Add inputDeviceID passthrough to AudioStreamTranscriber

Sources/WhisperKit/Core/Audio/AudioStreamTranscriber.swift

@@ -39,6 +39,10 @@
     private let transcribeTask: TranscribeTask
     private let audioProcessor: any AudioProcessing
     private let decodingOptions: DecodingOptions
+    /// Optional input device to capture from. nil = system default input.
+    /// Lets callers stream from a specific device (e.g. a virtual device) instead
+    /// of always using the system default. Passed through to startRecordingLive.
+    private let inputDeviceID: DeviceID?
 
     public init(
         audioEncoder: any AudioEncoding,
@@ -52,6 +56,7 @@
         silenceThreshold: Float = 0.3,
         compressionCheckWindow: Int = 60,
         useVAD: Bool = true,
+        inputDeviceID: DeviceID? = nil,
         stateChangeCallback: AudioStreamTranscriberCallback?
     ) {
         self.transcribeTask = TranscribeTask(
@@ -70,6 +75,7 @@
         self.silenceThreshold = silenceThreshold
         self.compressionCheckWindow = compressionCheckWindow
         self.useVAD = useVAD
+        self.inputDeviceID = inputDeviceID
         self.stateChangeCallback = stateChangeCallback
     }
 
@@ -80,10 +86,17 @@
             return
         }
         state.isRecording = true
-        try audioProcessor.startRecordingLive { [weak self] _ in
-            Task { [weak self] in
-                await self?.onAudioBufferCallback()
+        do {
+            try audioProcessor.startRecordingLive(inputDeviceID: inputDeviceID) { [weak self] _ in
+                Task { [weak self] in
+                    await self?.onAudioBufferCallback()
+                }
             }
+        } catch {
+            // Reset the flag so a failed start (e.g. an unavailable inputDeviceID)
+            // does not leave the actor stuck in a recording state that blocks retries.
+            state.isRecording = false
+            throw error
         }
         await realtimeLoop()
         Logging.info("Realtime transcription has started")
@@ -197,7 +210,7 @@
         options.clipTimestamps = [state.lastConfirmedSegmentEndSeconds]
         let checkWindow = compressionCheckWindow
         return try await transcribeTask
             .run(audioArray: samples, decodeOptions: options) { [options] progress in
             Task { [weak self] in
                 await self?.onProgressCallback(progress)
             }