[Kurtnoise]

Here is something more usable in C# :

Index: AviSynthAudioEncoder.cs
===================================================================
--- AviSynthAudioEncoder.cs	(revision 570)
+++ AviSynthAudioEncoder.cs	(working copy)
@@ -552,6 +552,46 @@
                         script.AppendFormat("NicMPG123Source(\"{0}\"){1}", audioJob.Input, Environment.NewLine);
                         break;
                     case ".wav":
+                        FileStream fs = new FileStream(audioJob.Input, FileMode.Open, FileAccess.ReadWrite);
+                        fs.Seek(20, SeekOrigin.Begin);                // AudioFormat offset
+                        byte[] aux = new byte[4]; // only a byte buffer
+
+                        fs.Read(aux, 1, 2);
+                        UInt16 AudioFormat = (UInt16)(((aux)[0] & 0xff) | ((aux)[1] << 8));  // Or something to read a LE int_16
+
+
+                        switch (AudioFormat)
+                        {
+
+                            case 0x0001:         // PCM Format Int
+                                fs.Seek(44, SeekOrigin.Current);   // DtsHeader offset
+
+                                fs.Read(aux, 1, 4);
+                                UInt32 DtsHeader = (UInt32)(((aux)[0] & 0xff) | ((aux)[1] << 8) | ((aux)[2] << 16) | ((aux)[3] << 24));  // Or something to read a LE int_32
+
+                                if (DtsHeader == 0xE8001FFF)
+                                {
+                                    script.AppendFormat("NicDtsSource(\"{0}\"){1}", audioJob.Input, Environment.NewLine);
+                                    break;
+                                }
+                                break;
+                            case 0x0003:         // IEEE Float
+                            case 0xFFFE:         // WAVE_FORMAT_EXTENSIBLE header
+                                script.AppendFormat("RaWavSource(\"{0}\", 2){1}", audioJob.Input, Environment.NewLine);
+                                break;
+                            case 0x0055:         // MPEG Layer 3
+                                script.AppendFormat("NicMPG123Source(\"{0}\"){1}", audioJob.Input, Environment.NewLine);
+                                break;
+                            case 0x2000:         // AC3
+                                script.AppendFormat("NicAc3Source(\"{0}\"){1}", audioJob.Input, Environment.NewLine);
+                                break;
+                            default:
+                                script.AppendFormat("WavSource(\"{0}\"){1}", audioJob.Input, Environment.NewLine);
+                                break;
+                        }
+
+                        fs.Close();
+                        break;
                     case ".w64":
                     case ".aif":
                     case ".au":

edit: doesn't seem to work correctly. WavSource(...) is always returned. Tested with MP3 & AC3...