Based on:
http://www.inb.uni-luebeck.de/~boehme/using_libavcodec.html
http://www.inb.uni-luebeck.de/~boehme/libavcodec_update.html
http://www.inb.uni-luebeck.de/~boehme/avcodec_sample.0.4.9.cpp
ConverterExample - Based on AVCodecSample and OutputExample
Converts a video file with the first video and the first audio stream to a new format given by filename extension.