue Editing for Motion Pictures: A Guide to the Invisible Art. In truth, I don't know a lot of picture editors that worry about getting dialogue in sync by nudging the tracks in subframes. Very often, when I look at dailies, I grimace because I can see certain scenes that are a frame or 2 out.

 

That's another T-Shirt: "I think it's a frame out."

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  • 1 month later...

Would it help if there was an indication on the sound report from the original recorder to show whether the files start on exact frame boundaries?

 

Wave Agent shows HH:MM:SS:FF  for timecode start/stop, but since the Sound Devices recorders are always on whole seconds, there's no reason to display otherwise.

Since the timestamp is actually in samples, and the timecode rate is in the metadata, it's possible to calculate the subframe value.

(There's another question, is it 80 subframes per frame or 100, seems to be different depending on the DAW or workflow).

 

Writing the subframe as 2 digits of decimal at the end of the timecode makes it impossible to read.

What about a ~ "twiddle" at the end of the Timecode to show it's a rounded figure, or some other character to signify "exact"

 

15:35:15:22     (unknown rounding)

16:35:15:22~   (known approximate)

16:35:15:22^    (known exact)

 

Or just a comment in the sound report "memo" field?

 

Tom.

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Would it help if there was an indication on the sound report from the original recorder to show whether the files start on exact frame boundaries?

 

Not to me, no. One conversation prior to the start of the production with the assistant editor should be fine.

 

BTW, as far as I know, the camera doesn't start on an exact :00 frame boundary, either. So this is a two-way street -- issues can happen on either side. If everybody's referenced, it's really not an issue. 

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  • 3 months later...

Hey y'all looks like Avid finally fixed this in Media Composer near the end of May this year.

The world can stagger on, and Zaxcom take a well deserved beach holiday. :)

 

The option -

Subframe Alignment to Broadcast WAV Start Time

is on by default apparently.

 

README_Avid_Editor_v7.0.4_and_v11.0.4(1).pdf

 

http://tinyurl.com/o6hcvfy

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If you've ever heard a producer say they prefer Sound Devices over Zaxcom, it may be because of issues like this. Sure, it's not Zaxcom's fault, but it's still their problem.

 

You can see the effect in posts like this:

This problem, if it is the same one, has been discussed on sound forums with the focus on which recorder originated the files. The problem, according to some editors, was from Zaxcom machines which timestamp the file to fractions of a frame. Sound Devices, on the other hand, backfill the start from the buffer to ensure every file starts on the start of a second. The editors were reporting the Avid somehow moves or adds time to zaxcom files to compensate, while Sound Devices files were fine. In effect they were saying they preferred Sound Devices file structure which saved them time. There was an enormous thread about it, with zaxcom denying it was a problem, putting the ball in Avid's court, but nothing as far as I know ever got resolved. It looks like this may be the same issue. I will have to hunt the thread down if you are interested.
The answer to your opening tweet is use Sound Devices recorders, or at least not zaxcom - don't know about how the others handle the start time of their files.

Source: http://www.pro-tools-expert.com/home-page/2014/7/30/does-avids-media-composer-shift-audio-out-of-sync.html#comment-1511646771

 

Again, while not Zaxcom's fault, it creates the perception that Sound Devices' recorders are better or at least create less issues. Glad to hear that this Media Composer issue seems to be corrected.

 

Mark O.

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I'm glad Avid fixed this issue, as it should be.  Avid needs a way to deal with audio on a frame basis, taking into consideration that the audio files don't have a frame reference, only a sample reference.

 

The whole this makes Zax look bad and SD look good is BS to me.  It's pointing fingers in the wrong place, and I won't make my choices as a professional based on other peoples naivety.

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