bevy/examples/audio/decodable.rs
Zachary Harrold 3c829d7f68
Remove everything except Instant from bevy_utils::time (#17158)
# Objective

- Contributes to #11478
- Contributes to #16877

## Solution

- Removed everything except `Instant` from `bevy_utils::time`

## Testing

- CI

---

## Migration Guide

If you relied on any of the following from `bevy_utils::time`:

- `Duration`
- `TryFromFloatSecsError`

Import these directly from `core::time` regardless of platform target
(WASM, mobile, etc.)

If you relied on any of the following from `bevy_utils::time`:

- `SystemTime`
- `SystemTimeError`

Instead import these directly from either `std::time` or `web_time` as
appropriate for your target platform.

## Notes

`Duration` and `TryFromFloatSecsError` are both re-exports from
`core::time` regardless of whether they are used from `web_time` or
`std::time`, so there is no value gained from re-exporting them from
`bevy_utils::time` as well. As for `SystemTime` and `SystemTimeError`,
no Bevy internal crates or examples rely on these types. Since Bevy
doesn't have a `Time<Wall>` resource for interacting with wall-time (and
likely shouldn't need one), I think removing these from `bevy_utils`
entirely and waiting for a use-case to justify inclusion is a reasonable
path forward.
2025-01-05 20:36:08 +00:00

104 lines
2.9 KiB
Rust

//! Shows how to create a custom [`Decodable`] type by implementing a Sine wave.
use bevy::{
audio::{AddAudioSource, AudioPlugin, Source},
math::ops,
prelude::*,
reflect::TypePath,
};
use core::time::Duration;
// This struct usually contains the data for the audio being played.
// This is where data read from an audio file would be stored, for example.
// This allows the type to be registered as an asset.
#[derive(Asset, TypePath)]
struct SineAudio {
frequency: f32,
}
// This decoder is responsible for playing the audio,
// and so stores data about the audio being played.
struct SineDecoder {
// how far along one period the wave is (between 0 and 1)
current_progress: f32,
// how much we move along the period every frame
progress_per_frame: f32,
// how long a period is
period: f32,
sample_rate: u32,
}
impl SineDecoder {
fn new(frequency: f32) -> Self {
// standard sample rate for most recordings
let sample_rate = 44_100;
SineDecoder {
current_progress: 0.,
progress_per_frame: frequency / sample_rate as f32,
period: std::f32::consts::PI * 2.,
sample_rate,
}
}
}
// The decoder must implement iterator so that it can implement `Decodable`.
impl Iterator for SineDecoder {
type Item = f32;
fn next(&mut self) -> Option<Self::Item> {
self.current_progress += self.progress_per_frame;
// we loop back round to 0 to avoid floating point inaccuracies
self.current_progress %= 1.;
Some(ops::sin(self.period * self.current_progress))
}
}
// `Source` is what allows the audio source to be played by bevy.
// This trait provides information on the audio.
impl Source for SineDecoder {
fn current_frame_len(&self) -> Option<usize> {
None
}
fn channels(&self) -> u16 {
1
}
fn sample_rate(&self) -> u32 {
self.sample_rate
}
fn total_duration(&self) -> Option<Duration> {
None
}
}
// Finally `Decodable` can be implemented for our `SineAudio`.
impl Decodable for SineAudio {
type DecoderItem = <SineDecoder as Iterator>::Item;
type Decoder = SineDecoder;
fn decoder(&self) -> Self::Decoder {
SineDecoder::new(self.frequency)
}
}
fn main() {
let mut app = App::new();
// register the audio source so that it can be used
app.add_plugins(DefaultPlugins.set(AudioPlugin {
global_volume: GlobalVolume::new(0.2),
..default()
}))
.add_audio_source::<SineAudio>()
.add_systems(Startup, setup)
.run();
}
fn setup(mut assets: ResMut<Assets<SineAudio>>, mut commands: Commands) {
// add a `SineAudio` to the asset server so that it can be played
let audio_handle = assets.add(SineAudio {
frequency: 440., // this is the frequency of A4
});
commands.spawn(AudioPlayer(audio_handle));
}