//! General conversion functions and utilities. mod stft; pub use stft::StftHelper; pub const MINUS_INFINITY_DB: f32 = -100.0; /// Convert decibels to a voltage gain ratio, treating anything below -100 dB as minus infinity. pub fn db_to_gain(dbs: f32) -> f32 { if dbs > MINUS_INFINITY_DB { 10.0f32.powf(dbs * 0.05) } else { 0.0 } } /// Convert a voltage gain ratio to decibels. Gain ratios that aren't positive will be treated as /// [`MINUS_INFINITY_DB`]. pub fn gain_to_db(gain: f32) -> f32 { if gain > 0.0 { gain.log10() * 20.0 } else { MINUS_INFINITY_DB } } /// Convert a MIDI note ID to a frequency at A4 = 440 Hz equal temperament and middle C = note 60 = /// C4. pub fn midi_note_to_freq(pitch: u8) -> f32 { 2.0f32.powf((pitch as f32 - 69.0) / 12.0) * 440.0 } #[cfg(test)] mod tests { use super::*; #[test] fn test_db_to_gain_positive() { assert_eq!(db_to_gain(3.0), 1.4125376); } #[test] fn test_db_to_gain_negative() { assert_eq!(db_to_gain(-3.0), 1.4125376f32.recip()); } #[test] fn test_db_to_gain_minus_infinity() { assert_eq!(db_to_gain(-100.0), 0.0); } #[test] fn test_gain_to_db_positive() { assert_eq!(gain_to_db(4.0), 12.041201); } #[test] fn test_gain_to_db_negative() { assert_eq!(gain_to_db(0.25), -12.041201); } #[test] fn test_gain_to_db_minus_infinity_zero() { assert_eq!(gain_to_db(0.0), MINUS_INFINITY_DB); } #[test] fn test_gain_to_db_minus_infinity_negative() { assert_eq!(gain_to_db(-2.0), MINUS_INFINITY_DB); } }