[MPlayer-users] mjpeg fps change

[Alex]

Hello,

I have a mjpeg video file with the following properties, as reported by 
mplayer:

VIDEO:  [MJPG]  320x240  24bpp  59.940 fps  7478.5 kbps (912.9 kbyte/s)

I would like to create a version of that file that plays at 1/2 the 
speed (i.e. twice the length at 29.97 fps).  Preferably, I'd like the 
frames to just be copied so that no re-compression is done.

Is there a way to do this?  One way I thought was to extract the jpg 
frames from the clip into individual files, then re-creating the movie 
from the files.   I saw that mencoder can create a mjeg file from 
individual files, but I didn't see how to do the opposite.

Any help would be appreciated.

Thanks,

Alex