[MEncoder-users] pullup question

[Scott W. Larson]

> Am Mittwoch, 21. Januar 2009 14:45:05 schrieb Scott W. Larson:
> That is what I see with some 1080i recordings. One of my local stations
> mangles some movies so bad that all postprocessing methods fail (mixed
> progressive, telecined and interlaced content all in one recording, and
> on top of that they speed up parts of a movie) .

On American broadcast networks all filmed content is telecined. Shows shot
on HD video like comedies are also usually telecined from 24 fps source
but there are some exceptions. Specials like the Academy Awards will
naturally have a mix of interlaced or 60 fps progressive (depending on the
network) and telecined filmed content. Another exception are Mark
Burnett's reality shows like "Survivor" which are all 30 fps. They felt
that was a good compromise between the look of video and film.

> Other stations broadcast mixed progressive and telecined, or plain
> telecined, and -vf pullup restores the original 24p framerate (almost)
> perfectly.

The problem is that as stations drop their bit rate to make room for
subchannels, the content becomes harder to detelecine (if that's the
word). The filters have more trouble matching fields and locking onto the
telecine pattern because any camera motion turns the content into a mass
of scrambled blocks. Before my local stations dropped their bit rates,
filmdint worked perfectly on 1080i content (with the patch). Now it
constantly gets lost and I haven't found any set of filmdint parameters
that work any more.

This has also affected 720p stations. Converting that to 24 fps used to be
as simple as throwing away half the frames and using decimate to get rid
of the duplicates. Now the problem is that on stations with reduced bit
rates, telecined material isn't a clear 2/3 duplicate pattern any more.
You'll find that often the first frame in pattern is missing a lot of
detail that couldn't be included in the lower bit rate but it's added in
the "duplicate" frame(s) that follow it. In other words, all the frames
are different so decimate can't find any duplicate frames to eliminate, It
will often let two frames that are duplicates (to our eyes) through
causing stutter.

Of course stations don't care about this. As long as the content looks
good to their viewers, these practices are acceptable to them. In fact
many people think the reduced bit rate 720p content looks better because
24 fps content looks smoother when each individual frame is smeared
between multiple frames.