[MPlayer-users] Re: mpeg's and inverse telecine question

[D Richard Felker III]

On Sun, Oct 12, 2003 at 03:32:57PM -0400, Steven Adeff wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> a few general questions on mplayer's IvTc and filters
> 
> How does mplayer's ivtc for hard telecined mpeg's compare to other offerings?

Here's my summary:

Various windows programs: Mostly work, but often give a few bad
frames, and they're very likely to botch vertical pans. Some (?) allow
you to manually override for individual frames, but that's a LOT of
work! I don't have any experience using them, so I'm just speaking
from what I've read and from the poor jobs I've seen on many anime
divx releases. In particular, they focus too much on the frame as a
whole rather than local properties, so they will often mess up if just
a small detail is moving (for example, mouths in anime).

MPlayer's "detc": Mostly works and fairly tolerant of noise. But it
can and will give a bad frame at certain scene changes. If you run a
linear blend after it, this won't look bad, but otherwise it's a big
problem.

MPlayer's "ivtc": Robust against telecine weirdness (non-2:3 patterns)
but at the expense of robustness against noise. If your input is noisy
(e.g. from analog tv) it will most likely fail. Denoising could help.

MPlayer's "pullup": By far the best algorithm of the three, and I
would suspect it's the best algorithm available outside of proprietary
hardware implementations. The code is written to be independent of
MPlayer, and in fact it doesn't work very well with MPlayer G1 because
of limitations in G1's filter architecture. (It needs to decode
several frames ahead to make its decisions.) Although the basic
algorithm is very solid, it's not as mature or well-tested as the
others, and the support for it in MPlayer G1 is less than perfect. One
advantage it does have, though, is that it can handle mixed hard- and
soft-telecine movies without needing the "softpulldown" filter loaded
first. Pullup will definitely be the inverse telecine engine of choice
once MPlayer/MEncoder G2 is ready for general use.

> Is it better to run the 3d noise filter before or after the ivtc ?

If you have very noisy content, denoising before doing ivtc might help
a lot. BUT !!! you can't just denoise the video as-is, because this
will mix fields which may not belong together. Instead you need to do
something like:

-vf il=d:d,denoise3d,il=i:i,ivtc=1

To understand why this works, just run mplayer with -vf il=d:d and
look at the output. It separates the fields, so you get to denoise
them by themselves rather than interleaved together. Then il=i:i puts
them back together.

Rich