Keep Coding

by using directshow.net i can able to record the video and with recording i am doing text overlay for this i configured sample grabber and in buffercb method i am working on frames here is the code..
int ISampleGrabberCB.BufferCB(double SampleTime, IntPtr pBuffer, int BufferLen)
{
Graphics g;
String s;
float sLeft;
float sTop;
SizeF d;
g = Graphics.FromImage(bitmapOverlay);
g.Clear(System.Drawing.Color.Transparent);
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
// Prepare to put the specified string on the image
g.DrawRectangle(System.Drawing.Pens.Transparent, 0, 0, 240 - 1, 176 - 1);
g.DrawRectangle(System.Drawing.Pens.Transparent, 1, 1, 240 - 3, 176 - 3);
d = g.MeasureString(m_String + "\n" + DateTime.Now.ToString("G"), fontOverlay);
sLeft = (240 - d.Width) / 2;
sTop = (176 - d.Height) / 2;
g.DrawString(m_String + "\n" + DateTime.Now.ToString("G"), fontOverlay, System.Drawing.Brushes.Black,
sLeft, sTop, System.Drawing.StringFormat.GenericTypographic);
// need to flip the bitmap so it's the same orientation as the
// video buffer
bitmapOverlay.RotateFlip(RotateFlipType.RotateNoneFlipY);
// create and copy the video's buffer image to a bitmap
Bitmap v;
v = new Bitmap(240, 176, 1056,
PixelFormat.Format24bppRgb, pBuffer);
g = Graphics.FromImage(v);
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
// draw the overlay bitmap over the video's bitmap
g.DrawImage(bitmapOverlay, 0, 0, bitmapOverlay.Width, bitmapOverlay.Height);
// dispose of the various objects
g.Dispose();
v.Dispose();
// Increment frame number. Done this way, frame are zero indexed.
m_Count++;
return 0;
}
my problem is,when i start program it shows me text overlay in preview window but when i open recorded file text overlay is not continues..i think i am missing some frames..on some frames overlay is their but its not continues..its flicking.
can any one help?

ok i got the problem!!
in the above code,BufferCB takes too long time to process the current video frame.its like let frame A is still in middle process before process complete frame B comes in.
so to minimize the processing in BufferCB i have remove the where bitmap image is set
this line of code i put into an function
g = Graphics.FromImage(bitmapOverlay);
g.Clear(System.Drawing.Color.Transparent);
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
// Prepare to put the specified string on the image
g.DrawRectangle(System.Drawing.Pens.Transparent, 0, 0, 240 - 1, 176 - 1);
g.DrawRectangle(System.Drawing.Pens.Transparent, 1, 1, 240 - 3, 176 - 3);
d = g.MeasureString(m_String + "\n" + DateTime.Now.ToString("G"), fontOverlay);
sLeft = (240 - d.Width) / 2;
sTop = (176 - d.Height) / 2;
g.DrawString(m_String + "\n" + DateTime.Now.ToString("G"), fontOverlay, System.Drawing.Brushes.Black,
sLeft, sTop, System.Drawing.StringFormat.GenericTypographic);
// need to flip the bitmap so it's the same orientation as the
// video buffer
bitmapOverlay.RotateFlip(RotateFlipType.RotateNoneFlipY);
and this function is called before media.run is called.