Video/Audio Mismatch question.

[OdeToBob]

Hey all.

I've got a question about working with video in PT. I'm afraid I know very little about the video world and hoped someone could sort me out.

I'm in HD10 on a Mac Pro with a 96IO.

I worked on a music video last year and had the issue that the video (and audio extracted from it) were ever so slightly shorter than the audio from the same song in my pro tools session. Meaning...by the end of the song, my original session audio was late compared to the video (and the audio extracted from the video).
I chocked it up to some sort of error on the video guy's side. I thought perhaps the video editing team had imported the song incorrectly into their program and had cut the entire video to a slightly time compressed mp3 file or something. I ended up being able to compensate on my end with some clever time expansion and got things "close enough"...but it was a royal pain.

Today, I'm working on a new project and having a similar issue...leading me to believe the problem may be with something I'm doing incorrectly.
This project's video has timecode printed across the bottom of the video.
I've got the session timecode settings set so that my Big Counter and the Timecode printed on the video match up all the way through the video. (The number on the track says 23.98 and the session setup has everything set to 23.976)
However, again, by the time I get a few minutes into the video the session audio is behind. The video and extracted audio line up together fine. The Timecode matches up between the video and PT counter. But the session audio drifts off (This is a live show, so I'm referencing the camera audio extracted from the video file against the 24 track board audio from the show).

Does this strike you guys as something wrong on the video editor's side or on mine?
...and what information should I be giving/questions should I be asking to verify where the issue lies or correct it?

I hope this all made sense. Please let me know if you need info I haven't given here to make sense of it.

Thanks guys!
Bob

[OdeToBob]

Just a quick update. The video editor got back to me this morning and says all of his footage is indeed at 23.976.

[EGS]

PT session settings must match incoming video settings. A good video editor will send an OMF, plus info re frame rate.

[OdeToBob]

So. It appears that I've been sent an h.264, AAC Mp4 file @ 23.976fps.
Session settings are correct at 23.976, but do you think the encoding/decoding between his system and mine (I believe I'm using the DV25 codec for video) could cause the squeezing of his video/audio?
I'll get the editor to bounce me out an OMF file and see if that plays nice with the existing tracks.
Thanks for the response.
-Bob

[Leverson]

First make sure not only your frame rates are matched up but also your sample rates. Film and video operate at 48khz while music is traditionally 44.1khz. That might cause an offset if your session is at the wrong sample rate or if you aren't doing a conversion when you bring CD music in.

Also if you are recording a live concert event that is long, know that unless all your cameras and audio devices are jam synced to one another there will be drift, as their timecode crystals won't be exact. For short things, like a song, this drift won't be noticeable, but for a full concert you'll see drift happen between recording devices. That's one of the reasons people use things like lokit boxes or other sync jammers.

Those would be the first two things I'd explore, but also how it's exported could be a factor. I don't know much about DV25, these days I think the most common are ProRes (I usually do ProRes Proxy) or DNxHd (I usually do DNxHD36).

[OdeToBob]

OK. Further Update.
The editor sent over an OMF and the dialogue boxes that accompanied the export.
(Which mentioned Pro Tools Specifically and made me think I was onto something)

I'm not sure how to upload images...but the text in the dialogue box was:

OMF Export started.
MZ 13 07 26
Make sure your Pro Tools settings match the export settings.
Check below for error messages
Start Time is: 00:00:00:00
ProTools Offset value is: 0:0.000
Frame Rate is: 23.976 fps
You can set this in Track Offset Options in Pro Tools.
Initializing OMF Export
13 3 28


Exiting OMF Export.


And the export settings are here:

https://www.dropbox.com/s/1withqc94i...tings.png?dl=0

But the gist of that dialogue box is:
Sample Rate: 48000
Bits per sample: 16
Files: Embedded Audio
Format: AIFF
Render: Copy Complete Audio Files


SO....
I created a new Pro Tools 10 Session set to 48/16. Set the Timecode Rate, Feet+Frames Rate, and Timecode 2 Rate all to 23.976. And tried to import the video. Pro Tools kicked back an error stating:
Unable to Import some files because the Avid engine is not installed

Then...after some searching on the forums I found some people suggesting that I attempt to open up the OMF at the "Open Session" stage, instead of attempting to import after the session was opened. This automatically opened a session with the correct bit depth/sample rate settings but only imported the audio....Which was still off when set side by side with the multitrack audio from the show.

Any guesses as to:
How to get PT to open an OMF video file?
or
how to install the Avid Engine that PT seems to want?
or
Why the audio would still be off given that all settings are the same between systems?
or
What I should do next?

Thanks again for all the help.
-Bob

[OdeToBob]

Also...i can't seem to find any info (on any of the forums or PT manual) on how to delete my current Quicktime Codec and replace it with something like DNxHD. Anyone know a spot I can look to for this process?
-Bob

[MIKEROPHONICS]

OMF cannot contain video files.


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