109 lines
3.6 KiB
Rust
109 lines
3.6 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 configuration and that they
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//! support 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 anyhow;
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extern crate cpal;
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extern crate ringbuf;
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use cpal::traits::{DeviceTrait, HostTrait, StreamTrait};
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use ringbuf::RingBuffer;
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const LATENCY_MS: f32 = 150.0;
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fn main() -> Result<(), anyhow::Error> {
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let host = cpal::default_host();
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// Default devices.
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let input_device = host
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.default_input_device()
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.expect("failed to get 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 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 configuration between streams to keep it simple.
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let config: cpal::StreamConfig = input_device.default_input_config()?.into();
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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) * config.sample_rate.0 as f32;
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let latency_samples = latency_frames as usize * config.channels as usize;
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// The buffer to share samples
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let ring = RingBuffer::new(latency_samples * 2);
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let (mut producer, mut consumer) = ring.split();
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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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// The ring buffer has twice as much space as necessary to add latency here,
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// so this should never fail
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producer.push(0.0).unwrap();
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}
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let input_data_fn = move |data: &[f32], _: &cpal::InputCallbackInfo| {
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let mut output_fell_behind = false;
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for &sample in data {
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if producer.push(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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let output_data_fn = move |data: &mut [f32], _: &cpal::OutputCallbackInfo| {
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let mut input_fell_behind = None;
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for sample in data {
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*sample = match consumer.pop() {
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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!(
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"input stream fell behind: {:?}: try increasing latency",
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err
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);
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}
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};
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// Build streams.
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println!(
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"Attempting to build both streams with f32 samples and `{:?}`.",
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config
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);
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let input_stream = input_device.build_input_stream(&config, input_data_fn, err_fn)?;
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let output_stream = output_device.build_output_stream(&config, output_data_fn, err_fn)?;
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println!("Successfully built streams.");
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// Play the streams.
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println!(
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"Starting the input and output streams with `{}` milliseconds of latency.",
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LATENCY_MS
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);
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input_stream.play()?;
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output_stream.play()?;
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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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drop(input_stream);
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drop(output_stream);
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println!("Done!");
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Ok(())
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}
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fn err_fn(err: cpal::StreamError) {
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eprintln!("an error occurred on stream: {}", err);
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}
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