106 lines
2.9 KiB
Rust
106 lines
2.9 KiB
Rust
//! General conversion functions and utilities.
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mod stft;
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pub mod window;
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pub use stft::StftHelper;
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pub const MINUS_INFINITY_DB: f32 = -100.0;
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pub const MINUS_INFINITY_GAIN: f32 = 1e-5; // 10f32.powf(MINUS_INFINITY_DB / 20)
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pub const NOTES: [&str; 12] = [
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"C", "C#", "D", "D#", "E", "F", "F#", "G", "G#", "A", "A#", "B",
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];
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/// Temporarily allow allocations within `func` if NIH-plug was configured with the
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/// `assert_process_allocs` feature.
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#[cfg(all(debug_assertions, feature = "assert_process_allocs"))]
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pub fn permit_alloc<T, F: FnOnce() -> T>(func: F) -> T {
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assert_no_alloc::permit_alloc(func)
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}
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/// Temporarily allow allocations within `func` if NIH-plug was configured with the
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/// `assert_process_allocs` feature.
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#[cfg(not(all(debug_assertions, feature = "assert_process_allocs")))]
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pub fn permit_alloc<T, F: FnOnce() -> T>(func: F) -> T {
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func()
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}
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/// Convert decibels to a voltage gain ratio, treating anything below -100 dB as minus infinity.
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#[inline]
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pub fn db_to_gain(dbs: f32) -> f32 {
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if dbs > MINUS_INFINITY_DB {
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10.0f32.powf(dbs * 0.05)
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} else {
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0.0
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}
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}
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/// Convert a voltage gain ratio to decibels. Gain ratios that aren't positive will be treated as
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/// [`MINUS_INFINITY_DB`].
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#[inline]
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pub fn gain_to_db(gain: f32) -> f32 {
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f32::max(gain, MINUS_INFINITY_GAIN).log10() * 20.0
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}
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/// Convert a MIDI note ID to a frequency at A4 = 440 Hz equal temperament and middle C = note 60 =
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/// C4.
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#[inline]
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pub fn midi_note_to_freq(note: u8) -> f32 {
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f32_midi_note_to_freq(note as f32)
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}
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/// The same as [`midi_note_to_freq()`], but for arbitrary note numbers including those outside of
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/// the MIDI range. This also supports fractional note numbers, which is useful when working with
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/// cents.
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#[inline]
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pub fn f32_midi_note_to_freq(note: f32) -> f32 {
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2.0f32.powf((note - 69.0) / 12.0) * 440.0
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}
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/// The inverse of [`f32_midi_note_to_freq()`]. This returns a fractional note number. Round to a
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/// whole number, subtract that from the result, and multiply the fractional part by 100 to get the
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/// number of cents.
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#[inline]
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pub fn freq_to_midi_note(freq: f32) -> f32 {
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((freq / 440.0).log2() * 12.0) + 69.0
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_db_to_gain_positive() {
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assert_eq!(db_to_gain(3.0), 1.4125376);
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}
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#[test]
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fn test_db_to_gain_negative() {
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assert_eq!(db_to_gain(-3.0), 1.4125376f32.recip());
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}
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#[test]
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fn test_db_to_gain_minus_infinity() {
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assert_eq!(db_to_gain(-100.0), 0.0);
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}
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#[test]
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fn test_gain_to_db_positive() {
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assert_eq!(gain_to_db(4.0), 12.041201);
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}
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#[test]
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fn test_gain_to_db_negative() {
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assert_eq!(gain_to_db(0.25), -12.041201);
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}
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#[test]
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fn test_gain_to_db_minus_infinity_zero() {
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assert_eq!(gain_to_db(0.0), MINUS_INFINITY_DB);
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}
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#[test]
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fn test_gain_to_db_minus_infinity_negative() {
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assert_eq!(gain_to_db(-2.0), MINUS_INFINITY_DB);
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}
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}
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