Implementing AMR encoder

I have 8k 16bit PCM and I want to implement algorithm for converting it to AMR. How should I proceed?

I need some kind of guide or tutorial explaining how to encode PCM开发者_开发问答 to AMR.

Note: For now I only need to be able to encode PCM to AMR without decoding mechanisms.

I found all I needed here http://en.wikipedia.org/wiki/Adaptive_Multi-Rate_audio_codec in the links section.