This project was conceived in ealy 2013 as a simple open iOS library for encoding and decoding Speex audio files, but was abandoned soon, because I had neither resources nor skill and motivation to implement it at the time.
However I decided to publish here a small demo Xcode project, which can be of some help as a rough reference about how the encoding can be done. It was initially posted about two years to illustrate my answer on Stackoverflow, but now the link there is not working anymore.