[MPlayer-users] Re: soft telecine for DVDs: can't this be applied (in principle) to framerates other than 24 or 24000/1001?

[Ivan Middleton]

> > I've noticed and made use of the "telecine" option for -mpegopts quite
> > often, and I notice there's also now a "film2pal" option which does
> > something similar for PAL format.
> >
> > I'm wondering if anyone thinks it's useful to implement more general
> > pulldown patterns.  If I'm not mistaken, the mpeg2 flags would seem to
> > allow you to increase effective framerate by up to 50% (by repeating a
> > field from each frame); and thus for instance one could implement a
> > soft telecine pulldown for NTSC dvds for framerates as low as
> > 20000/1001.
> >
> > I would potentially find this useful in two situations:
> > (1) Converting low-framerate video to dvd, e.g. from web videos or slides
> > (2) Converting PAL (25 fps) to NTSC
>
> yes. Patch welcome or have patience :)

Ok, so right now I'm trying to implement what would be the simplest
case, namely, pulling down 20 fps to 30 fps by setting RFF on every
frame and TFF on every other frame.

I don't have very much knowledge of MPEG2, so someone should stop me
if what I'm trying to do is either stupid or way out of line with the
specifications.

I'm running into a problem: the current code doesn't like to deal with
framerates (like 20 fps) that aren't allowed in MPEG2, so I can't just
make the obvious modifications to the soft_telecine function;
apparently I would need to muck with some other stuff.  (I was hoping
that I could just disable some of the checks, for instance, in
libavcodec/mpeg12.c, encode_init(), but that just led to a bus error
as soon as encoding started.)

Can someone with greater knowledge of libavcodec/libmpdemux internals
give me any advice?  I figure I should ask before trying to go much
further.

Cheers,
Ivan