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FCP + DeckLink audio drift when playing back 10-bit timelines

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Michael Miller
FCP + DeckLink audio drift when playing back 10-bit timelines
on Mar 15, 2011 at 8:17:55 pm

I recently purchased a DeckLink Extreme 3D card for my FCP station in order to provide a 10-bit uncompressed feed to other systems. I've constructed a timeline using a 10 second 10-bit test pattern with audio, copied a few hundred times.

After about 40 seconds of playback (4 times through the clip), audio drift becomes very noticeable, and grows very very quickly.

I find this especially strange since the audio is attached to the clip, so I've not done any kind of sliding or anything that could lead this to be my fault (that I know of :D). Is this a known issue with DeckLink cards, or a known problem with FCP? Does anyone know a workaround?


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Michael Gissing
Re: FCP + DeckLink audio drift when playing back 10-bit timelines
on Mar 15, 2011 at 9:09:29 pm

Firstly check that your Decklink drivers are up to date. This may have been a problem that has already been fixed.

The problem may also be that your footage is dropping frames in playback. You didn't tell us that codec, frame rate and hard drive spec you are using.

Finally it is essential that both the source audio is 48khz, 16 or 24 bit and the sequence settings are 32 bit 48khz.


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Michael Miller
Re: FCP + DeckLink audio drift when playing back 10-bit timelines
on Mar 15, 2011 at 9:20:22 pm

DeckLink drivers are indeed up to date.

I'm fairly certain we aren't dropping any frames, but I'll double-check that.

The storage medium is 3xOCZ Vertex 2 SSD RAID 0. Read speed is about 650MB/sec (bytes, not bits), so I don't think that's a concern. The clip is an MOV, 10-bit uncompressed 4:2:2. Both the clip and the sequence are set to one stereo channel of 16-bit 48KHz.


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Michael Gissing
Re: FCP + DeckLink audio drift when playing back 10-bit timelines
on Mar 15, 2011 at 9:27:04 pm

Should have plenty of speed in the drives. FCP sequence settings should be 32 bit float, 48khz, not 16 bit. That shouldn't make a difference but you need the higher bit rate to be able to mix audio. As it is the default setting, try it and see if that is the issue.


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Paul Jay
Re: FCP + DeckLink audio drift when playing back 10-bit timelines
on Mar 16, 2011 at 8:18:59 am

Which slot you installed Decklink?
What generation MacPro?


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