diff --git a/ArcFormats/AudioWMA.cs b/ArcFormats/AudioWMA.cs
index 1d33e783..dca846a3 100644
--- a/ArcFormats/AudioWMA.cs
+++ b/ArcFormats/AudioWMA.cs
@@ -112,43 +112,25 @@ namespace GameRes.Formats
     }
 
     /// <summary>
-    /// Custom implementation of MediaFoundationReader.
-    /// NAudio uses MFCreateMFByteStreamOnStreamEx API call which is not available in Windows 7.
+    /// Custom implementation of StreamMediaFoundationReader.
+    /// Extends it with Duration property.
     /// </summary>
-    internal class CustomMediaFoundationReader : MediaFoundationReader
+    internal class CustomMediaFoundationReader : StreamMediaFoundationReader
     {
-        private readonly Stream m_stream;
-
         /// <summary>
         /// Specifies the duration of a presentation, in 100-nanosecond units. 
         /// </summary>
         public long Duration { get; private set; }
 
         public CustomMediaFoundationReader (Stream stream, MediaFoundationReaderSettings settings = null)
+            : base (stream, settings)
         {
-            m_stream = stream;
-            Init (settings);
         }
 
         protected override IMFSourceReader CreateReader (MediaFoundationReaderSettings settings)
         {
-            const int MF_SOURCE_READER_ALL_STREAMS          = -2;
-            const int MF_SOURCE_READER_FIRST_AUDIO_STREAM   = -3;
-
-            IMFByteStream byteStream;
-            MFCreateMFByteStreamOnStream (new ComStream (m_stream), out byteStream);
-            var source_reader = MediaFoundationApi.CreateSourceReaderFromByteStream (byteStream);
-
-            source_reader.SetStreamSelection (MF_SOURCE_READER_ALL_STREAMS, false);
-            source_reader.SetStreamSelection (MF_SOURCE_READER_FIRST_AUDIO_STREAM, true);
-            source_reader.SetCurrentMediaType (MF_SOURCE_READER_FIRST_AUDIO_STREAM, IntPtr.Zero, new MediaType
-            {
-                MajorType = MediaTypes.MFMediaType_Audio,
-                SubType = settings.RequestFloatOutput ? AudioSubtypes.MFAudioFormat_Float : AudioSubtypes.MFAudioFormat_PCM
-            }.MediaFoundationObject);
-
+            var source_reader = base.CreateReader (settings);
             Duration = GetDuration (source_reader);
-
             return source_reader;
         }
 
@@ -173,96 +155,5 @@ namespace GameRes.Formats
                 Marshal.FreeHGlobal (variantPtr);
             }
         }
-
-        [DllImport("mfplat.dll", ExactSpelling = true, PreserveSig = false)]
-        static extern void MFCreateMFByteStreamOnStream (IStream pStream, out IMFByteStream ppByteStream);
-    }
-
-    /// <summary>
-    /// Implementation of Com IStream.
-    /// NAudio implementation is inaccessible (private).
-    /// </summary>
-    internal class ComStream : ProxyStream, IStream
-    {
-        public ComStream (Stream stream) : base (Synchronized (stream))
-        {
-        }
-
-        void IStream.Clone (out IStream ppstm)
-        {
-            ppstm = null;
-        }
-
-        void IStream.Commit (int grfCommitFlags)
-        {
-            Flush();
-        }
-
-        void IStream.CopyTo (IStream pstm, long cb, IntPtr pcbRead, IntPtr pcbWritten)
-        {
-        }
-
-        void IStream.LockRegion (long libOffset, long cb, int dwLockType)
-        {
-        }
-
-        void IStream.Read (byte[] pv, int cb, IntPtr pcbRead)
-        {
-            if (!CanRead)
-                throw new InvalidOperationException ("Stream is not readable.");
-            int read = Read (pv, 0, cb);
-            if (pcbRead != IntPtr.Zero)
-                Marshal.WriteInt32 (pcbRead, read);
-        }
-
-        void IStream.Revert()
-        {
-        }
-
-        void IStream.Seek (long dlibMove, int dwOrigin, IntPtr plibNewPosition)
-        {
-            SeekOrigin origin = (SeekOrigin) dwOrigin;
-            long val = Seek (dlibMove, origin);
-            if (plibNewPosition != IntPtr.Zero)
-                Marshal.WriteInt64 (plibNewPosition, val);
-        }
-
-        void IStream.SetSize (long libNewSize)
-        {
-            SetLength (libNewSize);
-        }
-
-        void IStream.Stat (out System.Runtime.InteropServices.ComTypes.STATSTG pstatstg, int grfStatFlag)
-        {
-            const int STGM_READ = 0x00000000;
-            const int STGM_WRITE = 0x00000001;
-            const int STGM_READWRITE = 0x00000002;
-
-            var tmp = new System.Runtime.InteropServices.ComTypes.STATSTG { type = 2, cbSize = Length, grfMode = 0 };
-
-            if (CanWrite && CanRead)
-                tmp.grfMode |= STGM_READWRITE;
-            else if (CanRead)
-                tmp.grfMode |= STGM_READ;
-            else if (CanWrite)
-                tmp.grfMode |= STGM_WRITE;
-            else
-                throw new ObjectDisposedException ("Stream");
-
-            pstatstg = tmp;
-        }
-
-        void IStream.UnlockRegion (long libOffset, long cb, int dwLockType)
-        {
-        }
-
-        void IStream.Write (byte[] pv, int cb, IntPtr pcbWritten)
-        {
-            if (!CanWrite)
-                throw new InvalidOperationException ("Stream is not writeable.");
-            Write (pv, 0, cb);
-            if (pcbWritten != IntPtr.Zero)
-                Marshal.WriteInt32 (pcbWritten, cb);
-        }
     }
 }