The VideoLAN Forums

When I tried to play a file downloaded from the net VLC player noted that its indexing was corrupt. Offered fixing and after that playing, and did so. I couldn't find a way however to save the reparation. Next time I had to wait a long time again until the playing could start. Of course I looked through the convert / save section in vain though.
Thanks a lot.

VLC can't do that. You need to remux the file with AviDemux or any other similar application.