std::env::set_var is not thread-safe on Unix (unsafe as of Rust 2024
edition) and calling it from a spawned capture thread while other
threads (tokio runtime, webview, Tauri plugins) may read the
environment is a data race risk. It also never got unset, so the
monitor source would leak into any later cpal/ALSA init in the same
process.
Replace the env-var indirection with direct device selection: when
pactl reports a monitor source name, search cpal's input device
enumeration for an exact match. Fall back to a substring match on
'monitor' (the original pactl-unavailable path), then the host's
default input device. This is the 'pass the source name directly to
cpal' option from the issue - no env mutation, no leakage between
capture sessions, and it still re-detects the current default sink's
monitor on every start_capture call.
Fixes#471
cpal 0.15 uses ALSA as its Linux backend, which does not expose
PulseAudio/PipeWire monitor sources. The previous approach searched
for 'monitor' in cpal device names, which never matched on most
Linux systems, silently falling back to the microphone input.
This fix:
- Detects the correct monitor source via 'pactl get-default-sink'
and 'pactl list short sources'
- Sets PULSE_SOURCE env var before cpal initialization so PulseAudio's
ALSA plugin routes the default input through the monitor
- Preserves the original name-based search as fallback when pactl is
unavailable
- No new dependencies added
Tested on PipeWire 1.0.5 with Realtek ALC897 (HD-Audio Generic).
Cherry-picked and adapted from PR #89 and #214:
- Linux audio capture via PulseAudio/PipeWire monitor sources (cpal)
- AMD ROCm GPU support: HSA_OVERRIDE_GFX_VERSION env var, ROCm detection
- Whisper Turbo model (openai/whisper-large-v3-turbo) in all endpoints
- Cleaner Whisper language handling via generate_kwargs
- tauri::async_runtime::spawn fix to prevent panic on app shutdown
- Enable Linux (ubuntu-22.04) in release CI matrix
