# Beat Detector - Audio Beat Detection Library Written In Rust

This is a Rust library that enables beat detection on live audio data input.
One use case is that you have an audio/aux-splitter on your computer where one 
end goes into the sound system whereas the other goes into the microphone input 
of a Raspberry Pi.

The crate provides multiple strategies that you can connect to the audio source.
So far it offers two strategies:
- **Simple Lowpass Filter**
  - not really good, must be more fine-tuned
- **Simple Spectrum Analysis**
  - good enough for most "simple" songs, like 90s pop hits or "Kids" by "MGMT"
- Super Awesome Analysis (TODO) - **CODE CONTRIBUTIONS ARE WELCOME**

I'm not an expert in audio analysis, but I'm proud what I achieved so far with the spectrum strategy.
This library needs a more "bulletproof" strategy, to cope with complex and fast songs.

Here's a demo I recorded in my room. Of course, it was synced to music, when I recorded it. :)

![Beat Detection Demo With WS2812 RGBs](demo.gif "Beat Detection Demo With WS2812 RGBs")

## How To Use
**Cargo.toml**
```toml
beat-detector = "<latest version>"
```

**code.rs**
(also see `examples/` in repository!)
```rust
//! Minimum example on how to use this library. Sets up the "callback loop".

use cpal::Device;
use beat_detector::StrategyKind;
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::Arc;

/// Minimum example on how to use this library. Sets up the "callback loop".
fn main() {
    let recording = Arc::new(AtomicBool::new(true));

    let recording_cpy = recording.clone();
    ctrlc::set_handler(move || {
        eprintln!("Stopping recording");
        recording_cpy.store(false, Ordering::SeqCst);
    }).unwrap();

    let dev = select_input_device();
    let strategy = select_strategy();
    let on_beat = |info| {
        println!("Found beat at {:?}ms", info);
    };
    // actually start listening in thread
    let handle = beat_detector::record::start_listening(
        on_beat,
        Some(dev),
        strategy,
        recording,
    ).unwrap();

    handle.join().unwrap();
}

fn select_input_device() -> Device {
    // todo implement user selection
    beat_detector::record::audio_input_device_list().into_iter().next().expect("At least one audio input device must be available.").1
}

fn select_strategy() -> StrategyKind {
    // todo implement user selection
    StrategyKind::Spectrum
}
```

## MSRV (Minimal Supported Rust Version)
1.52.1 stable