A Simple C# Wrapper for the AviFile Library

/* This class has been written by
 * Corinna John (Hannover, Germany)
 * cj@binary-universe.net
 * 
 * You may do with this code whatever you like,
 * except selling it or claiming any rights/ownership.
 * 
 * Please send me a little feedback about what you're
 * using this code for and what changes you'd like to
 * see in later versions. (And please excuse my bad english.)
 * 
 * WARNING: This is experimental code.
 * Please do not expect "Release Quality".
 * */

using System;
using System.IO;
using System.Runtime.InteropServices;

namespace AviFile
{
	public class AudioStream : AviStream{
		
		public int CountBitsPerSample{
			get{ return waveFormat.wBitsPerSample; }
		}

		public int CountSamplesPerSecond{
			get{ return waveFormat.nSamplesPerSec; }
		}
		
		public int CountChannels{
			get{ return waveFormat.nChannels; }
		}

		/// <summary>the stream's format</summary>
		private Avi.PCMWAVEFORMAT waveFormat = new Avi.PCMWAVEFORMAT();

		/// <summary>Initialize an AudioStream for an existing stream</summary>
		/// <param name="aviFile">The file that contains the stream</param>
		/// <param name="aviStream">An IAVISTREAM from [aviFile]</param>
		public AudioStream(int aviFile, IntPtr aviStream){
			this.aviFile = aviFile;
			this.aviStream = aviStream;
			
			int size = Marshal.SizeOf(waveFormat);
			Avi.AVIStreamReadFormat(aviStream, 0, ref waveFormat, ref size);
			Avi.AVISTREAMINFO streamInfo = GetStreamInfo(aviStream);
		}

		/// <summary>Read the stream's header information</summary>
		/// <param name="aviStream">The IAVISTREAM to read from</param>
		/// <returns>AVISTREAMINFO</returns>
		private Avi.AVISTREAMINFO GetStreamInfo(IntPtr aviStream){
			Avi.AVISTREAMINFO streamInfo = new Avi.AVISTREAMINFO();
			int result = Avi.AVIStreamInfo(aviStream, ref streamInfo, Marshal.SizeOf(streamInfo));
			if(result != 0) {
				throw new Exception("Exception in AVIStreamInfo: "+result.ToString());
			}
			return streamInfo;
		}

		/// <summary>Read the stream's header information</summary>
		/// <returns>AVISTREAMINFO</returns>
		public Avi.AVISTREAMINFO GetStreamInfo(){
			if(writeCompressed){
				return GetStreamInfo(compressedStream);
			}else{
				return GetStreamInfo(aviStream);
			}
		}
		
		/// <summary>Read the stream's format information</summary>
		/// <returns>PCMWAVEFORMAT</returns>
		public Avi.PCMWAVEFORMAT GetFormat(){
			Avi.PCMWAVEFORMAT format = new Avi.PCMWAVEFORMAT();
			int size = Marshal.SizeOf(format);
			int result = Avi.AVIStreamReadFormat(aviStream, 0, ref format, ref size);
			return format;
		}

		/// <summary>Returns all data needed to copy the stream</summary>
		/// <remarks>Do not forget to call Marshal.FreeHGlobal and release the raw data pointer</remarks>
		/// <param name="streamInfo">Receives the header information</param>
		/// <param name="format">Receives the format</param>
		/// <param name="streamLength">Receives the length of the stream</param>
		/// <returns>Pointer to the wave data</returns>
		public IntPtr GetStreamData(ref Avi.AVISTREAMINFO streamInfo, ref Avi.PCMWAVEFORMAT format, ref int streamLength){
			streamInfo = GetStreamInfo();
			
			format = GetFormat();
			//length in bytes = length in samples * length of a sample
			streamLength = Avi.AVIStreamLength(aviStream.ToInt32()) * streamInfo.dwSampleSize;
			IntPtr waveData = Marshal.AllocHGlobal(streamLength);
			
			int result = Avi.AVIStreamRead(aviStream, 0, streamLength, waveData, streamLength, 0, 0);
			if(result != 0){
				throw new Exception("Exception in AVIStreamRead: "+result.ToString());
			}
			
			return waveData;
		}

		/// <summary>Copy the stream into a new file</summary>
		/// <param name="fileName">Name of the new file</param>
		public override void ExportStream(String fileName){
			Avi.AVICOMPRESSOPTIONS_CLASS opts = new Avi.AVICOMPRESSOPTIONS_CLASS();
			opts.fccType         = (UInt32)Avi.mmioStringToFOURCC("auds", 0);
			opts.fccHandler      = (UInt32)Avi.mmioStringToFOURCC("CAUD", 0);
			opts.dwKeyFrameEvery = 0;
			opts.dwQuality       = 0;
			opts.dwFlags         = 0;
			opts.dwBytesPerSecond= 0;
			opts.lpFormat        = new IntPtr(0);
			opts.cbFormat        = 0;
			opts.lpParms         = new IntPtr(0);
			opts.cbParms         = 0;
			opts.dwInterleaveEvery = 0;
			
			Avi.AVISaveV(fileName, 0, 0, 1, ref aviStream, ref opts);
		}

	}
}