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use async_trait::async_trait;
use cpal::traits::{DeviceTrait, StreamTrait};
use futures::StreamExt;
use futures::stream::BoxStream;
use std::sync::{Arc, Mutex};
use crate::audio::device::AudioDevice;
use crate::audio::error::AudioResult;
use crate::audio::playback::AudioPlayback;
use crate::audio::types::{AudioBuffer, AudioConfig, SampleFormat};
use super::cpal_common;
/// Audio playback implementation using cpal.
pub struct CpalPlayback;
impl CpalPlayback {
/// Create a new cpal-based audio playback instance.
pub fn new() -> Self {
Self
}
}
impl Default for CpalPlayback {
fn default() -> Self {
Self::new()
}
}
#[async_trait]
impl AudioPlayback for CpalPlayback {
fn list_devices(&self) -> AudioResult<Vec<AudioDevice>> {
cpal_common::list_output_devices()
}
fn default_device(&self) -> AudioResult<Option<AudioDevice>> {
let devices = cpal_common::list_output_devices()?;
Ok(devices.into_iter().find(|d| d.is_default))
}
async fn play(&self, device: Option<&AudioDevice>, buffer: &AudioBuffer) -> AudioResult<()> {
if buffer.is_empty() {
return Ok(());
}
let cpal_device = cpal_common::find_output_device(device)?;
let stream_config = cpal_common::build_stream_config(&buffer.config);
let sample_format = buffer.config.sample_format;
// Shared cursor into the audio data
let data = Arc::new(buffer.data.clone());
let pos = Arc::new(Mutex::new(0usize));
let (done_tx, done_rx) = tokio::sync::oneshot::channel::<()>();
let done_tx = Arc::new(Mutex::new(Some(done_tx)));
// Spawn playback on a dedicated thread since cpal::Stream is !Send.
std::thread::spawn(move || {
let stream = match sample_format {
SampleFormat::I16 => {
let data = data.clone();
let pos = pos.clone();
let done_tx = done_tx.clone();
cpal_device.build_output_stream(
&stream_config,
move |output: &mut [i16], _: &cpal::OutputCallbackInfo| {
let mut p = pos.lock().expect("audio playback position lock poisoned");
for sample in output.iter_mut() {
if *p + 2 <= data.len() {
*sample = i16::from_le_bytes([data[*p], data[*p + 1]]);
*p += 2;
} else {
*sample = 0;
if let Some(tx) = done_tx
.lock()
.expect("audio playback done signal lock poisoned")
.take()
{
let _ = tx.send(());
}
}
}
},
move |err| {
tracing::error!("cpal playback error: {err}");
},
None,
)
}
SampleFormat::F32 => {
let data = data.clone();
let pos = pos.clone();
let done_tx = done_tx.clone();
cpal_device.build_output_stream(
&stream_config,
move |output: &mut [f32], _: &cpal::OutputCallbackInfo| {
let mut p = pos.lock().expect("audio playback position lock poisoned");
for sample in output.iter_mut() {
if *p + 4 <= data.len() {
*sample = f32::from_le_bytes([
data[*p],
data[*p + 1],
data[*p + 2],
data[*p + 3],
]);
*p += 4;
} else {
*sample = 0.0;
if let Some(tx) = done_tx
.lock()
.expect("audio playback done signal lock poisoned")
.take()
{
let _ = tx.send(());
}
}
}
},
move |err| {
tracing::error!("cpal playback error: {err}");
},
None,
)
}
};
match stream {
Ok(stream) => {
if let Err(e) = stream.play() {
tracing::error!("failed to start playback: {e}");
return;
}
// Block until done_tx fires (via the output callback)
// or until all data has been consumed
std::thread::park_timeout(std::time::Duration::from_secs(300));
drop(stream);
}
Err(e) => {
tracing::error!("failed to build output stream: {e}");
}
}
});
// Wait for playback to finish
let _ = done_rx.await;
// Small delay to let the audio device flush
tokio::time::sleep(std::time::Duration::from_millis(50)).await;
Ok(())
}
async fn play_stream(
&self,
device: Option<&AudioDevice>,
_config: &AudioConfig,
mut stream: BoxStream<'static, AudioResult<AudioBuffer>>,
) -> AudioResult<()> {
while let Some(result) = stream.next().await {
let buffer = result?;
self.play(device, &buffer).await?;
}
Ok(())
}
}