Add grouped device dropdown for PipeWire with USB/HDMI categorization

Backend changes:
- Add device_bus and is_hardware fields to AudioDevice
- Parse PipeWire Flags (HARDWARE) and device.bus property from pactl output

Frontend changes:
- DeviceDropdown now supports both ALSA and PipeWire backends
- ALSA grouping: Defaults, Bit-perfect, Plugin Hardware, Other
- PipeWire grouping: Defaults, USB Audio (BP capable), HDMI/DisplayPort, Other HW, Virtual
- BP badge shown for USB Audio devices in PipeWire mode

src-tauri/src/audio/alsa_backend.rs

@@ -204,6 +204,8 @@ impl AlsaBackend {
                         is_default: false,
                         max_sample_rate: Some(384000), // Assume high sample rate capability
                         supported_sample_rates: None, // Can't detect without CPAL access
+                        device_bus: None,
+                        is_hardware: true,
                     });
                 }
             } else {
@@ -235,6 +237,8 @@ impl AlsaBackend {
                     is_default: false,
                     max_sample_rate,
                     supported_sample_rates,
+                    device_bus: None,
+                    is_hardware: true,
                 });
             }
 
@@ -247,6 +251,8 @@ impl AlsaBackend {
                 is_default: false,
                 max_sample_rate: Some(384000),
                 supported_sample_rates: None, // plughw can convert, so all rates are "supported"
+                device_bus: None,
+                is_hardware: true,
             });
         }
 
@@ -326,6 +332,8 @@ impl AlsaBackend {
                 is_default,
                 max_sample_rate,
                 supported_sample_rates,
+                device_bus: None,
+                is_hardware: true,
             });
         }
 

src-tauri/src/audio/backend.rs

@@ -84,6 +84,12 @@ pub struct AudioDevice {
     /// Supported sample rates (common audio rates that the device supports)
     /// Contains values like 44100, 48000, 88200, 96000, 176400, 192000, etc.
     pub supported_sample_rates: Option<Vec<u32>>,
+
+    /// Device bus type (for PipeWire): "usb", "pci", "bluetooth", or None
+    pub device_bus: Option<String>,
+
+    /// Whether this is a hardware device (has HARDWARE flag in PipeWire)
+    pub is_hardware: bool,
 }
 
 /// Audio backend configuration

src-tauri/src/audio/pipewire_backend.rs

@@ -59,6 +59,8 @@ impl PipeWireBackend {
         let mut current_name: Option<String> = None;
         let mut current_description: Option<String> = None;
         let mut current_max_rate: Option<u32> = None;
+        let mut current_is_hardware: bool = false;
+        let mut current_device_bus: Option<String> = None;
 
         for line in stdout.lines() {
             let line = line.trim();
@@ -74,13 +76,20 @@ impl PipeWireBackend {
                         is_default,
                         max_sample_rate: current_max_rate.take(),
                         supported_sample_rates: None, // PipeWire handles sample rate conversion
+                        device_bus: current_device_bus.take(),
+                        is_hardware: current_is_hardware,
                     });
                 }
                 current_max_rate = None;
+                current_is_hardware = false;
+                current_device_bus = None;
             } else if line.starts_with("Name:") {
                 current_name = Some(line.trim_start_matches("Name:").trim().to_string());
             } else if line.starts_with("Description:") {
                 current_description = Some(line.trim_start_matches("Description:").trim().to_string());
+            } else if line.starts_with("Flags:") {
+                // Check for HARDWARE flag
+                current_is_hardware = line.contains("HARDWARE");
             } else if line.contains("Sample Specification:") {
                 // Try to parse sample rate from lines like "Sample Specification: s32le 2ch 192000Hz"
                 if let Some(hz_pos) = line.find("Hz") {
@@ -91,6 +100,10 @@ impl PipeWireBackend {
                         }
                     }
                 }
+            } else if line.starts_with("device.bus = ") {
+                // Parse device.bus property (e.g., "usb", "pci", "bluetooth")
+                let bus = line.trim_start_matches("device.bus = ").trim_matches('"').to_string();
+                current_device_bus = Some(bus);
             }
         }
 
@@ -104,13 +117,15 @@ impl PipeWireBackend {
                 is_default,
                 max_sample_rate: current_max_rate,
                 supported_sample_rates: None, // PipeWire handles sample rate conversion
+                device_bus: current_device_bus,
+                is_hardware: current_is_hardware,
             });
         }
 
         log::info!("[PipeWire Backend] Enumerated {} devices via pactl", devices.len());
         for (idx, dev) in devices.iter().enumerate() {
-            log::info!("  [{}] {} (id: {}, max_rate: {:?})",
-                idx, dev.name, dev.id, dev.max_sample_rate);
+            log::info!("  [{}] {} (id: {}, bus: {:?}, hw: {})",
+                idx, dev.name, dev.id, dev.device_bus, dev.is_hardware);
         }
 
         Ok(devices)