| // 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::{BoxError, SampleFormat, StreamSource, NoopStreamSource}; |
| //! use std::io::Write; |
| //! |
| //! const buffer_size: usize = 120; |
| //! const num_channels: usize = 2; |
| //! |
| //! # fn main() -> std::result::Result<(), BoxError> { |
| //! let mut stream_source = NoopStreamSource::new(); |
| //! let sample_format = SampleFormat::S16LE; |
| //! let frame_size = num_channels * sample_format.sample_bytes(); |
| //! |
| //! let (_, mut stream) = stream_source |
| //! .new_playback_stream(num_channels, sample_format, 48000, buffer_size)?; |
| //! // Play 10 buffers of DC. |
| //! let mut buf = Vec::new(); |
| //! buf.resize(buffer_size * frame_size, 0xa5u8); |
| //! for _ in 0..10 { |
| //! let mut stream_buffer = stream.next_playback_buffer()?; |
| //! assert_eq!(stream_buffer.write(&buf)?, buffer_size * frame_size); |
| //! } |
| //! # Ok (()) |
| //! # } |
| //! ``` |
| |
| use std::cmp::min; |
| 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::str::FromStr; |
| use std::time::{Duration, Instant}; |
| |
| #[derive(Copy, Clone, Debug, PartialEq)] |
| pub enum SampleFormat { |
| U8, |
| S16LE, |
| S24LE, |
| S32LE, |
| } |
| |
| impl SampleFormat { |
| pub fn sample_bytes(self) -> usize { |
| use SampleFormat::*; |
| match self { |
| U8 => 1, |
| S16LE => 2, |
| S24LE => 4, // Not a typo, S24_LE samples are stored in 4 byte chunks. |
| S32LE => 4, |
| } |
| } |
| } |
| |
| impl Display for SampleFormat { |
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| use SampleFormat::*; |
| match self { |
| U8 => write!(f, "Unsigned 8 bit"), |
| S16LE => write!(f, "Signed 16 bit Little Endian"), |
| S24LE => write!(f, "Signed 24 bit Little Endian"), |
| S32LE => write!(f, "Signed 32 bit Little Endian"), |
| } |
| } |
| } |
| |
| /// Valid directions of an audio stream. |
| #[derive(Copy, Clone, Debug, PartialEq)] |
| pub enum StreamDirection { |
| Playback, |
| Capture, |
| } |
| |
| /// Valid effects for an audio stream. |
| #[derive(Copy, Clone, Debug, PartialEq)] |
| pub enum StreamEffect { |
| NoEffect, |
| EchoCancellation, |
| } |
| |
| pub mod capture; |
| pub mod shm_streams; |
| |
| impl Default for StreamEffect { |
| fn default() -> Self { |
| StreamEffect::NoEffect |
| } |
| } |
| |
| /// Errors that can pass across threads. |
| pub type BoxError = Box<dyn error::Error + Send + Sync>; |
| |
| /// Errors that are possible from a `StreamEffect`. |
| #[derive(Debug)] |
| pub enum StreamEffectError { |
| InvalidEffect, |
| } |
| |
| impl error::Error for StreamEffectError {} |
| |
| impl Display for StreamEffectError { |
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| match self { |
| StreamEffectError::InvalidEffect => write!(f, "Must be in [EchoCancellation, aec]"), |
| } |
| } |
| } |
| |
| impl FromStr for StreamEffect { |
| type Err = StreamEffectError; |
| fn from_str(s: &str) -> std::result::Result<Self, Self::Err> { |
| match s { |
| "EchoCancellation" | "aec" => Ok(StreamEffect::EchoCancellation), |
| _ => Err(StreamEffectError::InvalidEffect), |
| } |
| } |
| } |
| |
| /// `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. |
| #[allow(clippy::type_complexity)] |
| fn new_playback_stream( |
| &mut self, |
| num_channels: usize, |
| format: SampleFormat, |
| frame_rate: u32, |
| buffer_size: usize, |
| ) -> Result<(Box<dyn StreamControl>, Box<dyn PlaybackBufferStream>), BoxError>; |
| |
| /// 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 `NoopStreamControl` and `NoopCaptureStream`. |
| #[allow(clippy::type_complexity)] |
| fn new_capture_stream( |
| &mut self, |
| num_channels: usize, |
| format: SampleFormat, |
| frame_rate: u32, |
| buffer_size: usize, |
| ) -> Result< |
| ( |
| Box<dyn StreamControl>, |
| Box<dyn capture::CaptureBufferStream>, |
| ), |
| BoxError, |
| > { |
| Ok(( |
| Box::new(NoopStreamControl::new()), |
| Box::new(capture::NoopCaptureStream::new( |
| num_channels, |
| format, |
| 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(&mut self) -> Result<PlaybackBuffer, BoxError>; |
| } |
| |
| /// `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 = min( |
| size / self.buffer.frame_size * self.buffer.frame_size, |
| self.buffer.buffer.len() - self.buffer.offset, |
| ); |
| 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 NoopStream { |
| buffer: Vec<u8>, |
| frame_size: usize, |
| interval: Duration, |
| next_frame: Duration, |
| start_time: Option<Instant>, |
| buffer_drop: NoopBufferDrop, |
| } |
| |
| /// NoopStream data that is needed from the buffer complete callback. |
| struct NoopBufferDrop { |
| which_buffer: bool, |
| } |
| |
| impl BufferDrop for NoopBufferDrop { |
| fn trigger(&mut self, _nwritten: usize) { |
| // When a buffer completes, switch to the other one. |
| self.which_buffer ^= true; |
| } |
| } |
| |
| impl NoopStream { |
| pub fn new( |
| num_channels: usize, |
| format: SampleFormat, |
| frame_rate: u32, |
| buffer_size: usize, |
| ) -> Self { |
| let frame_size = format.sample_bytes() * num_channels; |
| let interval = Duration::from_millis(buffer_size as u64 * 1000 / frame_rate as u64); |
| NoopStream { |
| buffer: vec![0; buffer_size * frame_size], |
| frame_size, |
| interval, |
| next_frame: interval, |
| start_time: None, |
| buffer_drop: NoopBufferDrop { |
| which_buffer: false, |
| }, |
| } |
| } |
| } |
| |
| impl PlaybackBufferStream for NoopStream { |
| fn next_playback_buffer(&mut self) -> Result<PlaybackBuffer, BoxError> { |
| if let Some(start_time) = self.start_time { |
| let elapsed = start_time.elapsed(); |
| if elapsed < self.next_frame { |
| std::thread::sleep(self.next_frame - 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 `NoopStream`s. |
| #[derive(Default)] |
| pub struct NoopStreamControl; |
| |
| impl NoopStreamControl { |
| pub fn new() -> Self { |
| NoopStreamControl {} |
| } |
| } |
| |
| impl StreamControl for NoopStreamControl {} |
| |
| /// Source of `NoopStream` and `NoopStreamControl` objects. |
| #[derive(Default)] |
| pub struct NoopStreamSource; |
| |
| impl NoopStreamSource { |
| pub fn new() -> Self { |
| NoopStreamSource {} |
| } |
| } |
| |
| impl StreamSource for NoopStreamSource { |
| #[allow(clippy::type_complexity)] |
| fn new_playback_stream( |
| &mut self, |
| num_channels: usize, |
| format: SampleFormat, |
| frame_rate: u32, |
| buffer_size: usize, |
| ) -> Result<(Box<dyn StreamControl>, Box<dyn PlaybackBufferStream>), BoxError> { |
| Ok(( |
| Box::new(NoopStreamControl::new()), |
| Box::new(NoopStream::new( |
| num_channels, |
| format, |
| 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 = NoopBufferDrop { |
| 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_all(&[0xa5u8; 480 * FRAME_SIZE]).unwrap(); |
| } |
| assert_eq!(test_drop.frame_count, 480); |
| } |
| |
| #[test] |
| fn sixteen_bit_stereo() { |
| let mut server = NoopStreamSource::new(); |
| let (_, mut stream) = server |
| .new_playback_stream(2, SampleFormat::S16LE, 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 = NoopStreamSource::new(); |
| let (_, mut stream) = server |
| .new_playback_stream(2, SampleFormat::S16LE, 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() |
| ); |
| } |
| } |