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Audio B-wav issues

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Sean Davison
Audio B-wav issues
on Jan 19, 2011 at 9:48:43 am

Can anyone shed any light on a very frustrating problem Im having with Protools B-wavs...

Workflow is...

Shot on one of the first Red Ones at 4k 24fps
Offlined Prores conversion (2k) 24fps
Media managed and clipfinder xml to link to color 24fps
graded and rendered out to Digital Cinema 2k prores 4444

Audio omf from Offline to Protools
5.1 audio mix 24fps
export 5.1 stems and stereo ltrt to Bwavs

Import to Online project.

All the B-wavs show incorrect start time and durations in FCP
Quicktime player shows them to have correct duration
SoundtrackPro likewise.

If I create a 25fps project and Import them FCP shows the correct duration and if I then create a 24fps sequence in this project and paste the audio files in everything is correct.

Pix pasted on top – all in sync. Online done.

24fps picture exported
Audio files exported (for DCP Creation)
All audio has reverted to the original duration (wrong length drifting)
The quicktime output shows the audio is in sync but the audio tracks are all in the wrong order and some are not there at all.

OSX 10.6 (latest version)
FCP 7.03
Fibrechannel Raid with Apple Fibrechannel card.

Im assuming the original B- wavs are fine as they seem OK everywhere but in FCP

Any light greatly appreciated!

Sean

Life on the Bleedin' Cutting Edge....

http://www.twotallmen.co.uk


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Bouke Vahl
Re: Audio B-wav issues
on Jan 19, 2011 at 12:37:20 pm

Sean,
BWF's in FCP is a bag of hurt.
FCP assumes the starttime not based on the current project, but on the last setup settings used.
It also tries to be smart on how to cope with 23.976 / 24 time difference.
Being smart is no problem, but not telling what logic it is following can be killing.
(look at the amount of threads on ' out of sync wave' there are here...)

To top it off, FCP has a memory for BWF files and their metadata, and you can't club it out its brains!
You need to rename the clip in order for FCP to re-read the metadata.
(you've found that one out, after importing them in 25 the metadata was stuck in the 24 project.)
Note, if the BWF starts on a round second, there should be no difference between 24 and 25, but there MUST be a difference with 23.976

My option would be to start over again.
Rename the BWF's, open your project, create a new project with the same settings as your working project. (To club FCP into submission), go to your user prefs and set BWF import on NTSC to Non-drop if it wasn't already. If you have to switch it, you need to restart FCP or the settings are not in effect)

Then, try again...
(and yes, this sucks....)

Also, see if the sample rate is indeed 48000 exact. If not, your problem might be there.
Another option is to remove the BWF timestamp.
(A QT export to Wave will do that for you)

hth,

Bouke

http://www.videotoolshed.com/
smart tools for video pros


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Matt Lyon
Re: Audio B-wav issues
on Jan 20, 2011 at 5:07:08 am

It's also vital that you have the correct default sequence settings selected in the "audio/video settings" dialog box when you import your files. This sequence setting must match the timebase of your incoming files.

I wrote a tutorial about the proper way to import audio:

http://library.creativecow.net/lyon_matt/fixing-fcp-assets/1

(you can skip to the second half)

Everything Bouke says is spot on. FCP is kinda nuts! But if you know how it thinks, you can get predictable results.

Matt Lyon
Editor
Toronto


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