#1 NTSC rates

[Adam Perry]

I'm being pedantic, but it it's a pedantic subject:

NTSC is not 29.97 frames per second. That's just a convenient number that's usually close enough.

It's actually 29.970026164311878597592883307169 frames per second, which is an ugly number (but hey, analog electronics don't care about decimal places...). It can be reduced to 1431818/47775 frames per second, but that's not pretty either.

It is fully explained, and the maths done, at http://www.ietf.org/mail-archive/web/avt/current/msg05118.html

This means that some fairly common sampling rates are wrong (mostly everywhere, as far as I can tell). The common NTSC-derived rate of ~44.056kHz, better described in the FAQ as 44055+9/10, is therefore also inaccurate. 44055+61/65 is closer, and not too ugly. 44055.93846153846153846153846153843 is closer yet, but even my pedantry has limits...

The discrepancy amounts to a difference of about 0.18 frames in a typical 2-hour film. Might not seem important, but it adds up...

(I'd like to say, "Aw, hogwash! Everyone knows it's 29.97 frames per second! There's no way that a modern DVD machine will play back at exactly 29.970026164311878597592883307169 FPS! But then I look at http://en.wikipedia.org/wiki/Colorburst#Crystals and see that everything NTSC (including DVD players, presumably) has been doing trying to do exactly that since, well, forever...)

Anyway, I hope this can be fixed with Scheme. If it can, I will do so, attach my changes.