One area where accuracy is important is not because of pitch (nobody can
hear 1ppm differences), but because of the need to synchronize sound
from different sources, particularly with video or motion picture frames.
1000 seconds (20 minutes, give or take) with the sampler off by 1ppm
will be 1 millisecond out of sync, which is probably hearable, and is
1/30th of a frame time. A 2 hour movie (about 7000 seconds) would be 7
ms out of sync.
Yes, we're not looking at needing Cs accuracy, but 10-20 ppm probably
isn't good enough. So you're pretty much not going to be able to use
the $10 oscillator in a can.
So maybe a decent Rb, which is good to 1E-9 without doing anything
special, wouldn't be a bad thing.
And yes, there's a whole art to synchronizing stuff which was recorded
or filmed with incorrect sample rates, or ones that are "slightly off".
It wasn't too long ago that "quartz lock" for a motion picture camera
was something that was a "special order" from the camera rental house.
I used to modify PC video cards for external clock input so I could
adjust the refresh rate to match the camera speed (aka gen lock).
There's a time nuts challenge... synchronizing something normally driven
off a quartz oscillator (however crummy) to a mechanical device (the
movie camera shutter).
And given the creative hierarchy on a set, it's going to be you that
adjusts to them, not vice versa.
There are directors who (for whatever motivation) also don't want things
like timebase correction used. Since I used to work for a physical
effects company, I thought that these guys and gals who are hung up on
the "purity of the process" were wonderful, since they typically wanted
"real" special effects, not something composited in later by optical or
computer techniques.
There's a whole industry supplying 24/48 Hz refresh hardware, as
well. Well.. there used to be.. I'm not in that business anymore, and I
don't see credits for 24fps video as much, so they probably just paint
the screen blue or green or put registration dots on it and comp in the
images later. (Yes, I'm one of those people who watch all the obscure
credits at the end for things like assistant hod carrier and such.)
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