Awedio  

A low-overhead and adaptable audio playback library for Rust.

Examples

Play a single sound file:

let (mut manager, backend) = awedio::start()?;
manager.play(awedio::sounds::open_file("test.wav")?);
# Ok::<(), Box<dyn std::error::Error>>(())

Play a sound with adjustable volume controllable after playback has started:

use awedio::Sound;
let (mut manager, backend) = awedio::start()?;
let (sound, mut controller) = awedio::sounds::SineWav::new(400.0)
    .with_adjustable_volume_of(0.25)
    .pausable()
    .controllable();
manager.play(Box::new(sound));
std::thread::sleep(std::time::Duration::from_millis(100));
controller.set_volume(0.5);
std::thread::sleep(std::time::Duration::from_millis(100));
controller.set_paused(true);
# Ok::<(), Box<dyn std::error::Error>>(())

Design Goals

• Usable in low resource environments such as the esp32 microcontroller. Currently does require std.
• Very low overhead. For example, a Wav file with i16 samples with the same same sample rate as the output device will have samples sent to the backend unchanged.
• Only pay the performance cost of features if they are needed. For example pausability, volume adjustment, or controlling a sound after playback has started are all added to a Sound only as needed. This is done by wrapping types that implement [Sound] similar to Iterator in the standard library.
• Samples are i16 for simplicity at least for now (if this prevents you from using this library please let me know your use case)

API Overview

• Sound trait - Provides samples of a sound to be played. Has functions to modify sounds with wrappers.
• Manager - Play Sounds to a backend.
• SoundList - A sequence of Sounds to play one after the other.

Current backends

• cpal - For popular environments such as Linux, Windows, Mac OS, Android... Enabled by the cpal feature (on by default).
• esp32 - For esp32 microcontrollers using esp-idf. Implemented in its own crate.

Backends are implemented by pulling samples from the Renderer.

Cargo Features

• async: Enable async features that depend on tokio-sync
• cpal: Enable the cpal backend.
• wav: Enable Wav file decoding using Hound
• mp3: Enable mp3 file decoding using rmp3

By default all features are enabled. Depending libraries should disable default features.

Motivation

Built for creating activities for 10 Buttons, a screen-less tablet for kids. Purposefully kept generic to be usable in other contexts.

Alternatives and Inspiration

Thanks to the following audio playback libraries which inspired and were a reference for this library:

• Rodio
  • Very popular crate for audio playback with Rust.
  • Tightly coupled to cpal.
  • Has a Sink which is similar to SoundList::new().pausable().with_adjustable_volume().controllable()...
  • mp3 libraries did not work for me on embedded.
  • Default mixer converts everything to an f32.
  • Uses the standard Iterator trait for its Source/Sound.
• Kira
  • Has very nice API for tweening and effects.
  • Sound trait requires a left/right track instead of supporting 1 or N tracks.
  • Samples are all f32.
  • Uses symphonia for audio format parsing and has several internal buffers requiring more memory.
  • All samples are resampled based on the timestamp and sample rate.

License

This project is licensed under either of Apache License, Version 2.0 or MIT license at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.