Take a mono raw audio stream, PCM 16bit little endian, as produced by the fifo output of mpd and generate a binary spectrum with a number of unsigned 8 bit lines for visual spectrum analyser projects like for Raspberry Pi.
Inspired by cava.
Differences:
- Only mono
- No audio drivers or other platform specific things (let other software interface the hardare, because, duh, that's simple!)
- Just output, no spectrum display (except test/spectrum.jl)
- Somewhat different handling of data (for example no frequency cutoff but you can omit lower- and higher-frequency bins)
- Logarithmic scaling of lines
- Usage of Julia for tests
This software is not ready for everybody's use. Not all options are implemented, also tests are still missing. It works, I get some nice spectrums however I need to make it more user-friendly, too.
- More tests (especially integration tests from generated audio from pcm.jl)
- Invalid parameter tests
- Gravity and other scaling options
- Options to make frequency calculations easier "so this spectrum line is at 440 Hz"
- Option
-rto average over several samples
First install fftw3 then $ make auspan.
-
Generate a sine wave and display it as a spectrum with 10 lines:
$ cd test$ pcm.jl -n 2048 "3000*sin(x/10)" | ../auspan -s 2048 -l 10 > asa-spectrum$ spectrum.jl -l 10 -
From mpd generate a 10-line spectrum about every 93 ms:
$ auspan -s 4096 -l 10 /tmp/mpd.fifo /tmp/spectrum.fifo
It's possible to configure mpd to output mono audio to a fifo. The audio data is PCM with signed 16bit little-endian integer samples at a sample rate of 44.1 kHz. The option-sdefines the sample span size for FFT. So we have a spectrum every 4096 / 44100 ≈ 93 ms.