If you are having troubles compiling FFMPEG and are seeing errors with LibGL such as:
No package ‘x11-xcb’ found
You need to do a few things.
Firstly upgrade X11: portupgrade libX11. This has been noted to solve a lot of problems so do this first, retry and see if it fixes it.
This however might fail in which case you are going to need to upgrade xproto first as X11 will look for a later version of Xproto than might already be on the server. doing a simple portupgrade might not work so:
So cd /usr/ports/x11/xproto & make clean & make deinstall & make reinstall
now you should be able to go into /usr/ports/x11/libX11 and:
make clean & make deinstall & make reinstall
and now finally LibGL will install properly and consequentially so will FFMPEG
