midix_synth 0.0.4

SoundFont compatible MIDI synthesizer for midix
Documentation 
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use std::f32::consts;

pub(crate) const HALF_PI: f32 = consts::PI / 2_f32;
pub(crate) const NON_AUDIBLE: f32 = 1.0e-3_f32;
pub(crate) const LOG_NON_AUDIBLE: f32 = -6.907_755_4_f32;

pub(crate) fn timecents_to_seconds(x: f32) -> f32 {
    2_f32.powf((1_f32 / 1200_f32) * x)
}

pub(crate) fn cents_to_hertz(x: f32) -> f32 {
    8.176_f32 * 2_f32.powf((1_f32 / 1200_f32) * x)
}

pub(crate) fn cents_to_multiplying_factor(x: f32) -> f32 {
    2_f32.powf((1_f32 / 1200_f32) * x)
}

pub(crate) fn decibels_to_linear(x: f32) -> f32 {
    10_f32.powf(0.05_f32 * x)
}

pub(crate) fn linear_to_decibels(x: f32) -> f32 {
    20_f32 * x.log10()
}

pub(crate) fn key_number_to_multiplying_factor(cents: i32, key: u8) -> f32 {
    timecents_to_seconds((cents * (60 - key as i32)) as f32)
}

pub(crate) fn exp_cutoff(x: f64) -> f64 {
    if x < LOG_NON_AUDIBLE as f64 {
        0_f64
    } else {
        x.exp()
    }
}