[MPlayer-users] A-V-sync in mencoder

[Ville Saari]

On Sun, Mar 21, 2004 at 11:41:34PM -0500, D Richard Felker III wrote:

> > > ROTFL! The phase is not set once, but hundreds or thousands of times
> > That's the magnitude of the number of frames in the movie. If the telecine
> 
> A movie typically has around 150000-200000 frames. So hundreds would
> be once every few hundred frames. I have content where the phase
> changes about that often. OK, thousands was an exaggeration. :)

Oops - sloppy reading - I misread your "or" as "of" and got "hundreds of
thousands" :(

By the way - for PAL DVDs thousands would not be an exaggeration at all.
I have seen DVD's where the field phase changes almost as often as it
would change in 3:2:2:2:2:2:2:2:2:2:2:2-pulldown, but irregularily without
any pattern.

> No, the only way to do this is to artificially duplicate frames. And
> this is dumb. In the general case, inverse-telecined material cannot
> be made to fit fixed-24-fps. You need a 1/120 sec base clock with most
> frames having 5-tick duration, but some varying at splice points.

It cannot be made to fit the DVD either (1/60s base). The telecine itself
is a process that artificially duplicates frames (fields actually).
Garbage in - garbage out, but at least our output garbage would have
much less timing gliches: only once per telecine phase change, while the
input has them five times per second.

> Only if you want fixed-fps output, which is a bad goal unless you're
> tagetting antiquated file formats like avi.

But the only possible goal with the current mencoder.

Would it work if I misuse avi as variable framerate container by encoding
to very high ofps - say 120, but actually output much less frames and let
mencoder duplicate each frame multiple times? I probably wouldn't be
wasting too many bits but would that be universally playable? And can
mencoder duplicate the same frame more than once?

> try making an inverse-telecine filter that actually works
> based on those claims. You'll find it doesn't work at all...

If the output format is fixed fps, then the fixed fps outputting
ivtc-filter can't do any more damage that what mencoder's frame
skipping/duplication would do if the filter outputs variable fps.

And the filter would most likely be able to find much more appropriate
frames to skip/duplicte than what mencoder's arbitrary selection would be.

-- 
 Ville