[MPlayer-users] converting 25 fps -> 23.976 fps?

[D Richard Felker III]

On Tue, Dec 16, 2003 at 12:45:05PM -0800, * wrote:
> > For making this conversion, you should instead use -speed 24/25 (or
> > 24000/25025 to be more precise) to slightly speed up both audio and
> > video. Keep in mind that you might have to resample audio too in order
> > to end up with an output rate that your codec will accept.
> >
> > Actually, I just checked and -speed only works in mplayer, not
> > mencoder. If you _really_ need it, someone might be able to add it to
> > mencoder.
> >
> Sorry, it's not important.  I just assumed it was a common conversion
> (one of the most common conversions!) going from PAL <-> NTSC.

It is common, and most studios botch it really bad. Fortunately it's
easy for movies (because you just change speed between 24/25 fps), but
television shows that are recorded at TV-rates usually look horrible
when they're converted between PAL and NTSC.

> > VOBS at 29.976 fps don't exist (you mean 29.96 fps), and 29.97 fps is
> > rare since most vobs come from movies. If the movie is 29.97 fps,
> > chances are it's hard-telecined, and you need to apply inverse
> > telecine or it will look horrible. As a bonus, this will inherently
> > reduce the framerate to 23.976 fps.
> >
> You're right- I meant 29.97 and now I see it's hard-telecined.  Could
> I ask if the accepted practice is to use -fps 29.97 -ofps 23.976 for
> 24fps progressive NTSC?  I tried all 4 inverse-telecine filters (detc,
> ivtc, pullup, filmdint) and got lots of duplicate frames for all but
> pullup (which says it will output more than 24 fps with -ofps 23.976)
> and filmdint (which says it will result in an uneven framerate during
> playback).  So maybe no filter is correct for this?  It looks okay
> with -fps 29.97 -ofps 23.976.

It it looks ok like that (no interlacing mess visible) then it's
probably soft-telecined. Do you get "skip frame!" messages? In the
case of soft telecine, all you need to do is use -ofps 23.976! Yep,
it's very easy. :)

> > BTW, why are you so interested in changing framerate?
> >
> Almost all the movies I come across on the internet have fps 23.976,
> maybe because most of them were encoded in the NTSC part of the world.
> I thought it would be better to have fps 23.976 to save the bits for
> more frame quality.  But perhaps any quality you would gain by that
> would be lost in the interpolation.

Yes, more will definitely be lost by interpolation.

Rich