/// <summary>Prepare for decompressing frames</summary>
/// <remarks>
/// This method has to be called before GetBitmap and ExportBitmap.
/// Release ressources with GetFrameClose.
/// </remarks>
public void GetFrameOpen()
{
GetStreamInfo(StreamPointer);
//Open frames
Avi.BITMAPINFOHEADER bih = new Avi.BITMAPINFOHEADER();
bih.biBitCount = CountBitsPerPixel;
bih.biClrImportant = 0;
bih.biClrUsed = 0;
bih.biCompression = 0;
bih.biPlanes = 1;
bih.biSize = Marshal.SizeOf(bih);
bih.biXPelsPerMeter = 0;
bih.biYPelsPerMeter = 0;
// Corrections by M. Covington:
// If these are pre-set, interlaced video is not handled correctly.
// Better to give zeroes and let Windows fill them in.
bih.biHeight = 0; // was (Int32)streamInfo.rcFrame.bottom;
bih.biWidth = 0; // was (Int32)streamInfo.rcFrame.right;
// Corrections by M. Covington:
// Validate the bit count, because some AVI files give a bit count
// that is not one of the allowed values in a BitmapInfoHeader.
// Here 0 means for Windows to figure it out from other information.
if (bih.biBitCount > 24)
{
bih.biBitCount = 32;
}
else if (bih.biBitCount > 16)
{
bih.biBitCount = 24;
}
else if (bih.biBitCount > 8)
{
bih.biBitCount = 16;
}
else if (bih.biBitCount > 4)
{
bih.biBitCount = 8;
}
else if (bih.biBitCount > 0)
{
bih.biBitCount = 4;
}
getFrameObject = Avi.AVIStreamGetFrameOpen(StreamPointer, ref bih);
if (getFrameObject == 0)
{
throw new Exception("Exception in VideoStreamGetFrameOpen!");
}
}