# checkout the latest version of the source
svn checkout svn://svn.ffmpeg.org/ffmpeg/trunk ffmpeg
# enable mp3 support (you need to install lame first. omit --enable-libmp3lame to build without it)
./configure --enable-libmp3lame --enable-shared --disable-mmx --arch=x86_64
sudo make install
Here are some of the commands I've run so far..
Rotate a video 90 degrees clockwise (good for films shot in portrait
ffmpeg -vf "transpose=1" -i input.mp4 output.mp4
Note that there are many tutorials on the web that suggest you should use --vfilter "rotate=90" to rotate a video. This no longer works, as vfilters has been renamed vf, and the rotate option has been removed. As of Dec 2010, the above command does work.
Convert a mp3 to a flv audio file
ffmpeg -y -i myfile.mp3 -f flv -acodec libmp3lame -ab 64 -ac 1 myfile.flv
I'm using this command as part of a project I'm working on, flv is better than mp3 as you can stream (using flowplayer) an flv in such a way that user can jump around to any point of the audio without needing to download it all to that point. However, this is quite fiddly, a future blog post will explain how I did this!