Prototyping an API for getting the supported min and max buffersizes

asio-sys/src/bindings/errors.rs

@@ -19,6 +19,7 @@ pub enum AsioError {
     HardwareStuck,
     NoRate,
     ASE_NoMemory,
+    InvalidBufferSize,
     UnknownError,
 }
 
@@ -63,6 +64,7 @@ impl fmt::Display for AsioError {
                 "sample clock or rate cannot be determined or is not present"
             ),
             AsioError::ASE_NoMemory => write!(f, "not enough memory for completing the request"),
+            AsioError::InvalidBufferSize => write!(f, "buffersize out of range for device"),
             AsioError::UnknownError => write!(f, "Error not in SDK"),
         }
     }
@@ -94,6 +96,7 @@ impl Error for AsioError {
             AsioError::HardwareStuck => "hardware is not running when sample position is inquired",
             AsioError::NoRate => "sample clock or rate cannot be determined or is not present",
             AsioError::ASE_NoMemory => "not enough memory for completing the request",
+            AsioError::InvalidBufferSize => "buffersize out of range for device",
             AsioError::UnknownError => "Error not in SDK",
         }
     }

asio-sys/src/bindings/mod.rs

@@ -385,6 +385,14 @@ impl Driver {
         Ok(channel)
     }
 
+    /// Get the min and max supported buffersize of the driver.
+    pub fn buffersize_range(&self) -> Result<(c_long, c_long), AsioError> {
+        let buffer_sizes = asio_get_buffer_sizes()?;
+        let min = buffer_sizes.min;
+        let max = buffer_sizes.max;
+        Ok((min, max))
+    }
+
     /// Get current sample rate of the driver.
     pub fn sample_rate(&self) -> Result<c_double, AsioError> {
         let mut rate: c_double = 0.0;
@@ -431,8 +439,14 @@ impl Driver {
     ///
     /// This will destroy any already allocated buffers.
     ///
-    /// The preferred buffer size from ASIO is used.
-    fn create_buffers(&self, buffer_infos: &mut [AsioBufferInfo]) -> Result<c_long, AsioError> {
+    /// If buffersize is None then the preferred buffer size from ASIO is used,
+    /// otherwise the desired buffersize is used if the requeted size is within
+    /// the range of accepted buffersizes for the device.
+    fn create_buffers(
+        &self,
+        buffer_infos: &mut [AsioBufferInfo],
+        buffer_size: Option<i32>,
+    ) -> Result<c_long, AsioError> {
         let num_channels = buffer_infos.len();
 
         // To pass as ai::ASIOCallbacks
@@ -449,6 +463,17 @@ impl Driver {
             );
         }
 
+        let buffer_size = match buffer_size {
+            Some(v) => {
+                if v <= buffer_sizes.max {
+                    v
+                } else {
+                    return Err(AsioError::InvalidBufferSize);
+                }
+            }
+            None => buffer_sizes.pref,
+        };
+
         // Ensure the driver is in the `Initialized` state.
         if let DriverState::Running = *state {
             state.stop()?;
@@ -460,23 +485,27 @@ impl Driver {
             asio_result!(ai::ASIOCreateBuffers(
                 buffer_infos.as_mut_ptr() as *mut _,
                 num_channels as i32,
-                buffer_sizes.pref,
+                buffer_size,
                 &mut callbacks as *mut _ as *mut _,
             ))?;
         }
         *state = DriverState::Prepared;
 
-        Ok(buffer_sizes.pref)
+        Ok(buffer_size)
     }
 
     /// Creates the streams.
     ///
+    /// `buffer_size` sets the desired buffer_size. If None is passed in, then the
+    /// default buffersize for the device is used.
+    ///
     /// Both input and output streams need to be created together as a single slice of
     /// `ASIOBufferInfo`.
     fn create_streams(
         &self,
         mut input_buffer_infos: Vec<AsioBufferInfo>,
         mut output_buffer_infos: Vec<AsioBufferInfo>,
+        buffer_size: Option<i32>,
     ) -> Result<AsioStreams, AsioError> {
         let (input, output) = match (
             input_buffer_infos.is_empty(),
@@ -489,7 +518,7 @@ impl Driver {
                 let mut all_buffer_infos = input_buffer_infos;
                 all_buffer_infos.append(&mut output_buffer_infos);
                 // Create the buffers. On success, split the output and input again.
-                let buffer_size = self.create_buffers(&mut all_buffer_infos)?;
+                let buffer_size = self.create_buffers(&mut all_buffer_infos, buffer_size)?;
                 let output_buffer_infos = all_buffer_infos.split_off(split_point);
                 let input_buffer_infos = all_buffer_infos;
                 let input = Some(AsioStream {
@@ -504,7 +533,7 @@ impl Driver {
             }
             // Just input
             (false, true) => {
-                let buffer_size = self.create_buffers(&mut input_buffer_infos)?;
+                let buffer_size = self.create_buffers(&mut input_buffer_infos, buffer_size)?;
                 let input = Some(AsioStream {
                     buffer_infos: input_buffer_infos,
                     buffer_size,
@@ -514,7 +543,7 @@ impl Driver {
             }
             // Just output
             (true, false) => {
-                let buffer_size = self.create_buffers(&mut output_buffer_infos)?;
+                let buffer_size = self.create_buffers(&mut output_buffer_infos, buffer_size)?;
                 let input = None;
                 let output = Some(AsioStream {
                     buffer_infos: output_buffer_infos,
@@ -537,17 +566,21 @@ impl Driver {
     ///
     /// `num_channels` is the desired number of input channels.
     ///
+    /// `buffer_size` sets the desired buffer_size. If None is passed in, then the
+    /// default buffersize for the device is used.
+    ///
     /// This returns a full AsioStreams with both input and output if output was active.
     pub fn prepare_input_stream(
         &self,
         output: Option<AsioStream>,
         num_channels: usize,
+        buffer_size: Option<i32>,
     ) -> Result<AsioStreams, AsioError> {
         let input_buffer_infos = prepare_buffer_infos(true, num_channels);
         let output_buffer_infos = output
             .map(|output| output.buffer_infos)
             .unwrap_or_else(Vec::new);
-        self.create_streams(input_buffer_infos, output_buffer_infos)
+        self.create_streams(input_buffer_infos, output_buffer_infos, buffer_size)
     }
 
     /// Prepare the output stream.
@@ -559,17 +592,21 @@ impl Driver {
     ///
     /// `num_channels` is the desired number of output channels.
     ///
+    /// `buffer_size` sets the desired buffer_size. If None is passed in, then the
+    /// default buffersize for the device is used.
+    ///
     /// This returns a full AsioStreams with both input and output if input was active.
     pub fn prepare_output_stream(
         &self,
         input: Option<AsioStream>,
         num_channels: usize,
+        buffer_size: Option<i32>,
     ) -> Result<AsioStreams, AsioError> {
         let input_buffer_infos = input
             .map(|input| input.buffer_infos)
             .unwrap_or_else(Vec::new);
         let output_buffer_infos = prepare_buffer_infos(false, num_channels);
-        self.create_streams(input_buffer_infos, output_buffer_infos)
+        self.create_streams(input_buffer_infos, output_buffer_infos, buffer_size)
     }
 
     /// Releases buffers allocations.

examples/enumerate.rs

@@ -11,6 +11,7 @@ fn main() -> Result<(), anyhow::Error> {
     for host_id in available_hosts {
         println!("{}", host_id.name());
         let host = cpal::host_from_id(host_id)?;
+
         let default_in = host.default_input_device().map(|e| e.name().unwrap());
         let default_out = host.default_output_device().map(|e| e.name().unwrap());
         println!("  Default Input Device:\n    {:?}", default_in);

src/host/alsa/mod.rs

@@ -3,10 +3,11 @@ extern crate libc;
 
 use self::alsa::poll::Descriptors;
 use crate::{
-    BackendSpecificError, BuildStreamError, ChannelCount, Data, DefaultStreamConfigError,
-    DeviceNameError, DevicesError, InputCallbackInfo, OutputCallbackInfo, PauseStreamError,
-    PlayStreamError, SampleFormat, SampleRate, StreamConfig, StreamError, SupportedStreamConfig,
-    SupportedStreamConfigRange, SupportedStreamConfigsError,
+    BackendSpecificError, BufferSize, BuildStreamError, ChannelCount, Data,
+    DefaultStreamConfigError, DeviceNameError, DevicesError, InputCallbackInfo, OutputCallbackInfo,
+    PauseStreamError, PlayStreamError, SampleFormat, SampleRate, StreamConfig, StreamError,
+    SupportedBufferSize, SupportedStreamConfig, SupportedStreamConfigRange,
+    SupportedStreamConfigsError,
 };
 use std::convert::TryInto;
 use std::sync::Arc;
@@ -339,6 +340,14 @@ impl Device {
             })
             .collect::<Vec<_>>();
 
+        let min_buffer_size = hw_params.get_buffer_size_min()?;
+        let max_buffer_size = hw_params.get_buffer_size_max()?;
+
+        let buffer_size_range = SupportedBufferSize::Range {
+            min: min_buffer_size as u32,
+            max: max_buffer_size as u32,
+        };
+
         let mut output = Vec::with_capacity(
             supported_formats.len() * supported_channels.len() * sample_rates.len(),
         );
@@ -349,6 +358,7 @@ impl Device {
                         channels: channels.clone(),
                         min_sample_rate: SampleRate(min_rate as u32),
                         max_sample_rate: SampleRate(max_rate as u32),
+                        buffer_size: buffer_size_range.clone(),
                         sample_format: sample_format,
                     });
                 }
@@ -869,7 +879,7 @@ fn set_hw_params_from_format<'a>(
     config: &StreamConfig,
     sample_format: SampleFormat,
 ) -> Result<alsa::pcm::HwParams<'a>, BackendSpecificError> {
-    let mut hw_params = alsa::pcm::HwParams::any(pcm_handle)?;
+    let hw_params = alsa::pcm::HwParams::any(pcm_handle)?;
     hw_params.set_access(alsa::pcm::Access::RWInterleaved)?;
 
     let sample_format = if cfg!(target_endian = "big") {
@@ -890,11 +900,14 @@ fn set_hw_params_from_format<'a>(
     hw_params.set_rate(config.sample_rate.0, alsa::ValueOr::Nearest)?;
     hw_params.set_channels(config.channels as u32)?;
 
-    // If this isn't set manually a overlarge buffer may be used causing audio delay
-    let mut hw_params_copy = hw_params.clone();
-    if let Err(_) = hw_params.set_buffer_time_near(100_000, alsa::ValueOr::Nearest) {
-        // Swap out the params with errors for a snapshot taken before the error was introduced.
-        mem::swap(&mut hw_params_copy, &mut hw_params);
+    match config.buffer_size {
+        BufferSize::Fixed(v) => hw_params.set_buffer_size(v as i64)?,
+        BufferSize::Default => {
+            // These values together represent a moderate latency and wakeup interval.
+            // Without them we are at the mercy of the device
+            hw_params.set_period_time_near(25_000, alsa::ValueOr::Nearest)?;
+            hw_params.set_buffer_time_near(100_000, alsa::ValueOr::Nearest)?;
+        }
     }
 
     pcm_handle.hw_params(&hw_params)?;

src/host/asio/device.rs

@@ -12,6 +12,7 @@ use DeviceNameError;
 use DevicesError;
 use SampleFormat;
 use SampleRate;
+use SupportedBufferSize;
 use SupportedStreamConfig;
 use SupportedStreamConfigRange;
 use SupportedStreamConfigsError;
@@ -77,9 +78,13 @@ impl Device {
                 continue;
             }
             for channels in 1..f.channels + 1 {
-                f.channels = channels;
-                f.sample_rate = rate;
-                supported_configs.push(SupportedStreamConfigRange::from(f.clone()));
+                supported_configs.push(SupportedStreamConfigRange {
+                    channels,
+                    min_sample_rate: rate,
+                    max_sample_rate: rate,
+                    buffer_size: f.buffer_size.clone(),
+                    sample_format: f.sample_format.clone(),
+                })
             }
         }
         Ok(supported_configs.into_iter())
@@ -110,9 +115,13 @@ impl Device {
                 continue;
             }
             for channels in 1..f.channels + 1 {
-                f.channels = channels;
-                f.sample_rate = rate;
-                supported_configs.push(SupportedStreamConfigRange::from(f.clone()));
+                supported_configs.push(SupportedStreamConfigRange {
+                    channels,
+                    min_sample_rate: rate,
+                    max_sample_rate: rate,
+                    buffer_size: f.buffer_size.clone(),
+                    sample_format: f.sample_format.clone(),
+                })
             }
         }
         Ok(supported_configs.into_iter())
@@ -122,13 +131,19 @@ impl Device {
     pub fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
         let channels = self.driver.channels().map_err(default_config_err)?.ins as u16;
         let sample_rate = SampleRate(self.driver.sample_rate().map_err(default_config_err)? as _);
+        let (min, max) = self.driver.buffersize_range().map_err(default_config_err)?;
+        let buffer_size = SupportedBufferSize::Range {
+            min: min as u32,
+            max: max as u32,
+        };
         // Map th ASIO sample type to a CPAL sample type
         let data_type = self.driver.input_data_type().map_err(default_config_err)?;
         let sample_format = convert_data_type(&data_type)
             .ok_or(DefaultStreamConfigError::StreamTypeNotSupported)?;
         Ok(SupportedStreamConfig {
             channels,
             sample_rate,
+            buffer_size,
             sample_format,
         })
     }
@@ -137,12 +152,18 @@ impl Device {
     pub fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
         let channels = self.driver.channels().map_err(default_config_err)?.outs as u16;
         let sample_rate = SampleRate(self.driver.sample_rate().map_err(default_config_err)? as _);
+        let (min, max) = self.driver.buffersize_range().map_err(default_config_err)?;
+        let buffer_size = SupportedBufferSize::Range {
+            min: min as u32,
+            max: max as u32,
+        };
         let data_type = self.driver.output_data_type().map_err(default_config_err)?;
         let sample_format = convert_data_type(&data_type)
             .ok_or(DefaultStreamConfigError::StreamTypeNotSupported)?;
         Ok(SupportedStreamConfig {
             channels,
             sample_rate,
+            buffer_size,
             sample_format,
         })
     }

src/host/asio/stream.rs

@@ -5,9 +5,9 @@ use self::num_traits::PrimInt;
 use super::parking_lot::Mutex;
 use super::Device;
 use crate::{
-    BackendSpecificError, BuildStreamError, Data, InputCallbackInfo, OutputCallbackInfo,
-    PauseStreamError, PlayStreamError, Sample, SampleFormat, StreamConfig, StreamError,
-    SupportedStreamConfig,
+    BackendSpecificError, BufferSize, BuildStreamError, Data, InputCallbackInfo,
+    OutputCallbackInfo, PauseStreamError, PlayStreamError, Sample, SampleFormat, StreamConfig,
+    StreamError,
 };
 use std;
 use std::sync::atomic::{AtomicBool, Ordering};
@@ -482,14 +482,20 @@ impl Device {
         }?;
         let num_channels = config.channels as usize;
         let ref mut streams = *self.asio_streams.lock();
+
+        let buffer_size = match config.buffer_size {
+            BufferSize::Fixed(v) => Some(v as i32),
+            BufferSize::Default => None,
+        };
+
         // Either create a stream if thers none or had back the
         // size of the current one.
         match streams.input {
             Some(ref input) => Ok(input.buffer_size as usize),
             None => {
                 let output = streams.output.take();
                 self.driver
-                    .prepare_input_stream(output, num_channels)
+                    .prepare_input_stream(output, num_channels, buffer_size)
                     .map(|new_streams| {
                         let bs = match new_streams.input {
                             Some(ref inp) => inp.buffer_size as usize,
@@ -523,14 +529,20 @@ impl Device {
         }?;
         let num_channels = config.channels as usize;
         let ref mut streams = *self.asio_streams.lock();
+
+        let buffer_size = match config.buffer_size {
+            BufferSize::Fixed(v) => Some(v as i32),
+            BufferSize::Default => None,
+        };
+
         // Either create a stream if thers none or had back the
         // size of the current one.
         match streams.output {
             Some(ref output) => Ok(output.buffer_size as usize),
             None => {
                 let output = streams.output.take();
                 self.driver
-                    .prepare_output_stream(output, num_channels)
+                    .prepare_output_stream(output, num_channels, buffer_size)
                     .map(|new_streams| {
                         let bs = match new_streams.output {
                             Some(ref out) => out.buffer_size as usize,
@@ -645,6 +657,7 @@ fn check_config(
     let StreamConfig {
         channels,
         sample_rate,
+        buffer_size,
     } = config;
     // Try and set the sample rate to what the user selected.
     let sample_rate = sample_rate.0.into();