fm95

FM95 is a audio processor for FM, it does:

• Pre-Emphasis
• Low Pass Filtering
• AGC
• Stereo
• BS412 (mpx power limiter, simplest implementation ever)

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, you could run chimer95 via here, also you have 5% allowed here by default to be guarenteed with no clipping, change how much headroom you have with the headroom option)
• RDS (via Unix Socket, expects RDS bits without differential encoding with checkwords, rds95 is recommended here)

and one output:

• MPX (via Pulse)

How to compile?

Note that you're required also to load submodules, if you don't know what that means, ask ChatGPT

To compile you need cmake, liquid-dsp 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, fine on a pi 3b (~30% cpu)

Other Apps

FM95 also includes some other apps, such as chimer95 which generates GTS tones each half hour, and vban95 now which is a buffered VBAN receiver. And now also SCA generation was moved to sca95 from fm95!

Usage of other projects

The apps use inih by Ben Hoyt.