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A warning for BWF / FCP

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Bouke Vahl
A warning for BWF / FCP
on Oct 4, 2009 at 11:06:32 am

A general word of warning:
BWF and FCP DO NOT play well together in NTSC.
You have to set FCP to use drop or non drop. (user preferences, second tab 'editing'). If you don't set it right, the TC will not be calculated right.
But besides the difference in TC calculation, FCP also changes the duration / playback rate of the clip if you set it to NON DROP.

This is PLAIN WRONG.

So always make sure you import your files trough QT if you want to work in NDF.

One way of doing so is using my BWf / QT merge application (it comes with the FCP aux TC reader)




Bouke

http://www.videotoolshed.com/
smart tools for video pro's


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Ty Ford
Re: A warning for BWF / FCP
on Oct 4, 2009 at 11:43:25 am

Hello Bouke,

The must be more to it than that. I've used tracks recorded from my Sound Devices 744T in FCP and had no problems in ND. I think there's some info on the Sound Devices site about their using BWF but tweeking it some way. It wasn't a problem here so I thought nothing of it.

Regards,

Ty

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Bouke Vahl
Re: A warning for BWF / FCP
on Oct 4, 2009 at 12:00:58 pm

Ty,
There is more to it..
(like always:)

I've looked up the manual for your recorder, it tells me this:
-------
48.048k and 48.048kF
The 48.048kF mode (F stands for
fake, faux, Fostex—take your pick)
is a specific compatibility mode
for use with the Fostex DV40 software
(1.74 and previous), Avid, Final Cut Pro,
and other post-production
environments that do not recognize audio files written at 48.048 kHz. In this mode files are
recorded at a 48.048 kHz sampling rate but are stamped at 48 kHz. When played, they will play back
0.1% slower than real time.
-------

So i assume you have recorded 48.048.
(I would like to see one of those files if you did not!)

That does NOT mean that FCP is wrong. A BWF file should import with the same duration no matter the Df / Ndf setting.

But the solution is easy if things go bad. Just change a few bytes in the file and FCP will play nice. (the sample rate is defined in the file, if you just change that and leave the entire file alone, everything will be fine.)



Bouke

http://www.videotoolshed.com/
smart tools for video pro's


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Ty Ford
Re: A warning for BWF / FCP
on Oct 4, 2009 at 12:04:59 pm

Bouke,

I'm pretty sure it was just plain 48k. I'm also pretty sure I don't have them any more.

And yes, digital can be very tricky.

Ty

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Bouke Vahl
Re: A warning for BWF / FCP
on Oct 4, 2009 at 12:41:38 pm

well, do a simple test.
Import a BWF file in FCP and look at the duration.
Now switch the BWF import, then import a copy of the same file.
You'll see the duration change.
This is not good...
(a 48Khz 20 min. clip imports as 20 min. in Drop, but as 19:58:06 in Non-drop...)

Anyways, for those who get bitten by this the archives will be there :-)



Bouke

http://www.videotoolshed.com/
smart tools for video pro's


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Robert Kennedy
Re: A warning for BWF / FCP
on Oct 9, 2009 at 10:59:34 pm

Hi Bouke,

FCP's handling of BWF has been slow and rudimentary. I have a long wish list of timecode funcitonality I would love to see in FCP. The basic function of syncing TC-stamped video to BWF files works for me but often is more tedious than syncing them manually in a sequence.

I fully expect the SMPTE Timecode duration of a file to be different when interpreted as non-drop-frame versus drop-frame. I expect it to differ at a rate of 18 frames every ~10 minutes which is exactly why drop-frame timecode was invented. The purpose of shooting in drop-frame is to compensate so the video timecode and playback rate would match "real-time" i.e. the clock on the wall.

As for 48048k or 48048kF (the False-stamp), I suggest this option only be used by professionals in limited circumstances. The notion of stamping the sample rate of a BWF file a different value than the value at which is was actually recorded can result in nightmares down the line (from telecine to decades later in archive revival). Thankfully, Sound Devices indicates the true sample rate that the file was actually recorded at in it's metadata.

Thanks,
Robert


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