| // Copyright 2019 The Chromium OS Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| //! Provides an interface for playing and recording audio. |
| //! |
| //! When implementing an audio playback system, the `StreamSource` trait is implemented. |
| //! Implementors of this trait allow creation of `PlaybackBufferStream` objects. The |
| //! `PlaybackBufferStream` provides the actual audio buffers to be filled with audio samples. These |
| //! buffers are obtained by calling `next_playback_buffer`. |
| //! |
| //! Users playing audio fill the provided buffers with audio. When a `PlaybackBuffer` is dropped, |
| //! the samples written to it are committed to the `PlaybackBufferStream` it came from. |
| //! |
| //! ``` |
| //! use audio_streams::{StreamSource, DummyStreamSource}; |
| //! use std::io::Write; |
| //! |
| //! const buffer_size: usize = 120; |
| //! const num_channels: usize = 2; |
| //! const frame_size: usize = num_channels * 2; // 16-bit samples are two bytes. |
| //! |
| //! # fn main() -> std::result::Result<(), Box<std::error::Error>> { |
| //! let mut stream_source = DummyStreamSource::new(); |
| //! |
| //! let (_, mut stream) = stream_source |
| //! .new_playback_stream(num_channels, 48000, buffer_size)?; |
| //! // Play 10 buffers of DC. |
| //! let pb_bufs = [[0xa5u8; buffer_size * frame_size]; 10]; |
| //! for pb_buf in &pb_bufs { |
| //! let mut stream_buffer = stream.next_playback_buffer()?; |
| //! assert_eq!(stream_buffer.write(pb_buf)?, buffer_size * frame_size); |
| //! } |
| //! # Ok (()) |
| //! # } |
| //! ``` |
| |
| use std::error; |
| use std::fmt::{self, Display}; |
| use std::io::{self, Write}; |
| use std::os::unix::io::RawFd; |
| use std::result::Result; |
| use std::time::{Duration, Instant}; |
| |
| pub mod capture; |
| |
| /// `StreamSource` creates streams for playback or capture of audio. |
| pub trait StreamSource: Send { |
| /// Returns a stream control and buffer generator object. These are separate as the buffer |
| /// generator might want to be passed to the audio stream. |
| fn new_playback_stream( |
| &mut self, |
| num_channels: usize, |
| frame_rate: usize, |
| buffer_size: usize, |
| ) -> Result<(Box<dyn StreamControl>, Box<dyn PlaybackBufferStream>), Box<dyn error::Error>>; |
| |
| /// Returns a stream control and buffer generator object. These are separate as the buffer |
| /// generator might want to be passed to the audio stream. |
| /// Default implementation returns `DummyStreamControl` and `DummyCaptureStream`. |
| fn new_capture_stream( |
| &mut self, |
| num_channels: usize, |
| frame_rate: usize, |
| buffer_size: usize, |
| ) -> Result< |
| ( |
| Box<dyn StreamControl>, |
| Box<dyn capture::CaptureBufferStream>, |
| ), |
| Box<dyn error::Error>, |
| > { |
| Ok(( |
| Box::new(DummyStreamControl::new()), |
| Box::new(capture::DummyCaptureStream::new( |
| num_channels, |
| frame_rate, |
| buffer_size, |
| )), |
| )) |
| } |
| |
| /// Returns any open file descriptors needed by the implementor. The FD list helps users of the |
| /// StreamSource enter Linux jails making sure not to close needed FDs. |
| fn keep_fds(&self) -> Option<Vec<RawFd>> { |
| None |
| } |
| } |
| |
| /// `PlaybackBufferStream` provides `PlaybackBuffer`s to fill with audio samples for playback. |
| pub trait PlaybackBufferStream: Send { |
| fn next_playback_buffer<'a>(&'a mut self) -> Result<PlaybackBuffer<'a>, Box<dyn error::Error>>; |
| } |
| |
| /// `StreamControl` provides a way to set the volume and mute states of a stream. `StreamControl` |
| /// is separate from the stream so it can be owned by a different thread if needed. |
| pub trait StreamControl: Send + Sync { |
| fn set_volume(&mut self, _scaler: f64) {} |
| fn set_mute(&mut self, _mute: bool) {} |
| } |
| |
| /// `BufferDrop` is used as a callback mechanism for `PlaybackBuffer` objects. It is meant to be |
| /// implemented by the audio stream, allowing arbitrary code to be run after a buffer is filled or |
| /// read by the user. |
| pub trait BufferDrop { |
| /// Called when an audio buffer is dropped. `nframes` indicates the number of audio frames that |
| /// were read or written to the device. |
| fn trigger(&mut self, nframes: usize); |
| } |
| |
| /// Errors that are possible from a `PlaybackBuffer`. |
| #[derive(Debug)] |
| pub enum PlaybackBufferError { |
| InvalidLength, |
| } |
| |
| impl error::Error for PlaybackBufferError {} |
| |
| impl Display for PlaybackBufferError { |
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| match self { |
| PlaybackBufferError::InvalidLength => write!(f, "Invalid buffer length"), |
| } |
| } |
| } |
| |
| /// `AudioBuffer` is one buffer that holds buffer_size audio frames and its drop function. |
| /// It is the inner data of `PlaybackBuffer` and `CaptureBuffer`. |
| struct AudioBuffer<'a> { |
| buffer: &'a mut [u8], |
| offset: usize, // Read or Write offset in frames. |
| frame_size: usize, // Size of a frame in bytes. |
| drop: &'a mut dyn BufferDrop, |
| } |
| |
| /// `PlaybackBuffer` is one buffer that holds buffer_size audio frames. It is used to temporarily |
| /// allow access to an audio buffer and notifes the owning stream of write completion when dropped. |
| pub struct PlaybackBuffer<'a> { |
| buffer: AudioBuffer<'a>, |
| } |
| |
| impl<'a> PlaybackBuffer<'a> { |
| /// Creates a new `PlaybackBuffer` that holds a reference to the backing memory specified in |
| /// `buffer`. |
| pub fn new<F>( |
| frame_size: usize, |
| buffer: &'a mut [u8], |
| drop: &'a mut F, |
| ) -> Result<Self, PlaybackBufferError> |
| where |
| F: BufferDrop, |
| { |
| if buffer.len() % frame_size != 0 { |
| return Err(PlaybackBufferError::InvalidLength); |
| } |
| |
| Ok(PlaybackBuffer { |
| buffer: AudioBuffer { |
| buffer, |
| offset: 0, |
| frame_size, |
| drop, |
| }, |
| }) |
| } |
| |
| /// Returns the number of audio frames that fit in the buffer. |
| pub fn frame_capacity(&self) -> usize { |
| self.buffer.buffer.len() / self.buffer.frame_size |
| } |
| |
| /// Writes up to `size` bytes directly to this buffer inside of the given callback function. |
| pub fn copy_cb<F: FnOnce(&mut [u8])>(&mut self, size: usize, cb: F) { |
| // only write complete frames. |
| let len = size / self.buffer.frame_size * self.buffer.frame_size; |
| cb(&mut self.buffer.buffer[self.buffer.offset..(self.buffer.offset + len)]); |
| self.buffer.offset += len; |
| } |
| } |
| |
| impl<'a> Write for PlaybackBuffer<'a> { |
| fn write(&mut self, buf: &[u8]) -> io::Result<usize> { |
| // only write complete frames. |
| let len = buf.len() / self.buffer.frame_size * self.buffer.frame_size; |
| let written = (&mut self.buffer.buffer[self.buffer.offset..]).write(&buf[..len])?; |
| self.buffer.offset += written; |
| Ok(written) |
| } |
| |
| fn flush(&mut self) -> io::Result<()> { |
| Ok(()) |
| } |
| } |
| |
| impl<'a> Drop for PlaybackBuffer<'a> { |
| fn drop(&mut self) { |
| self.buffer |
| .drop |
| .trigger(self.buffer.offset / self.buffer.frame_size); |
| } |
| } |
| |
| /// Stream that accepts playback samples but drops them. |
| pub struct DummyStream { |
| buffer: Vec<u8>, |
| frame_size: usize, |
| interval: Duration, |
| next_frame: Duration, |
| start_time: Option<Instant>, |
| buffer_drop: DummyBufferDrop, |
| } |
| |
| /// DummyStream data that is needed from the buffer complete callback. |
| struct DummyBufferDrop { |
| which_buffer: bool, |
| } |
| |
| impl BufferDrop for DummyBufferDrop { |
| fn trigger(&mut self, _nwritten: usize) { |
| // When a buffer completes, switch to the other one. |
| self.which_buffer ^= true; |
| } |
| } |
| |
| impl DummyStream { |
| // TODO(allow other formats) |
| pub fn new(num_channels: usize, frame_rate: usize, buffer_size: usize) -> Self { |
| const S16LE_SIZE: usize = 2; |
| let frame_size = S16LE_SIZE * num_channels; |
| let interval = Duration::from_millis(buffer_size as u64 * 1000 / frame_rate as u64); |
| DummyStream { |
| buffer: vec![0; buffer_size * frame_size], |
| frame_size, |
| interval, |
| next_frame: interval, |
| start_time: None, |
| buffer_drop: DummyBufferDrop { |
| which_buffer: false, |
| }, |
| } |
| } |
| } |
| |
| impl PlaybackBufferStream for DummyStream { |
| fn next_playback_buffer<'a>(&'a mut self) -> Result<PlaybackBuffer<'a>, Box<dyn error::Error>> { |
| if let Some(start_time) = self.start_time { |
| if start_time.elapsed() < self.next_frame { |
| std::thread::sleep(self.next_frame - start_time.elapsed()); |
| } |
| self.next_frame += self.interval; |
| } else { |
| self.start_time = Some(Instant::now()); |
| self.next_frame = self.interval; |
| } |
| Ok(PlaybackBuffer::new( |
| self.frame_size, |
| &mut self.buffer, |
| &mut self.buffer_drop, |
| )?) |
| } |
| } |
| |
| /// No-op control for `DummyStream`s. |
| #[derive(Default)] |
| pub struct DummyStreamControl; |
| |
| impl DummyStreamControl { |
| pub fn new() -> Self { |
| DummyStreamControl {} |
| } |
| } |
| |
| impl StreamControl for DummyStreamControl {} |
| |
| /// Source of `DummyStream` and `DummyStreamControl` objects. |
| #[derive(Default)] |
| pub struct DummyStreamSource; |
| |
| impl DummyStreamSource { |
| pub fn new() -> Self { |
| DummyStreamSource {} |
| } |
| } |
| |
| impl StreamSource for DummyStreamSource { |
| fn new_playback_stream( |
| &mut self, |
| num_channels: usize, |
| frame_rate: usize, |
| buffer_size: usize, |
| ) -> Result<(Box<dyn StreamControl>, Box<dyn PlaybackBufferStream>), Box<dyn error::Error>> |
| { |
| Ok(( |
| Box::new(DummyStreamControl::new()), |
| Box::new(DummyStream::new(num_channels, frame_rate, buffer_size)), |
| )) |
| } |
| } |
| |
| #[cfg(test)] |
| mod tests { |
| use super::*; |
| |
| #[test] |
| fn invalid_buffer_length() { |
| // Playback buffers can't be created with a size that isn't divisible by the frame size. |
| let mut pb_buf = [0xa5u8; 480 * 2 * 2 + 1]; |
| let mut buffer_drop = DummyBufferDrop { |
| which_buffer: false, |
| }; |
| assert!(PlaybackBuffer::new(2, &mut pb_buf, &mut buffer_drop).is_err()); |
| } |
| |
| #[test] |
| fn trigger() { |
| struct TestDrop { |
| frame_count: usize, |
| }; |
| impl BufferDrop for TestDrop { |
| fn trigger(&mut self, nwritten: usize) { |
| self.frame_count += nwritten; |
| } |
| } |
| let mut test_drop = TestDrop { frame_count: 0 }; |
| { |
| const FRAME_SIZE: usize = 4; |
| let mut buf = [0u8; 480 * FRAME_SIZE]; |
| let mut pb_buf = PlaybackBuffer::new(FRAME_SIZE, &mut buf, &mut test_drop).unwrap(); |
| pb_buf.write(&[0xa5u8; 480 * FRAME_SIZE]).unwrap(); |
| } |
| assert_eq!(test_drop.frame_count, 480); |
| } |
| |
| #[test] |
| fn sixteen_bit_stereo() { |
| let mut server = DummyStreamSource::new(); |
| let (_, mut stream) = server.new_playback_stream(2, 48000, 480).unwrap(); |
| let mut stream_buffer = stream.next_playback_buffer().unwrap(); |
| assert_eq!(stream_buffer.frame_capacity(), 480); |
| let pb_buf = [0xa5u8; 480 * 2 * 2]; |
| assert_eq!(stream_buffer.write(&pb_buf).unwrap(), 480 * 2 * 2); |
| } |
| |
| #[test] |
| fn consumption_rate() { |
| let mut server = DummyStreamSource::new(); |
| let (_, mut stream) = server.new_playback_stream(2, 48000, 480).unwrap(); |
| let start = Instant::now(); |
| { |
| let mut stream_buffer = stream.next_playback_buffer().unwrap(); |
| let pb_buf = [0xa5u8; 480 * 2 * 2]; |
| assert_eq!(stream_buffer.write(&pb_buf).unwrap(), 480 * 2 * 2); |
| } |
| // The second call should block until the first buffer is consumed. |
| let _stream_buffer = stream.next_playback_buffer().unwrap(); |
| let elapsed = start.elapsed(); |
| assert!( |
| elapsed > Duration::from_millis(10), |
| "next_playback_buffer didn't block long enough {}", |
| elapsed.subsec_millis() |
| ); |
| } |
| } |