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Introduce a buffer for a full period

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Writing to the pcm more often than necessary is
just a waste of resources and depending
on the pcm it can have quite an impact
on performance. The pcm expects full periods
anyway.
This commit is contained in:
sniperrifle2004 2020-06-14 05:20:14 +02:00
parent aaef07e819
commit 64081a12bb
1 changed files with 44 additions and 16 deletions
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60
playback/src/audio_backend/alsa.rs
View file

@ -1,12 +1,21 @@
use super::{Open, Sink};
use alsa::device_name::HintIter;
use alsa::pcm::{Access, Format, HwParams, PCM};
use alsa::pcm::{Access, Format, Frames, HwParams, PCM};
use alsa::{Direction, Error, ValueOr};
use std::cmp::min;
use std::ffi::CString;
use std::io;
use std::process::exit;
pub struct AlsaSink(Option<PCM>, String);
const PERIOD_SIZE: usize = 5512; // Period of roughly 125ms
const BUFFERED_PERIODS: usize = 4; // ~ 0.5s latency
pub struct AlsaSink {
pcm: Option<PCM>,
device: String,
buffer: [i16; PERIOD_SIZE as usize],
buffered_data: usize,
}
fn list_outputs() {
for t in &["pcm", "ctl", "hwdep"] {
@ -41,8 +50,8 @@ fn open_device(dev_name: &str) -> Result<(PCM), Box<Error>> {
hwp.set_format(Format::s16())?;
hwp.set_rate(44100, ValueOr::Nearest)?;
hwp.set_channels(2)?;
hwp.set_period_size_near(5512, ValueOr::Nearest)?; // Period of roughly 125ms
hwp.set_buffer_size_near(22048)?; // ~ 0.5s latency
hwp.set_period_size_near(PERIOD_SIZE as Frames, ValueOr::Nearest)?;
hwp.set_buffer_size_near((PERIOD_SIZE * BUFFERED_PERIODS) as Frames)?;
pcm.hw_params(&hwp)?;
let swp = pcm.sw_params_current()?;
@ -68,16 +77,21 @@ impl Open for AlsaSink {
}
.to_string();
AlsaSink(None, name)
AlsaSink {
pcm: None,
device: name,
buffer: [0; PERIOD_SIZE],
buffered_data: 0,
}
}
}
impl Sink for AlsaSink {
fn start(&mut self) -> io::Result<()> {
if self.0.is_none() {
let pcm = open_device(&self.1);
if self.pcm.is_none() {
let pcm = open_device(&self.device);
match pcm {
Ok(p) => self.0 = Some(p),
Ok(p) => self.pcm = Some(p),
Err(e) => {
error!("Alsa error PCM open {}", e);
return Err(io::Error::new(
@ -93,20 +107,34 @@ impl Sink for AlsaSink {
fn stop(&mut self) -> io::Result<()> {
{
let pcm = self.0.as_ref().unwrap();
let pcm = self.pcm.as_ref().unwrap();
pcm.drain().unwrap();
}
self.0 = None;
self.pcm = None;
Ok(())
}
fn write(&mut self, data: &[i16]) -> io::Result<()> {
let pcm = self.0.as_mut().unwrap();
let io = pcm.io_i16().unwrap();
match io.writei(&data) {
Ok(_) => (),
Err(err) => pcm.try_recover(err, false).unwrap(),
let mut processed_data = 0;
while processed_data < data.len() {
let data_to_buffer = min(
PERIOD_SIZE - self.buffered_data,
data.len() - processed_data,
);
let buffer_slice =
&mut self.buffer[self.buffered_data..self.buffered_data + data_to_buffer];
buffer_slice.copy_from_slice(&data[processed_data..processed_data + data_to_buffer]);
self.buffered_data += data_to_buffer;
processed_data += data_to_buffer;
if self.buffered_data == PERIOD_SIZE {
self.buffered_data = 0;
let pcm = self.pcm.as_mut().unwrap();
let io = pcm.io_i16().unwrap();
match io.writei(&self.buffer) {
Ok(_) => (),
Err(err) => pcm.try_recover(err, false).unwrap(),
}
}
}
Ok(())