[FFmpeg-user] Converting a 23.98p source to 29.97i ProRes w/interlaced 3:2 pulldown?

Mel Matsuoka melmatsuoka at gmail.com
Mon Oct 26 23:06:30 CET 2015

On Mon, Oct 26, 2015 at 10:39 AM, Moritz Barsnick <barsnick at gmx.net> wrote:

> > And I suppose this begs the question, where do the numbers 30000 and
> 1001 come from to begin with?
> From the same page, different section:
>   To make the resulting pattern less noticeable, designers adjusted the
>   original 60 Hz field rate down by a factor of 1.001 (0.1%), to
>   approximately 59.94 fields per second.
> So that's just how it was defined, in analog times: A factor applied to
> the synchronous rate of 30 or 60 Hz. (I wish they had solved it
> differently. What a pain these numbers are. But sort of appropriate for
> the land[s] of inches per yard per mile. I digress.)

Thanks for pointing out the 1.001 math. I'm totally aware of the reasons
why 29.97/59.94 exists, but I never internalized the actual math behind it.

So is the bottom line that FFmpeg favors overt pedanticism in regards to
defining frame rates, hence the need for the user to actually provide it
with the actual math required to define a true NTSC framerate?

Is it bad form to simply use the "ntsc" and/or "ntsc-film" aliases, instead
of using the fractional forms?

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