I found somewhere the format for wav files, my question was whether or not Qt provided some support in reading and interpreting, e.g. some object that abstracts from the layout of the file. I have been looking around and intend to write a simple object with just some functions for opening, closing and reading the data.
Wrt your question, the demodulators I support are analog, rtty, psk, mfsk, navtex, cw, and fax. All to a certain extent, and most of them based on or at least inspired by other software. All software - apart from the FFT library that I am using (fftw) - is written by me. I started the development as a hobby project, and it still is.
The gui is qt based, the supported device is the elektor card from 2007 (including the extension with an antenna filter.
Soundcard support is using portaudio, Qaudio doesn't work with alsa.