rill-io 0.5.0-beta.4

Audio I/O backends for Rill - CPAL, ALSA, PipeWire, JACK
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rill-io

Audio I/O backends — PortAudio, ALSA, PipeWire, JACK.

This crate provides I/O backends and the Output/Input graph nodes that own the reactive stream (process callback or similar).

All backends implement [IoBackend] — a trait for reactive stream processing: set_process_callback, read, write, run, stop.

The process callback receives the actual negotiated sample rate (f32) from the backend so that ClockTick always contains the true device rate.

Nodes

  • Output — Sink node. Borrows backend via [IoBackendPtr]. start() registers the process callback and drives the graph:

    let mut output = Output::<f32, 256>::with_channels(2);

  • Input — Source node (push model). Borrows backend via [IoBackendPtr]. start() registers the process callback.

In both cases the callback does:

  1. Drain MpscQueue<ParameterCommand> into graph nodes
  2. Create ClockTick with the backend‑supplied sample rate
  3. process_block() on the driver node
  4. Port::propagate() — recursive DAG traversal

Backends

Backend Feature Thread model
PortAudioBackend portaudio (default) RT callback, exact buffer size
PipewireBackend pipewire RT callback (PW thread)
JackBackend jack RT callback (JACK thread)
AlsaBackend alsa snd_pcm_wait() — poll‑driven, exact period required
NullBackend (always) No‑op, for testing

Sample rate negotiation:

  • JACK: reads client.sample_rate() after activation
  • ALSA: queries hw.get_rate() after set_rate(Nearest), checks hw.get_period_size() == BUF_SIZE
  • PipeWire: output uses requested rate, input reads negotiated rate atomically
  • PortAudio: opens stream with exact requested rate and buffer size
  • Null: uses config.sample_rate directly

Links