Audio latency is higher than it needs to be

[ivanstepanovftw]

Bevy version

main aaccbe8

[Optional] Relevant system information

• Fedora Linux 40 (Workstation Edition)

  $ uname -a
  Linux fedora 6.8.11-300.fc40.x86_64 #1 SMP PREEMPT_DYNAMIC Mon May 27 14:53:33 UTC 2024 x86_64 GNU/Linux
  

What you did

Basic audio playing on Space press or Mouse1 release:

use bevy::prelude::*;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Update, signal)
        .run();
}

fn signal(
    mut commands: Commands,
    asset_server: Res<AssetServer>,
    keyboard_input: Res<ButtonInput<KeyCode>>,
    mouse_button_input: Res<ButtonInput<MouseButton>>,
) {
    if keyboard_input.just_pressed(KeyCode::Space) || mouse_button_input.just_released(MouseButton::Left) {
        commands.spawn((
            AudioBundle {
                source: asset_server.load("sounds/breakout_collision.ogg"),
                settings: PlaybackSettings::DESPAWN
            },
        ));
    }
}

Then loopback desktop audio to microphone.

Pressed record button in Audacity. Measure latency in VLC program from click to sound by selecting range in Audacity:

Then latency can be then calculated from selection view below in Audacity:
$.498-.463=.035$ s.

Repeat for Bevy example:

$.639-.495=.144$ s.

What went wrong

• I have expected that latency in Bevy is lower than in VLC audio player.
• Instead, latency is 4 times higher in Bevy, than in VLC ($144/35=4.1$).

Additional information

• Tried changing ogg to wav with no improvement.
• Tried --release flag with no improvement.
• Tried to increase poll resolution:

  app
      .insert_resource(Time::<Fixed>::from_hz(600.0))
      .add_systems(FixedUpdate, signal)

  No improvement.
• Tried to preload audio to resource with no improvement.
• Tried Kira with preloading with no improvement.

[alice-i-cecile]

You almost certainly want to preload small sound effects into the asset storage, rather than loading them on demand as you did here. That's likely to be the major source of latency here (and something our examples should more clearly teach).

That said, once that's done, can you try this with bevy_kira_audio and let us know how it compares? We're considering swapping backends, and improvements here would be

[ivanstepanovftw]

Thank you for rapid response :)

Tried to preload audio into resource:

use bevy::prelude::*;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .add_systems(Update, signal)
        .run();
}

#[derive(Resource)]
struct SFX {
    collision_sound: Handle<AudioSource>,
}

fn setup(
    mut commands: Commands,
    asset_server: Res<AssetServer>,
) {
    commands.insert_resource(SFX {
        collision_sound: asset_server.load("sounds/breakout_collision.ogg"),
    });
}

fn signal(
    mut commands: Commands,
    keyboard_input: Res<ButtonInput<KeyCode>>,
    mouse_button_input: Res<ButtonInput<MouseButton>>,
    sfx: Res<SFX>,
) {
    if keyboard_input.just_pressed(KeyCode::Space) || mouse_button_input.just_released(MouseButton::Left) {
        commands.spawn((
            AudioBundle {
                source: sfx.collision_sound.clone(),
                settings: PlaybackSettings::DESPAWN
            },
        ));
    }
}

Cycle shown here is mouse press, then release, then observe for 2 clicks in VLC and 2 clicks in Bevy, so left part is VLC 2 clicks and right part is Bevy. Selected first click in Bevy with $597-484=113$ ms latency:

So, no improvement for preloading sound. Though I am not sure I've done it correctly (can I reference sound instead?).

Will check Kira in 10 minutes.

[alice-i-cecile]

Okay thanks, that's a much more realistic setup. The code you've supplied looks correct to me.

Very weird to see that this didn't help and to see it be delayed substantially more than a frame. I'll ask around (hi @inodentry?) to get opinions from people with more expertise.

[ivanstepanovftw]

Kira example:

bevy = { version = "0.13.2", features = ["dynamic_linking", "mp3", "wav"] }
bevy_kira_audio = "0.19.0"

use bevy_kira_audio::prelude::*;
use bevy::prelude::*;
use bevy_kira_audio::AudioSource;

fn main() {
    App::new()
        .add_plugins((DefaultPlugins, AudioPlugin))
        .add_systems(Startup, setup)
        .add_systems(Update, signal)
        .run();
}

#[derive(Resource)]
struct SFX {
    collision_sound: Handle<AudioSource>,
}

fn setup(
    mut commands: Commands,
    asset_server: Res<AssetServer>,
) {
    commands.insert_resource(SFX {
        collision_sound: asset_server.load("sounds/breakout_collision.ogg"),
    });
}

fn signal(
    keyboard_input: Res<ButtonInput<KeyCode>>,
    mouse_button_input: Res<ButtonInput<MouseButton>>,
    audio: Res<Audio>,
    sfx: Res<SFX>,
) {
    if keyboard_input.just_pressed(KeyCode::Space) || mouse_button_input.just_released(MouseButton::Left) {
        audio.play(sfx.collision_sound.clone());
    }
}

Had to rollback Bevy to 0.13.2
Latency $117$ and $105$ ms

[alice-i-cecile]

@ivanstepanovftw thank you very much for investigating this. I'm personally out of immediately actionable ideas, but for the sake of posterity what OS are you on?

[ivanstepanovftw]

It is Fedora Linux 40 (Workstation Edition)

$ uname -a
Linux fedora 6.8.11-300.fc40.x86_64 #1 SMP PREEMPT_DYNAMIC Mon May 27 14:53:33 UTC 2024 x86_64 GNU/Linux