protected void CalculateOutputRectangle(IMFMediaType pProposed, out MFRect prcOutput)
{
int srcWidth = 0, srcHeight = 0;
MFRatio inputPAR;
MFRatio outputPAR;
MFRect rcOutput = new MFRect();
MFVideoArea displayArea;
VideoTypeBuilder pmtProposed = null;
// Helper object to read the media type.
pmtProposed = new VideoTypeBuilder(pProposed);
// Get the source's frame dimensions.
pmtProposed.GetFrameDimensions(out srcWidth, out srcHeight);
// Get the source's display area.
pmtProposed.GetVideoDisplayArea(out displayArea);
// Calculate the x,y offsets of the display area.
int offsetX = (int)displayArea.OffsetX.GetOffset();
int offsetY = (int)displayArea.OffsetY.GetOffset();
// Use the display area if valid. Otherwise, use the entire frame.
if (displayArea.Area.Width != 0 &&
displayArea.Area.Height != 0 &&
offsetX + displayArea.Area.Width <= (srcWidth) &&
offsetY + displayArea.Area.Height <= (srcHeight))
{
rcOutput.left = offsetX;
rcOutput.right = offsetX + displayArea.Area.Width;
rcOutput.top = offsetY;
rcOutput.bottom = offsetY + displayArea.Area.Height;
}
else
{
rcOutput.left = 0;
rcOutput.top = 0;
rcOutput.right = srcWidth;
rcOutput.bottom = srcHeight;
}
// rcOutput is now either a sub-rectangle of the video frame, or the entire frame.
// If the pixel aspect ratio of the proposed media type is different from the monitor's,
// letterbox the video. We stretch the image rather than shrink it.
inputPAR = pmtProposed.GetPixelAspectRatio(); // Defaults to 1:1
outputPAR.Denominator = outputPAR.Numerator = 1; // This is an assumption of the sample.
// Adjust to get the correct picture aspect ratio.
prcOutput = CorrectAspectRatio(rcOutput, inputPAR, outputPAR);
pmtProposed.Dispose();
}