faad c# wrapper

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

namespace AACtoPCM
{
    public class libfaad
    {
        #region Structures

        [StructLayout(LayoutKind.Sequential)]
        public struct NeAACDecConfiguration
            {
                public char defObjectType;
                public int defSampleRate;
                public char outputFormat;
                public char downMatrix;
                public char useOldADTSFormat;
            }

        [StructLayout(LayoutKind.Sequential)]
        public struct NeAACDecFrameInfo
            {
                public Int32 bytesconsumed;
                public Int32 samples;
                public char channels;
                public char error;
                public Int32 samplerate;
                public char sbr;
                public char object_type;
                public char header_type;
                public char num_front_channels;
                public char num_side_channels;
                public char num_back_channels;
                public char num_lfe_channels;
                [MarshalAs(UnmanagedType.ByValArray, SizeConst = 64)]
                public char[] channel_position;
                public char ps;
            }


        #endregion

        const string libPath = "libfaad2.dll";

        #region Methods

            [DllImport(libPath)]public static extern IntPtr NeAACDecOpen();

            [DllImport(libPath)]public static extern IntPtr NeAACDecGetCurrentConfiguration(IntPtr hpDecoder);

            [DllImport(libPath)]public static extern char NeAACDecSetConfiguration(IntPtr hpDecoder, IntPtr config);

            [DllImport(libPath)]public static extern int NeAACDecInit(IntPtr hpDecoder, byte[] buffer, int buffer_size, IntPtr samplerate, IntPtr channels);

            [DllImport(libPath)]public static extern char NeAACDecInit2 (IntPtr hpDecoder, IntPtr pBuffer, int SizeOfDecoderSpecificInfo, IntPtr samplerate, IntPtr channels);

            [DllImport(libPath)]public static extern IntPtr NeAACDecDecode(IntPtr hpDecoder, out NeAACDecFrameInfo hInfo, byte[] buffer, int buffer_size);

            [DllImport(libPath)]public static extern void NeAACDecClose(IntPtr hpDecoder);

            [DllImport(libPath, CharSet=CharSet.Ansi)]public static extern string NeAACDecGetErrorMessage(char errcode);

            [DllImport(libPath)]public static extern char NeAACDecAudioSpecificConfig(IntPtr pBuffer, int buffer_size, IntPtr mp4ASC);

        #endregion
    }
}