The purpose of minidemod-wfm.c is to have a few lines of code that can actually demodulate WFM from an I/Q input.
The whole DSP chain is built by OS pipes, just like this:
rtl_sdr -s 240000 -f 89500000 -g 20 - | tcc -lm -run minidemod-wfm.c \
| sox -t raw -r 240000 -e unsigned -b 8 -c 1 - -t raw - rate 48000 \
| mplayer -quiet -rawaudio samplesize=1:channels=1:rate=48000 -demuxer rawaudio -
Read like this:
rtl_sdr (acquires samples) | minidemod-wfm (demodulates) \
| sox (low pass filter + decimation) | mplayer (audio output) `
To run it, you will need a Linux box with rtl_sdr tcc sox mplayer installed.
I've also added minidemod-wfm-atan.c with a detailed explanation of the demodulation process. It does sound better, but uses more CPU (still not more than 10% on my box).
András Retzler ha7ilm@sdr.hu
Also tnx dnet for the small fixes.