[MPlayer-users] slightly OT - converting divx files

[Alexander Roalter]

Daniel Harris wrote:
> Hello all
> 
> I have been experiencing problems when converting divx files to dvd.  The
> problem seems to be the divx files are usually encoded with a frame fate of
> 23.9 but I try to set them to 25fps to watch on a pal dvd.  The conversion
> process makes the dvd freeze slightly every now and again on playback.  What
> is the correct way to do this type of conversion to ensure smooth playback
> on dvd/tv.
> 
> Thanks in advance for any feedback..
> 
> I must admit that for the conversion process I usually use ffmpeg.
> 
That depends on what you mean with "every now and again".

Playing 23.9 (or 24) fps as 25 fps would meen a freeze every second, as 
one frame has to be shown twice as long as the other ones. Normal TV 
sets do some special interleaving, so you see two half frames per second 
twice.

What's usually done is speeding up the video to 25 frames, thus making 
the sound half a note higher and the video 4% shorter, where such 
jittering should not occur. As what the steps are to achieve this with 
mencoder I'm not all that familiar now.

If you're even stuck with 29.9 fps NTSC content, the things are even 
more complicated, since you have to create again a 23.9 fps video and 
then go the same way as before.
This is only possible if your input video was created from a 24fps 
source, as then in a 29.9fps video 6 frames are simply duplicates from 
others (or 12 half-frames). If its natively shot in 29.9 fps, you have 
to drop either 6 frames and speed up the thing or drop 5 frames and 
retain the original speed.

-- 
cheers,
Alex