static void InPackets(IntPtr clientData, int numberBytes, int numberPackets, IntPtr inputData, IntPtr packetDescriptions) { GCHandle handle = GCHandle.FromIntPtr(clientData); var afs = handle.Target as AudioFileStream; var desc = AudioFile.PacketDescriptionFrom(numberPackets, packetDescriptions); afs.OnPacketDecoded(numberBytes, inputData, desc); }