[MEncoder-users] Juddering problem

[Rich Felker]

On Sun, Sep 09, 2007 at 11:15:45AM +0100, Ross Clement wrote:
> Hello all. I apologise for asking what I still think is a newbie question,
> but I've searched and experimented, and can't solve my problem.
> 
> I want to be able to take dv files from a camcorder, and convert them into a
> form suitable for playing on my DVD player. I'm able to create DVD suitable
> mpegs using both mencoder and ffmpeg. And I've been creating divxs using the
> attached script ( encode.bash)  and I attach a "script file" (encode.script
> ).
> 
> Generally the quality is OK except for an awful "juddering" effect on fast
> moving objects. They move in a "juddering" way. Say if you have a fast
> moving arm, then I don't see a single arm making a smooth movement, but see
> what seems to be an arm making jerky movement, and it's almost like seeing
> the same arm in several positions at once.
> 
> I'm guessing this is a standard newbie problem, but can't find how to fix
> it.
> 
> Can anyone please help how I can fix this problem?

The problem is wrong field order. Interlaced video consists of 2
fields that are sampled at distinct moments in time. When these fields
are artificially paired up for encoding, sometimes top-field-first
order is used and sometimes bottom-field-first order is used.

If you deinterlace, this would be a non-issue but it will effectively
lose half the framerate/quality of your video. If you're preserving
the interlacing, lavc has options to select which field is first and
there's a filter to actually change the phase of the video too. See
the man page or html manual on encoding.

Rich