Add supported sample rates detection and display for ALSA devices

Backend changes:
- Add supported_sample_rates field to AudioDevice struct
- Detect common audio sample rates (44.1, 48, 88.2, 96, 176.4, 192, 352.8, 384 kHz)
- Use CPAL's supported_output_configs() to check rate support for hw: devices

Frontend changes:
- Display sample rates as subtitle in DeviceDropdown (e.g., "44.1, 48, 96, 192 kHz")
- Only shown for bit-perfect devices where detection is available
- Search not sensitive to sample rates field (per user request)

src-tauri/src/audio/alsa_backend.rs

@@ -17,6 +17,49 @@ use rodio::{
 };
 use std::process::Command;
 
+/// Common audio sample rates to check for device support
+const COMMON_SAMPLE_RATES: &[u32] = &[
+    44100,  // CD quality
+    48000,  // DVD/DAT quality
+    88200,  // 2x CD
+    96000,  // DVD-Audio
+    176400, // 4x CD
+    192000, // High-res audio
+    352800, // DSD64 equivalent
+    384000, // Ultra high-res
+];
+
+/// Extract supported sample rates from a CPAL device
+fn get_supported_sample_rates(device: &rodio::cpal::Device) -> Option<Vec<u32>> {
+    use rodio::cpal::traits::DeviceTrait;
+
+    let configs = device.supported_output_configs().ok()?;
+    let configs_vec: Vec<_> = configs.collect();
+
+    if configs_vec.is_empty() {
+        return None;
+    }
+
+    let mut supported = Vec::new();
+
+    for rate in COMMON_SAMPLE_RATES {
+        let sample_rate = rodio::cpal::SampleRate(*rate);
+        // Check if any config supports this rate
+        let is_supported = configs_vec.iter().any(|config| {
+            sample_rate >= config.min_sample_rate() && sample_rate <= config.max_sample_rate()
+        });
+        if is_supported {
+            supported.push(*rate);
+        }
+    }
+
+    if supported.is_empty() {
+        None
+    } else {
+        Some(supported)
+    }
+}
+
 pub struct AlsaBackend {
     host: rodio::cpal::Host,
 }
@@ -151,7 +194,7 @@ impl AlsaBackend {
             if !can_open {
                 // Try to get supported configs to validate device exists
                 // Create a test device to check if it's valid
-                if let Ok(test_devices) = self.host.output_devices() {
+                if let Ok(_test_devices) = self.host.output_devices() {
                     // CPAL may not enumerate hw: devices but can still open them
                     // We'll add them anyway and let the backend handle errors
                     devices.push(AudioDevice {
@@ -160,33 +203,38 @@ impl AlsaBackend {
                         description: Some(format!("{} (Direct Hardware - Bit-perfect)", card_desc)),
                         is_default: false,
                         max_sample_rate: Some(384000), // Assume high sample rate capability
+                        supported_sample_rates: None, // Can't detect without CPAL access
                     });
                 }
             } else {
-                // CPAL found it, get real max sample rate
+                // CPAL found it, get real sample rate info
-                let max_sample_rate = self.host
+                let cpal_device = self.host
                     .output_devices()
                     .ok()
                     .and_then(|mut devs| {
                         devs.find(|d| d.name().ok().as_deref() == Some(&hw_device_id))
-                    })
-                    .and_then(|device| {
-                        device
-                            .supported_output_configs()
-                            .ok()
-                            .and_then(|mut configs| {
-                                configs
-                                    .max_by_key(|c| c.max_sample_rate().0)
-                                    .map(|c| c.max_sample_rate().0)
-                            })
                     });
 
+                let max_sample_rate = cpal_device.as_ref().and_then(|device| {
+                    device
+                        .supported_output_configs()
+                        .ok()
+                        .and_then(|mut configs| {
+                            configs
+                                .max_by_key(|c| c.max_sample_rate().0)
+                                .map(|c| c.max_sample_rate().0)
+                        })
+                });
+
+                let supported_sample_rates = cpal_device.as_ref().and_then(get_supported_sample_rates);
+
                 devices.push(AudioDevice {
                     id: hw_device_id.clone(),
                     name: hw_device_id.clone(),
                     description: Some(format!("{} (Direct Hardware - Bit-perfect)", card_desc)),
                     is_default: false,
                     max_sample_rate,
+                    supported_sample_rates,
                 });
             }
 
@@ -198,6 +246,7 @@ impl AlsaBackend {
                 description: Some(format!("{} (Plugin Hardware)", card_desc)),
                 is_default: false,
                 max_sample_rate: Some(384000),
+                supported_sample_rates: None, // plughw can convert, so all rates are "supported"
             });
         }
 
@@ -267,12 +316,16 @@ impl AlsaBackend {
                         .map(|c| c.max_sample_rate().0)
                 });
 
+            // Get supported sample rates
+            let supported_sample_rates = get_supported_sample_rates(&device);
+
             devices.push(AudioDevice {
                 id: id.clone(),
                 name: name.clone(),
                 description: None,  // CPAL doesn't provide descriptions
                 is_default,
                 max_sample_rate,
+                supported_sample_rates,
             });
         }
 

src-tauri/src/audio/backend.rs

@@ -80,6 +80,10 @@ pub struct AudioDevice {
 
     /// Maximum supported sample rate (if known)
     pub max_sample_rate: Option<u32>,
+
+    /// 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>>,
 }
 
 /// Audio backend configuration

src-tauri/src/audio/pipewire_backend.rs

@@ -73,6 +73,7 @@ impl PipeWireBackend {
                         description: None,
                         is_default,
                         max_sample_rate: current_max_rate.take(),
+                        supported_sample_rates: None, // PipeWire handles sample rate conversion
                     });
                 }
                 current_max_rate = None;
@@ -102,6 +103,7 @@ impl PipeWireBackend {
                 description: None,
                 is_default,
                 max_sample_rate: current_max_rate,
+                supported_sample_rates: None, // PipeWire handles sample rate conversion
             });
         }
 

src/lib/components/DeviceDropdown.svelte

@@ -12,6 +12,7 @@
     value: string;        // Display name
     id: string;           // Device ID (for categorization)
     isDefault?: boolean;
+    sampleRates?: number[]; // Supported sample rates in Hz (e.g., 44100, 48000, 96000, 192000)
   }
 
   interface DeviceGroup {
@@ -94,6 +95,17 @@
     return groups;
   });
 
+  // Format sample rates for display (e.g., "44.1, 48, 96, 192 kHz")
+  function formatSampleRates(rates: number[] | undefined): string | null {
+    if (!rates || rates.length === 0) return null;
+    const formatted = rates.map(r => {
+      const kHz = r / 1000;
+      // Show decimal only for 44.1, 88.2, 176.4, 352.8
+      return kHz % 1 !== 0 ? kHz.toFixed(1) : kHz.toString();
+    });
+    return formatted.join(', ') + ' kHz';
+  }
+
   // Filtered groups based on search
   const filteredGroups = $derived.by(() => {
     if (!searchQuery.trim()) return groupedDevices;
@@ -298,13 +310,20 @@
         <div class="group">
           <div class="group-header">{group.label}</div>
           {#each group.devices as device (device.value)}
+            {@const sampleRatesText = formatSampleRates(device.sampleRates)}
             <button
               class="option"
               class:selected={device.value === value}
+              class:has-subtitle={!!sampleRatesText}
               onclick={() => handleOptionClick(device)}
               title={device.id !== device.value ? `${device.value}\n${device.id}` : device.value}
             >
-              <span class="option-text">{device.value}</span>
+              <div class="option-content">
+                <span class="option-text">{device.value}</span>
+                {#if sampleRatesText}
+                  <span class="option-sample-rates">{sampleRatesText}</span>
+                {/if}
+              </div>
               {#if group.key === 'bitperfect'}
                 <span class="badge bit-perfect">BP</span>
               {/if}
@@ -451,8 +470,8 @@
 
   .option {
     width: 100%;
-    height: 36px;
+    min-height: 36px;
-    padding: 0 12px;
+    padding: 6px 12px;
     display: flex;
     align-items: center;
     justify-content: space-between;
@@ -464,14 +483,34 @@
     border: none;
     cursor: pointer;
     transition: background-color 150ms ease, color 150ms ease;
-    white-space: nowrap;
     flex-shrink: 0;
   }
 
+  .option.has-subtitle {
+    min-height: 44px;
+    padding: 4px 12px;
+  }
+
+  .option-content {
+    flex: 1;
+    min-width: 0;
+    display: flex;
+    flex-direction: column;
+    gap: 1px;
+  }
+
   .option-text {
     overflow: hidden;
     text-overflow: ellipsis;
-    flex: 1;
+    white-space: nowrap;
+  }
+
+  .option-sample-rates {
+    font-size: 10px;
+    color: var(--text-muted);
+    white-space: nowrap;
+    overflow: hidden;
+    text-overflow: ellipsis;
   }
 
   .option:hover {

src/lib/components/views/SettingsView.svelte

@@ -465,7 +465,7 @@
   // Device options for grouped dropdown (ALSA Direct only)
   let groupedDeviceOptions = $derived.by(() => {
     // System Default is always first
-    const options: { value: string; id: string; isDefault?: boolean }[] = [
+    const options: { value: string; id: string; isDefault?: boolean; sampleRates?: number[] }[] = [
       { value: 'System Default', id: 'system-default', isDefault: true }
     ];
 
@@ -488,7 +488,8 @@
       options.push({
         value: displayName,
         id: device.id,
-        isDefault: device.is_default
+        isDefault: device.is_default,
+        sampleRates: device.supported_sample_rates ?? undefined
       });
     });
 
@@ -1082,6 +1083,7 @@
     description: string | null;
     is_default: boolean;
     max_sample_rate: number | null;
+    supported_sample_rates: number[] | null;
   }
 
   interface AlsaPluginInfo {