3.13.0-61.100) is not available, but a newer one is (3.13.0-166.216). We redirected you there.
/usr/share/avconv/libx264-medium_firstpass.avpreset is in libav-tools 6:9.11-2ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | preset=medium
fastfirstpass=1
|