109 lines
4.3 KiB
Rust
109 lines
4.3 KiB
Rust
//! Feeds back the input stream directly into the output stream.
|
|
//!
|
|
//! Assumes that the input and output devices can use the same stream format and that they support
|
|
//! the f32 sample format.
|
|
//!
|
|
//! Uses a delay of `LATENCY_MS` milliseconds in case the default input and output streams are not
|
|
//! precisely synchronised.
|
|
|
|
extern crate cpal;
|
|
extern crate failure;
|
|
extern crate ringbuf;
|
|
|
|
use cpal::traits::{DeviceTrait, EventLoopTrait, HostTrait};
|
|
use ringbuf::RingBuffer;
|
|
|
|
const LATENCY_MS: f32 = 150.0;
|
|
|
|
fn main() -> Result<(), failure::Error> {
|
|
let host = cpal::default_host();
|
|
let event_loop = host.event_loop();
|
|
|
|
// Default devices.
|
|
let input_device = host.default_input_device().expect("failed to get default input device");
|
|
let output_device = host.default_output_device().expect("failed to get default output device");
|
|
println!("Using default input device: \"{}\"", input_device.name()?);
|
|
println!("Using default output device: \"{}\"", output_device.name()?);
|
|
|
|
// We'll try and use the same format between streams to keep it simple
|
|
let mut format = input_device.default_input_format()?;
|
|
format.data_type = cpal::SampleFormat::F32;
|
|
|
|
// Build streams.
|
|
println!("Attempting to build both streams with `{:?}`.", format);
|
|
let input_stream_id = event_loop.build_input_stream(&input_device, &format)?;
|
|
let output_stream_id = event_loop.build_output_stream(&output_device, &format)?;
|
|
println!("Successfully built streams.");
|
|
|
|
// Create a delay in case the input and output devices aren't synced.
|
|
let latency_frames = (LATENCY_MS / 1_000.0) * format.sample_rate.0 as f32;
|
|
let latency_samples = latency_frames as usize * format.channels as usize;
|
|
|
|
// The buffer to share samples
|
|
let ring = RingBuffer::new(latency_samples * 2);
|
|
let (mut producer, mut consumer) = ring.split();
|
|
|
|
// Fill the samples with 0.0 equal to the length of the delay.
|
|
for _ in 0..latency_samples {
|
|
// The ring buffer has twice as much space as necessary to add latency here,
|
|
// so this should never fail
|
|
producer.push(0.0).unwrap();
|
|
}
|
|
|
|
// Play the streams.
|
|
println!("Starting the input and output streams with `{}` milliseconds of latency.", LATENCY_MS);
|
|
event_loop.play_stream(input_stream_id.clone())?;
|
|
event_loop.play_stream(output_stream_id.clone())?;
|
|
|
|
// Run the event loop on a separate thread.
|
|
std::thread::spawn(move || {
|
|
event_loop.run(move |id, result| {
|
|
let data = match result {
|
|
Ok(data) => data,
|
|
Err(err) => {
|
|
eprintln!("an error occurred on stream {:?}: {}", id, err);
|
|
return;
|
|
}
|
|
};
|
|
|
|
match data {
|
|
cpal::StreamData::Input { buffer: cpal::UnknownTypeInputBuffer::F32(buffer) } => {
|
|
assert_eq!(id, input_stream_id);
|
|
let mut output_fell_behind = false;
|
|
for &sample in buffer.iter() {
|
|
if producer.push(sample).is_err() {
|
|
output_fell_behind = true;
|
|
}
|
|
}
|
|
if output_fell_behind {
|
|
eprintln!("output stream fell behind: try increasing latency");
|
|
}
|
|
},
|
|
cpal::StreamData::Output { buffer: cpal::UnknownTypeOutputBuffer::F32(mut buffer) } => {
|
|
assert_eq!(id, output_stream_id);
|
|
let mut input_fell_behind = None;
|
|
for sample in buffer.iter_mut() {
|
|
*sample = match consumer.pop() {
|
|
Ok(s) => s,
|
|
Err(err) => {
|
|
input_fell_behind = Some(err);
|
|
0.0
|
|
},
|
|
};
|
|
}
|
|
if let Some(_) = input_fell_behind {
|
|
eprintln!("input stream fell behind: try increasing latency");
|
|
}
|
|
},
|
|
_ => panic!("we're expecting f32 data"),
|
|
}
|
|
});
|
|
});
|
|
|
|
// Run for 3 seconds before closing.
|
|
println!("Playing for 3 seconds... ");
|
|
std::thread::sleep(std::time::Duration::from_secs(3));
|
|
println!("Done!");
|
|
Ok(())
|
|
}
|