Audio captcha decoder using MFCC features and support vector machines
This was built a few years ago, I'm releasing part of it now since it's probably no longer relevant and won't cause trouble.
Uses MFCC extractors from https://code.google.com/p/speech-recognition-java-hidden-markov-model-vq-mfcc/
Uses Java Wav File class from http://www.labbookpages.co.uk/audio/javaWavFiles.html
Uses LibSVM https://www.csie.ntu.edu.tw/~cjlin/libsvm/