TASK 4 ship step 4: WASAPI audio capture — NAudio loopback + mic behind an IAudioSource seam, AudioMixer driving AudioLevel while live, pure level meter + WaveToFloat, NAudio.Wasapi 2.2.1 (MIT, notices item 9) — 139 tests passing, 0 warnings

Services/Audio/WaveToFloat.cs

@@ -0,0 +1,41 @@
+using NAudio.Dmo;
+using NAudio.Wave;
+
+namespace ytLive.Services.Audio;
+
+/// <summary>
+/// Converts NAudio's raw WASAPI capture buffers (byte[], whatever bit depth the
+/// device's mix format reports) into interleaved PCM float samples. Pure —
+/// unit-tested; the two WASAPI sources share it.
+/// </summary>
+public static class WaveToFloat
+{
+    public static float[] Convert(byte[] buffer, int bytesRecorded, WaveFormat format)
+    {
+        if (format.Encoding == WaveFormatEncoding.IeeeFloat && format.BitsPerSample == 32)
+            return ConvertIeeeFloat(buffer, bytesRecorded);
+        if (format.Encoding == WaveFormatEncoding.Pcm && format.BitsPerSample == 16)
+            return ConvertPcm16(buffer, bytesRecorded);
+        if (format is WaveFormatExtensible extensible
+            && extensible.SubFormat == AudioMediaSubtypes.MEDIASUBTYPE_IEEE_FLOAT)
+            return ConvertIeeeFloat(buffer, bytesRecorded);
+        return ConvertPcm16(buffer, bytesRecorded);
+    }
+
+    private static float[] ConvertIeeeFloat(byte[] buffer, int bytesRecorded)
+    {
+        var count = bytesRecorded / 4;
+        var result = new float[count];
+        Buffer.BlockCopy(buffer, 0, result, 0, count * 4);
+        return result;
+    }
+
+    private static float[] ConvertPcm16(byte[] buffer, int bytesRecorded)
+    {
+        var count = bytesRecorded / 2;
+        var result = new float[count];
+        for (var i = 0; i < count; i++)
+            result[i] = BitConverter.ToInt16(buffer, i * 2) / 32768f;
+        return result;
+    }
+}