102 lines
4.1 KiB
Rust
102 lines
4.1 KiB
Rust
//! Feeds back the input stream directly into the output stream.
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//!
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//! Assumes that the input and output devices can use the same stream format and that they support
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//! the f32 sample format.
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//!
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//! Uses a delay of `LATENCY_MS` milliseconds in case the default input and output streams are not
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//! precisely synchronised.
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extern crate cpal;
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extern crate failure;
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const LATENCY_MS: f32 = 150.0;
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fn main() -> Result<(), failure::Error> {
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let event_loop = cpal::EventLoop::new();
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// Default devices.
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let input_device = cpal::default_input_device().expect("failed to get default input device");
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let output_device = cpal::default_output_device().expect("failed to get default output device");
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println!("Using default input device: \"{}\"", input_device.name()?);
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println!("Using default output device: \"{}\"", output_device.name()?);
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// We'll try and use the same format between streams to keep it simple
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let mut format = input_device.default_input_format()?;
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format.data_type = cpal::SampleFormat::F32;
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// Build streams.
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println!("Attempting to build both streams with `{:?}`.", format);
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let input_stream_id = event_loop.build_input_stream(&input_device, &format)?;
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let output_stream_id = event_loop.build_output_stream(&output_device, &format)?;
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println!("Successfully built streams.");
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// Create a delay in case the input and output devices aren't synced.
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let latency_frames = (LATENCY_MS / 1_000.0) * format.sample_rate.0 as f32;
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let latency_samples = latency_frames as usize * format.channels as usize;
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// The channel to share samples.
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let (tx, rx) = std::sync::mpsc::sync_channel(latency_samples * 2);
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// Fill the samples with 0.0 equal to the length of the delay.
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for _ in 0..latency_samples {
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tx.send(0.0)?;
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}
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// Play the streams.
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println!("Starting the input and output streams with `{}` milliseconds of latency.", LATENCY_MS);
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event_loop.play_stream(input_stream_id.clone())?;
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event_loop.play_stream(output_stream_id.clone())?;
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// Run the event loop on a separate thread.
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std::thread::spawn(move || {
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event_loop.run(move |id, event| {
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let data = match event {
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cpal::StreamEvent::Data(data) => data,
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cpal::StreamEvent::Close(cpal::StreamCloseCause::Error(err)) => {
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eprintln!("stream {:?} closed due to an error: {}", id, err);
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return;
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}
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_ => return,
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};
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match data {
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cpal::StreamData::Input { buffer: cpal::UnknownTypeInputBuffer::F32(buffer) } => {
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assert_eq!(id, input_stream_id);
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let mut output_fell_behind = false;
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for &sample in buffer.iter() {
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if tx.try_send(sample).is_err() {
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output_fell_behind = true;
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}
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}
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if output_fell_behind {
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eprintln!("output stream fell behind: try increasing latency");
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}
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},
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cpal::StreamData::Output { buffer: cpal::UnknownTypeOutputBuffer::F32(mut buffer) } => {
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assert_eq!(id, output_stream_id);
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let mut input_fell_behind = None;
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for sample in buffer.iter_mut() {
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*sample = match rx.try_recv() {
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Ok(s) => s,
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Err(err) => {
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input_fell_behind = Some(err);
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0.0
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},
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};
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}
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if let Some(err) = input_fell_behind {
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eprintln!("input stream fell behind: {}: try increasing latency", err);
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}
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},
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_ => panic!("we're expecting f32 data"),
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}
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});
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});
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// Run for 3 seconds before closing.
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println!("Playing for 3 seconds... ");
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std::thread::sleep(std::time::Duration::from_secs(3));
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println!("Done!");
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Ok(())
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}
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