jpg to avi

[Barry]

'mencoder "mf://~/photos/bdtram/dcp_0092.jpg" -mf fps=25 -o output.avi 
-ovc lavc -lavcopts vcodec=mpeg4'
will produce a avi file with but a single frame. How do I alter the cmd 
to produce a avi file with many frames of the same jpg so it wil display 
for a set period of time eg 1sec, 2sec etc?

TIA
Barry