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Add faster decibel<->gain conversion functions

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Robbert van der Helm 2023-01-04 16:55:31 +01:00
parent 74a9e294b1
commit c55fb02982
1 changed files with 28 additions and 0 deletions
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28
src/util.rs
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@ -42,6 +42,34 @@ pub fn gain_to_db(gain: f32) -> f32 {
f32::max(gain, MINUS_INFINITY_GAIN).log10() * 20.0
}
/// An approximation of [`db_to_gain()`] using `exp()`. Does not treat values below
/// [`MINUS_INFINITY_DB`] as 0.0 gain to avoid branching. Will run faster on most architectures, but
/// the result may be slightly different.
#[inline]
pub fn db_to_gain_fast(dbs: f32) -> f32 {
const CONVERSION_FACTOR: f32 = std::f32::consts::LN_10 / 20.0;
(dbs * CONVERSION_FACTOR).exp()
}
/// [`db_to_gain_fast()`], but this version does truncate values below [`MINUS_INFINITY_DB`] to 0.0.
/// Bikeshedding over a better name is welcome.
#[inline]
pub fn db_to_gain_fast_branching(dbs: f32) -> f32 {
if dbs > MINUS_INFINITY_DB {
db_to_gain_fast(dbs)
} else {
0.0
}
}
/// An approximation of [`gain_to_db()`] using `ln()`. Will run faster on most architectures, but
/// the result may be slightly different.
#[inline]
pub fn gain_to_db_fast(gain: f32) -> f32 {
const CONVERSION_FACTOR: f32 = std::f32::consts::LOG10_E * 20.0;
f32::max(gain, MINUS_INFINITY_GAIN).ln() * CONVERSION_FACTOR
}
/// Convert a MIDI note ID to a frequency at A4 = 440 Hz equal temperament and middle C = note 60 =
/// C4.
#[inline]