Libav has a defined coding style, sadly ancient code doesn't adhere to it, your task is to pick a file, reformat it properly and send an patch to the mailing list (also upload it here).

You can clone the source using git, clone git.libav.org/libav.git or fork on github .

The coding style is defined here

The quick git tutorial is available here

Ask on #libav on irc.freenode.net for help and guidance. Every file with more than 1500 lines cleaned up grants an hard task.

You are supposed to know how to use git send-email in order to send the patch on libav-devel

This task doesn't have a limit in how many times you can take it.