Signal Processing in Go

I have come up with an idea for an audio project and it looks like Go is a useful language for implementing it. However, it requires the ability to apply filters to incoming audio, and Go doesn't appear to have any sort of audio processing package. I can use cgo to call C code, but every signal processing library I find uses C++ classes which cgo cannot handle. It looks like libsox may work. Are there any others?

What libsox can provide and what I need is to take an incoming audio stream and divide it into frequency bands. If I can do this while only reading the file once, then bonus! I am not sure if libsox can do this.

If you want to use a C++ library you could try SWIG, but you'll have to get it out of Subversion. The next release (2.0.1) will be the first released version to support Go. In my experience the Go support is still a little rough, but then again the library I tried to wrap is a monster.

Alternatively, you could still create your own bindings through cgo using the same method SWIG does, but it will be painful and tedious. The basic idea is that you first create a C wrapper, then let cgo create a Go wrapper around your C wrapper.

I don't know anything about signal processing or libsox, though. Sorry.

There is a relatively new project called ZikiChombo
which contains so far some basic DSP functionality geared toward audio, see here

The dsp part of the project has filters on its roadmap, but they are not yet there. On the other hand some infrastructure for implementing filters, such as real fft and block convolution is there. Meaning that if you want FIRs, and can compute the coefficients by some other means, you can run them via convolution in zc currently with sound in real time.

Basic filtering design support (FIR,Biquad), for example using an ideal filter as a starting point will be the next step for zc. There are numerous small self-contained open source projects for basic and more advanced FIR and IIR filter design, most notably Iowa Hills which might be more accessible than a larger project to compute filter coefficients outside of Go.

More advanced filtering such as Butterworth, and filters based on polynomial solving and the bilinear transform will take more time for zc.

There is also some software defined radio Golang projects with some code related to filtering, sorry don't have the links offhand but a search for the topic may lead you to them.

Finally, there is a gonum Fourier package which also supplies fft.

So Go is growing some interesting and potentially stuff in this domain, but still has quite a ways to go compared to older projects (which are mostly in C/C++, or perhaps with a Python wrapper via numpy for example).

I am using this pure golang repo to perform Fourier Transforms with good effect

https://github.com/mjibson/go-dsp

just supply the FFT call with a

import (
    "github.com/mjibson/go-dsp/fft" //  https://github.com/mjibson/go-dsp
)

var audio_wave []float64
// ... now populate audio_wave with your audio PCM samples

var complex_fft []complex128

// input time domain ... output frequency domain of equally spaced freq bins 
complex_fft = fft.FFTReal(audio_wave)