converting MJPG to H.264

[mulargui]

Hi,
I'm trying to convert my camera's movies to h.264. The files are MJPG hi res 1280x720 and 24 frame rate. I've been playing a while with the configuration to adjust quality and now I'm pretty happy with it. Nevertheless, the resulting file plays MUCH slower, looks like half speed (not verified). what do I need to do to set the proper speed?

Thank you in advance for the help and support.