fix(alsa): stalling callbacks when start threshold is not met

Author: roderickvd

CHANGELOG.md

@@ -12,20 +12,21 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `DeviceBusy` error variant for retriable device access errors (EBUSY, EAGAIN).
 - **ALSA**: `Debug` implementations for `Host`, `Device`, `Stream`, and internal types.
 - **ALSA**: Example demonstrating ALSA error suppression during enumeration.
-- **WASAPI**: Allow non-native sample rates to be used via as-necessary resampling in the WASAPI server process.
+- **WASAPI**: Enable as-necessary resampling in the WASAPI server process.
 
 ### Changed
 
 - Overall MSRV increased to 1.78.
 - **ALSA**: Update `alsa` dependency from 0.10 to 0.11.
-- **ALSA**: MSRV increased from 1.77 to 1.82 (required by alsa-sys 0.4.0).
+- **ALSA**: MSRV increased from 1.77 to 1.82.
 
 ### Fixed
 
 - **ALSA**: Enumerating input and output devices no longer interferes with each other.
 - **ALSA**: Device handles are no longer exclusively held between operations.
-- **ALSA**: Valgrind memory leak reports from ALSA global configuration cache.
+- **ALSA**: Reduce Valgrind memory leak reports from ALSA global configuration cache.
 - **ALSA**: Fix possible race condition on drop.
+- **ALSA**: Fix audio callback stalling when start threshold is not met.
 
 ## [0.17.1] - 2026-01-04
 

src/host/alsa/mod.rs

@@ -1449,26 +1449,8 @@ fn set_sw_params_from_format(
             }
             alsa::Direction::Capture => 1,
         };
-        sw_params.set_start_threshold(start_threshold.try_into().unwrap())?;
-
-        // Set avail_min based on stream direction. For playback, "avail" means space available
-        // for writing (buffer_size - frames_queued). For capture, "avail" means data available
-        // for reading (frames_captured). These opposite semantics require different values.
-        let target_avail = match stream_type {
-            alsa::Direction::Playback => {
-                // Wake when buffer level drops to one period remaining (avail >= buffer - period).
-                // This ensures we can always write one full period. Works correctly regardless
-                // of total periods: 2-period buffer wakes at period, 4-period at 3*period, etc.
-                buffer - period
-            }
-            alsa::Direction::Capture => {
-                // Wake when one period of data is available to read (avail >= period).
-                // Using buffer - period here would cause excessive latency as capture would
-                // wait for nearly the entire buffer to fill before reading.
-                period
-            }
-        };
-        sw_params.set_avail_min(target_avail as alsa::pcm::Frames)?;
+        sw_params.set_start_threshold(start_threshold as alsa::pcm::Frames)?;
+        sw_params.set_avail_min(period as alsa::pcm::Frames)?;
 
         period as usize * config.channels as usize
     };