DuFFMpeg
Tools for FFmpeg and Adobe After Effects
You will need FFMpeg binaries which can be downloaded here: http://ffmpeg.org/download.html More info about FFMpeg on the official website: http://ffmpeg.org/
The folder DuFFmpeg contains a stand alone UI for FFmpeg in Qt/C++. Its development has just begun but it can already be tested.
The folder ExtendScript-After_Effects contains the scripts developped use FFmpeg easily in After Effects (Library and UI)