Modified WaveOut and WaveOutEvent to read the actual volume

Added additional code to WaveOut and WaveOutEvent to read the actual volume from the system rather than returning a cached value.

NAudio/Wave/WaveOutputs/WaveOut.cs

@@ -15,7 +15,6 @@ namespace NAudio.Wave
         private IWaveProvider waveStream;
         private volatile PlaybackState playbackState;
         private readonly WaveInterop.WaveCallback callback;
-        private float volume = 1;
         private readonly WaveCallbackInfo callbackInfo;
         private readonly object waveOutLock;
         private int queuedBuffers;
@@ -276,14 +275,28 @@ namespace NAudio.Wave
         /// </summary>
         public float Volume
         {
-            get => volume;
-            set 
+            get
+            {
+                return GetWaveOutVolume(hWaveOut, waveOutLock);
+            }
+            set
             {
                 SetWaveOutVolume(value, hWaveOut, waveOutLock);
-                volume = value;
             }
         }
 
+        internal static float GetWaveOutVolume(IntPtr hWaveOut, object lockObject)
+        {
+            int stereoVolume;
+            MmResult result;
+            lock (lockObject)
+            {
+                result = WaveInterop.waveOutGetVolume(hWaveOut, out stereoVolume);
+            }
+            MmException.Try(result, "waveOutGetVolume");
+            return (stereoVolume & 0xFFFF) / (float)0xFFFF;
+        }
+
         internal static void SetWaveOutVolume(float value, IntPtr hWaveOut, object lockObject)
         {
             if (value < 0) throw new ArgumentOutOfRangeException(nameof(value), "Volume must be between 0.0 and 1.0");

NAudio/Wave/WaveOutputs/WaveOutEvent.cs

@@ -18,7 +18,6 @@ namespace NAudio.Wave
         private IWaveProvider waveStream;
         private volatile PlaybackState playbackState;
         private AutoResetEvent callbackEvent;
-        private float volume = 1.0f;
 
         /// <summary>
         /// Indicates playback has stopped automatically
@@ -281,15 +280,17 @@ namespace NAudio.Wave
         }
 
         /// <summary>
-        /// Obsolete property
+        /// Volume for this device 1.0 is full scale
         /// </summary>
         public float Volume
         {
-            get { return volume; }
+            get
+            {
+                return WaveOut.GetWaveOutVolume(hWaveOut, waveOutLock);
+            }
             set
             {
                 WaveOut.SetWaveOutVolume(value, hWaveOut, waveOutLock);
-                volume = value;
             }
         }