diff --git a/playback/src/audio_backend/alsa.rs b/playback/src/audio_backend/alsa.rs index e572f953..4f82a097 100644 --- a/playback/src/audio_backend/alsa.rs +++ b/playback/src/audio_backend/alsa.rs @@ -4,16 +4,18 @@ use crate::convert::Converter; use crate::decoder::AudioPacket; use crate::{NUM_CHANNELS, SAMPLE_RATE}; use alsa::device_name::HintIter; -use alsa::pcm::{Access, Format, HwParams, PCM}; +use alsa::pcm::{Access, Format, Frames, HwParams, PCM}; use alsa::{Direction, ValueOr}; use std::cmp::min; use std::process::exit; -use std::time::Duration; use thiserror::Error; -// 0.5 sec buffer. -const PERIOD_TIME: Duration = Duration::from_millis(100); -const BUFFER_TIME: Duration = Duration::from_millis(500); +const MAX_BUFFER: Frames = (SAMPLE_RATE / 2) as Frames; +const MIN_BUFFER: Frames = (SAMPLE_RATE / 10) as Frames; +const ZERO_FRAMES: Frames = 0; + +const MAX_PERIOD_DIVISOR: Frames = 4; +const MIN_PERIOD_DIVISOR: Frames = 10; #[derive(Debug, Error)] enum AlsaError { @@ -195,28 +197,187 @@ fn open_device(dev_name: &str, format: AudioFormat) -> SinkResult<(PCM, usize)> e, })?; - hwp.set_buffer_time_near(BUFFER_TIME.as_micros() as u32, ValueOr::Nearest) - .map_err(AlsaError::HwParams)?; + // Clone the hwp while it's in + // a good working state so that + // in the event of an error setting + // the buffer and period sizes + // we can use the good working clone + // instead of the hwp that's in an + // error state. + let hwp_clone = hwp.clone(); - hwp.set_period_time_near(PERIOD_TIME.as_micros() as u32, ValueOr::Nearest) - .map_err(AlsaError::HwParams)?; + // At a sampling rate of 44100: + // The largest buffer is 22050 Frames (500ms) with 5512 Frame periods (125ms). + // The smallest buffer is 4410 Frames (100ms) with 441 Frame periods (10ms). + // Actual values may vary. + // + // Larger buffer and period sizes are preferred as extremely small values + // will cause high CPU useage. + // + // If no buffer or period size is in those ranges or an error happens + // trying to set the buffer or period size use the device's defaults + // which may not be ideal but are *hopefully* serviceable. - pcm.hw_params(&hwp).map_err(AlsaError::Pcm)?; + let buffer_size = { + let max = match hwp.get_buffer_size_max() { + Err(e) => { + trace!("Error getting the device's max Buffer size: {}", e); + ZERO_FRAMES + } + Ok(s) => s, + }; - let swp = pcm.sw_params_current().map_err(AlsaError::Pcm)?; + let min = match hwp.get_buffer_size_min() { + Err(e) => { + trace!("Error getting the device's min Buffer size: {}", e); + ZERO_FRAMES + } + Ok(s) => s, + }; + + let buffer_size = if min < max { + match (MIN_BUFFER..=MAX_BUFFER) + .rev() + .find(|f| (min..=max).contains(f)) + { + Some(size) => { + trace!("Desired Frames per Buffer: {:?}", size); + + match hwp.set_buffer_size_near(size) { + Err(e) => { + trace!("Error setting the device's Buffer size: {}", e); + ZERO_FRAMES + } + Ok(s) => s, + } + } + None => { + trace!("No Desired Buffer size in range reported by the device."); + ZERO_FRAMES + } + } + } else { + trace!("The device's min reported Buffer size was greater than or equal to it's max reported Buffer size."); + ZERO_FRAMES + }; + + if buffer_size == ZERO_FRAMES { + trace!( + "Desired Buffer Frame range: {:?} - {:?}", + MIN_BUFFER, + MAX_BUFFER + ); + + trace!( + "Actual Buffer Frame range as reported by the device: {:?} - {:?}", + min, + max + ); + } + + buffer_size + }; + + let period_size = { + if buffer_size == ZERO_FRAMES { + ZERO_FRAMES + } else { + let max = match hwp.get_period_size_max() { + Err(e) => { + trace!("Error getting the device's max Period size: {}", e); + ZERO_FRAMES + } + Ok(s) => s, + }; + + let min = match hwp.get_period_size_min() { + Err(e) => { + trace!("Error getting the device's min Period size: {}", e); + ZERO_FRAMES + } + Ok(s) => s, + }; + + let max_period = buffer_size / MAX_PERIOD_DIVISOR; + let min_period = buffer_size / MIN_PERIOD_DIVISOR; + + let period_size = if min < max && min_period < max_period { + match (min_period..=max_period) + .rev() + .find(|f| (min..=max).contains(f)) + { + Some(size) => { + trace!("Desired Frames per Period: {:?}", size); + + match hwp.set_period_size_near(size, ValueOr::Nearest) { + Err(e) => { + trace!("Error setting the device's Period size: {}", e); + ZERO_FRAMES + } + Ok(s) => s, + } + } + None => { + trace!("No Desired Period size in range reported by the device."); + ZERO_FRAMES + } + } + } else { + trace!("The device's min reported Period size was greater than or equal to it's max reported Period size,"); + trace!("or the desired min Period size was greater than or equal to the desired max Period size."); + ZERO_FRAMES + }; + + if period_size == ZERO_FRAMES { + trace!("Buffer size: {:?}", buffer_size); + + trace!( + "Desired Period Frame range: {:?} (Buffer size / {:?}) - {:?} (Buffer size / {:?})", + min_period, + MIN_PERIOD_DIVISOR, + max_period, + MAX_PERIOD_DIVISOR, + ); + + trace!( + "Actual Period Frame range as reported by the device: {:?} - {:?}", + min, + max + ); + } + + period_size + } + }; + + if buffer_size == ZERO_FRAMES || period_size == ZERO_FRAMES { + trace!( + "Failed to set Buffer and/or Period size, falling back to the device's defaults." + ); + + trace!("You may experience higher than normal CPU usage and/or audio issues."); + + pcm.hw_params(&hwp_clone).map_err(AlsaError::Pcm)?; + } else { + pcm.hw_params(&hwp).map_err(AlsaError::Pcm)?; + } + + let hwp = pcm.hw_params_current().map_err(AlsaError::Pcm)?; // Don't assume we got what we wanted. Ask to make sure. let frames_per_period = hwp.get_period_size().map_err(AlsaError::HwParams)?; let frames_per_buffer = hwp.get_buffer_size().map_err(AlsaError::HwParams)?; + let swp = pcm.sw_params_current().map_err(AlsaError::Pcm)?; + swp.set_start_threshold(frames_per_buffer - frames_per_period) .map_err(AlsaError::SwParams)?; pcm.sw_params(&swp).map_err(AlsaError::Pcm)?; - trace!("Frames per Buffer: {:?}", frames_per_buffer); - trace!("Frames per Period: {:?}", frames_per_period); + trace!("Actual Frames per Buffer: {:?}", frames_per_buffer); + trace!("Actual Frames per Period: {:?}", frames_per_period); // Let ALSA do the math for us. pcm.frames_to_bytes(frames_per_period) as usize