fix: use BufferSize::Default for PipeWire ALSA devices on Linux

crates/recording/src/feeds/microphone.rs

@@ -987,12 +987,31 @@ fn stream_config_with_latency(
     let buffer_size_frames = desired_buffer_size_frames(config, device_name);
 
     if let Some(frames) = buffer_size_frames {
-        stream_config.buffer_size = BufferSize::Fixed(frames);
+        if uses_pulse_backend(device_name) {
+            stream_config.buffer_size = BufferSize::Default;
+        } else {
+            stream_config.buffer_size = BufferSize::Fixed(frames);
+        }
     }
 
     (stream_config, buffer_size_frames)
 }
 
+#[cfg(target_os = "linux")]
+fn uses_pulse_backend(device_name: Option<&str>) -> bool {
+    device_name
+        .map(|n| {
+            let lower = n.to_ascii_lowercase();
+            lower == "default" || lower == "pulse" || lower == "pipewire"
+        })
+        .unwrap_or(false)
+}
+
+#[cfg(not(target_os = "linux"))]
+fn uses_pulse_backend(_device_name: Option<&str>) -> bool {
+    false
+}
+
 fn desired_buffer_size_frames(
     config: &SupportedStreamConfig,
     device_name: Option<&str>,

crates/recording/src/sources/screen_capture/linux.rs

@@ -941,6 +941,14 @@ fn select_system_audio_monitor() -> anyhow::Result<SelectedSystemAudioInput> {
         return Ok(selected);
     }
 
+    if !pactl_available() {
+        return Err(anyhow!(
+            "Linux system audio capture needs `pactl` to discover monitor sources, but it was not found on PATH. \
+            Install it (e.g. `apt install pulseaudio-utils`, `dnf install pulseaudio-utils`, `pacman -S libpulse`) and try again. \
+            Available cpal input devices: {available:?}."
+        ));
+    }
+
     Err(anyhow!(
         "No PulseAudio/PipeWire monitor input was found for Linux system audio. \
         Available input devices: {available:?}. Select a monitor source with --mic, or enable a monitor source in your audio server."
@@ -1029,6 +1037,14 @@ fn pactl_monitor_rank(name: &str) -> Option<u8> {
     }
 }
 
+fn pactl_available() -> bool {
+    Command::new("pactl")
+        .arg("--version")
+        .output()
+        .map(|o| o.status.success())
+        .unwrap_or(false)
+}
+
 fn pactl_default_source() -> Option<String> {
     let output = Command::new("pactl")
         .arg("get-default-source")