mumble-web2/gui/src/imp/native_audio.rs

use crate::effects::{AudioProcessor, AudioProcessorSender, TransmitState};
use color_eyre::eyre::{eyre, Error};
use cpal::traits::{DeviceTrait, HostTrait, StreamTrait as _};
use std::mem::replace;
use std::sync::Arc;
use std::sync::Mutex;
use tracing::{error, info, warn};

pub struct NativeAudioSystem {
    output: cpal::Device,
    input: cpal::Device,
    processors: AudioProcessorSender,
    recording_stream: Option<cpal::Stream>,
}

const SAMPLE_RATE: u32 = 48_000;
const PACKET_SAMPLES: u32 = 960;
// Divide by 1000 to get samples per ms, then multiply by 60ms for max Opus frame size.
const MAX_DECODE_SAMPLES: usize = SAMPLE_RATE as usize / 1000 * 60;

fn encode_and_send(
    state: TransmitState,
    output_buffer: &mut Vec<f32>,
    encoder: &mut opus::Encoder,
    each: &mut impl FnMut(Vec<u8>, bool),
) {
    let (is_terminator, should_encode) = match state {
        TransmitState::Silent => return,
        TransmitState::Transmitting => (false, output_buffer.len() >= PACKET_SAMPLES as usize),
        TransmitState::Terminator => {
            output_buffer.resize(PACKET_SAMPLES as usize, 0.0);
            (true, true)
        }
    };

    if should_encode {
        let remainder = output_buffer.split_off(PACKET_SAMPLES as usize);
        let frame = replace(output_buffer, remainder);
        match encoder.encode_vec_float(&frame, frame.len() * 2) {
            Ok(encoded) => each(encoded, is_terminator),
            Err(e) => error!("error encoding {} samples: {e:?}", frame.len()),
        }
    }
}

type Buffer = Arc<Mutex<dasp_ring_buffer::Bounded<Vec<i16>>>>;

impl NativeAudioSystem {
    fn choose_config(
        &self,
        configs: impl Iterator<Item = cpal::SupportedStreamConfigRange>,
    ) -> Result<cpal::StreamConfig, Error> {
        let mut supported_configs: Vec<_> = configs
            .filter_map(|cfg| cfg.try_with_sample_rate(cpal::SampleRate(SAMPLE_RATE)))
            .filter(|cfg| cfg.sample_format() == cpal::SampleFormat::I16)
            .map(|cfg| cpal::StreamConfig {
                buffer_size: cpal::BufferSize::Fixed(match *cfg.buffer_size() {
                    cpal::SupportedBufferSize::Range { min, max } => 480.clamp(min, max),
                    cpal::SupportedBufferSize::Unknown => 480,
                }),
                ..cfg.config()
            })
            .collect();
        supported_configs.sort_by(|a, b| {
            let cpal::BufferSize::Fixed(a_buf) = a.buffer_size else {
                unreachable!()
            };
            let cpal::BufferSize::Fixed(b_buf) = b.buffer_size else {
                unreachable!()
            };
            Ord::cmp(&a.channels, &b.channels).then(Ord::cmp(&a_buf, &b_buf))
        });
        supported_configs
            .get(0)
            .cloned()
            .ok_or(eyre!("no supported stream configs"))
    }
}

impl super::AudioSystemInterface for NativeAudioSystem {
    type AudioPlayer = NativeAudioPlayer;

    async fn new() -> Result<Self, Error> {
        let host = cpal::default_host();
        let name = host.id();
        let processors = AudioProcessorSender::default();
        Ok(NativeAudioSystem {
            output: host
                .default_output_device()
                .ok_or(eyre!("no output devices from {name:?}"))?,
            input: host
                .default_input_device()
                .ok_or(eyre!("no input devices from {name:?}"))?,
            processors,
            recording_stream: None,
        })
    }

    fn set_processor(&self, processor: AudioProcessor) {
        self.processors.store(Some(processor))
    }

    fn start_recording(
        &mut self,
        mut each: impl FnMut(Vec<u8>, bool) + Send + 'static,
    ) -> Result<(), Error> {
        let config = self.choose_config(self.input.supported_input_configs()?)?;
        info!(
            "creating recording on {:?} with {:#?}",
            self.input.name()?,
            config
        );
        let mut encoder =
            opus::Encoder::new(SAMPLE_RATE, opus::Channels::Mono, opus::Application::Voip)?;
        let mut current_processor = AudioProcessor::new_plain();
        let mut output_buffer = Vec::new();
        let processors = self.processors.clone();
        let error_callback = move |e: cpal::StreamError| error!("error recording: {e:?}");
        let data_callback = move |frame: &[f32], _: &cpal::InputCallbackInfo| {
            if let Some(new_processor) = processors.take() {
                current_processor = new_processor;
            }
            let state =
                current_processor.process(frame, config.channels as usize, &mut output_buffer);
            encode_and_send(state, &mut output_buffer, &mut encoder, &mut each);
        };

        match self
            .input
            .build_input_stream(&config, data_callback, error_callback, None)
        {
            Ok(stream) => {
                stream.play()?;
                self.recording_stream = Some(stream);
                Ok(())
            }
            Err(err) => {
                self.recording_stream = None;
                Err(err.into())
            }
        }
    }

    fn create_player(&mut self) -> Result<NativeAudioPlayer, Error> {
        let config = self.choose_config(self.output.supported_output_configs()?)?;
        info!(
            "creating player on {:?} with {:#?}",
            self.output.name().ok(),
            &config
        );
        let buffer = Arc::new(Mutex::new(dasp_ring_buffer::Bounded::from_raw_parts(
            0,
            0,
            vec![
            0;
            SAMPLE_RATE as usize/4 // 250ms of buffer
        ],
        )));
        let decoder = opus::Decoder::new(SAMPLE_RATE, opus::Channels::Mono)?;
        let stream = {
            let buffer = buffer.clone();
            self.output.build_output_stream(
                &config,
                move |frame, _info| {
                    let mut buffer = buffer.lock().unwrap();
                    for x in frame.chunks_mut(config.channels as usize) {
                        match buffer.pop() {
                            Some(y) => {
                                x.fill(y);
                            }
                            None => {
                                x.fill(0);
                            }
                        }
                    }
                },
                move |err| error!("could not create output stream {err:?}"),
                None,
            )?
        };
        stream.play()?;
        Ok(NativeAudioPlayer {
            decoder,
            stream,
            buffer,
            tmp: vec![0; MAX_DECODE_SAMPLES],
        })
    }
}

pub struct NativeAudioPlayer {
    decoder: opus::Decoder,
    stream: cpal::Stream,
    buffer: Buffer,
    tmp: Vec<i16>,
}

impl super::AudioPlayerInterface for NativeAudioPlayer {
    fn play_opus(&mut self, payload: &[u8]) {
        let len = match self.decoder.decode(payload, &mut self.tmp, false) {
            Ok(l) => l,
            Err(e) => {
                error!("opus decode error {e:?}");
                return;
            }
        };

        let mut buffer = self.buffer.lock().unwrap();
        let mut overrun = 0;
        for x in &self.tmp[..len] {
            if let Some(_) = buffer.push(*x) {
                overrun += 1;
            }
        }
        if overrun > 0 {
            warn!("playback overrun by {overrun} samples");
        }
    }
}