I like to download video files from the Internet, and I have faced annoying problem: Broken or missing AVI indexes. My initial search for a solution was turning up paid software, but I persisted and found a nice open source solution using our old friend ffmeg. The command to use on the command line is:
ffmpeg -i input.avi -c copy output.avi
I found this to be very quick and easy, and I got the new output file in seconds.
Links
https://superuser.com/questions/4570/how-can-i-repair-a-broken-avi-file
https://www.palain.com/