Video acceleration is 16 times?

mencoder with the-speed option.
Manuals Google full, but may require selection of parameters.

you can try mencoder with-ovc copy -oac copy — not to perekodirovat and -ofps — increased fourfold output fps
\r
\r

mencoder-noskip -ofps 95.904 -ovc copy -oac copy $inputfile -o $outputfile

where 95.904 — 4x23.976 fps source
if a ride — -ovc copy -oac copy will be forced to use processor and hard drive

forum.doom9.org/showthread.php?t=124648
But most likely the processor does not pull.
\r
If you want to change the FPS, throwing away the footage, without transcoding can not do.

Rebuild the video and audio in mkv container, there you can set a frame rate.