[MEncoder-users] 23.976 --> 25 fps conversion problem

[Grozdan]

On Wed, Jun 30, 2010 at 2:21 PM, Tamas Selmeci <tselmeci at open-st.eu> wrote:
> Hi all!
>
> My task is to convert any incoming .AVI video into a well-defined format:
> AVI container, Xvid encoder, 25 fps @ 1800 kbps video, MP3 @ 48000 Hz, 128
> kbps.
>
> Everything seemed to work fine until I've received a recent movie with an
> fps value of 23.976. What mencoder does is just duplicating the last frame
> after every 24 frames, thus producing a 25 fps output file. But in case of a
> bit more action in the scene, the viewer will realize a small "stop" in the
> movie flow and it destroys the "movie experience".
>
> With the correct mixture/selection of noskip, -mc 0, etc. I was able to make
> mencoder not duplicating the last frame after each 24 frames, but then the
> A/V sync broke. Obviously, the sound was arriving much later, since a 23.976
> fps video was played at 25 fps.
>
> According to Wikipedia, telecine/pullup methods are for solving these
> problems for the case e.g. 23.976 fps --> 30 fps. In the case of mine 25 fps
> is fixed, can not be changed at all.
>
> Is there any way I can produce 25 fps movie output from 23.976 fps material
> with frame interpolation/appropriate telecine/pullup? -vf pullup did not
> solve my problem. That annoying "stop" in movie flow must not be present at
> all.

Not with mencoder. You can do the reverse (eg, 25 -> 23.976) but not
what you ask. There are no filters/ways current to do that with
mencoder

also note that -mc 0 *completely* disables the mencoder A/V sync algo,
so the probability of having sync issues increases (dramatically in
some cases)

>
> (My rescue idea is to recode video at 25 fps without frame duplication, thus
> the movie duration will decrease by ~4% [23.976/25], and the audio is
> resampled at a 4% higher frequency to keep A/V sync)

This is a very common used technique, even by major studios. They just
speed it up

>
> Thanks in advance!
> --
> Selmeci, Tamas
> http://www.open-st.eu
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