Unusual Audio Sample Rate

I am digitising some 20 year old archive that was shot on Hi8. I am playing the tapes from a Sony Digital 8 camera via FW400 into FCP6 with capture settings Non-controllable Device and DV PAL 48KHz. All this works fine, but I now notice that the Aud Rate column in the bin shows some clips at 48.0KHz and others at 47998.0Hz or 47997.9Hz.

It's not a major problem - obviously the clips with the unusual sample rate display the green preview render bar in a 48KHz timeline - but everything else seems fine.

How can this be I wonder ? It seems to me that if the Digital 8 camera was outputting an odd sample rate, FCP would have put up a warning about the mis-match.

Any comments much appreciated...

That it "pulled down" audio rate -- usually happens after a telecine step.
You should still be able to use it, no? You won't hear the difference by .01% the only thing that 'might' happen if it is a long take or segment, is that video sync might be off.

But then what do I know. I'm a sound dude.

Jeff

NTSC is a slowed down format. To get 29.97fps from 30p, everything is slowed down by 0.01% percent. Audio that is sampled at 48khz flat would then become 47.997kHz.



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Thanks for the replies.

I understand what you're both saying, but perhaps I needed to emphasise that I'm in NZ - PAL-land. The original footage was PAL and I'm working in a PAL timeline.

As you say, Jeff, it's all perfectly usable - I'm just trying to figure out why it's happened.

It may just be something unstable about a picture coming off a low end tape format playing off an old consumer piece of gear. It could be that the frame speed when you start the capture is fluctuating slightly and confusing FC.

There's no pull down happening.

You are not capturing an old format like that through a timebase corrector which would stabilize the signal. This is what TBC's are for, take an unstable picture in, buffer a few lines of it, and feed it out on a new clean and stable signal with perfect cadence.

NTSC 29.97 is not a slowed down format any more than 24 is a slowed down format from 30.
It's just the real speed frame rate that is, inconveniently for post, not the nice clean number
30 would be.

>NTSC 29.97 is not a slowed down format

Okay, you got me there. I must have remembered it wrong... Boy would I get into trouble trying to work BWF...



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You're absolutely right Sprocketz - it should be done through a TBC. But - no budget, etc, etc...

Sometimes I wonder how all you guys working with NTSC manage to keep your sanity. I mean - maybe we still don't have iPads down here, but we have had PAL for about 50 years...

>but we have had PAL for about 50 years...

Good times.



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