How do I compile ffmpeg on a QNAP NAS

Tested on QNAP TS-419p+ with ARM CPU, but should work the same way for others.
Install “Optware (IPKG)” qpkg from http://www.qnap.com/qpkg.asp
In case the “ipkg update” fails, try to adjust the following two config files:

[/opt/etc/ipkg] # more tsx19-kmod.conf
src/gz cs08q1armel http://ipkg.nslu2-linux.org/feeds/optware/cs08q1armel/cross/unstable
[/opt/etc/ipkg] # more tsx19.conf
src/gz cs08q1armel http://ipkg.nslu2-linux.org/feeds/optware/cs08q1armel/cross/unstable

ipkg update
ipkg install optware-devel
ipkg install git
ipkg install yasm
ipkg install lame

mkdir /opt/compile
cd /opt/compile
git clone git://git.videolan.org/ffmpeg.git

cd ffmpeg
./configure --enable-ssse3 --prefix=/opt --extra-cflags='-I/opt/include' --extra-ldflags='-L/opt/lib' --enable-static --disable-shared --disable-ffplay --disable-ffserver --enable-libmp3lame
make
make install

replace built-in ffmpeg with link to new version

rm /usr/bin/ffmpeg
ln -s /opt/bin/ffmpeg /usr/bin

http://bubblesoftapps.com/bubbleupnpserver/#faq7