Sometimes you may run across AVI files with a corrupted index, especially when watching old AVI files. The index helps the multimedia players to fast forwarding or reversing rapidly within the movie file. Without an index or with a corrupted index jumping within the movie file either doesn’t work or might take a long time.

There are two ways to repair AVI files with a corrupted index using powerful open source software:

• Mencoder
• FFmpeg

The easiest way to install both of this tools under macOS is using ‘Brew‘. ‘Brew’ is a package manager for macOS. If you want to use ‘Mencoder’ oder ‘FFmpeg’ under another operation system you might use Google for installation notes.

The following commands will install ‘Brew’, ‘MPlayer’ (‘Mencoder’ is part of ‘Mplayer’) and ‘FFmpeg’. You have to copy and paste these commands into your macOS Terminal. Note: In order to install ‘Brew’ your macOS user account needs administrator rights.

/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
brew install mplayer
brew install ffmpeg

After having installed the software packages you might use either of these two tools to fix a corrupted AVI file index.

mencoder -idx input.avi -ovc copy -oac copy -o output.avi
-or-
ffmpeg -i input.avi -vcodec copy -acodec copy output.avi