[MPlayer-users] how to prevent mencoder from framedropping while converting videos?

[DrakeGuan]

I'm using the following to convert one video from divx to mjpeg

mencoder -o /tmp/output.avi input.avi -ovc
lavc -lavcopts vcodec=mjpeg -oac mp3lame -srate 48000 

but it always outputs 'skipping frame' blah blah, 
but I don't wanna any skipping @@

I have tried -noskip but it has no effect! weird? 

has any idea?