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WIP - Add ALSA timestamp implementation. 

I think this is mostly complete, however there are two major TODOs:

- There seems to be a bug where timestamps are not reported when the
  target device is `pulse`. This causes a `panic!` as the trigger
  timestamp should always precede the timestamp when retrieved while the
  stream is running.
- We need to specify the timestamp type as MONOTONIC_RAW, however the
  `alsa` and `alsa-sys` crates do not yet expose the necessary
  `set_tstamp_type` function.
This commit is contained in:
mitchmindtree 2020-04-27 18:00:40 +02:00
parent 777a6b2bd1
commit a49297ec2c
1 changed files with 87 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

110
src/host/alsa/mod.rs
View File

@ -8,6 +8,7 @@ use crate::{
PlayStreamError, SampleFormat, SampleRate, StreamConfig, StreamError, SupportedStreamConfig,
SupportedStreamConfigRange, SupportedStreamConfigsError,
};
use std::convert::TryInto;
use std::sync::Arc;
use std::thread::{self, JoinHandle};
use std::vec::IntoIter as VecIntoIter;
@ -208,7 +209,7 @@ impl Device {
channel: handle,
sample_format,
num_descriptors,
num_channels: conf.channels as u16,
conf: conf.clone(),
buffer_len,
period_len,
can_pause,
@ -421,8 +422,8 @@ struct StreamInner {
// Format of the samples.
sample_format: SampleFormat,
// Number of channels, ie. number of samples per frame.
num_channels: u16,
// The configuration used to open this stream.
conf: StreamConfig,
// Number of samples that can fit in the buffer.
buffer_len: usize,
@ -479,7 +480,8 @@ fn input_stream_worker(
PollDescriptorsFlow::Continue => continue,
PollDescriptorsFlow::Return => return,
PollDescriptorsFlow::Ready {
available_frames: _,
avail_frames: _,
delay_frames,
stream_type,
} => {
assert_eq!(
@ -487,10 +489,8 @@ fn input_stream_worker(
StreamType::Input,
"expected input stream, but polling descriptors indicated output",
);
report_error(
process_input(stream, &mut ctxt.buffer, data_callback),
error_callback,
);
let res = process_input(stream, &mut ctxt.buffer, delay_frames, data_callback);
report_error(res, error_callback);
}
}
}
@ -514,7 +514,8 @@ fn output_stream_worker(
PollDescriptorsFlow::Continue => continue,
PollDescriptorsFlow::Return => return,
PollDescriptorsFlow::Ready {
available_frames,
avail_frames,
delay_frames,
stream_type,
} => {
assert_eq!(
@ -522,13 +523,15 @@ fn output_stream_worker(
StreamType::Output,
"expected output stream, but polling descriptors indicated input",
);
process_output(
let res = process_output(
stream,
&mut ctxt.buffer,
available_frames,
avail_frames,
delay_frames,
data_callback,
error_callback,
);
report_error(res, error_callback);
}
}
}
@ -555,7 +558,8 @@ enum PollDescriptorsFlow {
Return,
Ready {
stream_type: StreamType,
available_frames: usize,
avail_frames: usize,
delay_frames: usize,
},
}
@ -614,7 +618,8 @@ fn poll_descriptors_and_prepare_buffer(
}
};
// Get the number of available samples for reading/writing.
let available_samples = get_available_samples(stream)?;
let (avail_frames, delay_frames) = get_avail_delay(stream)?;
let available_samples = avail_frames * stream.conf.channels as usize;
// Only go on if there is at least `stream.period_len` samples.
if available_samples < stream.period_len {
@ -624,11 +629,11 @@ fn poll_descriptors_and_prepare_buffer(
// Prepare the data buffer.
let buffer_size = stream.sample_format.sample_size() * available_samples;
buffer.resize(buffer_size, 0u8);
let available_frames = available_samples / stream.num_channels as usize;
Ok(PollDescriptorsFlow::Ready {
stream_type,
available_frames,
avail_frames,
delay_frames,
})
}
@ -636,6 +641,7 @@ fn poll_descriptors_and_prepare_buffer(
fn process_input(
stream: &StreamInner,
buffer: &mut [u8],
delay_frames: usize,
data_callback: &mut (dyn FnMut(&Data, &InputCallbackInfo) + Send + 'static),
) -> Result<(), BackendSpecificError> {
stream.channel.io().readi(buffer)?;
@ -643,7 +649,13 @@ fn process_input(
let data = buffer.as_mut_ptr() as *mut ();
let len = buffer.len() / sample_format.sample_size();
let data = unsafe { Data::from_parts(data, len, sample_format) };
let info = crate::InputCallbackInfo {};
let callback = stream_timestamp(stream)?;
let delay_duration = frames_to_duration(delay_frames, stream.conf.sample_rate);
let capture = callback
.sub(delay_duration)
.expect("`capture` occurs before origin of alsa `StreamInstant`");
let timestamp = crate::InputStreamTimestamp { callback, capture };
let info = crate::InputCallbackInfo { timestamp };
data_callback(&data, &info);
Ok(())
@ -656,16 +668,23 @@ fn process_output(
stream: &StreamInner,
buffer: &mut [u8],
available_frames: usize,
delay_frames: usize,
data_callback: &mut (dyn FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static),
error_callback: &mut dyn FnMut(StreamError),
) {
) -> Result<(), BackendSpecificError> {
{
// We're now sure that we're ready to write data.
let sample_format = stream.sample_format;
let data = buffer.as_mut_ptr() as *mut ();
let len = buffer.len() / sample_format.sample_size();
let mut data = unsafe { Data::from_parts(data, len, sample_format) };
let info = crate::OutputCallbackInfo {};
let callback = stream_timestamp(stream)?;
let delay_duration = frames_to_duration(delay_frames, stream.conf.sample_rate);
let playback = callback
.add(delay_duration)
.expect("`playback` occurs beyond representation supported by `StreamInstant`");
let timestamp = crate::OutputStreamTimestamp { callback, playback };
let info = crate::OutputCallbackInfo { timestamp };
data_callback(&mut data, &info);
}
loop {
@ -693,6 +712,47 @@ fn process_output(
}
}
}
Ok(())
}
// Use the duration since the start of the stream.
//
// This ensures positive values that are compatible with our `StreamInstant` representation.
fn stream_timestamp(stream: &StreamInner) -> Result<crate::StreamInstant, BackendSpecificError> {
let status = stream.channel.status()?;
let trigger_ts = status.get_trigger_htstamp();
// TODO: This is returning `0` on ALSA where default device forwards to pulse.
// Possibly related: https://bugs.freedesktop.org/show_bug.cgi?id=88503
let ts = status.get_htstamp();
let nanos = timespec_diff_nanos(ts, trigger_ts)
.try_into()
.unwrap_or_else(|_| {
panic!(
"get_htstamp `{:?}` was earlier than get_trigger_htstamp `{:?}`",
ts, trigger_ts
);
});
Ok(crate::StreamInstant::from_nanos(nanos))
}
// Adapted from `timestamp2ns` here:
// https://fossies.org/linux/alsa-lib/test/audio_time.c
fn timespec_to_nanos(ts: libc::timespec) -> i64 {
ts.tv_sec as i64 * 1_000_000_000 + ts.tv_nsec
}
// Adapted from `timediff` here:
// https://fossies.org/linux/alsa-lib/test/audio_time.c
fn timespec_diff_nanos(a: libc::timespec, b: libc::timespec) -> i64 {
timespec_to_nanos(a) - timespec_to_nanos(b)
}
// Convert the given duration in frames at the given sample rate to a `std::time::Duration`.
fn frames_to_duration(frames: usize, rate: crate::SampleRate) -> std::time::Duration {
let secsf = frames as f64 / rate.0 as f64;
let secs = secsf as u64;
let nanos = ((secsf - secs as f64) * 1_000_000_000.0) as u32;
std::time::Duration::new(secs, nanos)
}
impl Stream {
@ -759,16 +819,16 @@ impl StreamTrait for Stream {
}
}
// Determine the number of samples that are available to read/write.
fn get_available_samples(stream: &StreamInner) -> Result<usize, BackendSpecificError> {
match stream.channel.avail_update() {
// Determine the number of frames that are available to read/write along with the latency.
fn get_avail_delay(stream: &StreamInner) -> Result<(usize, usize), BackendSpecificError> {
match stream.channel.avail_delay() {
Err(err) if err.errno() == Some(nix::errno::Errno::EPIPE) => {
// buffer underrun
// TODO: Notify the user some how.
Ok(stream.buffer_len)
Ok((stream.buffer_len, 0))
}
Err(err) => Err(err.into()),
Ok(available) => Ok(available as usize * stream.num_channels as usize),
Ok((avail, delay)) => Ok((avail as usize, delay as usize)),
}
}
@ -830,6 +890,10 @@ fn set_sw_params_from_format(
(buffer, period)
};
sw_params.set_tstamp_mode(true)?;
// TODO: `sw_params.set_tstamp_type(CLOCK_MONOTONIC_RAW)`
// Pending addressing https://github.com/diwic/alsa-sys/issues/6
pcm_handle.sw_params(&sw_params)?;
Ok((buffer_len, period_len))