diff --git a/NTwain/Data/Types.cs b/NTwain/Data/Types.cs
index 6f7ec43..b45743c 100644
--- a/NTwain/Data/Types.cs
+++ b/NTwain/Data/Types.cs
@@ -83,10 +83,8 @@ namespace NTwain.Data
     {
         [MarshalAs(UnmanagedType.ByValArray, SizeConst = 3)]
         TWDecodeFunction[] _decode;
-        // TODO: research jagged aray mapping (3x3). 
-        // maybe can only have 1-D
         [MarshalAs(UnmanagedType.ByValArray, SizeConst = 9)]
-        TWFix32[][] _mix;
+        TWFix32[] _mix;
     }
 
     [StructLayout(LayoutKind.Sequential, Pack = 2)]
@@ -230,61 +228,58 @@ namespace NTwain.Data
         TWInfo[] _info;
     }
 
-    [StructLayout(LayoutKind.Explicit, Pack = 2),
+    [StructLayout(LayoutKind.Sequential, Pack = 2),
     BestFitMapping(false, ThrowOnUnmappableChar = true)]
     partial class TWFileSystem
     {
-        // TODO: verify all field offset #s
-
-        [FieldOffset(0)]
+        //[FieldOffset(0)]
         [MarshalAs(UnmanagedType.ByValTStr, SizeConst = TwainConst.String255)]
         string _inputName;
 
-        [FieldOffset(TwainConst.String255)]
+        //[FieldOffset(TwainConst.String255)]
         [MarshalAs(UnmanagedType.ByValTStr, SizeConst = TwainConst.String255)]
         string _outputName;
 
-        [FieldOffset(512)]
+        //[FieldOffset(512)]
         TW_MEMREF _context;
 
-        //TODO: verify this field offset in 64bit due to previous pointer
-        [FieldOffset(520)]
-        short _recursive;
-        [FieldOffset(520)]
+        //[FieldOffset(520)]
+        //short _recursive;
+        //[FieldOffset(520)]
         TW_BOOL _subdirectories;
 
-        [FieldOffset(524)]
+        //[FieldOffset(524)]
         TW_INT32 _fileType;
-        [FieldOffset(524)]
-        TW_UINT32 _fileSystemType;
+        //[FieldOffset(524)]
+        //TW_UINT32 _fileSystemType;
 
-        [FieldOffset(528)]
+        //[FieldOffset(528)]
         TW_UINT32 _size;
 
-        [FieldOffset(532)]
+        //[FieldOffset(532)]
         [MarshalAs(UnmanagedType.ByValTStr, SizeConst = TwainConst.String32)]
         string _createTimeDate;
 
-        [FieldOffset(566)]
+        //[FieldOffset(566)]
         [MarshalAs(UnmanagedType.ByValTStr, SizeConst = TwainConst.String32)]
         string _modifiedTimeDate;
 
-        [FieldOffset(600)]
+        //[FieldOffset(600)]
         TW_UINT32 _freeSpace;
 
-        [FieldOffset(604)]
+        //[FieldOffset(604)]
         TW_INT32 _newImageSize;
 
-        [FieldOffset(608)]
+        //[FieldOffset(608)]
         TW_UINT32 _numberOfFiles;
 
-        [FieldOffset(612)]
+        //[FieldOffset(612)]
         TW_UINT32 _numberOfSnippets;
 
-        [FieldOffset(616)]
+        //[FieldOffset(616)]
         TW_UINT32 _deviceGroupMask;
 
-        [FieldOffset(620)]
+        //[FieldOffset(620)]
         [MarshalAs(UnmanagedType.ByValArray, SizeConst = 508)]
         TW_INT8[] _reserved;
     }
diff --git a/NTwain/Data/TypesExtended.cs b/NTwain/Data/TypesExtended.cs
index 25abb27..345604b 100644
--- a/NTwain/Data/TypesExtended.cs
+++ b/NTwain/Data/TypesExtended.cs
@@ -470,9 +470,21 @@ namespace NTwain.Data
         /// </summary>
         public TWDecodeFunction[] Decode { get { return _decode; } set { _decode = value; } }
         /// <summary>
-        /// 3x3 matrix that specifies how channels are mixed in.
+        /// Flattened 3x3 matrix that specifies how channels are mixed in.
         /// </summary>
-        public TWFix32[][] Mix { get { return _mix; } set { _mix = value; } }
+        public TWFix32[] Mix { get { return _mix; } set { _mix = value; } }
+
+        /// <summary>
+        /// Gets the <see cref="Mix"/> value as matrix.
+        /// </summary>
+        /// <returns></returns>
+        public TWFix32[,] GetMixMatrix()
+        {
+            // from http://stackoverflow.com/questions/3845235/convert-array-to-matrix, haven't tested it
+            TWFix32[,] mat = new TWFix32[3, 3];
+            Buffer.BlockCopy(_mix, 0, mat, 0, _mix.Length * 4);
+            return mat;
+        }
     }
 
     /// <summary>
@@ -1606,9 +1618,8 @@ namespace NTwain.Data
         /// all subdirectories in the directory being deleted; or copies all
         /// sub-directories in the directory being copied.
         /// </summary>
-        public short Recursive { get { return _recursive; } set { _recursive = value; } }
-        public bool Subdirectories { get { return _subdirectories == TwainConst.True; } }
-
+        public bool Recursive { get { return _subdirectories == TwainConst.True; } set { _subdirectories = value ? TwainConst.True : TwainConst.False; } }
+        
         /// <summary>
         /// Gets the type of the file.
         /// </summary>
@@ -1616,8 +1627,7 @@ namespace NTwain.Data
         /// The type of the file.
         /// </value>
         public FileType FileType { get { return (FileType)_fileType; } set { _fileType = (int)value; } }
-        public uint FileSystemType { get { return _fileSystemType; } set { _fileSystemType = value; } }
-
+        
         /// <summary>
         /// If <see cref="NTwain.Values.FileType.Directory"/>, total size of media in bytes.
         /// If <see cref="NTwain.Values.FileType.Image"/>, size of image in bytes.
diff --git a/NTwain/Triplets/DGControl/DGControl.XferGroup.cs b/NTwain/Triplets/DGControl/DGControl.XferGroup.cs
index f3a0e11..65fa674 100644
--- a/NTwain/Triplets/DGControl/DGControl.XferGroup.cs
+++ b/NTwain/Triplets/DGControl/DGControl.XferGroup.cs
@@ -17,7 +17,7 @@ namespace NTwain.Triplets
 		/// </summary>
 		/// <param name="value">The value.</param>
 		/// <returns></returns>
-		public ReturnCode Get(ref uint value)
+        public ReturnCode Get(ref DataGroups value)
 		{
             Session.VerifyState(4, 6, DataGroups.Control, DataArgumentType.XferGroup, Message.Get);
             return PInvoke.DsmEntry(Session.GetAppId(), Session.SourceId, DataGroups.Control, DataArgumentType.XferGroup, Message.Get, ref value);
@@ -30,7 +30,7 @@ namespace NTwain.Triplets
         /// </summary>
         /// <param name="value">The value.</param>
         /// <returns></returns>
-        public ReturnCode Set(uint value)
+        public ReturnCode Set(DataGroups value)
 		{
 			Session.VerifyState(6, 6, DataGroups.Control, DataArgumentType.XferGroup, Message.Set);
             return PInvoke.DsmEntry(Session.GetAppId(), Session.SourceId, DataGroups.Control, DataArgumentType.XferGroup, Message.Set, ref value);
diff --git a/NTwain/Triplets/PInvoke.Linux.cs b/NTwain/Triplets/PInvoke.Linux.cs
index 5e24741..80d386d 100644
--- a/NTwain/Triplets/PInvoke.Linux.cs
+++ b/NTwain/Triplets/PInvoke.Linux.cs
@@ -28,7 +28,7 @@ namespace NTwain.Triplets
         //        DataGroups dg,
         //        DataArgumentType dat,
         //        Message msg,
-        //        ref uint data);
+        //        ref DataGroups data);
 
         //    [DllImport("/usr/local/lib/libtwaindsm.so", EntryPoint = "#1")]
         //    public static extern ReturnCode DsmEntryLinux(
diff --git a/NTwain/Triplets/PInvoke.Win32.cs b/NTwain/Triplets/PInvoke.Win32.cs
index 52f7b67..1d8f049 100644
--- a/NTwain/Triplets/PInvoke.Win32.cs
+++ b/NTwain/Triplets/PInvoke.Win32.cs
@@ -25,7 +25,7 @@ namespace NTwain.Triplets
                 DataGroups dg,
                 DataArgumentType dat,
                 Message msg,
-                ref uint data);
+                ref DataGroups data);
 
 			[DllImport("twain_32", EntryPoint = "#1")]
 			public static extern ReturnCode DsmEntry32(
diff --git a/NTwain/Triplets/PInvoke.Win64.cs b/NTwain/Triplets/PInvoke.Win64.cs
index 0664a5f..a78cd2f 100644
--- a/NTwain/Triplets/PInvoke.Win64.cs
+++ b/NTwain/Triplets/PInvoke.Win64.cs
@@ -25,7 +25,7 @@ namespace NTwain.Triplets
                 DataGroups dg,
                 DataArgumentType dat,
                 Message msg,
-                ref uint data);
+                ref DataGroups data);
 
 			[DllImport("twaindsm", EntryPoint = "#1")]
 			public static extern ReturnCode DsmEntry64(
diff --git a/NTwain/Triplets/PInvoke.cs b/NTwain/Triplets/PInvoke.cs
index 4e44162..1d5aa00 100644
--- a/NTwain/Triplets/PInvoke.cs
+++ b/NTwain/Triplets/PInvoke.cs
@@ -53,7 +53,7 @@ namespace NTwain.Triplets
             DataGroups dg,
             DataArgumentType dat,
             Message msg,
-            ref uint data)
+            ref DataGroups data)
         {
             if (CanUseTwainDSM) { return NativeMethods.DsmEntry64(origin, destination, dg, dat, msg, ref data); }
             else { return NativeMethods.DsmEntry32(origin, destination, dg, dat, msg, ref data); }
diff --git a/NTwain/TwainSession.cs b/NTwain/TwainSession.cs
index c36643a..01c2d8a 100644
--- a/NTwain/TwainSession.cs
+++ b/NTwain/TwainSession.cs
@@ -603,7 +603,7 @@ namespace NTwain
                 // My guess is the DS needs to see the Success return code first before letting transfer happen
                 // so this is an hack to make it happen.
 
-                // TODO: find a better method.
+                // TODO: find a better method without needing a SynchronizationContext.
                 ThreadPool.QueueUserWorkItem(o =>
                 {
                     var ctx = o as SynchronizationContext;
@@ -669,12 +669,19 @@ namespace NTwain
         /// </summary>
         protected virtual void DoTransferRoutine()
         {
-            // TODO: better way to determine what's being xfered?
-            if ((SourceId.DataGroup & DataGroups.Image) == DataGroups.Image)
+            DataGroups xferGroup = DataGroups.None;
+
+            if (DGControl.XferGroup.Get(ref xferGroup) != ReturnCode.Success)
+            {
+                xferGroup = DataGroups.None;
+            }
+
+            // support one or the other or both?
+            if ((xferGroup & DataGroups.Image) == DataGroups.Image)
             {
                 DoImageXfer();
             }
-            else if ((SourceId.DataGroup & DataGroups.Audio) == DataGroups.Audio)
+            else if ((xferGroup & DataGroups.Audio) == DataGroups.Audio)
             {
                 DoAudioXfer();
             }
@@ -725,8 +732,7 @@ namespace NTwain
                     rc = DGControl.PendingXfers.Reset(pending);
                     if (rc == ReturnCode.Success)
                     {
-                        // TODO: verify if audio exit directly?
-                        return;
+                        break;
                     }
                 }
                 else if (!preXferArgs.CancelCurrent)
diff --git a/NTwain/TwainSessionOld.cs b/NTwain/TwainSessionOld.cs
index 82ebea7..741cc38 100644
--- a/NTwain/TwainSessionOld.cs
+++ b/NTwain/TwainSessionOld.cs
@@ -97,8 +97,6 @@ namespace NTwain
 
                     #region do xfer
 
-                    // TODO: expose all swallowed exceptions somehow later
-
                     IntPtr dataPtr = IntPtr.Zero;
                     IntPtr lockedPtr = IntPtr.Zero;
                     string file = null;