[MPlayer-dev-eng] Re: Interlaced MPEG streams

[Rémi Guyomarch]

On Fri, Jul 05, 2002 at 02:59:17AM +0200, Kim Minh Kaplan wrote:
> Hello,
> 
> I recently tried to encode a movie that looks like interlaced MPEG
> (Dune).  This is a 25fps movie but each frame is plit in two parts.
> For some reason, mencoder skips all frames (skip frame!!!).  If I
> force the encoding into 50fps then things are fine except that this is
> not what I want, I want to do a 25fps encoding.  I came up with some
> patch for that, but first am I missing some options that should solve
> the problem without my hacking the sources?
> 
> You can find a small chapter of the movie at
> <URL:http://kloug.dyndns.org/~kmkaplan/dune-chapter-10.mpg> if you
> want to see what I mean...

I have seen many DVDs encoded like that and I'm seeing people here
having the exact same problem. Right now I'm quite sure there's no
built-in solution to this problem, beside -ofps 50 which is by far non
optimal.
I tried to hack a bit mencoder but so far I didn't produced something
useful. Did you succeded to produce a 25fps avi ? Could you share your
hacks ? :)

Arpi : Those mpeg streams have half-frames encoded separately, I mean
video_read_frame() in mencoder.c:919 return with sh_video->num_frames
like xx.5 for each odd frame.
The solution would be to decode two frames at once in a buffer and
only then send this decoded 'real frame' to the other video filters
down to ve_*.c encoders. But the architecture of mencoder doesn't
makes it easy. At least to me :)

-- 
Rémi