Added Pitch as an alternative sound source (#9225)

# Objective
My attempt at implementing #7515

## Solution

Added struct `Pitch` and implemented on it `Source` trait.

## Changelog

 ### Added
- File pitch.rs to bevy_audio crate
- Struct `Pitch` and type aliases for `AudioSourceBundle<Pitch>` and
`SpatialAudioSourceBundle<Pitch>`
- New example showing how to use `PitchBundle`

### Changed
- `AudioPlugin` now adds system for `Pitch` audio

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>

Cargo.toml

@@ -1043,6 +1043,16 @@ description = "Shows how to play spatial audio, and moving the emitter in 3D"
 category = "Audio"
 wasm = true
 
+[[example]]
+name = "pitch"
+path = "examples/audio/pitch.rs"
+
+[package.metadata.example.pitch]
+name = "Pitch"
+description = "Shows how to directly play a simple pitch"
+category = "Audio"
+wasm = true
+
 # Diagnostics
 [[example]]
 name = "log_diagnostics"

crates/bevy_audio/src/lib.rs

@@ -27,6 +27,7 @@
 mod audio;
 mod audio_output;
 mod audio_source;
+mod pitch;
 mod sinks;
 
 #[allow(missing_docs)]
@@ -34,13 +35,14 @@ pub mod prelude {
     #[doc(hidden)]
     pub use crate::{
         AudioBundle, AudioSink, AudioSinkPlayback, AudioSource, AudioSourceBundle, Decodable,
-        GlobalVolume, PlaybackSettings, SpatialAudioBundle, SpatialAudioSink,
-        SpatialAudioSourceBundle, SpatialSettings,
+        GlobalVolume, Pitch, PitchBundle, PlaybackSettings, SpatialAudioBundle, SpatialAudioSink,
+        SpatialAudioSourceBundle, SpatialPitchBundle, SpatialSettings,
     };
 }
 
 pub use audio::*;
 pub use audio_source::*;
+pub use pitch::*;
 
 pub use rodio::cpal::Sample as CpalSample;
 pub use rodio::source::Source;
@@ -77,6 +79,8 @@ impl Plugin for AudioPlugin {
             app.add_audio_source::<AudioSource>();
             app.init_asset_loader::<AudioLoader>();
         }
+
+        app.add_audio_source::<Pitch>();
     }
 }
 

crates/bevy_audio/src/pitch.rs

@@ -0,0 +1,38 @@
+use crate::{AudioSourceBundle, Decodable, SpatialAudioSourceBundle};
+use bevy_reflect::{TypePath, TypeUuid};
+use rodio::{source::SineWave, source::TakeDuration, Source};
+
+/// A source of sine wave sound
+#[derive(Debug, Clone, TypeUuid, TypePath)]
+#[uuid = "cbc63be3-b0b9-4d2c-a03c-88b58f1a19ef"]
+pub struct Pitch {
+    /// Frequency at which sound will be played
+    pub frequency: f32,
+    /// Duration for which sound will be played
+    pub duration: std::time::Duration,
+}
+
+impl Pitch {
+    /// Creates a new note
+    pub fn new(frequency: f32, duration: std::time::Duration) -> Self {
+        Pitch {
+            frequency,
+            duration,
+        }
+    }
+}
+
+impl Decodable for Pitch {
+    type DecoderItem = <SineWave as Iterator>::Item;
+    type Decoder = TakeDuration<SineWave>;
+
+    fn decoder(&self) -> Self::Decoder {
+        SineWave::new(self.frequency).take_duration(self.duration)
+    }
+}
+
+/// Bundle for playing a bevy note sound
+pub type PitchBundle = AudioSourceBundle<Pitch>;
+
+/// Bundle for playing a bevy note sound with a 3D position
+pub type SpatialPitchBundle = SpatialAudioSourceBundle<Pitch>;

examples/README.md

@@ -195,6 +195,7 @@ Example | Description
 [Audio](../examples/audio/audio.rs) | Shows how to load and play an audio file
 [Audio Control](../examples/audio/audio_control.rs) | Shows how to load and play an audio file, and control how it's played
 [Decodable](../examples/audio/decodable.rs) | Shows how to create and register a custom audio source by implementing the `Decodable` type.
+[Pitch](../examples/audio/pitch.rs) | Shows how to directly play a simple pitch
 [Spatial Audio 2D](../examples/audio/spatial_audio_2d.rs) | Shows how to play spatial audio, and moving the emitter in 2D
 [Spatial Audio 3D](../examples/audio/spatial_audio_3d.rs) | Shows how to play spatial audio, and moving the emitter in 3D
 

examples/audio/pitch.rs

@@ -0,0 +1,55 @@
+//! This example illustrates how to play a single-frequency sound (aka a pitch)
+
+use bevy::prelude::*;
+use std::time::Duration;
+
+fn main() {
+    App::new()
+        .add_plugins(DefaultPlugins)
+        .add_event::<PlayPitch>()
+        .add_systems(Startup, setup)
+        .add_systems(Update, (play_pitch, keyboard_input_system))
+        .run();
+}
+
+#[derive(Event, Default)]
+struct PlayPitch;
+
+#[derive(Resource)]
+struct PitchFrequency(f32);
+
+fn setup(mut commands: Commands) {
+    commands.insert_resource(PitchFrequency(220.0));
+}
+
+fn play_pitch(
+    mut pitch_assets: ResMut<Assets<Pitch>>,
+    frequency: Res<PitchFrequency>,
+    mut events: EventReader<PlayPitch>,
+    mut commands: Commands,
+) {
+    for _ in events.iter() {
+        info!("playing pitch with frequency: {}", frequency.0);
+        commands.spawn(PitchBundle {
+            source: pitch_assets.add(Pitch::new(frequency.0, Duration::new(1, 0))),
+            settings: PlaybackSettings::DESPAWN,
+        });
+        info!("number of pitch assets: {}", pitch_assets.len());
+    }
+}
+
+fn keyboard_input_system(
+    keyboard_input: Res<Input<KeyCode>>,
+    mut frequency: ResMut<PitchFrequency>,
+    mut events: EventWriter<PlayPitch>,
+) {
+    if keyboard_input.just_pressed(KeyCode::Up) {
+        frequency.0 *= 2.0f32.powf(1.0 / 12.0);
+    }
+    if keyboard_input.just_pressed(KeyCode::Down) {
+        frequency.0 /= 2.0f32.powf(1.0 / 12.0);
+    }
+    if keyboard_input.just_pressed(KeyCode::Space) {
+        events.send(PlayPitch);
+    }
+}