[MEncoder-users] Adding a silent soundtrack to a video-only file?

[GuyWithDogs]

I've got some files in various formats - AVI, DivX/AVI, WMV, MPEG-1, etc. - 
that have no audio track. I'm working on a Windows box, and I used Windows 
Movie Maker to add an audio track of "silence" to one of the WMV files. It 
worked, but it's a pain to try and do the bunch of files I have.

I thought mencoder would be able to help, but I'm not able to sort out 
enough of the docs to understand whether I really can do this. The 
silence.mp3 file I have is about 3 seconds long, and the video files range 
from 10 to 60 seconds in length.

Is there some way I can coerce mencoder to create a new output file of the 
same format as the input file, but with the silence.mp3 added as the 
"soundtrack" (repeated as many times as necessary to match the length of the 
video clip)?

Thanks.