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roderickvdroderickvd
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feat(audioworklet): add mic loopback recording demo
Also fixes the build under a recent nightly rustc/LLVM, which stopped auto-exporting __heap_base, needed by wasm-bindgen's threading post-processing.
1 parent b691cbd commit 503ae6c

4 files changed

Lines changed: 133 additions & 3 deletions

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‎examples/audioworklet-beep/.cargo/config.toml‎

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@@ -16,6 +16,8 @@ rustflags = [
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"link-arg=--export=__tls_align",
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"-C",
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"link-arg=--export=__tls_base",
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"-C",
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"link-arg=--export=__heap_base",
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]
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[unstable]

‎examples/audioworklet-beep/Cargo.toml‎

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@@ -27,6 +27,9 @@ wasm-bindgen = "0.2"
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# logging them with `console.error`.
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console_error_panic_hook = "0.1"
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# The `ringbuf` crate provides a lock-free ring buffer for passing audio between streams.
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ringbuf = "0.4"
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# The `web-sys` crate allows you to interact with the various browser APIs,
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# like the DOM.
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[dependencies.web-sys]

‎examples/audioworklet-beep/index.html‎

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@@ -9,6 +9,9 @@
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<body>
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<input id="play" type="button" value="beep" />
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<input id="stop" type="button" value="stop" />
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<input id="record" type="button" value="record" />
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<input id="stop-record" type="button" value="stop recording" />
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<p>Recording plays your microphone back live. Wear headphones to avoid feedback howl.</p>
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</body>
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</html>

‎examples/audioworklet-beep/src/lib.rs‎

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@@ -1,9 +1,13 @@
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use std::{cell::Cell, rc::Rc};
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use cpal::{
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traits::{DeviceTrait, HostTrait, StreamTrait},
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Device, Error, ErrorKind, FromSample, HostId, Sample, SampleFormat, SizedSample, Stream,
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StreamConfig,
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traits::{DeviceTrait, HostTrait, StreamTrait},
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};
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use ringbuf::{
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HeapCons, HeapProd, HeapRb,
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traits::{Consumer, Producer, Split},
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};
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use wasm_bindgen::prelude::*;
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use web_sys::console;
@@ -19,6 +23,8 @@ pub fn main_js() -> Result<(), JsValue> {
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let document = gloo::utils::document();
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let play_button = document.get_element_by_id("play").unwrap();
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let stop_button = document.get_element_by_id("stop").unwrap();
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let record_button = document.get_element_by_id("record").unwrap();
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let stop_record_button = document.get_element_by_id("stop-record").unwrap();
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// stream needs to be referenced from the "play" and "stop" closures
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let stream = Rc::new(Cell::new(None));
@@ -45,12 +51,36 @@ pub fn main_js() -> Result<(), JsValue> {
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closure.forget();
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}
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// input stream needs its own slot; recording and playback run independently
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let record_stream = Rc::new(Cell::new(None));
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// set up record button
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{
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let record_stream = record_stream.clone();
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let closure = Closure::<dyn FnMut(_)>::new(move |_event: web_sys::MouseEvent| {
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record_stream.set(Some(record()));
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});
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record_button
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.add_event_listener_with_callback("mousedown", closure.as_ref().unchecked_ref())?;
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closure.forget();
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}
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// set up stop-record button
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{
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let closure = Closure::<dyn FnMut(_)>::new(move |_event: web_sys::MouseEvent| {
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// stop the stream by dropping it; releases the microphone
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record_stream.take();
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});
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stop_record_button
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.add_event_listener_with_callback("mousedown", closure.as_ref().unchecked_ref())?;
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closure.forget();
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}
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Ok(())
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}
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fn beep() -> Stream {
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let host =
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cpal::host_from_id(HostId::AudioWorklet).expect("AudioWorklet host not available");
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let host = cpal::host_from_id(HostId::AudioWorklet).expect("AudioWorklet host not available");
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let device = host
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.default_output_device()
@@ -98,6 +128,98 @@ where
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stream
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}
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/// Captures microphone input into a ring buffer and immediately plays it back, so you can hear
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/// your own voice. Wear headphones: routing a live mic to speakers risks feedback howl.
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fn record() -> (Stream, Stream) {
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let host = cpal::host_from_id(HostId::AudioWorklet).expect("AudioWorklet host not available");
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let input_device = host
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.default_input_device()
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.expect("failed to find a default input device");
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let output_device = host
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.default_output_device()
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.expect("failed to find a default output device");
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let input_config = input_device.default_input_config().unwrap();
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let output_config = output_device.default_output_config().unwrap();
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// Bound end-to-end latency; once full, the producer drops the newest samples instead of
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// blocking.
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let max_buffered_samples =
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output_config.sample_rate() as usize * output_config.channels() as usize / 2;
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let ring = HeapRb::<f32>::new(max_buffered_samples);
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let (producer, consumer) = ring.split();
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let input_stream = match input_config.sample_format() {
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SampleFormat::F32 => build_input::<f32>(&input_device, input_config.into(), producer),
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SampleFormat::I16 => build_input::<i16>(&input_device, input_config.into(), producer),
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SampleFormat::U16 => build_input::<u16>(&input_device, input_config.into(), producer),
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_ => panic!("unsupported sample format"),
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};
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let output_stream = match output_config.sample_format() {
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SampleFormat::F32 => build_output::<f32>(&output_device, output_config.into(), consumer),
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SampleFormat::I16 => build_output::<i16>(&output_device, output_config.into(), consumer),
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SampleFormat::U16 => build_output::<u16>(&output_device, output_config.into(), consumer),
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_ => panic!("unsupported sample format"),
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};
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(input_stream, output_stream)
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}
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fn build_input<T>(device: &Device, config: StreamConfig, mut producer: HeapProd<f32>) -> Stream
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where
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T: Sample + SizedSample,
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f32: FromSample<T>,
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{
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let err_fn = |err: Error| match err.kind() {
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ErrorKind::DeviceChanged | ErrorKind::RealtimeDenied => {
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console::log_1(&format!("{err}").into())
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}
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_ => console::error_1(&format!("Stream error: {err}").into()),
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};
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let stream = device
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.build_input_stream(
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config,
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move |data: &[T], _| {
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producer.push_iter(data.iter().map(|&s| f32::from_sample(s)));
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},
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err_fn,
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None,
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)
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.unwrap();
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stream.start().unwrap();
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stream
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}
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fn build_output<T>(device: &Device, config: StreamConfig, mut consumer: HeapCons<f32>) -> Stream
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where
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T: Sample + SizedSample + FromSample<f32>,
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{
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let err_fn = |err: Error| match err.kind() {
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ErrorKind::DeviceChanged | ErrorKind::RealtimeDenied => {
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console::log_1(&format!("{err}").into())
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}
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_ => console::error_1(&format!("Stream error: {err}").into()),
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};
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let stream = device
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.build_output_stream(
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config,
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move |data: &mut [T], _| {
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for sample in data.iter_mut() {
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let value = consumer.try_pop().unwrap_or(f32::EQUILIBRIUM);
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*sample = T::from_sample(value);
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}
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},
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err_fn,
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None,
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)
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.unwrap();
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stream.start().unwrap();
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stream
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}
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fn write_data<T>(output: &mut [T], channels: usize, next_sample: &mut dyn FnMut() -> f32)
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where
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T: Sample + FromSample<f32>,

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