audio-visualizer 0.2.4

Super basic and simple audio visualization library which is especially useful for developers to visually check audio samples, e.g. by waveform or spectrum. (So far) this library is not capable of doing nice visualizations for end users.
Documentation 
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use std::f64::consts::PI;

/// Creates a sine (sinus) wave function for a given frequency.
/// Don't forget to scale up the value to the audio resolution.
/// So far, amplitude is in interval `[-1; 1]`. The parameter
/// of the returned function is the point in time in seconds.
///
/// * `frequency` is in Hertz
pub fn sine_wave(frequency: f64) -> Box<dyn Fn(f64) -> f64> {
    Box::new(move |t| (t * frequency * 2.0 * PI).sin())
}

/// See [`sine_wave_audio_data_multiple`]
pub fn sine_wave_audio_data(frequency: f64, sampling_rate: u32, duration_ms: u32) -> Vec<i16> {
    sine_wave_audio_data_multiple(&[frequency], sampling_rate, duration_ms)
}

/// Like [`sine_wave_audio_data`] but puts multiple sinus waves on top of each other.
/// Returns a audio signal encoded in 16 bit audio resolution which is the sum of
/// multiple sine waves on top of each other. The amplitudes will be scaled from
/// `[-1; 1]` to `[i16::min_value(); i16::max_value()]`
///
/// * `frequency` frequency in Hz for the sinus wave
/// * `sampling_rate` sampling rate, i.e. 44100Hz
/// * `duration_ms` duration of the audio data in milliseconds
pub fn sine_wave_audio_data_multiple(
    frequencies: &[f64],
    sampling_rate: u32,
    duration_ms: u32,
) -> Vec<i16> {
    if frequencies.is_empty() {
        return vec![];
    }

    // Generate all sine wave function
    let sine_waves = frequencies
        .iter()
        .map(|f| sine_wave(*f))
        .collect::<Vec<Box<dyn Fn(f64) -> f64>>>();

    // How many samples to generate with each sine wave function
    let sample_count = (sampling_rate as f64 * (duration_ms as f64 / 1000_f64)) as usize;

    // Calculate the final sine wave
    let mut sine_wave = Vec::with_capacity(sample_count);
    for i_sample in 0..sample_count {
        // t: time
        let t = (1.0 / sampling_rate as f64) * i_sample as f64;

        // BEGIN: add sine waves
        let mut acc = 0.0;
        for i_sine_wave in 0..sine_waves.len() {
            acc += sine_waves[i_sine_wave](t);
        }
        // END: add sine waves

        // BEGIN: scale
        // times 0.6 to prevent to harsh clipping if multiple sinus waves are added above each other
        let acc = acc * i16::max_value() as f64 * 0.6;
        // END: scale

        // BEGIN: truncate in interval
        let acc = if acc > i16::max_value() as f64 {
            i16::max_value()
        } else if acc < i16::min_value() as f64 {
            i16::min_value()
        } else {
            acc as i16
        };
        // END: truncate in interval

        sine_wave.push(acc)
    }

    sine_wave
}