Pitch bending

tracker/agb-midi-core/src/lib.rs

@@ -236,7 +236,25 @@ pub fn parse_midi(midi_info: &MidiInfo) -> TokenStream {
                         });
                     }
                     midly::MidiMessage::Aftertouch { .. } => {}
-                    midly::MidiMessage::PitchBend { .. } => {}
+                    midly::MidiMessage::PitchBend { bend } => {
+                        // bend is between 0 and 8192 where 0 = -2 semitones and 8193 is +2 semitones (I think)
+                        let amount = (bend.0.as_int() as f64 - (8192.0 / 2.0)) / (8192.0 / 2.0);
+
+                        // amount is now between -1 and 1
+                        let two_semitones_multiplier = 493.88 / 440.0; // B4 / A4
+                        let amount = if amount < 0.0 {
+                            1.0 / two_semitones_multiplier * (-amount)
+                        } else {
+                            two_semitones_multiplier * amount
+                        };
+
+                        pattern.push(PatternSlot {
+                            speed: 0.into(),
+                            sample: 0,
+                            effect1: PatternEffect::PitchBend(Num::from_f64(amount)),
+                            effect2: PatternEffect::None,
+                        });
+                    }
                     midly::MidiMessage::ProgramChange { program } => {
                         let mut lookup_id = program.as_int().into();
                         if channel_id == 9 {

tracker/agb-tracker-interop/src/lib.rs

@@ -69,6 +69,8 @@ pub enum PatternEffect {
     SetFramesPerTick(Num<u32, 8>),
     SetGlobalVolume(Num<i32, 8>),
     GlobalVolumeSlide(Num<i32, 8>),
+    /// Increase / decrease the pitch by the specified amount immediately
+    PitchBend(Num<u32, 8>),
 }
 
 #[cfg(feature = "quote")]
@@ -311,6 +313,10 @@ impl quote::ToTokens for PatternEffect {
                 let amount = amount.to_raw();
                 quote! { GlobalVolumeSlide(agb_tracker::__private::Num::from_raw(#amount)) }
             }
+            PatternEffect::PitchBend(amount) => {
+                let amount = amount.to_raw();
+                quote! { PitchBend(agb_tracker::__private::Num::from_raw(#amount)) }
+            }
         };
 
         tokens.append_all(quote! {

tracker/agb-tracker/src/lib.rs

@@ -428,6 +428,12 @@ impl TrackerChannel {
 
                     channel.playback(self.base_speed.change_base());
                 }
+                PatternEffect::PitchBend(amount) => {
+                    if tick == 0 {
+                        self.base_speed *= amount.change_base();
+                        channel.playback(self.base_speed.change_base());
+                    }
+                }
                 // These are global effects handled below
                 PatternEffect::SetTicksPerStep(_)
                 | PatternEffect::SetFramesPerTick(_)