[MEncoder-users] Choppy video when changing framerate

[Manuel Carro]

Hello.  I know this is a recurrent topic in mencoder (and probably in
other similar tools, too).  I have had a quite thorough look @ the
messages so far but I am afraid I found no definitive answer.  Please
bear with me if this is not the case (and please point me to the
appropriate message).

    I am trying to reduce the framerate of video files (whatever their
original framerate is - 23.97 FPS, 24 FPS, 25 FPS, etc.) to something
in the range 18 FPS to 20 FPS.  The reason is that I want to play them
in a media player -- a Meizu M6.  This involves as well scaling (to
QVGA) and rotating, but this is not a problem.  The Meizu needs and
AVI container and the audio codec can be mp3, and can decode divx /
xvid (tried with both xvidenc and lavc without problems, although the
presence of B frames makes it freeze).

    Using the -ofps option makes the video to definitely look choppy.
And it is not a question of the player itself: the same video (after
reducing the framerate) looks choppy when using mplayer, xine, totem,
etc.  I assume that, to go e.g. from 25 to 20 (my current benchmark)
-ofps could remove one out of each five frames.  But, when playing
back, it looks as if those removals were not happening evenly, but
rather in groups every second or so.  I do not think mencoder is doing
that (is it?).  Any hint of what could be the problem (and the
solution)?

Many thanks in advance for any suggestion!

        MCL (mcarro_at_fi_dot_upm_dot_es)
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