[OT] Convert .mpeg file from stereo to mono?

[LeeUKHA <mailinglists@xxxxxxxxxxx>]

Slightly OT, but only just...

I've borrowed a Pinnacle analog video capture card, to get all my
family/holiday/home videos onto DVD (and my media server).
Now that I've spent a few weeks transferring  many hours of video to the
PC, I've found that due to not paying attention when I plugged it all
together, all the .mpeg files are in stereo, but as the camcorder is
only mono, the sound is on the left channel and the right channel is
silent...

Playing it through VLC has a 'mix stereo to mono' option which works
great, but I can't find anything to permanently fix this in the .mpeg
files. Anyone know of anything?

Cheers,
Lee