/// <summary>Initialize a VideoStream for an existing stream</summary>
/// <param name="aviFile">The file that contains the stream</param>
/// <param name="aviStream">An IAVISTREAM from [aviFile]</param>
public VideoStream(int aviFile, IntPtr aviStream)
{
this.aviFile = aviFile;
this.aviStream = aviStream;
Avi.BITMAPINFOHEADER bih = new Avi.BITMAPINFOHEADER();
int size = Marshal.SizeOf(bih);
Avi.AVIStreamReadFormat(aviStream, 0, ref bih, ref size);
Avi.AVISTREAMINFO streamInfo = GetStreamInfo(aviStream);
this.frameRate = (float)streamInfo.dwRate / (float)streamInfo.dwScale;
this.width = (int)streamInfo.rcFrame.right;
this.height = (int)streamInfo.rcFrame.bottom;
this.frameSize = bih.biSizeImage;
this.countBitsPerPixel = bih.biBitCount;
this.firstFrame = Avi.AVIStreamStart(aviStream.ToInt32());
this.countFrames = Avi.AVIStreamLength(aviStream.ToInt32());
}