This task is very free-form, and can thus be done many times, but each time it's different. Concept is simple: go to http://bugzilla.libav.org/, find a (coding) bug, reproduce it, and fix it. Each fixed bug earns you points.

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.

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