[MEncoder-users] framerate control question

[Trent Piepho]

On Mon, 20 Nov 2006 pfile at pacbell.net wrote:
> lets say i have a video which was encoded at 60000/1001, with 10,000
> frames. through decimation of 3 frames out of every 5, i now have a
> video with 4,000 frames intended to be played back at 24000/1001. in
> theory, these two movies should have the same playback time.
>
> in this situation, why does mencoder have to insert duplicate frames
> to maintain the proper framerate? are the extra frames required
> solely due to rounding error in the frame display time? i've observed
> that with -noskip -noencodedups, the video is always about 6% shorter
> than it is supposed to be.

How are you removing 3 out of 5 frames?  Could it be some problem where not
enough frames are getting dropped by whatever you are using to do inverse
telecine?  Of if it's ending up short, maybe too many frames are getting
dropped?

> i'm wondering how in heck to get a nice smooth 24p version of a 60p
> ATSC transmission which doesnt require timestretching the audio.

I wrote a filter that does the inverse telecine for progressive content
(drops the duplicate frames) and encode with -ofps 24000/1001 -mc .042 and
it appears to work very well.  I'm using -oac copy to preserve the original
AC3 audio.