After a succesful compilation of rtl_fm (I can elaborate, if needed), I'm currently facing various issues for a "complete" FM receiver.
1/ As "play" (from the sox package) can't find any default device (how to set that ?), I used aplay instead from the ALSA package. After much testing it appears the current sound driver (and/or aplay) only accept raw files sampled at 44100 and 48000 Hz. When using other sampling rates files, aplay doesn't complain, no sound is output, the raspi just hangs, and a reboot is required. I guess it is a sound driver bug (or a limitation ?).
2/ Thus, I used the 44100 sampling rate (a bit wide for NBFM), but it only works few seconds before hanging.
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rtl_fm -f 144800000 -s 44100 -g 9 -l 10 - | aplay -t raw -r 44100 -c 1 -f S16_LE
(-l 10 ensures I can hear the FM background noise).
There are some indications of underrun, which mutes the audio for few milliseconds, and few seconds after, no more sound, no more network (I'm using SSH for now), and a reboot is required.
I'm using the 2012-07-15-wheezy-raspbian image.
If you own a DVB-T dongle and you are more proficient in linux that me, please try it and report your results !
Larry - F6FVY