visualizer2

Audio-Visualization in Rust. visualizer2 is my second (actually third) attempt at creating pretty visuals that somehow behave in sync with a live audio signal. The first attempt can be found here.

Visualizers

There are a few ready to use visualizers in this repository:

noambition

Based on the noambition visualizer from pa-visualizer, which in turn is based on the demo No Ambition by Quite & T-Rex. That said, this version no longer has a lot of similarities ...

noa-35c3

Version of noambition that was adapted for 35c3.

no-midi

A visualizer which sends MIDI commands. These MIDI commands can be fed into a lighting controller to then control fancy event lighting equipment.

Check the no-midi README for more info.

spectral

A debug spectral display.

Project Structure

The core concept of visualizer2 is the following: The vis-core crate contains all the glue logic and building blocks for analyzing the audio signal. The goal is that creating a new visualizer needs as little boilerplate as possible. In practice, the following code is all you need to get started:

// The data-type for storing analyzer results
#[derive(Debug, Clone)]
pub struct AnalyzerResult {
    spectrum: vis_core::analyzer::Spectrum<Vec<f32>>,
    volume: f32,
    beat: f32,
}

fn main() {
    // Initialize the logger.  Take a look at the sources if you want to customize
    // the logger.
    vis_core::default_log();

    // Load the default config source.  More about config later on.  You can also
    // do this manually if you have special requirements.
    vis_core::default_config();

    // Initialize some analyzer-tools.  These will be moved into the analyzer closure
    // later on.
    let mut analyzer = vis_core::analyzer::FourierBuilder::new()
        .length(512)
        .window(vis_core::analyzer::window::nuttall)
        .plan();

    let spectrum = vis_core::analyzer::Spectrum::new(vec![0.0; analyzer.buckets], 0.0, 1.0);

    let mut frames = vis_core::Visualizer::new(
        AnalyzerResult {
            spectrum,
            volume: 0.0,
            beat: 0.0,
        },
        // This closure is the "analyzer".  It will be executed in a loop to always
        // have the latest data available.
        move |info, samples| {
            analyzer.analyze(samples);

            info.spectrum.fill_from(&analyzer.average());
            info.volume = samples.volume(0.3) * 400.0;
            info.beat = info.spectrum.slice(50.0, 100.0).max() * 0.01;
            info
        },
    )
    // Build the frame iterator which is the base of your loop later on
    .frames();

    for frame in frames.iter() {
        // This is just a primitive example, your vis core belongs here

        frame.lock_info(|info| {
            for _ in 0..info.volume as usize {
                print!("#");
            }
            println!("");
        });
        std::thread::sleep_ms(30);
    }
}

Architecture

In live mode, visualizer2 runs three loops:

1. The recorder, which acquires samples from somewhere (pulseaudio by default) and pushes them into the sample-buffer.
2. The analyzer, which calculates some information from the sample-buffer. Common are spectral analysis or beat-detection. The analyzer is actually written by you, so you have maximum freedom with what you need.
3. The renderer, which is the applications main thread. Here you consume the latest info from the analyzer and create visuals with it.

Recorder

By default, visualizer2 uses pulseaudio, but it is really easy to use another audio source. You just have to implement an alternative recorder. For an example take a look at the pulse recorder.

Analyzer

The analyzer consists of a closure and a data-type that contains all info shared with the renderer. There are a few things to note:

• To enable lock-free sharing of the info, the info-type needs to be Clone.
• While the analyzer gets an &mut info, you can not make any assumptions about its contents apart from it being filled with either the initial value or the result of some (most likely not the last!) analyzer run.
• If you need data from the last analyzer run, you have to keep track of that locally, easiest by capturing a variable in the analyzer closure.

Renderer

This part is completely up to you. vis-core gives you an iterator that you should trigger once a frame and that allows access to the info from the analyzer. In most cases you will be using a loop like this:

for frame in frames.iter() {
    println!("Frame: {}", frame.frame);
    println!("Time since start: {}", frame.time);
}

Configuration

During the process of writing multiple different versions of this system I also wrote ezconf. This is now the configuration system used in all parts of vis-core. The design philosophy is the following:

• Components (like a FourierAnalyzer or a BeatDetector) are created using a builder pattern.
• All fields not explicitly set with the builder will be read from the configuration source. This allows easily changing parameters without recompiling each time.

Additionally, the final configuration will be logged in debug builds.

I encourage using the same system for your graphics code because it allows quickly iterating on certain settings which is more fun than waiting for the compiler each time. To use the config:

let some_configurable_setting = vis_core::CONFIG.get_or(
    // Toml path to the value
    "myvis.foo.bar",
    // Default value, type will be inferred from this
    123.456
)

Config Source

By default, when calling vis_core::default_config(), vis-core searches for a file named visualizer.toml in the current working directory. If you want a different file to be used, you can instead initialize the config yourself manually.

Analyzer Tools

vis-core includes a few tools for analyzing the audio signal. Look at each ones docs for more info:

• FourierAnalyzer - Does a fourier transform on the latest samples and returns a spectrum
• Spectrum - A flexible representation of a spectrum. Has methods for taking a subspectrum (slice), filling into a smaller number of buckets (fill_buckets), and finding maxima (find_maxima). There is also average_spectrum to average multiple spectra.
• BeatDetector - A beat detector that allows triggering certain effects as soon as a beat happens. Tries to introduce as little delay as possible!

License

visualizer2 is licensed under the GNU General Public License v3.0 or later. See LICENSE for more info.