[MEncoder-users] inverse telecine with 60 fps progressive video

[D Richard Felker III]

On Fri, Apr 08, 2005 at 01:38:03PM -0700, Scott W. Larson wrote:
> 
> > Perhaps the video actually has this many extra frames, to increase the
> > length by 1/7? Without seeing a sample I have no idea..
> 
> I think this is unlikely but I'll step through this part of the video
> tonight and see if the 2:3 pattern is consistant through it. I definitely
> don't see any choppiness in the original.

Even a 2:3 pattern is extremely choppy..

> > What's happening is that
> > _mencoder_ is skipping frames to drop down to only 24 frames per
> > second. If the phase of mencoder's skipping is lined up with the
> > telecine pattern, you'll get the exact right sequence.
> 
> And I should be able to prove this is what's happening by running mencoder
> with no filters at all with fps set to 59.97 and ofps set to 23.967. The

Never set -fps manually; mencoder knows the input fps. Also, the
numbers are 60000/1001 and 24000/1001, NOT 59.97 and 23.967.

> > Filmdint on the other hand will do some skipping on its own to make
> > the output 24 fps. However, I don't think it will try to match up
> > which frames are duplicates in any sane manner.
> 
> The man page says filmdint was "designed to handle any pulldown pattern".
> I guess I shouldn't interpret that claim that too literally.

This "progresive telecine" nonsense of HDTV did not exist when that
was written, or none of us had ever heard of it. Anyway, what you have
is not pulldown, imo.

My definition of pulldown: any process for converting a sequence of
progressive frames to a sequence of fields.

Notice the word fields. If the output is still progressive, I call it
framerate conversion by frame duplication, not pulldown. But this is
getting into silly semantics.

> Well, it would be great if there were a filter that could lock onto the
> 2:3 progressive pattern. I wonder if decimate could just remove all the
> duplicate frames leaving 24 fps output.

Possibly, with the right settings. You need to adjust the thresholds
so it doesn't drop too much or too little.

> The man page claims that pullup can handle 30 fps progressive material.
> Would I be taking this claim too literally to think I can simply drop
> every other 60 fps frame and expect it to inverse telecine the result
> correctly?

No. What that means is that it will pass progressive content through
UNCHANGED. This is not what you want. The duplicate frames will still
be there.

Rich