[LAD] Identify Peek in Drum Samples

Hello I bought the natural drum samples (http://www.naturaldrum.com/). It contains WAVs and presets for Kontakt and Halion. Now I'd like to create some gigasampler files in order to use it with linuxsampler. The documentation of the natural drum sample library is quite good. The only thing missing is the "loudness" of each sample in order to map each sample to a velocity level from 0-127. What would you recommend in order to calculate the "peek" of each drum sample automatically? Is there a library which could do this? I would also be happy with a command line tool like this: $ peek bla.wav Peek value: 12345 I could then write a C++-App using libgig. Any ideas? Libraries? Algorithms? Thanks! Oliver