fm95

FM95 is a audio processor for FM, it does:

• Pre-Emphasis
• Stereo
• Polar Stereo
• SCA

Supports these inputs:

• Audio (via Pulse)
• MPX (via Pulse, basically passthrough, i don't recommend this unless you have something else than rds or sca to modulate)
• RDS (via Pulse, expects unmodulated RDS, stereo, left channel on 57 KHz, right on 66.5, rds95 is recommended here, in modulation this is inphase to the pilot)
• SCA (via Pulse, by default on 67 khz with a 7 khz deviation)

and one output:

• MPX (via Pulse)

How to compile?

To compile you need cmake and libpulse-dev, if you have those then do these commands:

mkdir build
cd build
cmake ..
make

Done!

CPU Usage?

Should run completly fine on a pi 5, right now with the preemp and rds2, on a pi 3b, its 25%-27%

Recommendations

use a lpf, for example swh-plugins's lowpass_iir, for example:

pactl load-module module-null-sink sink_name=FM_Audio rate=48000 # this goes to fm95
pactl load-module module-ladspa-sink sink_name=FM_Audio_lpf sink_master=FM_Audio plugin=lowpass_iir_1891 label=lowpass_iir control=15000,6 rate=48000 # use 4 poles minimum, i recommend 6
pactl load-module module-loopback source=radio_audio.monitor sink=FM_Audio_lpf rate=48000 # from the apps to the filter

Other Apps

FM95 also includes some other apps, such as chimer95 which generates GTS tones each half hour, and dcf95 which creates a DCF77 compatible signal